                                  PRECEDENTIAL


      UNITED STATES COURT OF APPEALS
           FOR THE THIRD CIRCUIT
                _____________

  Nos. 15-3506, 15-3507, 15-3508, 15-3509, 15-3510,
15-3511, 15-3512, 15-3513, 15-3514, 15-3515, 15-3564,
15-3639, 15-3640, 15-3641, 15-3642, 15-3643, 15-3644,
15-3645, 15-3646, 15-3647, 15-3648, 15-3649, 15-3650,
15-3651, 15-3652, 15-3653, 15-3654, 15-3655, 15-3656,
15-3657, 15-3658, 15-3659, 15-3660, 15-4075, 15-4076,
        15-4077, 15-4078, 16-1694, & 16-1965
                   _____________

MICHELLE MCMUNN, personal representative of the
             Estate of Eva Myers;
  CARA D. STEELE; YVONNE SUE ROBINSON;
            EDWARD J. MYERS;
LEVI DANIEL STEELE; HAROLD ROBINSON, et al

                         v.

 BABCOCK & WILCOX POWER GENERATION
                   GROUP, INC.;
 B&W TECHNICAL SERVICES, INC., FKA B&W
                Nuclear Environmental
Services, Inc.; ATLANTIC RICHFIELD COMPANY,
               predecessors-in-interest,
 successors-in-interest, subdivisions and subsidiaries;
 BABCOCK & WILCOX TECHNICAL SERVICES
                    GROUP, INC.

           Apollo Facility Plaintiffs, Appellants
           in Nos. 15-3506, 15-3507, 15-3508,
           15-3509, 15-3510, 15-3511, 15-3512,
           15-3513, 15-3514, 15-3515, 15-3564,
           15-4075, 15-4076, 15-4077, 15-4078,
           16-1964 and 16-1965

           Babcock & Wilcox Power Generation
           Group, Inc. and Babcock & Wilcox
           Technical Services Group, Inc., Appellants
           in Nos. 15-3640, 15-3642, 15-3644,
           15-3646, 15-3648, 15-3650, 15-3652,
           15-3654,15-3656, 15-3658 and 15-3660

          Atlantic Richfield Company, Appellant in
          Nos. 15-3639, 15-3641, 15-3643, 15-3645,
          15-3647, 15-3649, 15-3651, 15-3653,
          15-3655, 15-3657 and 15-3659
_____________

   On Appeal from the United States District Court
        for the Western District of Pennsylvania
  District Court Nos. 2-10-cv-00143, 2-10-cv-00368,
   2-10-cv-00650, 2-10-cv-00728, 2-10-cv-00744,
   2-10-cv-00908, 2-10-cv-01736, 2-11-cv-00898,
                           2
    2-11-cv-01381, 2-12-cv-01221, 2-12-cv-01459,
    2-13-cv-00186, 2-13-cv-00704, 2-13-cv-01527,
    2-14-cv-00639, 2-15-cv-00844, 2-15-cv-01423
    District Judge: The Honorable David S. Cercone

             Argued November 10, 2016

Before: SMITH, Chief Judge, McKEE, and RESTREPO,
                  Circuit Judges

               (Filed: August 23, 2017)

Louis M. Bograd                [ARGUED]
Motley Rice
3333 K Street, N.W.
Suite 450
Washington, DC 20007

Jonathan D. Orent
Motley Rice
321 South Main Street
P.O. Box 6067
Providence, RI 02904

Anne McGinness Kearse
Motley Rice
28 Bridgeside Boulevard
Mount Pleasant, SC 29464


                           3
David B. Rodes
Goldberg Persky & White P.C.
11 Stanwix Street
Suite 1800
Pittsburgh, PA 15222
       Counsel for Appellants

Stephen B. Kinnaird
Paul Hastings LLP
875 15th Street, N.W.
Suite 1000
Washington, DC 20005

Peter C. Meier
John P. Phillips                [ARGUED]
Sean D. Unger
Paul Hastings LLP
55 Second Street
24th Floor
San Francisco, CA 94105

Nancy G. Milburn                [ARGUED]
Philip H. Curtis
Reuben S. Koolyk
Arnold & Porter LLP
399 Park Avenue
34th Floor
New York, NY 10022


                          4
Geoffrey J. Michael
Arnold & Porter LLP
601 Massachusetts Avenue, N.W.
Washington, DC 20001

      Counsel for Appellees

          _____________________________

             OPINION OF THE COURT
          _____________________________


SMITH, Chief Judge, joined by RESTREPO, Circuit
Judge, who also joins in the Concurrence.
       Plaintiffs assert that they developed cancer1 after
being exposed to excessive radiation emissions from the
Nuclear Material and Equipment Company (“NUMEC”)
facility in Apollo, Pennsylvania (the “Apollo facility”).
Plaintiffs do not challenge the District Court’s
conclusions that their common-law claims against




1
  For simplicity’s sake, we refer to the individuals
diagnosed with cancer as “Plaintiffs” even though several
of those individuals have died and the executors of those
individuals’ estates have been substituted as plaintiffs.

                            5
Defendants2 were preempted by the Price-Anderson Act
and that only their Price-Anderson “public liability”
claims are at issue in this appeal. Although the Price-
Anderson Act preempted Plaintiffs’ common-law
negligence claims, Plaintiffs’ Price-Anderson public
liability claims require Plaintiffs to prove versions of the
traditional negligence elements—(1) duty, (2) breach,
(3) causation, and (4) damages.
       The District Court held that Defendants were
entitled to summary judgment as a matter of law on the
Price-Anderson claims because Plaintiffs failed to show
that there was a genuine dispute of material fact as to
elements of duty, breach, and damages. Plaintiffs
appealed. We agree with the District Court: Plaintiffs
are missing critical elements, and therefore their claims
fail.


2
   Defendants are Atlantic Richfield Company and
Babcock & Wilcox Power Generation Group, Inc.,
Babcock & Wilcox Technical Services Group Inc., and
B&W Technical Services Inc.           Atlantic Richfield
Company and Babcock & Wilcox Power Generation
Group, Inc., were owners of the NUMEC facility at
different points in time. See, e.g., JA1467 (stating that
Atlantic Richfield bought the Apollo facility from
NUMEC in 1967 and Babcock & Wilcox purchased the
facility in 1971).

                             6
       Accordingly, we will affirm the judgment of the
District Court.

                   BACKGROUND
         I. THE PARTIES AND EMISSIONS

A. The Parties
       Plaintiffs are more than seventy individuals3 in a
group of consolidated cases who claim that excessive
radiation emitted by Defendants—more specifically,
radiation from uranium effluent from the Apollo
facility—caused them to develop various cancers.

      Almost all of the Plaintiffs lived near Apollo,
Pennsylvania, for many years, including the 1960s, and
almost all of the Plaintiffs were diagnosed with at least
one form of cancer between 2007 and 2011.4 The


3
  At oral argument, even Plaintiffs’ counsel was unable to
fix the exact number of plaintiffs. See Oral Arg. Tr. at
4:6–19.
4
   This period of time when most Plaintiffs were
diagnosed with cancer may reflect that another group of
individuals who developed cancer had previously sued
Babcock & Wilcox and Atlantic Richfield Co. Their
lawsuit apparently settled before trial. See Docket, Hall
v. Babcock & Wilcox, No. 94-951 (W.D. Pa.); see also
                            7
similarities among the Plaintiffs end there. By our count,
Plaintiffs alleged that they suffered from more than a
dozen different types of cancer.5 Plaintiffs were of
widely varying ages at the times of their diagnoses—with
at least one individual under 30 and at least five
individuals over 80. See JA3460 (81); JA3478 (82);
JA3479 (88); JA3482 (81); JA3485 (29); JA3491 (82).
Many of the Plaintiffs had extensive smoking histories,
and some had multiple cancer diagnoses over their
lifetimes. See, e.g., JA3474 (“smoked about half a pack
per day for 40 years”); JA3463 (“diagnosed with breast
cancer in 1986 and then again in 2008 at the age of 67”).




Hall v. Babcock & Wilcox, No. 94-951, 2007 WL
1740852 (W.D. Pa. June 14, 2007). The diagnosis date
range here may also reflect statute of limitations
concerns. The statute of limitations is not an issue in this
appeal.
5
  See, e.g., JA3447 (“Non Hodgkin’s Lymphoma”);
JA3448 (“lung cancer”); JA3449 (“breast cancer”);
JA3450 (“esophageal cancer”); JA3451 (“colorectal
cancer”); JA3455 (“thyroid cancer”); JA3457 (“kidney
cancer”); JA3458 (“endometrial cancer”); JA3459
(“bladder cancer”); JA3465 (“melanoma”); JA3474
(“prostate cancer”); JA3479 (“metastatic ovarian
cancer”); JA3485 (“squamous cell tumor of her pelvis”).

                             8
B. The Facility
       The Apollo facility was a “warehouse style
building that was not specifically constructed to house
the complex manufacturing operation involving
radioactive materials.”       JA1427.      As Plaintiffs
emphasize, the Apollo facility was adjacent to a steel mill
and “in the immediate neighborhood of residential
areas.” JA1576.

      The Apollo facility operated from approximately
1953 to 1983 with uranium fuel manufacture beginning
in 1958 and decommissioning beginning in 1978. See
JA1467; McMunn v. Babcock & Wilcox Power
Generation Grp., 131 F. Supp. 3d 352, 356 (W.D. Pa.
2015).
      The Atomic Energy Commission (“AEC”) was the
federal regulatory body in charge of overseeing the
Apollo facility. During the time that the Apollo facility
operated, the Nuclear Regulatory Commission (“NRC”)
became “the statutory successor to the Atomic Energy
Commission.” In re TMI, 67 F.3d 1103, 1112 (3d Cir.
1995).

       The Apollo facility emitted radiation as a
necessary byproduct of manufacturing uranium fuel.
Plaintiffs argue that that radiation was in excess of
regulatory limits. The focus in this dispute is on
radiation emitted from the stacks, vents, and fans on the
Apollo facility’s roof.
                            9
C. Evidence of Excessive Emissions
       Much of Plaintiffs’ evidence of excessive
emissions indicates that emissions from the stacks or
vents on the roof exceeded the maximum permissible
concentration (“MPC”) for the facility. Plaintiffs do not
contest that the relevant maximum permissible
concentration is 8.8 disintegrations per minute per cubic
meter (dpm/m3). See McMunn, 131 F. Supp. 3d at 373
n.24; Pls.’ Br. 10; cf. JA3642.
       As discussed below, under the applicable
regulations, the maximum permissible concentration is
determined at the boundary of the “unrestricted area.”
Defendants argue that the boundary of the unrestricted
area is the boundary of the roof, while Plaintiffs argue
that any emissions from any part of the roof—including
emission from any stack, vent, or fan—should be less
than the maximum permissible concentration.

       Plaintiffs point to evidence that they believe
supports their position. In a June 5, 1964 letter, the
Director of the Division of State and Licensee Relations
of the AEC implied that the NUMEC had not shown that
the roof was a restricted area: “[T]he roof area of the
NUMEC facility is an unrestricted area unless access to
this area is controlled from the radiation safety
standpoint.” JA5314. Consistent with the 1964 letter
implying that the entire roof may be unrestricted,
Plaintiffs argue that NUMEC and AEC’s course of
conduct shows that they both thought that stack
                           10
emissions were a regulatory concern because NUMEC
and AEC compared stack emissions to the maximum
permissible concentration. For instance, in a 1967 report,
a NUMEC employee wrote, “[T]he measured stack
concentration frequently exceeds permissible levels.”
JA5201. The AEC similarly expressed concern about
releases from stacks, as though the regulations created
limitations on the stacks. In a February 5, 1969 letter, the
Director of the Division of Compliance of the AEC
warned, “Based on your recorded data, the concentrations
of radioactive material released from the facility through
exhaust stacks to unrestricted areas exceed the limits
specified in Appendix B, Table II of 10 CFR 20, contrary
to 10 CFR 20.105(a), ‘Concentrations in effluents to
unrestricted areas.’” JA4700.

       In addition to the evidence about emissions from
the stacks or vents, Plaintiffs’ evidence of excessive
emissions fits into one or more of the following three
categories: (1) evidence that the monitoring of emissions
was not completely comprehensive; (2) data that there
was excessive radiation in the area surrounding the
facility; and (3) data showing excessive radiation being
released but seemingly only for specific, and short,




                            11
periods of time (such as when the facility’s incinerator
was being used).6

       Plaintiffs marshaled a large number of documents
that they alleged created a genuine issue of material fact.
The highlights of Plaintiffs’ documents are below:

          In an April 20, 1964 letter, NUMEC
           Manager E.V. Barry wrote to Eber R. Price
           at the AEC that “average yearly
           concentrations at our property line” were
           being exceeded “when the winds are from
           the south quadrant” or in sections “when the
           winds are from the east quadrant.” JA5163.




6
  Our summary of Plaintiffs’ evidence mirrors Plaintiffs’
own summary presented at the conclusion of oral
argument. When asked about “discharges measured at
the roof edge,” Plaintiffs’ counsel (1) asserted that
Defendants’ “roof edge monitoring . . . is remarkably
incomplete”; (2) pointed to an April 20, 1964 letter
(discussed below) in which NUMEC admitted that it
sometimes exceeded permissible concentrations at the
boundary of the roof; (3) highlighted the airborne
concentrations of effluent when the plant’s incinerator
was operating; and (4) noted “environmental monitors in
the community.” Oral Arg. Tr. at 39:10–40:20.

                            12
 Data for part of the year 1966 shows a high
  of 41.5 dpm/m3 and an average of 13.0
  dpm/m3. See JA5188. But, as Plaintiffs
  admit, the “high” refers to only one day.
  See Pls.’ Br. 47–48 (referring to “the same
  day” that the sampler gave its “highest
  reading”). Additionally, this data comes
  from a nearby building and not the roof of
  the Apollo facility. Compare JA5188, with
  JA5189.

 An August 18, 1967 internal memorandum
  about the Apollo facility’s incinerator states,
  “Ever since the incinerator has been in
  operation it has been a consistent source of
  airborne contamination causing an over
  exposure [sic] to the operators and air levels
  above the M.P.C. in and out of the plant.”
  JA4428.

 In a February 5, 1969 letter, the Director of
  the Division of Compliance of the AEC
  wrote, among other things, “Based on your
  recorded data, the concentrations of
  radioactive material released from the
  facility through exhaust stacks to
  unrestricted areas exceed the limits specified
  in Appendix B, Table II of 10 CFR 20,
  contrary     to     10    CFR      20.105(a),


                  13
   ‘Concentrations in effluents to unrestricted
   areas.’” JA4700.

 A     November        30,   1972     internal
  memorandum memorializing a phone call
  from the AEC states that the AEC
  commented that “NUMEC has been the
  worst offender of AEC regulations over the
  years,” that “[t]he AEC is strongly
  considering imposing civil penalties,” and
  mentions NUMEC was implementing
  corrective actions in, among other things, its
  “Liquid Waste Management Program,” and
  “Building Ventilation and Surveillance
  Program.” See JA4439–40.

 In a February 12, 1974 letter, a NUMEC
  employee criticized the Apollo facility for
  releasing too much radiation. See JA4422
  (“It is . . . apparent from review of the data
  that said operations at the Apollo Site are
  not conducted so as to provide a minimal
  radiological         impact       on       the
  environment . . . .”). The same letter further
  states that there was heightened radioactivity
  in the area near the Apollo facility, many
  times in multiple of the background
  radiation because of “radiologically
  contaminated gaseous effluents.” Id.


                 14
          A July 9, 1974 internal memorandum
           complains about “stack and liquid discards
           of SNM [special nuclear material] from the
           Apollo Plant” and tremendous losses of
           uranium through “gross irresponsibility.”
           See JA4427.

       However, AEC/NRC approved NUMEC’s
operations at least three times. First, in a report
timestamped July 29, 1966, the AEC wrote, “No item of
noncompliance       with     respect   to    [NUMEC’s]
concentrations of radioactive effluents released to
unrestricted areas was noted as a result of this
investigation.” JA5051. Second, in 1968, the AEC
concluded that NUMEC’s roof edge samples were below
the maximum permissible concentrations. JA5057 (“As
can be seen, these average sample results are below 8.8
[dpm/m3].”). On May 26, 1969, the AEC granted an
amendment to NUMEC’s license, “authoriz[ing] the
discharge of radioactive material from any stack
effluent . . . in concentrations up to one-hundred . . .
times the applicable limits . . . in accordance with the
statements, representations and conditions specified in
your application dated March 5, 1969.” JA5112.
       Finally, in 1995, the NRC issued a report
investigating another NUMEC facility in Parks,
Pennsylvania. See 60 Fed. Reg. 35,571, 35,573 (1995).
In that report, the NRC stated that, despite the 1969
license amendment setting limits for stack emissions, the

                           15
regulatory limits were set at the boundary of the roof:
“Accordingly, even though NUMEC was authorized to
discharge at the stack up to 100 times the value specified
in Appendix B, Table II, [under the 1969 license
amendment,] NUMEC was still required to meet the
limits at the site boundary (see footnote 8).” 60 Fed.
Reg. 35,571, 35,573 (1995). Footnote 8, in turn, states,
“The values set forth in 10 CFR Part 20, Appendix B,
Table II, are the regulatory limits applicable at the site
boundary, not at the stack.” 60 Fed. Reg. 35,571, 35,573
n.8 (1995).

           II. THE SCIENCE OF CANCER
       This Court’s previous opinion, In re TMI
Litigation, 193 F.3d 613 (3d Cir. 1999), set forth the
basic scientific principles regarding the relationship
between radiation and cancer. See 193 F.3d at 629–55.
No party disputes those background principles. Because
we rely on these principles here, we consider it helpful to
summarize them. Ionizing radiation can damage human
cells. Id. at 639–40. “If cellular damage is not repaired,
[the damage] may prevent the cell from surviving or
reproducing, or it may result in a viable but modified
cell.” Id. at 640. When an irradiated cell is only
“modified rather than killed,” stochastic (or probabilistic)
effects result. Id. at 642.
       As the word “probabilistic” indicates, what
happens next to the modified cell is uncertain. In some
cases, “cancer induction” occurs. Id. As we explained in
                           16
In re TMI Litigation, any increase in radiation exposure
above zero is believed to increase the probability of
carcinogenesis7:

      The probability that cancer will result from
      radiation increases proportionally with dose.
      However, it is currently believed that there
      is no threshold dose below which the
      probability of cancer induction is zero. . . .
      The linear risk model posits that each time
      energy is deposited in a cell or tissue, there
      is a probability of the induction of cancer.

Id. at 642–43 (citations omitted).
       Even with state-of-the-art data, it is impossible to
determine with certainty that radiation is the cause of a
given incidence of cancer for three reasons. First,
numerous factors other than radiation may cause cancer.
That is, “a given percentage of a defined population will
contract cancer even absent any exposure to ionizing
radiation.” Id. a 643–44.8 Second, there is no clear


7
  “Carcinogenesis is currently believed to be a multistep
process requiring two or more intracellular events to
transform a normal cell into a cancer cell.” In re TMI
Litig., 193 F.3d 613, 643 (3d Cir. 1999).
8
  “[T]he task of establishing causation is greatly
complicated by the reality that a given percentage of a
                          17
difference between cancers caused by radiation or by
other factors. No characteristic of a given cancer (such
as its type or severity) are known to suggest that
“manmade” radiation or even any radiation was the
cancer’s cause. See id. at 643 (“[M]edical evaluation, by
itself, can neither prove nor disprove that a specific
malignancy was caused by a specific radiation
exposure.”). Third, because the relevant changes occur
on the cellular level, they are not detected or detectable at
the time they occur. It can take many years—seemingly
a variable number of years—between an exposure to
radiation and the “possible detection of a resulting
cancer.” Id. (defining the “latency period” as “[t]he
period between exposure to radiation and possible
detection”). Thus, in a case like this one, the factfinder
will always have to use ex-post data to ascertain whether
any radiation—let alone any particular radioactive
exposure—disrupted the cell in the past.




defined population will contract cancer even absent any
exposure to ionizing radiation.       In industrialized
countries where the life expectancy averages about 70
years, about 30% of the population will develop cancer
and about 20% of the population will die of cancer.” In
re TMI Litig., 193 F.3d at 643–44.

                             18
    III. THE DISTRICT COURT’S RELEVANT
                   RULINGS
       We are reviewing the orders granting Defendants’
motion for summary judgment. In its summary judgment
orders, the District Court adopted the reasoning of the
Magistrate Judge to whom all pretrial motions had been
referred. See Order, McMunn v. Babcock & Wilcox
Power Generation Grp., No. 2:10-cv-00143-DSC-RCM
(W.D. Pa. Aug. 24, 2011), ECF No. 79.
       Two earlier rulings set the stage for the summary
judgment motion. Those two rulings are (1) a September
12, 2012 order following a “Lone Pine” case
management order,9 and (2) a February 27, 2014 order
adopting in part and rejecting in part the Magistrate
Judge’s recommendations with regard to excluding the
parties’ experts under Daubert v. Merrell Dow
Pharmaceuticals, Inc., 509 U.S. 579 (1993).




9
  A Lone Pine order is a pretrial order, based on Lore v.
Lone Pine Corp., No. L-33606-85, 1986 WL 637507
(N.J. Super. Ct. Law Div. Nov. 18, 1986), that “require[s]
plaintiffs to provide facts in support of their claims”
including by expert evidence “or risk having their cases
dismissed.” In re Asbestos Prods. Liab. Litig. (No. VI),
718 F.3d 236, 240 & n.2 (3d Cir. 2013).

                           19
A. Lone Pine
        On January 25, 2012, the Magistrate Judge issued
the Lone Pine order, requiring Plaintiffs to provide prima
facie evidence of, among other things, the “name of the
specific radionuclide(s) released from Defendants’
facilities in excess of the applicable federal permissible
limits” and “an identification of each exposure
pathway(s) through which each Plaintiff was exposed to
each specific radionuclide.” Order at 1, McMunn v.
Babcock & Wilcox Power Generation Grp., No. 2:10-cv-
0143-DSC-RCM (W.D. Pa. Jan. 25, 2012), ECF No. 109.
       On September 12, 2012, following the parties’
responses to the Lone Pine order, the Magistrate Judge
issued an order limiting Plaintiffs’ theories of recovery.
See McMunn v. Babcock & Wilcox Power Generation
Grp., 896 F. Supp. 2d 347 (W.D. Pa. 2012). In that
order, the Magistrate Judge held that the Plaintiffs would
be allowed only “to pursue, offer or rely upon evidence
referring or relating to any claim based upon exposure
through . . . airborne exposure to uranium . . . from . . .
the Apollo facility during its years of operation.” Id. at
358–61; see also id. at 364. Plaintiffs do not challenge
this Lone Pine order on appeal.

B. Daubert
     On July 12, 2013, the Magistrate Judge
recommended that the District Court (1) grant some of
Defendants’ Daubert motions; (2) deny the remainder of
                            20
Defendants’ Daubert motions; and (3) deny all of
Plaintiffs’ Daubert motions. See McMunn v. Babcock &
Wilcox Power Generation Grp., Nos. 10-143 et al., 2013
WL 3487560 (W.D. Pa. July 12, 2013). Specifically, the
Magistrate Judge recommended excluding the testimony
of Plaintiffs’ three general causation experts—Dr.
Howard Hu, Dr. Joseph Ring, and Mr. Bernd Franke—
and Plaintiffs’ specific causation expert, Dr. James
Melius. Only the rulings with regard to Melius’s
testimony bear directly on this appeal.

       Melius’s expert report used the methodology of
differential diagnosis. Melius provided a roughly one-
page summary of each Plaintiff’s background and alleged
exposure and then concluded for each Plaintiff: “[I]t is
my professional medical opinion that [Plaintiff’s]
exposures to uranium and other radioactive materials
released from the Apollo nuclear facility made a
significant contribution to the development of” his or her
cancer. E.g., JA3448, 3465, 3490. For most of the
Plaintiffs, Melius added language substantially like the
following: “This is reinforced by the lack of other risk
factors in [her or his] history that would account for the
development of this illness.” E.g., JA3448.10



10
   For a handful of Plaintiffs—but only some of the
Plaintiffs with a history of smoking—Melius identified
smoking as the only confounding factor. E.g., JA3451
                            21
       The Magistrate Judge recommended excluding
Melius’s testimony because Melius failed to rule out
other confounding factors and did not have information
about doses of radiation to which each Plaintiff was
exposed. With regard to confounding factors, the
Magistrate Judge criticized Melius’s “differential
diagnosis” because Melius “fail[ed] to explain why he
did not rule out smoking, obesity, genetic factors,
benzene exposure, radon and many other possible and
obvious alternative causes in order to conclude in each
instance that uranium is the cause of the individual’s
cancer.” McMunn, 2013 WL 3487560, at *28. With
regard to dose, the Magistrate Judge criticized Melius for
failing to make or use any estimate of any Plaintiff’s dose
“or the maximum or minimum amount to which the
person was exposed.” Id. at *29. Instead, to determine
that Plaintiffs’ exposures were sufficient to serve as a
“significant contribution” to their cancers, Melius relied
on general testimony about radiation—Dr. Hu’s
testimony that radiation from uranium could cause
cancer—and the assumption that Plaintiffs were exposed
to dangerous levels of radiation because “the Plaintiffs
lived or worked within 1.5 miles of the Apollo facility.”


(“This is reinforced by the lack of other risk factors in his
history that would account for the development of this
illness other than smoking which also would have made a
contribution.”).

                             22
Id. at *28. The Magistrate Judge’s two criticisms
dovetailed with a particular flaw in Melius’s testimony:
Melius “rule[d] out oral contraceptive use if the dose was
small and smoking if the person quit 10–15 years ago,
thereby taking dose into account.” Id. at *29. The
Magistrate Judge concluded that Melius’s methodology
“has not been generally accepted in the medical and
scientific communities” and was “untestable.” Id. at *29.
       On February 27, 2014, the District Court rejected
the Magistrate Judge’s report and recommendation to the
extent that the Magistrate Judge recommended granting
Defendants’ Daubert motions with regard to Melius and
Plaintiffs’ general causation experts.11 With regard to
Melius specifically, the District Court placed great
weight on (1) this Court’s past discussion of differential
diagnosis methodology and (2) the fact that Melius did
not have access to perfect information. First, the District
Court held that Melius “adequately addressed other
possible causes of Plaintiffs’ cancers, both known and


11
  The District Court adopted the portion of the report and
recommendation in which the Magistrate Judge
recommended denying the exclusion of Defendants’
experts and denying the exclusion of most of Plaintiffs’
experts. See McMunn v. Babcock & Wilcox Power
Generation Grp., Nos. 2:10cv143 et al., 2014 WL
814878, at *20 (W.D. Pa. Feb. 27, 2014).

                            23
unknown” because Melius reviewed information about
the Plaintiffs. McMunn v. Babcock & Wilcox Power
Generation Grp., Nos. 2:10cv143 et al., 2014 WL
814878, at *14 (W.D. Pa. Feb. 27, 2014). The District
Court also cited and quoted In re Paoli Railroad Yard
PCB Litigation, 35 F.3d 717 (3d Cir. 1994), and Heller v.
Shaw Industries, Inc., 167 F.3d 146 (3d Cir. 1999), for
the propositions that a medical expert performing a
differential diagnosis does not need to rule out every
alternative factor and that medical experts are permitted
to exercise their judgments when conducting a
differential diagnosis. See McMunn, 2014 WL 814878,
at *15.
       Second, with regard to dose, the District Court
held that there was “enough support in the record for the
contention that the Plaintiffs’ exposure levels exceeded
the normal background level” for Melius to use a
“qualitative analysis” rather than a “quantitative dose
analysis.” Id. at *14. In particular, Melius could rely on
“NUMEC’s failure to monitor emissions.” Id. Because
Melius’s analysis relied on the absence of data, the
District Court agreed with Melius that a “quantitative
dose calculation . . . may in fact be far more speculative
than a qualitative analysis.” Id.

       The District Court further held that a dose analysis
was not necessary for Plaintiffs’ claims to succeed. The
District Court stated that In re TMI Litigation, 193 F.3d
613 (3d Cir. 1999), “did not require a plaintiff prove a

                            24
quantified dose in order to prove personal injuries caused
by the release of radiation.” McMunn, 2014 WL 814878,
at *13. Then, the District Court cited to other cases that
did not require a dose. Id. at *13–14 (quoting and citing
Kannankeril v. Terminix Int’l, 128 F.3d 802, 808–09 (3d
Cir. 1997), Bonner v. ISP Techs., Inc., 259 F.3d 924 (8th
Cir. 2001), and Westberry v. Gislaved Gummi AB, 178
F.3d 257 (4th Cir. 1999)).
      At Defendants’ request, the District Court certified
the Daubert order for interlocutory appeal. See McMunn
v. Babcock & Wilcox Power Generation Grp., Nos.
2:10cv143 et al., 2014 WL 12530940 (W.D. Pa. May 7,
2014). We denied Defendants’ petition for interlocutory
appeal. See McMunn v. Babcock & Wilcox Power
Generation Grp., No. 14-8074 (3d Cir. June 16, 2014).

C. Summary Judgment
       On May 7, 2015, the Magistrate Judge filed a very
thorough report recommending that the District Court
grant Defendants’ motion for summary judgment on
Plaintiffs’ Price-Anderson public liability claims and
Defendants’ motion for a judgment on the pleadings on
all of Plaintiffs’ common-law claims. See McMunn v.
Babcock & Wilcox Power Generation Grp., 131 F. Supp.




                           25
3d 352, 359–404 (W.D. Pa. Sept. 15, 2015) (republishing
the report and recommendation).12

       The Magistrate Judge recommended that the
District Court grant summary judgment because
Plaintiffs (1) failed “to raise a genuine issue for trial on
breach of duty” and (2) failed “to proffer evidence of
exposure and dose.” Id. at 389, 404.13 First, with regard
to the breach of duty, the Magistrate Judge held that
“[t]he regulatory standard applicable to the emission of
radionuclides in airborne effluent to off-site areas . . .
when the Apollo facility operated . . . was 10 C.F.R.
§ 20.106”—“not some other regulation, license
requirement or other issue.” Id. at 368–69, 388; see also
In re TMI, 67 F.3d 1103, 1108 n.10 (3d Cir. 1995)



12
   Because Plaintiffs did not appeal the District Court’s
adoption of the Magistrate Judge’s recommendation to
dismiss Plaintiffs’ common-law claims, we need not
discuss the common-law claims.
13
   The Magistrate Judge did not reach any other issues
regarding Plaintiffs’ Price-Anderson public liability
claims. As the Magistrate Judge noted, Defendants
raised other issues in separate summary judgment
motions that the District Court denied as moot or denied
without prejudice to refile. See McMunn, 131 F. Supp.
3d at 361 & n.3, 404.

                            26
(applying “the relevant federal regulations . . . in place at
the time” of the radioactive release caused by Three Mile
Island accident at issue).

      Section 20.106 prohibited a licensee from
“releas[ing] to an unrestricted area radioactive material in
concentrations which exceed the limits specified in
Appendix ‘B’, Table II of this part.” 10 C.F.R.
§ 20.106(a) (1980). The regulation further states that
“the concentration limits in Appendix ‘B’, Table II of
this part shall apply at the boundary of the restricted
area.” 10 C.F.R. § 20.106(d).
       The Magistrate Judge rejected Plaintiffs’ argument
that the Table II maximum permissible concentration
applied directly to the uranium effluent released from the
stacks on the roof.         First, the Magistrate Judge
determined that the roof of the Apollo facility was a
restricted area. McMunn, 131 F. Supp. 3d at 386–87.
Second, the Magistrate Judge held that the measurements
of uranium effluent to be compared to the maximum
permissible concentration should be those taken “at the
roof boundary.” Id. at 387–88. Because Plaintiffs’ only
expert testimony about breach applied the concentration
limits at the stacks and not at the roof boundaries, the
Magistrate Judge held that Plaintiffs failed to proffer
expert evidence of a breach that raised a genuine issue of
material fact. See id. at 389.

      With regard to exposure and dose, the Magistrate
Judge held that Plaintiffs’ causation case failed because
                            27
Plaintiffs failed to show that each Plaintiff was exposed
to enough radiation to cause his or her cancer. First, the
Magistrate Judge granted Defendants’ motion to deem
certain facts admitted. See id. at 394; Plaintiffs’ Local
Rule 56.C.1 Response, No. 2:10-cv-001343-DSC-RCM
(W.D. Pa. filed Dec. 5, 2014), ECF No. 342. Then, the
Magistrate Judge explained that, under In re TMI
Litigation, 193 F.3d 613 (3d Cir. 1999), each Plaintiff
had to show that he or she was exposed to “inhaled
uranium from the Apollo plant in excess of normal
background radiation amounts.” McMunn, 131 F. Supp.
3d at 396–97, 399. Thus, the Magistrate Judge held that
“Plaintiffs must provide . . . an estimate of the dose they
received which caused their cancers.” Id. at 399. As
discussed above, Melius relied on Plaintiffs’ other
experts for exposure, but none of Plaintiffs’ other experts
calculated exposure or dose for any of the Plaintiffs. See
id.
       Further, the Magistrate Judge rejected Plaintiffs’
argument that Defendants were “estopped from
contesting [Plaintiffs’] lack of evidence of exposure and
dose” because Defendants failed to keep accurate
records. Id. at 402–04. The Magistrate Judge also
rejected Plaintiffs’ argument that law of the case required
the Magistrate Judge to deny summary judgment on
causation because the District Court had ruled that
Melius’s testimony was admissible in its Daubert ruling.
See id. at 399–402.

                            28
       On September 15, 2015, the District Court adopted
the Magistrate Judge’s report and recommendation over
Plaintiffs’ objections. See id. at 357. The District Court
stated that it “review[ed] . . . the record of these
cases, . . . the Magistrate Judge’s Report and
Recommendation, and the Objections thereto,” but
offered no further explanation for its decision. Id.

      Certain related cases were not consolidated with
the main case when the District Court issued its
September 15, 2015 Memorandum Order. The District
Court ultimately entered orders adopting the reasoning of
the September 15, 2015 Memorandum Order in those
cases. See JA281–92; SJa3–SJa8.
      Timely notices of appeal followed in each case
before us.14 Additionally, Defendants cross-appealed
many—but not all—of the cases before us, requesting
that we reverse the District Court’s Daubert order.




14
  Plaintiffs’ Notices of Appeal also objected to orders
excluding the expert report of Dr. Steve Wing. See, e.g.,
Ja1. Because Plaintiffs presented no argument regarding
Dr. Wing’s report, any issues or objections concerning it
have been waived.

                           29
                   JURISDICTION
       The District Court had subject-matter jurisdiction
over these actions under 42 U.S.C. § 2210(n)(2) because
this is a public liability action arising out of a nuclear
incident in the Western District of Pennsylvania. This
Court has jurisdiction over Plaintiffs’ appeals under 28
U.S.C. § 1291.
       Plaintiffs argue that we did not have jurisdiction
over Defendants’ cross-appeal relating to the District
Court’s denial of their Daubert motion regarding Melius
because Defendants are not aggrieved by that denial. As
the Supreme Court observed in Deposit Guaranty
National Bank v. Roper, “Ordinarily, only a party
aggrieved by a judgment or order of a district court may
exercise the statutory right to appeal therefrom. A party
who receives all that he has sought generally is not
aggrieved by the judgment affording the relief and cannot
appeal from it.” 445 U.S. 326, 333 (1980); see also
Nanavati v. Burdette Tomlin Mem’l Hosp., 857 F.2d 96,
102 (3d Cir. 1988) (“Because they are completely
satisfied with the final judgment and object only to
interlocutory rulings of the district court, we lack
jurisdiction over their appeal.”).

       We need not determine whether we have
jurisdiction. We simply follow Third Circuit practice and
dismiss Defendants’ cross-appeals as “superfluous.”
Smith v. Johnson & Johnson, 593 F.3d 280, 283 n.2 (3d
Cir. 2010) (“Yet a party, without taking a cross-appeal,
                           30
may urge in support of an order from which an appeal
has been taken any matter appearing in the record, at
least if the party relied on it in the district court.”). As
such, we consider the parties’ Daubert arguments to
concern causation only as an “alternate ground for
affirmance.” Nanavati, 857 F.2d at 102. Accordingly,
we have disregarded Defendants’ reply brief in support
of their cross-appeal.

              STANDARD OF REVIEW
       The standard of review on summary judgment is
well known: “Because we are reviewing a grant of
summary judgment, our standard of review is plenary.
Summary judgment is appropriate ‘if the movant shows
that there is no genuine dispute as to any material fact
and the movant is entitled to judgment as a matter of
law.’” Constitution Party of Pa. v. Cortes, 824 F.3d 386,
393 (3d Cir. 2016) (citations omitted) (quoting Fed. R.
Civ. P. 56(a)).

                      DISCUSSION
      We will affirm the judgment of the District Court
because Plaintiffs failed to raise an issue of fact that
would allow a reasonable jury to find that Defendants
breached their duty and because Melius’s conclusory
expert report would not allow a reasonable jury to find
that Defendants’ radiation was a substantial factor in
causing Plaintiffs’ cancers.

                            31
                        I. DUTY
       The District Court15 held that Plaintiff failed to
establish a genuine issue of material fact as to whether
Defendants breached their duty to Plaintiffs. We agree
with the District Court that Defendants’ duty was defined
by § 20.106.

       In three different ways, Plaintiffs try to show that
Defendants owed a duty other than to prevent the release
of uranium effluent that exceeds the maximum
permissible concentrations at the boundary of the roof,
when the effluent is averaged over a full year. First,
Plaintiffs argue that any emission from the roof counts
under § 20.106. Second, Plaintiffs argue that more
onerous maximum permissible concentrations for roof
emissions were created by the 1969 amendment to
NUMEC’s license. And, third, Plaintiffs argue that they
had the option to decline annual averaging, allowing
them to find breaches of duty where emissions exceeded



15
   Because the District Court “adopt[ed] the Report and
Recommendation as the Opinion of [the District] Court,”
McMunn v. Babcock & Wilcox Power Generation Grp.,
131 F. Supp. 3d 352, 357 (W.D. Pa. 2015), “we will refer
to the adopted opinion as that of the district court,” USX
Corp. v. Liberty Mut. Ins. Co., 444 F.3d 192, 197 n.8 (3d
Cir. 2006).

                            32
the maximum permissible concentration over short
periods of time. As discussed below, these attempts to
redefine the duty fail because they all conflict with
§ 20.106 and because we owe Auer deference to the
NRC’s interpretation of § 20.106.

A. The Roof Was a Restricted Area
       Under § 20.106(d), the maximum permissible
concentrations are assessed “at the boundary of the
restricted area.” 10 C.F.R. § 20.106(d). A “restricted
area” is any area where “access . . . is controlled by the
licensee for purposes of protection of individuals from
exposure to radiation and radioactive materials.” 10
C.F.R. § 20.3(a)(14). Plaintiffs argue that the entire roof
was unrestricted16 such that emissions from anywhere on
the roof—including the stacks and fans—should count
directly against the limits. Plaintiffs’ argument is
undermined by a 1995 NRC report that states that the
“regulatory limits [are] applicable at the site boundary,



16
   The definition of “unrestricted area” is merely a mirror
of the definition of “restricted area”: “‘Unrestricted area’
means any area access to which is not controlled by the
licensee for purposes of protection of individuals from
exposure to radiation and radioactive materials, and any
area used for residential quarters.”            10 C.F.R.
§ 20.3(a)(17).

                            33
not at the stack.”   60 Fed. Reg. 35,571, 35,573 n.8
(1995).

       Plaintiffs present two arguments as to why the roof
is unrestricted: (1) an historical argument based on a
series of letters between the AEC and NUMEC and (2) a
functional argument that questions whether access to the
roof was “controlled by the licensee for purposes of
protection of individuals from exposure to radiation and
radioactive materials.”
       With regard to the historical argument, Plaintiffs’
strongest support is a June 5, 1964 letter, in which the
Director of the Division of State and Licensee Relations
of the AEC stated that the roof would be “unrestricted” if
access were not controlled: “[T]he roof area of the
NUMEC facility is an unrestricted area unless access to
this area is controlled from the radiation safety
standpoint.” JA5314.

      Plaintiffs also rely on other correspondence in
which NUMEC and AEC compared stack emissions to
the applicable maximum permissible concentration. For
instance, in a 1967 report, a NUMEC employee wrote,
“[T]he measured stack concentration frequently exceeds
permissible levels.” JA5201. The AEC similarly
expressed concern about releases from stacks, as though
the regulations created limitations on the stacks. In a
February 5, 1969 letter, the Director of the Division of
Compliance of the AEC warned, “Based on your
recorded data, the concentrations of radioactive material
                           34
released from the facility through exhaust stacks to
unrestricted areas exceed the limits specified in Appendix
B, Table II of 10 CFR 20, contrary to 10 CFR 20.105(a),
‘Concentrations in effluents to unrestricted areas.’”
JA4700. Additionally, the fact that NUMEC sought—
and the AEC granted in 1969—approval to exceed the
maximum permissible concentration by one-hundred
times at the stack, see JA5112, suggests that there was a
pre-existing regulatory limit at the stack.
       Plaintiffs’ functional argument focuses on the
definition of a restricted area in the regulation. The
regulation states that a “restricted area” is any area where
“access . . . is controlled by the licensee for purposes of
protection of individuals from exposure to radiation and
radioactive materials.” 10 C.F.R. § 20.3(a)(14). It is
uncontested that the roof could only be accessed by
locked hatches from ladders located inside the building.
See JA5035–36 (“There are no outside ladders on
NUMEC’s property. We have two inside ladders with
normally closed and locked hatches at the top.”); JA5317
(“The roof hatch is kept locked with keys in the
possession of the health and safety technician.”).17



17
  Plaintiffs argue that NUMEC conceded that the roof is
unrestricted based on the 1966 letter from NUMEC to the
AEC that states, “We regard the roof area as an
unrestricted area.”      JA4649.     The District Court
                            35
      Plaintiffs argue that these hatches do not show that
the roof was “controlled . . . for purposes of
protection . . . from exposure to radiation.” Relying on a
1965 NUMEC letter, they argue that certain safety
measures—e.g., alpha survey instruments—are required
to show why the access is controlled. See Pls.’ Br. 40–
41.




concluded that “unrestricted” was “a typographical
error.” McMunn v. Babcock & Wilcox Generation Grp.,
131 F. Supp. 3d 352, 378 (W.D. Pa. 2015). At summary
judgment, district courts should not determine whether a
particular phrasing is a scrivener’s error when other
possibilities are reasonable. See, e.g., Coffill v. Coffill,
656 F.3d 93, 95–96 (1st Cir. 2011) (holding that it was
error to rule that a purported scrivener’s error existed
“without evidentiary hearing and evidentiary basis”). We
agree with the District Court that, in the context of the
correspondence in the record and the surrounding
sentences, it would be unreasonable or absurd to read that
sentence in the 1966 letter as a concession that NUMEC
considered the roof “unrestricted.” The same paragraph
explains the unrestricted areas were at the “roof edge”:
“[T]he roof edge air samplers are measuring directly the
concentration being discharged to unrestricted areas.”
JA5317.

                            36
        Ultimately, we defer to the expertise of the NRC as
to where the restricted area of the Apollo facility ended.
In 1995, the NRC issued a report investigating another
NUMEC facility in Parks, Pennsylvania. 60 Fed. Reg.
35,571, 35,573 (1995). Even though the report was about
the Parks facility, the NRC referred to the 1969 letter that
allowed NUMEC to exceed regulatory limits at the
Apollo facility’s stacks. The NRC stated that, despite a
1969 license amendment setting limits for stack
emissions, the regulatory limits were set at the boundary
of the roof. “Accordingly, even though NUMEC was
authorized to discharge at the stack up to 100 times the
value specified in Appendix B, Table II, [under a 1969
license amendment,] NUMEC was still required to meet
the limits at the site boundary (see footnote 8).” Id.
Footnote 8, in turn, stated, “The values set forth in 10
CFR Part 20, Appendix B, Table II, are the regulatory
limits applicable at the site boundary, not at the stack.”
Id. at 35,573 n.8.
       Under Auer v. Robbins, 519 U.S. 452, 461–62
(1997), we defer to the NRC’s “fair and considered
judgment” of its interpretation of its regulation. One
could argue that the NRC should receive less deference
to the extent that the NRC’s 1995 position conflicts with
Plaintiffs’ historical evidence. In this case, we believe
we still owe full deference. The Supreme Court’s main
concern with an agency switching positions has been
with circumstances in which the new position could
cause “unfair surprise.” Long Island Care at Home, Ltd.
                            37
v. Coke, 551 U.S. 158, 170–71 (2007) (“[A]s long as
interpretive changes create no unfair surprise[,] . . . the
change in interpretation alone presents no separate
ground for disregarding the Department’s present
interpretation.”). Here, our Auer deference would not
harm any reliance interests.

       Even if we did not defer to the NRC, Defendants’
interpretation of a “restricted area” is more consistent
with our precedent than is Plaintiffs’ functional
argument. In 1995, we held that “[t]he definitions of
‘restricted’ and ‘unrestricted areas’ demonstrate that the
C.F.R. sections governing persons in ‘unrestricted areas’
were intended to cover persons outside a nuclear plant’s
boundaries, i.e., the general public.” In re TMI, 67 F.3d
at 1114 (footnote omitted). Although denial of access to
the “general public” alone does not turn a space into a
restricted area, our understanding has been focused more
on whether a licensee exercises control rather than on the
precise safety measures chosen by the licensee. Other
than the isolated statements by NUMEC, Plaintiffs give
us no reason to believe that more than locked hatches
were needed to control access to the roof for purposes of
protecting individuals from radiation.

B. The License Did Not Create a Duty
      As noted above, in 1969, the AEC approved
NUMEC’s request to amend its license to allow “the
discharge of radioactive material from any stack . . . in
concentrations up to one-hundred (100) times the
                          38
applicable limits specified in Appendix B, Table II,”
contingent on satisfactory sampling “at the plant roof
perimeter” and “in the neighboring unrestricted areas of
[the] plant.” JA5112. Plaintiffs argue that this 1969
license amendment now creates a tort duty that
Defendants violated by discharging more than 100 times
the maximum permissible concentration at the stacks.

       In a Price-Anderson public liability claim, “federal
law preempts state tort law on the standard of care.” In
re TMI, 67 F.3d at 1107. Our 1995 opinion in In re TMI
instructs that the duty that survives preemption must be a
regulatory requirement meant to protect people like
Plaintiffs. Following In re TMI, we look to the principles
of negligence per se (by analogy) and to other courts’
interpretation of duty under the Price-Anderson Act.
Because this license requirement was only meant to make
it easier to assess whether NUMEC violated 10 C.F.R.
§ 20.106 at the boundary of the restricted area—not to
create an independent obligation—we hold this license
requirement does not supply a tort duty.
       In the 1995 TMI case, plaintiffs argued that the “as
low as is reasonably achievable” principle (“ALARA”)
established the tort duty. This Court held instead that 10
C.F.R. §§ 20.105, 106 established the relevant duty. Two
of our major considerations were that (1) §§ 20.105 and
20.106 indicated they should apply to effluent emissions
to the public, In re TMI, 67 F.3d at 1114, and (2) the
ALARA regulation states that it was not “to be construed

                            39
as radiation protection standards” but was rather meant to
be a discretionary tool for regulatory agencies, id. at
1114–15 (internal quotation mark omitted). Thus, we see
that our concerns in 1995 reflected (1) whether the
regulation was meant to cover the persons allegedly
affected and (2) whether the regulation was meant to
establish actual standards or operating principles for the
agency. These same considerations are not present here.
The limitations on the stacks were meant to show levels
below which there could not be a violation at the
boundary. Thus, they were not directly protective of
persons in unrestricted areas and were a discretionary
choice by the AEC to make policing NUMEC easier.
       The 1995 TMI case also instructs us to consider
principles from negligence per se. In that case, we
explained that the duty analysis under the Price-Anderson
Act “is analogous to the practice followed by many
jurisdictions with negligence per se cases. In such cases,
where defendants violated the relevant statute or
regulation, courts have held as a matter of law that
plaintiffs have satisfied the first two elements of their
cause of action: the duty and breach of duty.” In re TMI,
67 F.3d at 1118.

       Plaintiffs’ objection that we would nullify the
license requirements if we refused to use them as the




                           40
standard of care18 assumes that every legal requirement
must be enforceable by a civil plaintiff. That assumption
is contrary to fundamental principles of negligence per
se, under which courts must ask “whether the policy
behind the legislative enactment will be appropriately
served by using it to impose and measure civil damage
liability.” Frederick L. v. Thomas, 578 F.2d 513, 517 n.8
(3d Cir. 1978).
      Negligence per se only attaches to a statutory or
administrative duty when its direct effect is to prevent the
harm at issue to the type of person allegedly injured. See
Byrne v. Matczak, 254 F.2d 525, 528 (3d Cir. 1958)
(“[T]he general principle is that the violation of a statute
will not create a liability unless it is the efficient cause of
the injury.”); Congini ex rel. Congini v. Portersville
Valve Co., 470 A.2d 515, 518 (Pa. 1983); Restatement
(Second) Torts § 286.19 We have held that “general


18
  “To hold that NUMEC had no duty to obey the AEC’s
regulatory caps stated in its license would be tantamount
to holding that the AEC had no authority to set those
limits.” Pls.’ Br. 35.
19
  When we adopted 10 C.F.R. §§ 20.105 and 20.106 as
the standard of care, we cited Restatement (Second) of
Torts for the proposition that a court can adopt
regulations as the standard of care. See In re TMI, 67
F.3d at 1113 n.24.
                              41
licensing or permit schemes do not usually establish
standards of competence; they do not usually represent
judgments that a violation of the licensing scheme will
generally constitute the breach of a duty to a particular
person rather than to the state.” Beaver Valley Power
Co. v. Nat’l Eng’g & Contracting Co., 883 F.2d 1210,
1221–22 (3d Cir. 1989); see also Talley v. Danek Med.,
Inc., 179 F.3d 154, 159 (4th Cir. 1999) (“Even if the
regulatory scheme as a whole is designed to protect the
public or to promote safety, the licensing duty itself is not
a standard of care, but an administrative requirement.”);
Restatement (Second) of Torts § 288 (“The court will not
adopt as the standard of conduct . . . the requirements
of . . . administrative regulation whose purpose is found
to be exclusively . . . to protect the interests of the state or
any subdivision of it as such.”).20



20
   Following oral argument, Plaintiffs filed a letter under
Rule 28(j) of the Federal Rules of Appellate Procedure
with additional cases that showed regulations creating
tort duties. None of them is contrary to the reasoning
above. Rather, Plaintiffs’ 28(j) cases pertain to situations
in which statutes explicitly create a duty for license
violations, see 33 U.S.C. § 1365(a) (“[A]ny citizen may
commence a civil action on his own behalf . . . against
any person . . . who is alleged to be in violation of . . . .
an effluent standard.”); 33 U.S.C. § 1365(f) (“[T]he term
‘effluent standard or limitation under this chapter’
                            42
       Finally, as in 1995, we look to other circuits’
caselaw as “instructive.” In re TMI, 67 F.3d at 1113.
Here, we see that no other circuit has adopted Plaintiffs’
proposed standard. See Adkins v. Chevron Corp., 960 F.
Supp. 2d 761, 766, 772–73 (E.D. Tenn. 2012) (holding
that license violations do not create duty in a Price-
Anderson public liability action).

      The history of the license amendment shows that
its purpose was not to create an independent duty to
minimize discharge from the stacks. On November 13,
1968, Roger D. Caldwell, NUMEC Manager, Health and
Safety, sent a letter to Donald A. Nussbaumer at the
AEC. The letter requested a change to NUMEC’s license
that would “permit[] concentrations up to 100 MPCa in
any stack’s effluent, providing the concentration at the
roof edge is permissible.” JA5073. Caldwell justified



means . . . a permit or condition thereof . . . .”); N.Y.
Veh. & Traffic Law § 509(3) (“Whenever a permit or
license is required to operate a motor vehicle, no person
shall operate any motor vehicle in violation of any
restriction contained on, or applicable to, the permit or
license.”), or situations where preemption of alternative
laws is not as complete as here, see Gomez v. St. Jude
Medical Daig Div. Inc., 442 F.3d 919, 928–30 (5th Cir.
2006) (discussing the scope of preemption relating to the
Medical Device Amendments).

                           43
the request by pointing to empirical data relating to
diffusion factors at the Apollo facility—that is, by
showing that amounts released at the stacks would be
much less at the roof edge. See JA5074–76.

       On February 5, 1969, Lawrence D. Low, AEC,
Director, Division of Compliance wrote to Zalman
Shapiro, NUMEC President. Low wrote that “the
concentrations of radioactive material released from the
facility through exhaust stacks to unrestricted areas
exceed the limits . . . contrary to 10 CFR 20.106(a).”
JA5079–80. In the same section of the letter, Low
acknowledged NUMEC’s request that its license “be
amended to permit use of a dilution factor for stack
effluents.” JA6080.
       On February 25, 1969, Shapiro responded,
explaining that a higher concentration limit could be
applied at the stacks to determine whether NUMEC
violated its maximum permissible concentration at the
roof edge:
      We recognize the necessity for an
      amendment to our license which would
      reflect appropriately the means of varifying
      [sic] the effectiveness of atmospheric
      dilution in reducing concentration in
      unrestricted areas. In this connection, we
      submitted on November 13, 1968 a request
      for an amendment to our license which
      would place primary reliance on roof
                            44
      perimeter sampling in lieu of stack sampling
      as a means of measuring releases to
      unrestricted areas. At a meeting on January
      17, 1969 with Licensing and Compliance
      personnel, it was concluded that the off-site
      environment sampling program should be
      included as a part of our license amendment
      application to provide additional assurance
      with respect to the effectiveness of
      atmospheric dilution. Accordingly, we are
      preparing and will submit by March 7, 1969
      a revised application which, if approved,
      should provide an acceptable means of
      varifying [sic] compliance with Part 20.

JA5083–84.
       On March 10, 1969, Caldwell submitted a “revised
application to permit concentration to 100 MPCa in any
stack’s effluent.” JA5087. Again, Caldwell “justified”
the proposed limits by pointing to empirical data showing
dilution factors at the roof perimeter. Id.

      On May 26, 1969, Nussbaumer at the AEC wrote
to Caldwell at NUMEC granting the amendment to
NUMEC’s license “to authorize the discharge of
radioactive material from any stack effluent . . . in
concentrations up to one-hundred . . . times the
applicable limits . . . in accordance with the statements,
representations and conditions specified in your
application dated March 5, 1969.” JA5112 (emphasis
                              45
added).      Nussbaumer added, “We consider the
environmental sampling program required by Condition
2 above to be a means for providing backup data and
evidence that your roof edge sampling results are
adequately representative of the concentrations released
to the unrestricted areas.” JA5112–13 (emphasis added).
Thus, even at the time, the AEC, via Nussbaumer,
accepted NUMEC’s “representations” about the
relationship between the stack discharges and the roof
edge and that the roof edge monitors would be used to
determine the concentrations “released to the unrestricted
areas.”

       In 1995, the NRC agreed that NUMEC’s purpose
in seeking the amendment assumed that all requirements
would be met if the emission at the boundaries were
below the maximum permissible concentration: “By
application dated November 13, 1968, and supplement
dated March 5, 1969, and pursuant to 10 CFR 20.106(b),
NUMEC requested that License SNM-145 be amended to
permit concentrations up to 100 times the limits specified
in Part 20, Appendix B, Table II, in any stack effluent,
provided that concentrations at the roof edge and in the
local environment complied with 10 CFR Part 20 limits.”
In re Babcock & Wilcox Co., 41 N.R.C. 489, 492–93
(June 26, 1995); see also 10 C.F.R. § 20.106(b). Thus, it
is clear that the stack-discharge license restriction was
created as a threshold to test for emissions at the
boundary of the restricted area.

                           46
       Because the license requirement was only an
administrative safe harbor for NUMEC’s compliance
with the emissions maximum set at the boundary of the
restricted area, it does not create a tort duty here.

C. Plaintiffs Had to Show that Maximum Permissible
Concentration was Exceeded on Average Over a Full
Year
       Section 20.106 states, “For purposes of this
section[,] concentrations may be averaged over a period
not greater than one year.” 10 C.F.R. § 20.106(a) (1980).
The District Court’s holding that Plaintiffs failed to show
a genuine issue of material fact regarding duty was based
on Plaintiffs’ failure to show a violation of § 20.106
when averaged over the course of a year: “Plaintiffs
have pointed to no genuine issues of material fact that the
annual average concentration of uranium effluent ever
exceeded 1.7 x 10-2 microcuries/milliliter during the
period 1957–1960, or that it ever exceeded 4.0 x 10-12
microcuries/milliliter during the period 1961–1983.”
McMunn, 131 F. Supp. 3d at 388. On appeal, Plaintiffs
continue to argue that they could show a violation based
on a discharge that exceeds the maximum permissible
concentration over any length of time. Plaintiffs are
plainly wrong.

      Plaintiffs’ argument is based entirely on the word
“may” in the phrase “concentrations may be averaged
over a period not greater than one year.” They argue,
“The term may is permissive, not mandatory. There is no
                           47
requirement to take an average.” Pls.’ Br. 43 (footnote
omitted). We agree with Plaintiffs that “may” is
permissive. See, e.g., Simpson v. Kay Jewelers, Div. of
Sterling, Inc., 142 F.3d 639, 650–51 (3d Cir. 1998)
(comparing “the more flexible and permissive ‘may’” to
“the mandatory ‘must’” (quoting Torre v. Casio, Inc., 42
F.3d 825, 831 n.6 (3d Cir. 1994))).

       But Plaintiffs’ reliance on a single word in that
phrase ignores the fact that it is part of a sentence that
speaks in the passive voice. “Phrases constructed in the
passive voice use an implied subject or actor who carries
out the verb.” Sci. Drilling Int’l, Inc. v. Pathfinder
Energy Servs., Inc., No. H-06-1634, 2006 WL 2882863,
at *3 (S.D. Tex. Oct. 4, 2006). Thus, the question is who
has the discretion to decide whether to average annually.

       Given the context of the regulation, the obvious
answer is that such discretion lies in the AEC because it
is the entity charged with determining whether a licensee
violates its regulatory duties. Cf. United States v.
Brumbaugh, 909 F.2d 289, 291 (7th Cir. 1990) (“The use
of the passive voice in the statutory language requires us
to infer a subject; the most logical inference is that the
Attorney General, who has been charged with granting
credit under section 3568 for over thirty years, is the
intended subject of the sentence.”). Plaintiffs’ unwritten
assumption that the AEC intended for tort plaintiffs or
district courts to have discretion to use annual averaging
is mistaken. Giving tort plaintiffs the power to determine

                           48
retroactively the period over which a violation is assessed
“would allow [them] to fix the standard case by case and
plant by plant. An operator acting in the utmost good
faith and diligence could still find itself liable for failing
to meet such an elusive and undeterminable standard.”
In re TMI, 67 F.3d at 1115. Under § 20.106, Plaintiffs
were required to show a breach using annual averaging.
Their data relating to individual moments in time fails to
show a breach.
                            ***

      Plaintiffs’ attempts to expand Defendants’ duty
must fail. The maximum permissible concentration is
assessed at the boundary of the roof, the license
requirement does not create a duty, and Plaintiffs must
show that the maximal permissible concentration was
exceeded when the emissions are averaged annually.

                       II. BREACH
      The District Court held that Plaintiffs failed to
show there was a dispute of fact as to whether
Defendants emitted excessive radiation at the boundary
of the roof because Plaintiffs failed to offer appropriate
expert testimony.21 On appeal, Plaintiffs again rely



21
  See McMunn, 131 F. Supp. 3d at 389 (“In addition, to
establish a breach of duty, Plaintiffs must offer evidence
                            49
almost entirely on data from the stacks and roof fans,
which, as was established above, are legally irrelevant.
See, e.g., Pls.’ Reply Br. 15–16 (“NUMEC officials were
all too aware of the problem with the roof fans.”).
Putting aside the stacks and fans data, we agree that
Plaintiffs’ argument for breach fails for lack of expert
evidence in this highly technical area.

      Moreover, Plaintiffs argue that they are “entitled”
to “adverse inferences” that allow them to show a breach
(and also causation). See Pls.’ Br. 22. This, too, fails
because Plaintiffs did not show that the District Court
abused its discretion in denying the adverse inference.

A. Plaintiffs Needed Experts
       Plaintiffs failed to provide an expert who could
testify that the data upon which they rely (stacks, vents,
and readings from outside the facility) could show a
violation of the maximum permissible concentration of
uranium effluent at the boundary of the roof when
averaged annually.
       Expert evidence is generally required when an
issue is beyond the ken of a lay jury. For instance, in a
medical monitoring claim, we explained that the plaintiff


from a qualified expert that the Apollo facility’s
emissions exceeded regulatory limits.”).

                           50
had to prove he or she suffered a “significantly increased
risk of contracting a serious latent disease” and other
factors “by competent expert testimony.” Redland
Soccer Club, Inc. v. Dep’t of Army of U.S., 55 F.3d 827,
845–46, 852 (3d Cir. 1995).22 Similarly, then-Judge
Sotomayor wrote for the Second Circuit that expert
testimony would be “necessary” where “an injury has
multiple potential etiologies.” Wills v. Amerada Hess
Corp., 379 F.3d 32, 46 (2d Cir. 2004).



22
   Cf. also Boring v. Kozakiewicz, 833 F.2d 468, 473 (3d
Cir. 1987) (“In some situations in which the seriousness
of injury or illness would be apparent to a lay person,
expert testimony would not be required, e.g., a gunshot
wound. However, those circumstances are not present
here.” (citation omitted)); Breidor v. Sears, Roebuck &
Co., 722 F.2d 1134, 1140–41 (3d Cir. 1983) (stating that
expert testimony was necessary to rebut the defendants’
contention in a products liability case); Lentino v. Fringe
Emp. Plans, Inc., 611 F.2d 474, 480 (3d Cir. 1979)
(“Expert testimony is required to establish the relevant
standard and whether the defendant complied with that
standard, except where the matter under investigation is
so simple, and the lack of skill so obvious, as to be within
the range of the ordinary experience and comprehension
of non-professional persons.” (citations omitted)
(Pennsylvania medical malpractice case)).

                            51
       Perhaps recognizing their failure to transmute vent
data into roof data, Plaintiffs try to borrow an “average
dilution factor of 50” from an isolated 1968 document.
See Pls.’ Br. 45. But these kinds of calculations are best
suited to experts—not lawyers or lay factfinders.

B. The District Court Did Not Abuse Its Discretion in
Holding That Plaintiffs Were Not Entitled to an
Inference Sufficient to Survive Summary Judgment
       Objecting to the report and recommendation,
Plaintiffs argued that Defendants’ poor recordkeeping
allowed them to request an inference under which a jury
could assume that Defendants had breached the above-
described duty. [See Dist. Ct. ECF No. 376, at 50–53.]
By adopting the Magistrate Judge’s report and
recommendation, the District Court rejected this
argument. See McMunn, 131 F. Sup. 3d 352.

       We review the District Court’s denial of the
adverse inference for abuse of discretion. See, e.g., In re
Hechinger Inv. Co. of Del., Inc., 489 F.3d 568, 574 (3d
Cir. 2007) (“We also review the [bankruptcy court’s]
denial of UFP's motion seeking an evidentiary inference
based on spoliation of evidence for abuse of discretion.”);
Davis v. White, 858 F.3d 1155, 1160 (8th Cir. 2017)
(“The district court’s refusal to sanction the officers with
an adverse inference instruction was not an abuse of
discretion.”).


                            52
      Plaintiffs have failed to show that the District
Court abused its discretion when determining that an
adverse inference was not warranted here.23 Plaintiffs
simply have not developed their argument sufficient to
show an abuse of discretion. [See Pls.’ Br. 21–22.] In
cases where this argument is more developed, an adverse
inference may be appropriate. See United States ex rel.
Scutellaro v. Capitol Supply, Inc., No. 10-1094 (BAH),
2017 WL 1422364, at *11 (D.D.C. Apr. 19, 2017)
(noting several circuits have held that the failure to
maintain records allows for an adverse inference). This
can be seen by analogy to spoliation cases. In spoliation
cases, where there is evidence that one party has
destroyed or altered evidence, the opposing party can
obtain a “‘spoliation inference,’ that the destroyed
evidence would have been unfavorable to the position of
the offending party.” Schmid v. Milwaukee Elec. Tool
Corp., 13 F.3d 76, 78 (3d Cir. 1994). Here, because


23
   Plaintiffs’ recordkeeping argument also relates to their
failure to provide expert evidence relating to any
individual Plaintiff’s exposure. See, e.g., Pls.’ Reply Br.
18 (“NUMEC’s failure to collect data makes calculations
impossible—and it should not now benefit from its own
malfeasances.”). Plaintiffs have also failed to show the
District Court abused its discretion when it denied an
adverse inference with regard to causation.             See
McMunn, 131 F. Supp. 3d at 394–96.

                            53
Plaintiffs failed to show an abuse of discretion, we need
not analyze further.

                   III. CAUSATION
       The District Court held that Plaintiffs’ case also
must be dismissed because Plaintiffs’ experts failed to
provide “evidence of [Plaintiffs’] exposure to inhaled
uranium from the Apollo plant and an estimate of the
dose they received which caused their cancers.”
McMunn, 131 F. Supp. 3d at 399. On appeal, Plaintiffs
argue they showed causation even though they did not
show a dose for any individual plaintiff because (1)
Plaintiffs needed only to show “frequency, regularity,
and proximity”—not dose—and (2) the law of the case
requires us to assume that Melius’s testimony would be
sufficient to show causation because the District Court
ruled Melius’s testimony was admissible in its Daubert
motion. These arguments are unpersuasive because
Plaintiffs’ experts failed to show that any of the
individual Plaintiffs had sufficient exposure—looking at
the frequency, regularity, and proximity to the
radiation—and Plaintiffs were not prejudiced by the
District Court’s inconsistent reasoning.

A. Plaintiffs Do Not Show Sufficient Frequency,
Regularity, and Proximity
      Unlike with duty and breach discussed above,
causation for Price-Anderson public liability actions is
evaluated under state law. See In re TMI, 67 F.3d 1103,
                           54
1117 n.33 (3d Cir. 1995) (“As we have noted, the 1988
Amendments retroactively required the applicable law
for ‘public liability actions’ be ‘the law of the State in
which the nuclear incident involved occurs, unless such
law is inconsistent’ with federal law.”); see also In re
Hanford Nuclear Reservation Litig., 534 F.3d 986, 1010
(9th Cir. 2007) (“Under the PAA, Washington state law
controls the standard of causation to be used in this
case.”). Here, that state law is Pennsylvania law.
       Pennsylvania requires a plaintiff to show that a
defendant’s acts were a substantial factor in causing a
plaintiff’s injury. As the Pennsylvania Supreme Court
recently stated, “To establish proximate causation, a
plaintiff must adduce evidence to show that the
defendant’s act was a substantial factor in bringing about
the plaintiff’s harm.” Rost v. Ford Motor Co., 151 A.3d
1032, 1049 (Pa. 2016); see also Summers v. Certainteed
Corp., 997 A.2d 1152, 1164–65 (Pa. 2010) (“[T]he
requirements of proving substantial-factor causation
remain the same.”).
      Until recently, the Pennsylvania Supreme Court
had suggested that proving substantial-factor causation
required showing the dose to which plaintiff was exposed
because otherwise the “substantiality” of the substantial
factor would not be shown to the jury. See Betz v.
Pneumo Abex LLC, 44 A.3d 27, 58 (Pa. 2012)
(“Certainly a complete discounting of the substantiality


                           55
in exposure would be fundamentally inconsistent with
Pennsylvania law.”).

       However, following oral argument in the case
before us, the Pennsylvania Supreme Court issued its
decision in an asbestos case, Rost v. Ford Motor Co. In
Rost, the Pennsylvania Supreme Court retreated from its
earlier statements, emphasizing that it had previously
“adopted the ‘frequency, regularity, and proximity’ test,
as refined and applied by the United States Court of
Appeals for the Seventh Circuit in Tragarz v. Keene
Corp., 980 F.2d 411 (7th Cir. 1992).” Rost, 151 A.3d at
1043.

      It may well be that Rost applies only in
mesothelioma cases because of unique public policy
concerns about mesothelioma.24 Yet we need not decide



24
   See, e.g., Rost, 151 A.3d at 1042–43 (describing the
“test on motions for summary judgment in mesothelioma
cases”); id. at 1044 n.7 (“It is important to recognize that
this Court settled on these principles based on a policy
concern: that it is fundamentally unfair to hold a
defendant jointly and severally liable for a mesothelioma
plaintiff’s injuries for a de minimis contribution to the
plaintiff’s overall exposure.”); id. at 1052 (stating that the
frequency, regularity, and proximity test applied “for all
exposures to asbestos”). This makes particular sense to
the extent that Rost relies on Tragarz, which, in turn is
                             56
based on an Illinois appellate court’s reliance on the
nature of asbestos-related diseases:

      Given the various diseases which are
      associated with asbestos exposure, the
      medical evidence presented, the types of
      asbestos involved, the manner in which the
      products are handled, and the tendency of
      those asbestos products to release asbestos
      fibers into the air, the amount of evidence
      needed to establish the regularity and
      frequency of exposure will differ from case
      to case. For example, none of the plaintiffs
      in this case were diagnosed with
      mesothelioma, an asbestos-related disease
      which is caused after only minor exposure to
      asbestos dust.

Wehmeier v. UNR Indus., Inc., 572 N.E.2d 320, 337 (Ill.
App. Ct. 1991) (citation omitted).

Mesothelioma is a “signature” disease relating to
asbestos exposure; individuals do not usually develop
mesothelioma without asbestos exposure. See Daley v.
A.W. Chesterton, 37 A.3d 1175, 1177 n.4 (Pa. 2012)
(“Moreover, because mesothelioma, in general, is so rare,
‘any case occurring after a well attested and substantial
asbestos exposure is commonly accepted as being caused
                           57
by that exposure.’”); see also Ford Motor Co. v. Boomer,
736 S.E.2d 724, 728 (Va. 2013) (“Mesothelioma is a
signature disease: it was uncontroverted at trial that the
cause of mesothelioma is exposure to asbestos at some
point during an individual's lifetime.”).

By contrast, the cancers suffered by the Plaintiffs have
numerous and sometimes even unknowable causes, as
Melius conceded. See JA3236 (“We're evaluating a
disease that’s multi-causal. We don’t have any way of
testing the cancer to determine what caused it, what
specific factor caused it.”); JA3237 (“There are many
cancers that occur where we don’t identify the cause of
that cancer or the causes of that cancer.”); JA3311 (“In
an individual patient I think it’s more appropriate to use
risk factors because it implies -- otherwise it implies that
we know the factor that caused their specific individual
cancer and in most cases we probably do not.”); see also
Risk Factors for Cancer, Nat’l Cancer Institute,
https://www.cancer.gov/about-cancer/causes-
prevention/risk (last visited Oct. 15, 2016) (identifying
age, alcohol, cancer-causing substances, chronic
inflammation, diet, hormones, immunosuppression,
infectious agents, obesity, radiation, sunlight, and
tobacco as risk factors for cancer).

Indeed, in 1999, we explained that establishing causation
for a given cancer was extremely difficult. See In re TMI
                           58
whether Rost is limited to mesothelioma cases because
Plaintiffs’ evidence would not allow a jury to find
sufficient frequency, proximity, and regularity. Rost
requires a plaintiff at summary judgment to have
propounded “evidence that exposure to defendant’s
asbestos-containing product was sufficiently ‘frequent,
regular, and proximate’ to support a jury’s finding that
defendant’s product was substantially causative of the
disease.” Rost, 151 A.3d at 1044 (emphasis added). For


Litig., 193 F.3d at 643 (“Consequently, medical
evaluation, by itself, can neither prove nor disprove that a
specific malignancy was caused by a specific radiation
exposure.”). Modern secondary sources continue to
agree with that assessment. See, e.g., Steve C. Gold,
When Certainty Dissolves into Probability: A Legal
Vision of Toxic Causation for the Post-Genomic Era, 70
Wash. & Lee L. Rev. 237, 279–81 (2013); William D.
O’Connell, Note, Causation’s Nuclear Future: Applying
Proportional Liability to the Price-Anderson Act, 64
Duke L.J. 333, 357, 359 (2014) (“Radiation-protection
scientists are in agreement that differential diagnosis
cannot confidently identify the ultimate source of a
plaintiff’s cancer.”); cf. Wilcox v. Homestake Mining Co.,
619 F.3d 1165, 1167 (10th Cir. 2010) (“[N]or do we see
a basis for alternative liability where only one potential
wrongdoer has been identified and the injury may simply
have resulted from natural causes.”).

                            59
instance, the Rost Court noted that the plaintiff’s expert
testified to more than three months of exposure “while
noting studies showing that a single month of regular
exposure to asbestos can double one’s likelihood of
developing mesothelioma.”        Id. at 1046.        Even
Lohrmann—the original frequency, regularity, and
proximity case, which stated that the court was creating
“a de minimis rule” for proving asbestosis causation
under Maryland law—explained that “a plaintiff must
prove more than a casual or minimum contact with the
product.” Lohrmann v. Pittsburgh Corning Corp., 782
F.2d 1156, 1162 (4th Cir. 1986). Here, where Plaintiffs
(1) simply rely on the existence of any frequency,
regularity, and proximity and (2) fail to offer any
individualized evidence of exposure for any given
Plaintiff, they come up short. Even were this evidence
substantively permissible under Pennsylvania law, it
would fail to be admissible under Daubert for three
reasons.
      First, Melius’s testimony is insufficient to create a
genuine issue of fact regarding causation because it is
nothing more than a radiation version of the
impermissible “any breath” theory in Gregg v. V-J Auto
Parts (the case in which that court first adopted the
frequency, regularity, and proximity test in mesothelioma
cases). See Summers, 997 A.2d at 1161 n.14 (“In Gregg
v. V-J Auto Parts, Co., 596 Pa. 274, 943 A.2d 216
(2007), this Court recently rejected the viability of the
‘each and every exposure’ or ‘any breath’ theory.”). The
                            60
Gregg Court explained that, in a so-called “any breath”
theory of asbestos exposure, a plaintiff alleges that “any
exposure to asbestos, no matter how minimal, is a
substantial contributing factor in asbestos disease.”
Gregg v. V-J Auto Parts, Co., 943 A.2d 216, 226 (Pa.
2007); see also Howard v. A.W. Chesterton Co., 78 A.3d
605, 608 (Pa. 2013) (per curiam) (“Bare proof of some de
minimus [sic] exposure to a defendant’s product is
insufficient to establish substantial-factor causation for
dose-responsive diseases.”).

       Melius assumes that anyone who lived in the area
of the Apollo facility was exposed to a sufficient amount
of radiation. In Melius’s words, he “estimated that -- that
they had a, um, substantial or significant exposure.”
JA3227. Yet he did not “estimate a specific or associate
a specific level of exposure with a -- with those terms.”
Id. When asked about “significant exposure,” Melius
agreed that “any exposure to a plaintiff that was above
that plaintiff’s background would be a substantial
exposure.” JA3315.25 Similarly, Melius said that,


25
   This is in contradiction to, for instance, his admissions
that he relied on different levels of cigarette usage to
determine substantiality. See JA3300, 3308; see also
JA3321 (“For cigarette smoking and lung cancer, it is
reduced to ten or twenty percent increased risk compared
to somebody who has never smoked after a period of say
twenty years, maybe even after ten or fifteen years.”).
                            61
“[d]epending on how you use the meaning of
significant,” he “would say” one millirem above
background was “substantial.” JA3315–16.

       Second, Melius failed to offer individualized
testimony as he was required to do for each Plaintiff. For
instance, in Howard v. A.W. Chesterton Co., the
Pennsylvania Supreme Court explained, “Relative to the
testimony of an expert witness addressing substantial-
factor causation in a dose-responsive disease case, some
reasoned, individualized assessment of a plaintiff’s or
decedent’s exposure history is necessary.” 78 A.3d at
608; cf. also Black v. M&W Gear Co., 269 F.3d 1220,
1237–38 (10th Cir. 2001) (holding that a district court
did not abuse its discretion in excluding an expert’s
testimony when that expert “had not based his conclusion
on the results of tests or calculations specific to” the
plaintiff). Although Melius describes each Plaintiff’s
smoking history and a few other features for most
Plaintiffs, Melius fails to offer any “reasoned . . .
assessment” of any individual’s exposure to radiation
from uranium effluent. See, e.g., JA4782–84 (relying on
reports about radiation released from the facility that do
not show exposure to any of the individual Plaintiffs).
He merely offers the conclusion that each Plaintiff’s
“exposures to uranium and other radioactive materials
released from the Apollo nuclear facility made a
significant contribution to the development of” her or his
cancer. E.g., JA3448. Even if such a conclusion were
permissibly individualized, it would still be insufficient
                           62
to generate a genuine issue of fact because, under the
Lone Pine order, only exposure to uranium is at issue
here.

       Although Rost stresses that causation is an issue
for the jury, we have never hesitated to grant summary
judgment where one side fails to establish a genuine issue
of fact concerning causation. See, e.g., In re TMI Litig.,
193 F.3d 613, 722–23 (3d Cir. 1999) (affirming summary
judgment where plaintiff’s expert testimony “was
insufficient to create a genuine issue of material fact”
regarding causation); Heller v. Shaw Indus., Inc., 167
F.3d 146, 150 (3d Cir. 1999) (“[B]ecause the District
Court did not abuse its discretion in excluding the key
elements of Heller’s experts’ testimony necessary to
prove causation, the grant of summary judgment will be
affirmed.”).

       Finally, the Federal Rules of Evidence impose a
duty on a district judge to act as a gatekeeper of expert
testimony even when considering elements of a cause of
action derived from state law. See Forrest v. Beloit
Corp., 424 F.3d 344, 358 n.9 (3d Cir. 2005) (explaining
that “evidentiary issues in this case are governed by
federal . . . law” while Pennsylvania substantive law
affected what facts would be relevant); see also Hendrix
ex rel. G.P. v. Evenflo Co., Inc., 609 F.3d 1183, 1193
(11th Cir. 2010) (“Although the standards for finding
causation are governed by Florida law, we apply federal
law to determine whether the expert testimony proffered

                           63
to prove causation is sufficiently reliable to submit it to
the jury.”); cf. Daubert v. Merrell Dow Pharm., Inc., 509
U.S. 579, 597 (1993) (“[A] gatekeeping role for the
judge . . . is the balance that is struck by Rules of
Evidence . . . .”).
       Thus, even assuming arguendo that Rost
resuscitated “any breath” causation, Melius’s testimony
would be too insubstantial to survive Daubert. Melius’s
testimony provides only a perfunctory narrative for each
Plaintiff, and an unexplained conclusion that radiation
was the cause, presumably because each Plaintiff was
exposed to some radiation. Such conclusory opinions of
medical causation, even by qualified experts, are
insufficient to establish causation of cancer by exposure
to uranium effluent. See Tamraz v. Lincoln Elec. Co.,
620 F.3d 665, 671 (6th Cir. 2010) (“Whatever Dr. Carlini
understood by ‘with a reasonable degree of medical
certainty,’ the phrase—the conclusion by itself—does not
make a causation opinion admissible. The ‘ipse dixit of
the expert’ alone is not sufficient to permit the admission
of an opinion.” (quoting Gen. Elec. Co. v. Joiner, 522
U.S. 136, 146 (1997))).

      Although we have held that an expert can offer an
opinion “absent hard evidence of the level of exposure to
the chemical in question,” we have only done so where
an expert could rely “on the temporal relationship and the
nature of the plaintiff’s complaints.” Heller, 167 F.3d at
157. This, too, does not require a dose. But it requires

                            64
more than an assumption about the effect of living within
a mile of the Apollo facility.

                          ***

       Consider how a trial would unfold. Plaintiffs
would present a general causation expert who opines that
any amount of ionizing radiation could cause cancer.
Then, Plaintiffs would present Melius who would state
that each of the Plaintiffs lived or worked near the Apollo
facility and would therefore be assumed to have been
exposed to some radiation from airborne uranium
effluent from the Apollo facility. Melius would then
presumably testify that he is certain that the additional
radiation specifically from the airborne uranium was a
substantial factor in causing the cancer of each of the
Plaintiffs.26 Finally, the jury would decide whether more
than a dozen different illnesses suffered by more than
seventy people were each caused by the radiation from
the airborne uranium from the Apollo facility.
       How? Without any ability to compare any
plaintiff’s frequency, proximity, or regularity to any
evidence showing that a given frequency, proximity, or
regularity is correlated with any particular increase in


26
   Plaintiffs would also have to ensure they have
sufficient testimony relating only to uranium effluent
under the Lone Pine order.

                            65
risk—let alone the ability to perform the ideal
comparison between dose and the dose-responsiveness of
a given illness—the jury would be engaging in rank
speculation.

       It is true that demanding more than evidence of
“any exposure” makes it more burdensome for most
plaintiffs to recover for injuries from radiation. But the
evidentiary regime that must apply in these cases
necessarily requires that a jury find radiation was a
substantial factor in causing a plaintiff’s injury—and
requires, now, at summary judgment, that we be able to
hold that a reasonable jury could so find. See Gregg, 943
A.2d at 225–26 (“We appreciate the difficulties facing
plaintiffs in this and similar settings, where they have
unquestionably suffered harm on account of a disease
having a long latency period and must bear a burden of
proving specific causation under prevailing Pennsylvania
law which may be insurmountable.”); see also Fed. R.
Civ. P. 56(a). We can demand no less.

B. District Court Law of the Case Does Not Bind This
Court, and, in Any Event, Plaintiffs Were Not
Prejudiced
      Pointing to the inconsistency between the District
Court’s Daubert opinion, which suggested Melius’s
testimony was strong, and the District Court’s opinion
granting summary judgment to Defendants, which held
that Melius’s testimony did not create a genuine issue of
material fact, Plaintiffs argue that the District Court was
                             66
bound to adhere to its Daubert opinion at summary
judgment. Such concerns are irrelevant where, as here,
(a) this Court is not bound by the District Court’s
Daubert opinion and (b) Plaintiff cannot show prejudice.

       Plaintiffs are correct that the District Court’s
Daubert opinion appears to be inconsistent with its
summary judgment opinion. The Daubert opinion
strongly implied that Melius’s testimony would be
enough to get the case to the jury, holding that his
testimony should not be excluded because there was
“enough support in the record for the contention that the
Plaintiffs’ exposure levels exceeded the normal
background level.” McMunn v. Babcock & Wilcox
Power Generation Grp., Nos. 2:10cv143 et al., 2014 WL
814878, at *14 (W.D. Pa. Feb. 27, 2014). By contrast,
the District Court’s summary judgment opinion held that
“Plaintiffs must provide . . . an estimate of the dose they
received which caused their cancers.” McMunn, 131 F.
Supp. 3d at 399.
        But, as a general matter, we fail to see what
difference law of the case makes at this stage of the
litigation. We are not bound by either of the District
Court’s rulings, and we have addressed the Plaintiffs’
arguments on their own merits.

       At all events, Plaintiffs’ law-of-the-case argument
fails on its own merits. Two values animate law-of-the-
case doctrine: judicial economy and unfair prejudice.
See, e.g., Roberts v. Ferman, 826 F.3d 117, 126 (3d Cir.
                             67
2016) (“We also have held that ‘the law of the case
doctrine does not limit the power of trial judges to
reconsider their prior decisions,’ but have noted that
when a court does so, it must explain on the record why it
is doing so and ‘take appropriate steps so that the parties
are not prejudiced by reliance on the prior ruling.’”
(quoting Williams v. Runyon, 130 F.3d 568, 573 (3d Cir.
1997))).
       Here, Plaintiffs have failed to show any prejudice
from the District Court’s change in position. Had the
District Court ruled against them in its Daubert order,
Plaintiffs’ case would have been dismissed as the
Magistrate Judge recommended. Plaintiffs would not
have had an opportunity to create new expert reports in
response to a Daubert ruling that more clearly reflected
the District Court’s legal rulings on causation at
summary judgment.

      Perhaps Plaintiffs could have argued that they
were prejudiced because they were lulled into failing to
challenge Defendants’ uncontested facts. But, because
we do not rely on any of those uncontested facts when we
hold that Plaintiffs fail to show a genuine dispute of
material fact with regard to causation, not even the
admission of the uncontested facts demonstrates
prejudice.
                          ***


                            68
       Because Plaintiffs failed to offer evidence from
which a jury could find that each plaintiff was exposed to
radiation from Defendants’ uranium effluent sufficiently
frequently, regularly, and proximately to substantially
cause their illnesses, and further because the law-of-the-
case doctrine does not require us to conclude otherwise,
we hold that Defendants have failed to demonstrate
issues of material fact on causation.

                    CONCLUSION
       Defendants are entitled to judgment as a matter of
law because Plaintiffs failed to show a genuine issue of
material fact with regard to duty, breach, and causation.
Therefore, we will affirm the judgment of the District
Court.




                           69
McMunn, et al. v. Babcock & Wilcox Power Generation
Group, Inc., et al., No. 15-3506

MCKEE, Circuit Judge, concurring, joined by RESTREPO,
Circuit Judge.

    While I agree that summary judgment is appropriate here,
I write to stress that the law in this area is simply inadequate
to address claims arising under the Price-Anderson Act based
on exposure to excess radiation.

    As the Majority explains, this is a Public Liability Action
under the Price-Anderson Act.1 Federal law therefore
controls our inquiry into whether Defendants owed Plaintiffs
a duty, and if so, whether the duty was breached. State law
controls the inquiry into whether the breach, if proven, caused
Plaintiffs’ injuries.2 As I will explain, existing law places an
almost insurmountable burden on plaintiffs who try to recover
under the Price-Anderson Act. Under the existing law,
Plaintiffs cannot establish causation, even if they have
established that Defendants owed them a duty that was
breached.

    Suits for injuries allegedly resulting from radiation
exposure have no analogous counterpart in traditional tort
law, and existing law ignores the unique problems inherent in
claims based on exposure to “manmade” radiation. As a
result, plaintiffs will rarely, if ever, recover in these types of
actions, and this will continue unless states (or Congress)
recognize the unique problems endemic in proving that a
plaintiff’s illness was proximately caused by exposure to
radiation from a given facility or event.
                      I. BREACH OF DUTY
       I believe that Plaintiffs’ submissions (as itemized in
the Majority Opinion) are more than adequate to survive
Defendants’ motion for summary judgment as to breach of
duty.3  For example, an internal memorandum, dated



1
  Maj. Op. at 5.
2
  See In re TMI, 67 F.3d 1103, 1117 n.33 (3d Cir. 1995).
3
  See Maj. Op. at 10-12.

                                 1
November 29, 1972, regarding NUMEC’s meeting with AEC
Compliance stated:
     P. Nelson [AEC personnel] opened by
     explaining the purpose of the meeting. He
     stated that Compliance was concerned about the
     recurring nature and seriousness of NUMEC
     violations. He explained that the AEC could
     now impose civil penalties for those types of
     violations. . . . NUMEC has been the worst
     offender of AEC regulations over the years. .
     . . AEC had given NUMEC a grace period after
     the B&W takeover, but that little improvement
     was evident. The AEC is strongly considering
     imposing civil penalties against NUMEC.4

Another letter from the AEC stated: “It appears that certain of
your activities were not conducted in full compliance with . . .
and the requirements of the AEC’s ‘Standards for Protection
Against Radiation,’ Part 20, and ‘Special Nuclear Material’ . .
. .”5 Based on this, there could be enough evidence to support
Plaintiffs’ claimed breach of duty.

         The Majority affirms the District Court’s conclusion
that much of Plaintiffs’ evidence is of either limited value or
irrelevant because the only expert whose testimony survived
the Daubert motion (Dr. Melius) primarily focused on
radiation levels at the stacks or vents and not at the roof top
boundary.6 Although I agree that Plaintiffs must establish the
levels of radiation at the roof boundary rather than levels at
the vents or stacks, levels at the vents or stacks could
nevertheless be very relevant to establishing levels at the
boundary if that evidence had been properly developed. This
follows from the fact that different radioactive substances
have different half-lives. I will not wade into the quantum
mechanical weeds of half-lives here as that was discussed in
some detail in our 1999 opinion in In re TMI Litigation (TMI
II).7 Rather, I will merely note that half-lives vary from as
short as less than a second to as long as many billions of

4
  JA4439-40 (emphasis added).
5
  JA4693.
6
  See Maj. Op. at 23, 29-34.
7
  193 F.3d 613 (3d Cir. 1999).
                               2
                               2
years, depending on the substance involved.8 Accordingly, if
byproducts of the uranium produced at Defendants’ facility
included substances with sufficiently long half-lives, their
levels at the stacks and vents would be very relevant to
determining exposure at the roof boundary and beyond. A
fact finder could readily conclude that the levels at the vents
and stacks persisted with no discernable diminution (even
after allowing for dilution as they dispersed into the
surrounding community) long enough for residents of the
community to be exposed to those levels. The probative
value of this evidence could be particularly compelling if the
effluents that comprise the byproducts of uranium production
are not otherwise found in the environment. They would thus
become much more analogous to toxins that cause diseases
such as mesothelioma which I discuss in more detail below.

          However, we do not know the extent to which
byproducts of uranium production have an exceedingly short
half-life or whether they have exceptionally low energies. If
they have a momentary short half-life or exceptionally low
energies, their presence at the stacks and vents would be
irrelevant to determining levels at the roof boundary. This is
because they would have disintegrated into sub particles
before reaching the roof boundary and would likely not have
had enough energy to cause any damage even if they reached
the roof’s perimeter and beyond into the community.
Plaintiffs did not offer any evidence that would allow a fact
finder to conclude that the levels at vents and stacks persisted
at the roof boundary. Accordingly, evidence of the levels at
the stacks and vents cannot satisfy their burden of
establishing a breach at the relevant point—the roof
boundary.

         I also have reservations about the Majority’s
conclusion that 10 C.F.R. § 20.106(a) requires averaging as
opposed to merely allowing Plaintiffs to average exposure
over a year.9 However, here again, Plaintiffs’ proof is
deficient because they did not attempt to introduce any
evidence about the actual content of the uranium effluent that
was discharged. If that effluent contained substances that

8
    See id. at 632.
9
    See Maj. Op. at 41-43.

                               3
were particularly toxic (such as plutonium), exposure to a
given amount for a few days (perhaps even for a matter of
hours) could cause cancer even though the exposure would
appear minimal when averaged out over a year.10 There is an
even more fundamental problem with Plaintiffs’ case that
prevents them from surviving summary judgment, and that is
why I feel compelled to write separately.

          In order for Plaintiffs to succeed, they must do more
than show a breach of a duty resulting in exposure to excess
radiation. They must show that the breach resulted in an
exposure that proximately caused their injuries. It is here that
Plaintiffs’ claims fail regardless of the quality of all of their
other proof. Thus, even assuming a genuine issue of fact as
to the exposure levels and Defendants’ breach, the evidence is
still not sufficient to defeat summary judgment under the
Price-Anderson Act because causation is lacking.
                        II. CAUSATION
A.        The Problems of Radiation Toxicity
          The Majority thoroughly and correctly explains
causation as it applies to “toxic torts” under Pennsylvania
law. However, the legal principle of causation has evolved
from suits arising from exposure to manmade toxic
substances such as asbestos.           As the Majority notes,
mesothelioma is caused by exposure to asbestos, and it is
therefore a “signature” disease. The disease almost never
occurs absent exposure to asbestos.11 The problems of proof
in such cases are quite similar to problems of causation in
cases involving polychlorinated biphenyls (PCBs)12 or

10
   See George L. Voelz, Plutonium and Health: How Great is
the Risk?, Los Alamos Sci. 83 (2000),
https://fas.org/sgp/othergov/doe/lanl/pubs/00818013.pdf;
Katherine Harmon, Health Risk Fears Escalate as Japan
Nuclear Plant’s Radioactive Release Remains Uncertain, Sci.
Am. (Mar. 18, 2011),
https://www.scientificamerican.com/article/health-risk-
fukushima/ (“Plutonium is of graver concern because of its
exceptionally long half-life (about 24,000 years) and its
propensity to cause lung cancer if inhaled.”).
11
   Maj. Op. at 50-51.
12
   See In re Paoli R.R. Yard PCB Litig., 35 F.3d 717 (3d Cir.
1994).
                               4
                                4
pneumoconiosis (black lung disease),13 to name but a few of
the pathological byproducts of modernization. In such cases,
a pathology is caused by contact (usually ingestion) with a
foreign substance that the injured person would not have
otherwise been exposed to, or would have been exposed to
only in relatively insignificant quantities, and that pathology
almost never occurs in the absence of exposure to that toxic
substance. Accordingly, causation can be established by
showing that defendant made (or controlled) a substance,
plaintiff has a disease that almost never occurs absent contact
with defendant’s substance, and plaintiff had sufficient
contact with defendant’s product (i.e. “frequency, regularity,
and proximity of exposure”) to allow a fact finder to conclude
that the defendant’s product was a substantial factor in the
plaintiff’s death or injury.14 Radiation is different.

         In TMI II, we discussed the “scientific principles
regarding the relationship between radiation and cancer.” 15
As the Majority explains, “[m]anmade ionizing radiation can
damage human cells.”16 An ion is nothing more than an
electron that has been displaced from its orbit.17 Unlike with


13
   See Mancia v. Dir., Office of Workers’ Comp. Programs,
U.S. Dep’t of Labor, 130 F.3d 579 (3d Cir. 1997).
14
   See Rost v. Ford Motor Co., 151 A.3d 1032 (Pa. 2016).
15
   Maj. Op. at 13-15; see TMI II, 193 F.3d 613.
16
   Maj. Op. at 13 (citing TMI II, 193 F.3d at 639-40).
Although we used the term “manmade” in TMI II, it is
actually a misnomer that obscures some of the very important
distinctions between environmental radiation naturally
occurring and radiation from substances that are, in fact,
manmade. The latter radiation is not actually “manmade.” It
consists of natural elementary particles that are transformed
by human activity. The resulting radiation is nevertheless the
result of quantum mechanical processes. However, for the
sake of convenience, we will also refer to this radiation as
“manmade” as we did in TMI II.
17
   TMI II, 193 F.3d at 639 (“[A]n atom is ionized when an
electron is ejected from its orbit and expelled from the
atom.”). It is actually a sweeping generalization to refer to all
ionizing radiation as resulting from a single displaced
electron. A very detailed description of the process of

                                5
PCBs, asbestos or tobacco byproducts, we are constantly
exposed to radiation on a daily basis. We are exposed from
numerous natural sources including the sun,18 or naturally
occurring radioactive elements such as radon in the ground
surrounding our homes.19

         It is now beyond dispute that radiation can cause
various types of cancer. However, unlike with asbestos and
diseases, such as mesothelioma, radiation wreaks havoc with
our bodies, not because it is a foreign substance (it is not), but
because it transfers extra energy to our cells. This energy
can, in turn, damage our DNA in numerous ways that are
described in detail in TMI II.20

       Asbestos fibers cause mesothelioma by damaging the
“mesothelial cells that control cell reproduction. Some
damaged cells die and tumor suppressor genes stop others


ionization (including the all important Columb Force) can be
found at TMI II, 193 F.3d at 632-38.

    However, the complex distinctions are not important for
purposes of this discussion. Therefore, rather than attempt
more precision by distinguishing between the different types
of ionizing particles and ionizing energy as we did in TMI II,
we will refer to all ions as if they only consisted of electrons
without attempting to distinguish between alpha, beta or
gamma radiation or between orbital electrons and electrons
created through nuclear reactions. The important thing for
purposes of this discussion is that “[w]hen a charged particle
passes through matter, it excites and ionizes atoms in its
path.” Id. at 635. This is what happens to human tissue that
is exposed to radiation.
18
   Id. at 644-47.
19
   See Natural background radiation, Am. Cancer Soc’y,
https://www.cancer.org/cancer/cancer-causes/radiation-
exposure/x-rays-gamma-rays/natural-background-
radiation.html (last revised Feb. 24, 2015) (explaining that
radon is but one source of the background radiation that we
are potentially exposed to on a daily basis and is listed only
for purposes of illustration).
20
   See TMI II, 193 F.3d at 640.
                                6
                                6
from reproducing.”21 However, “[w]here suppressor genes do
not stop the reproduction process, . . . the damaged cells
divide, replicating the damage in the sister cells.”22 Over
decades of continued growth of these cells, tumors develop.
“This explains why mesothelioma has an extremely long
latency period, as mesothelial cells have a very slow growth
rate.”23 As expert testimony in a recent case from the
Supreme Court of Pennsylvania established, “it is not
scientifically possible to identify the particular exposure or
exposures that caused a patient’s mesothelioma[.] . . .
[I]nstead, the causative agent is ‘the series of exposures.’”24
However, even though it is not possible to identify a
particular exposure as causing a given occurrence of the
disease, there is now no dispute that asbestos is responsible
for mesothelioma.

          Although the disease process described above for
mesothelioma is quite similar to that which is triggered by
radiation after the cell is irradiated, there is a key difference
that is very relevant to our discussion. As noted above, we do
not normally develop diseases such as mesothelioma in the
absence of exposure to the manmade carcinogens that can
cause it. Thus, if a plaintiff can produce evidence of
sufficient frequency, regularity, and proximity of exposure to
asbestos to establish that it is more likely than not that that
exposure was a substantial cause of subsequent disease, the
plaintiff then need only prove that defendant manufactured or
controlled the substance that plaintiff had been exposed to in
order to recover. The same is true with any other “signature”
disease.

       Unlike products such as asbestos and PCBs, radiation
is not a foreign substance. All of us are exposed to it every
second of every day both inside of buildings and outdoors.
Yet, radiation can “damage structures within the human body
as cells are disrupted or killed by the ionizing radiation
[energy] itself, and as energy is transferred to cells triggering


21
   Rost, 151 A.3d at 1039 (citations omitted).
22
   Id.
23
   Id.
24
   Id.

                                7
second-order chemical changes.”25 “Unlike a chemical
product, which may be traceable to a particular manufacturer,
different sources of radiation are not distinguishable, nor is
there any noticeable difference between cancers caused by
nuclear-power production and those caused by other sources
of radiation.”26
       [M]edical evaluation, by itself, can neither
       prove nor disprove that a specific malignancy
       was caused by a specific radiation exposure [or
       series of exposures]. Therefore, the primary
       basis to link specific cancers with specific
       radiation exposures is data that has been
       collected regarding the increased frequency of
       malignancies following exposure to ionizing
       radiation. In other words, causation can only be
       established (if at all) from epidemiological
       studies of populations exposed to ionizing
       radiation.27

        However, epidemiological studies of exposed
populations can only establish the percentage by which the
incidence of given cancers in that population exceeds the rate
for those same cancers in similar populations not exposed to
the source of radiation. No study can determine whether the
cancer of a given member of that population was the result of
exposure to a defendant’s product or to radiation released
from a defendant’s facility. As we explained in TMI II, “the
task of establishing causation is greatly complicated by the
reality that a given percentage of a defined population will
contract cancer even absent any exposure to ionizing



25
   William D. O’Connell, Causation’s Nuclear Future:
Applying Proportional Liability to the Price-Anderson Act, 64
Duke L.J. 333, 348 (2014) [hereinafter O’Connell] (citing
James E. Turner, Atoms, Radiation, and Radiation Protection
421 (3d ed. 2007) [hereinafter Turner], available at
http://nuclear.dababneh.com/Radiation-Undergrad-
2/Atoms,%20Radiation,%20and%20Radiation%20Protection.
pdf.
26
   Id. at 350 (citing Turner at 468).
27
   TMI II, 193 F.3d at 643 (citations omitted).
                              8
                               8
radiation.”28 This probability conundrum is even more of an
issue when we try to compare members of a population who
have only been exposed to natural radiation with members of
the same population who have been exposed to that radiation
plus radiation emanating from a defendant’s product or
facility.

       Plaintiffs who must prove that exposure to a particular
source of radiation was a substantial cause of their injuries
therefore face an insurmountable task that the law has yet to
satisfactorily address. The task is further complicated by the
fact that radiation includes different kinds of particles (i.e.
alpha, gamma, beta), each with different properties including
different levels of energy and thus having a different
capability of damaging human cells.29 As the NRC has
explained:
       [N]atural radiation . . . is always present in the
       environment. It includes cosmic radiation which
       comes from the sun and stars, terrestrial
       radiation which comes from the Earth,
       and internal radiation which exists in all living
       things. The typical average individual exposure
       in the United States from natural background
       sources is about 300 millirems per year.30

Yet, although there is general scientific agreement that
radiation can cause cancer, we are still at the rudimentary
stages of understanding the etiology of cancers. 31

       As if this does not make plaintiffs’ task in such cases
difficult enough, two additional considerations further
complicate inquiries into causation. First, as has already been
mentioned, not all radiation has the same energy level. Some
radiation can be filtered out by barriers no more substantial

28
   Id. at 643-44. For a detailed explanation of the two major
sources of natural radiation and average doses, see id. at 644-
48.
29
   For a detailed discussion of this, see id.
30
   U.S. Nuclear Regulatory Comm’n, Background radiation,
https://www.nrc.gov/reading-rm/basic-
ref/glossary/background-radiation.html.
31
   See TMI II, 193 F.3d at 644-48.

                               9
than sunscreen, or surface tissue, yet some radiation is
capable of penetrating lead.32 Thus, mere proximity to a
source of radiation does not necessarily establish a sufficient
“absorbed dose” to link an individual’s illness to that
proximity.33 This point is illustrated in the extreme by the
fact that “[c]rews of nuclear submarines have possibly the
lowest radiation exposure of anyone, despite living within a
few meters of a nuclear reactor, since they are exposed to less
natural background radiation than the rest of us [(the ocean
shelters them)], and the reactor compartment is well
shielded.”34

       Second, the difficulty of linking a potentially
radiation-related pathology to a defendant instead of to
background radiation is made exponentially more difficult by
the fact that some people have a genetic predisposition to
diseases associated with radiation exposure, while others have
a genetic composition that seems to protect them from the
otherwise harmful effects of radiation. Indeed, more than one
physician has counseled that the best way to guard against
contracting cancer is to “choose your parents carefully.”35
Genetic research has even led researchers to conclude that:
       [P]erhaps a fortunate genetic endowment
       protects some lifelong smokers from lung
       cancer, while a genetic mischance induces lung
       cancer in some non-smokers.                 Both
       environmental and genetic differences between
       individuals appear responsible for at least some

32
    See id. at 637 n.36.
33
   Id. at 637 (“The absorbed energy per unit mass of material
is termed the ‘absorbed dose.’”).
34
    World Nuclear Ass’n, Nuclear Radiation and Health
Effects, http://www.world-nuclear.org/information-
library/safety-and-security/radiation-and-health/nuclear-
radiation-and-health-effects.aspx.
35
    See, e.g., Huber R. Warner, If You Wish to Live a Long
Time in Good Health, Choose Your Parents Carefully, 62A J.
of Gerontology: Biological Scis. 575 (2007), available at
https://www.ncbi.nlm.nih.gov/pubmed/17595411; see also
Steve C. Gold, When Certainty Dissolves into Probability: A
Legal Vision of Toxic Causation for the Post-Genomic Era,
70 Wash. & Lee L. Rev. 237, 259 (2013) [hereinafter Gold].
                              10
                               10
       of the variation in individuals’ responses to
       toxic exposures. For the most part, it has been
       impossible (or at least impractical) to identify,
       quantify, and tease apart these possibilities
       using the investigatory tools of toxicology,
       environmental epidemiology, conventional
       biochemistry, and classical genetics.36

Yet, Plaintiffs such as those here, must produce evidence that
will establish that their injuries are more likely than not
caused by effluents from Defendants’ uranium plant. I
simply do not see any way they can do that given the current
state of the law.

B. Congress’s Response to Causation Issues

        Congress has recognized the problems inherent in
attempting to prove causation in Public Liability Actions
almost from the very beginning of our attempts to harness the
power of the atom. The Atomic Energy Act of 1946 created
the Joint Committee on Atomic Energy to correct the
deficiencies of the Price-Anderson Act, including the
stringent burden of establishing causation.37 The Committee

36
  Gold at 258-59.
37
  Taylor Meehan, Lessons from the Price-Anderson Nuclear
Industry Indemnity Act for Future Clean Energy
Compensatory Models, 18 Conn. Ins. L.J. 339, 346 (2012)
[hereinafter Meehan]; see also Michael Flynn, A Debt Long
Overdue, Bulletin of the Atomic Scientists 41-42 (2001) (The
Energy Employees Occupational Illness Compensation Act
acknowledged that “nuclear weapons workers were put at risk
building the country’s arsenal.” Acknowledging the
difficulties associated with establishing causation, and
“[b]ecause the government failed to adequately track
exposures at these sites, [the Act] assumes that workers’
cancers are work related, thus relieving the workers of the
near-impossible task of having to prove the connection.”
Further, the Act “establishes the possibility that other sites
and illnesses may be added to the cohort at a later date.”); see
also David Rocchio, The Price-Anderson Act: Allocation of
the Extraordinary Risk of Nuclear Generated Electricity: A
Model Punitive Damage Provision, 14 B.C. Envtl. Aff. L.

                                11
was also concerned with state statutes of limitation that could
nullify meritorious claims because of the latency of injuries
caused by radiation.38 Consequently, the 1966 amendments
to the Act included a provision for the waiver of various
defenses under state tort law in the event of an “extraordinary
nuclear occurrence.”39 An “extraordinary nuclear occurrence”
was defined as:
       [A]ny event causing a discharge or dispersal of .
       . . byproduct material from its intended place of
       confinement in amounts offsite, . . . which the
       Nuclear Regulatory Commission or the
       Secretary of Energy. . . determines to be
       substantial, and which the Nuclear Regulatory
       Commission or the Secretary of Energy. . .
       determines has resulted or will probably result
       in substantial damages to persons offsite . . ..40

“This provision was enacted in order to assure that the
victim’s entitlement to compensation would be determined
under a strict liability standard, instead of the negligence
standard that most state courts require.”41 The amendments
also included a provision that waived state statutes of
limitation that were more limited than the three-year limit
established under the Price-Anderson Act.42 However, the
overarching problem of causation was not impacted by
attempts to augment statutes of limitation or impose strict

Rev. 521, 538-39 (1987) [hereinafter Rocchio] (citing
Hearings Before the Joint Committee on Atomic Energy on
Proposed Amendments to the Price-Anderson Act Relating to
Waiver of Defenses, 89th Cong., 2d Sess. 105-07 (1966),
available at
https://www.loc.gov/resource/conghear08.00170174379/?sp=
10).
38
    Rocchio at 539.
39
   42 U.S.C. § 2014(j).
40
    Id.
41
    Meehan at 347.
42
    Id.; see 42 U.S.C. § 2210(n)(1)(F)(iii) (The Act allows “any
issue or defense based on any statute of limitations if suit is
instituted within three years from the date on which the
claimant first knew, or reasonably could have known, of his
injury or damage and the cause thereof.”).
                              12
                                12
liability. In either case, a plaintiff would still have to
establish that a given pathology was caused by exposure to a
defendant’s radiation rather than background radiation,
heredity or some other factor. Accordingly, this legislative
effort was only helpful in the exceedingly rare cases where
that evidentiary gap could be bridged.

        In 1988, Congress created the Presidential
Commission on Catastrophic Nuclear Accidents to “conduct a
comprehensive study of appropriate means of fully
compensating victims of a catastrophic nuclear accident that
exceeds the aggregate public liability . . . in the statute . . . .”43
In its final report to Congress, the Commission “sought to
identify the ‘next best’ approach, since attaining the ‘best’
solution, compensating only those whose cancers or other
latent illnesses were caused by the accident, is not currently
possible.”44 The options included:
               Option A, relaxing traditional
               notions of proof of causation and
               paying something to everyone
               who gets cancer; Option B,
               retaining and rigorously applying
               traditional standards, which would
               result in paying few, if any,
               claims; and Option C, adopting
               some proxy for direct proof of
               causation, such as imputing group
               risk to individuals who actually
               develop cancer and paying those
               claims where the association
               between radiation exposure and a
               particular cancer is the strongest
               (or at least at some minimum
               level), with the option, where a
               strong association is required for a
               “full” award, of also paying lesser

43
   Presidential Comm’n on Catastrophic Nuclear Accidents,
Report to the Congress from the Presidential Commission on
Catastrophic Nuclear Accidents, Letter to the Senate (August
1990) [hereinafter Report], available at
http://www.state.nv.us/nucwaste/news/rpccna/pcrcna02.htm.
44
   Id. at ch. 4.IV.B.

                                  13
              amounts on those claims with a
              somewhat weaker association.45

The Commission ultimately recommended Option C46 and
provided three possible ways to implement that Option, while
noting that better techniques can be developed in the future: 47
              The first would pay the full
              amount for any diagnosed cancer
              where the probability of causation
              (PC) is .5 or greater, and a
              declining amount down to a cutoff
              of PC = .2, at which compensation
              would be 20 percent of the full
              award, determined in accordance
              with Chapter 3.

              The second variation would pay
              the full amount for any diagnosed
              cancer where the PC is .5 or
              greater, and a declining amount
              down to a PC of .2, at which
              compensation would be 30
              percent of a full award.

              The third variation, which is most
              like Option A, above, would
              simply pay a benefit to anyone in
              the affected area with a diagnosed
              cancer whose radiation exposure
              indicated a PC of 20 percent or
              greater. Congress might elect to
              make this a full award determined
              in accordance with Chapter 3, or a
              fixed     dollar    amount,     or
              reimbursement for actual medical
              expenses.48



45
   Id.
46
   This option is known as the “probability of causation” rule.
47
   Report at ch. 4.II.
48
   Id. at ch. 4.IV.B. (citation omitted).
                              14
                               14
Courts have adopted variations of these and other options as
discussed below. However, despite these efforts, the problem
of establishing causation in these suits remains because we
continue to approach such claims the same way we approach
injuries resulting from asbestos, defective brakes, holes in
pavement, and falls in the aisles of the neighborhood
supermarket.

C. Evolving Case Law: Relaxing Standards

       Some courts have responded by implementing a more
relaxed analytical framework for these suits. None of these
approaches has yet won general acceptance, and each
contains certain flaws.49

1. The Preponderance Rule

        The preponderance rule is very similar to the typical
preponderance of the evidence burden. It requires a plaintiff
to prove that the defendant’s activity was more likely than not
either the but-for causation or a substantial factor in causing
the plaintiff’s injuries.50 Courts have equated the “more

49
   The following discussion of evolving law is not intended as
an exhaustive survey. Rather, I mention it only to offer
additional examples of the problem and some solutions that
have been suggested.
50
   Shelly Brinker, Opening the Door to the Indeterminate
Plaintiff: An Analysis of the Causation Barriers Facing
Environmental Toxic Tort Plaintiffs, 46 UCLA L. Rev. 1289,
1303-04 (1999) [hereinafter Brinker]; see Sterling v. Velsicol
Chemical Corp., 855 F.2d 1188, 1201 (6th Cir. 1988)
(“Whereas numerous jurisdictions have rejected medical
experts’ conclusions based upon a ‘probability,’ a
‘likelihood,’ and an opinion that something is ‘more likely
than not’ as insufficient medical proof, the Tennessee courts
have adopted a far less stringent standard of proof and have
required only that the plaintiffs prove a causal connection
between their injuries and the defendant’s tortious conduct by
a preponderance of the evidence. While, in accordance with
Tennessee common law, plaintiffs’ proof by a reasonable
medical certainty requires them only to establish that their
particular injuries more likely than not were caused by

                               15
likely than not” element of this rule to a level of certainty
greater than 50%.51 The preponderance rule does not reduce a
plaintiff’s burden of showing cause-in-fact, it allows the
plaintiff to present individualized and statistical evidence to
establish that the defendant’s activities were likely a
substantial contributor to plaintiff’s injury.52

        Because of the 50% threshold requirement, plaintiffs
who cannot demonstrate a greater than 50% likelihood that
the defendant caused their injuries do not recover anything.
However, if plaintiffs are able to show, for example, that
defendant is responsible for causing injuries to 51% of the
exposed population, every plaintiff recovers even though the
evidence only proved that 51% of the individuals in the
exposed population suffered injuries because of defendant’s
activities.

       This is basically the way causation is now determined
in Pennsylvania, as explained in the Majority’s discussion of
Rost v. Ford Motor Co.,53 except that it allows group recovery
if any group member of the group is successful in showing
his/her disease was proximately caused (i.e. by a 51%
probability) by a defendant.

      There are several obvious problems with this
approach. As we have explained above, because everyone in

ingesting the contaminated water, their proofs may be neither
speculative nor conjectural.”).
51
   In re Agent Orange Prod. Liab. Litig., 597 F. Supp. 740,
835-37 (E.D.N.Y. 1984), aff’d sub nom. In re Agent Orange
Prod. Liab. Litig. MDL No. 381, 818 F.2d 145 (2d Cir. 1987)
(quoting Jackson v. Johns-Manville Sales Corp., 727 F.2d
506, 516 (5th Cir. 1984), on reh'g, 750 F.2d 1314 (5th Cir.
1985)) (The rule provides an “‘all or nothing’ approach,
whereby [assuming all other elements of the cause of action
are proven], the plaintiff becomes entitled to full
compensation for those . . . damages that are proved to be
‘probable’ (a greater than 50 percent chance), but is not
entitled to any compensation if the proof does not establish a
greater than 50 percent chance.”).
52
   Id. at 835.
53
   See Maj. Op. at 49-52 (citing Rost, 151 A.3d 1032).
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                               16
the population will have been exposed to radiation during
their lifetime, and since it is not yet possible to isolate the
effect of radiation from a particular source, the same
problems of causation remain.           This approach merely
suspends proof of causation for everyone else if anyone in the
group can prove causation. All recover based on the showing
that someone should recover. However the nearly impossible
burden of proving causation remains.          Moreover, if the
burden can somehow be satisfied by any one plaintiff or a
subset of plaintiffs, the result imposes “crushing liability” on
defendants that could negatively impact some efforts to find
alternative energy sources.54 In addition, this approach
allows plaintiffs whose injury is probably genetic or due to
background radiation to recover along with those who can
trace their injury to the disputed source. But, the fact that one
or more plaintiffs in a given population have been injured by
exposure to a given source certainly does not mean that
everyone in that population has been. Yet, everyone would
ride along on the claims of those who can show a defendant
proximately caused his/her injury.

2. The Proportionality Rule

        Alternatively, some courts have used the
proportionality rule. This rule presumes causation when a
plaintiff presents statistical evidence showing that it is likely
that a defendant’s activities caused an injury to a proportion
of the individuals in the exposed population.55 This approach
may, at first, also appear to resemble Pennsylvania’s
“frequency, regularity and proximity” test. However, under a
pure implementation of this proportionality rule, plaintiffs are
not required to present individualized proof. For example, if
100 plaintiffs alleged that defendant’s disposal of hazardous
wastes caused their injury and the risk of developing such
injury in the exposed population is 55%, then every plaintiff
will recover 55%.56 However, plaintiffs will likely never

54
   Brinker at 1309-10.
55
   Id. at 1313.
56
   Sindell v. Abbott Labs., 607 P.2d 924, 937 (Cal. 1980); see
Cottle v. Superior Court, 5 Cal. Rptr. 2d 882, 905 (Ct. App.
1992) (Johnson, J., dissenting) (“Instead of choosing between
the extremes of overcompensation and no compensation at all

                                17
obtain complete recovery under such a tort regime.57 In
addition, this rule still allows plaintiffs whose injuries or
deaths were likely attributable primarily to background
radiation or genetics (or a combination of the two) to recover.

3. The Allen Rule

      The United States District Court for the District of Utah
presented another option in Allen v. United States, which
involved a dispute arising from atmospheric testing. That
court resorted to burden shifting. A rebuttable presumption of
liability arises if a plaintiff can show a correlation between
his or her injuries and the increased risk resulting from a
defendant’s negligent release of radiation. The problem here
is that correlation is not the same as causation.58 Yet, using
this approach, Allen held that
        [w]here a defendant who negligently creates a
        radiological hazard which puts an identifiable
        population group at increased risk, and a
        member of that group at risk develops a
        biological condition which is consistent with
        having been caused by the hazard to which he
        has been negligently subjected, such
        consistency having been demonstrated by

this solution allows plaintiffs to recover a percentage of their
damages from those responsible for their exposure to the
toxic. Under this formula defendants responsible for the toxic
exposure are liable to all those who were exposed and later
suffered injury—including those who may have suffered the
injury even if they had never come near the toxic
substance. But defendants are only liable for a percentage of
plaintiffs’ damages equal to the degree this exposure
increased plaintiffs’ risk of injury. For example, assume a
chemical increases the risk of cancer by 15 percent among
those exposed to the toxin. All exposed to this chemical who
later came down with cancer would be entitled to recover 15
percent of their total damages from those responsible for the
exposure.”).
57
   Brinker at 1318 (citation omitted).
58
   For example, the height of males and females correlates to
whether they play professional basketball. However, playing
professional basketball does not cause players to grow taller.
                              18
                                18
       substantial, appropriate, persuasive and
       connecting factors, a fact finder may reasonably
       conclude that the hazard caused the condition
       absent persuasive proof to the contrary offered
       by the defendant.59

        In undertaking this inquiry, the fact finder considers
the following non-exhaustive list of factors:
        (1) the probability that plaintiff was exposed to
        ionizing radiation due to nuclear fallout from
        atmospheric testing at the . . . Test Site at rates
        in excess of natural background radiation; (2)
        that plaintiff's injury is of a type consistent with
        those known to be caused by exposure to
        radiation; and (3) that plaintiff resided in
        geographical proximity to the . . . Test Site . . . .
        Other factual connections may include but are
        not limited to such things as time and extent of
        exposure to fallout, radiation sensitivity factors
        such as age or special sensitivities of the
        afflicted organ or tissue, retroactive internal or
        external dose estimation by current researchers,
        a latency period consistent with a radiation
        etiology, or an observed statistical incidence of
        the alleged injury greater than the expected
        incidence in the same population.60

59
   Allen v. United States, 588 F. Supp. 247, 415 (D. Utah
1984), rev’d on other grounds, 816 F.2d 1417 (10th Cir.
1987).
60
   Id.; see also Restatement (Second) of Torts § 433 (1965)
(“The following considerations are in themselves or in
combination with one another important in determining
whether the [defendant’s] conduct is a substantial factor in
bringing about harm to another: (a) the number of other
factors which contribute in producing the harm and the extent
of the effect which they have in producing it; (b) whether the
actor’s conduct has created a force or series of forces which
are in continuous and active operation up to the time of the
harm, or has created a situation harmless unless acted upon by
other forces for which the actor is not responsible; (c) lapse of
time.”); see also O’Connell (proposing a species of
proportionality tests that allows compensation based upon

                                19
The problem here is that because this rule presents several
factors that courts can consider, consistency may be elusive
and courts addressing substantially identical circumstances
may reach different results. Nevertheless, this approach
appears to be the most promising and the most consistent with
the realities of the risk created by an activity that can expose a
population to radiation. It may be that the only realistic
approach is to compensate an identified population for the
increased risk occasioned by a given activity. I do not,
however, suggest that such nagging questions as the amount
of that compensation, identifying the population that is at
increased risk, or countless other factors lend themselves to
easy or equitable resolution.

       None of these approaches have yet gained wide
acceptance and, as should be evident from this discussion,
none of these approaches is close to perfect. Rather, they are
sorely needed attempts to adopt (or augment) the traditional
rules requiring a direct and linear cause-in-fact relationship
with no intervening causes, to the reality of exposure to
ionizing radiation resulting from human activities.

                     III. CONCLUSION

       For reasons I have explained, my concerns about some
of the District Court’s rulings are not sufficient to cause me to
conclude that the court erred in granting summary judgment
against these Plaintiffs and dismissing the complaint.
Problems with the Plaintiffs’ proof (and lack thereof) and the
Herculean task of trying to produce enough evidence to get to
a fact finder on the issue of causation are simply too
formidable for these claims to survive.

        As I have explained, this will almost always be the
case until state supreme courts, state legislatures and/or
Congress devise a way to more fairly address the very real
and substantial dangers posed by activities that increase the
risk of exposing communities to ionizing radiation. However,

increased risk once that risk exceeds a certain threshold. The
threshold is, of course, a policy matter and can be determined
by legislatures after hearings on this issue.).
                               20
                                 20
since that day is not yet here, I agree that Defendants were
entitled to summary judgment. I can only hope that the dues
that we pay for the comforts of living in the atomic age will
one day not require us to forego remedies for the harmful
effects of the nuclear byproducts of that modernization, which
we are still trying to understand.




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