                          PUBLISHED

UNITED STATES COURT OF APPEALS
                FOR THE FOURTH CIRCUIT


CONSOLIDATION COAL COMPANY,           
                       Petitioner,
                 v.
BILLY D. WILLIAMS; DIRECTOR,                   No. 05-2108
OFFICE OF WORKERS’ COMPENSATION
PROGRAMS, UNITED STATES
DEPARTMENT OF LABOR,
                      Respondents.
                                      
            On Petition for Review of an Order of the
                     Benefits Review Board.
                          (04-756-BLA)

                      Argued: May 26, 2006

                      Decided: July 13, 2006

    Before MOTZ, GREGORY, and DUNCAN, Circuit Judges.



Petition denied by published opinion. Judge Gregory wrote the opin-
ion, in which Judge Motz and Judge Duncan joined.


                            COUNSEL

ARGUED: William Steele Mattingly, JACKSON & KELLY,
P.L.L.C., Morgantown, West Virginia, for Petitioner. Helen Hart Cox,
UNITED STATES DEPARTMENT OF LABOR, Office of Workers’
Compensation Programs, Washington, D.C.; Robert F. Cohen, Jr.,
COHEN, ABATE & COHEN, Morgantown, West Virginia, for
2                CONSOLIDATION COAL CO. v. WILLIAMS
Respondents. ON BRIEF: Howard M. Radzely, Solicitor of Labor,
Christian P. Barber, Counsel for Appellate Litigation, UNITED
STATES DEPARTMENT OF LABOR, Office of the Solicitor,
Washington, D.C., for Respondent Director, Office of Workers’ Com-
pensation Programs.


                              OPINION

GREGORY, Circuit Judge:

   Consolidation Coal Company ("Consolidation") petitions for
review of a final decision issued by the Benefits Review Board
("Board") of the Department of Labor ("DOL") affirming an award of
black lung benefits by an Administrative Law Judge ("ALJ") to Billy
D. Williams under the Federal Coal Mine Health & Safety Act of
1969 ("Act"), 30 U.S.C. § 901 et seq. For the reasons that follow, we
affirm the Board’s decision and deny the petition.

                                   I.

   Billy D. Williams was a coal miner for at least thirty years. In
1957, Williams began his employment as a mechanic and welder in
one of Consolidation’s preparation plants. In his last position, he per-
formed the same duties at one of Consolidation’s outside coal mine
shops from 1981 to 1987, at which point he retired due to shortness
of breath.

   On July 27, 1995, Williams filed his first claim for black lung ben-
efits before the DOL. While the claim was pending, Dr. Jerome J.
Lebovitz examined Williams on September 28, 1995, and sent a letter
dated November 9, 1995 with attached reports to Williams’s counsel.
Dr. Lebovitz’s letter stated his view that Williams was "permanently
and totally disabled secondary to the entity of Coal Worker’s Pneu-
moconiosis." J.A. 23. Despite receiving the letter, neither Williams
nor his counsel sent it to the DOL.

  At the DOL’s request, Dr. Andrzej J. Jaworski examined Williams
on October 30, 1995. Dr. Jaworski ultimately concluded that Wil-
                 CONSOLIDATION COAL CO. v. WILLIAMS                   3
liams’s respiratory impairments would not prevent him from perform-
ing his position as a shop mechanic. Thereafter, on January 11, 1996,
the DOL denied Williams’s claim for benefits.

   On June 6, 2001, Williams filed a second claim for black lung ben-
efits. In connection with this claim, five physicians examined Wil-
liams. First, Dr. Prasad V. Devabhaktuni took x-rays of Williams’s
lungs on July 31, 2001, and diagnosed Williams with hypertension,
chronic obstructive pulmonary disease secondary to smoking, and
coal worker’s pneumoconiosis secondary to occupational dust expo-
sure. During his deposition, Dr. Devabhaktuni testified that Wil-
liams’s chronic obstructive pulmonary disease resulted primarily from
his smoking habits, but that his coal mine dust exposure could have
contributed to the impairment. In addition, Dr. Devabhaktuni stated
that he diagnosed coal worker’s pneumoconiosis based on the x-rays
and Williams’s occupational history.

   Second, Dr. Joseph J. Renn, III examined Williams on October 31,
2001, and determined that Williams suffered from chronic bronchitis
with obstruction secondary to cigarette smoking. Dr. Renn also con-
cluded that coal mine dust exposure did not contribute to Williams’s
chronic bronchitis, and that Williams did not have pneumoconiosis.
Finally, Dr. Renn opined that Williams would be able to perform his
last position as a shop mechanic.

    Third, Dr. John E. Parker performed pulmonary function studies on
Williams, and reviewed the reports prepared by Drs. Devabhaktuni
and Renn. In reviewing Williams’s x-rays, Dr. Parker concluded that
they did not establish pneumoconiosis. Nevertheless, Dr. Parker cited
several studies in support of his view that "people with coal mine dust
exposure may have airflow obstruction with a normal radiograph
. . . ." J.A. 168. Based on these studies, Dr. Parker opined that people
with pneumoconiosis could exhibit small opacities of the 0/1 type,
and that it was unusual for an elderly patient such as Williams to have
rounded changes of that nature. For these reasons, Dr. Parker con-
cluded that Williams’s lungs likely contained some macules of pneu-
moconiosis.

  Dr. Parker further determined that Williams suffered from chronic
obstructive pulmonary disease resulting from a "combination of
4                CONSOLIDATION COAL CO. v. WILLIAMS
tobacco smoke inhalation as well as work place dust exposure." J.A.
85. Dr. Parker admitted that it was impossible to apportion the cause
of Williams’s airflow obstruction between exposure to cigarette
smoking or coal mine dust. However, Dr. Parker declined to rule out
coal dust exposure as a cause of Williams’s airflow obstruction using
Dr. Renn’s approach, which examined the mid-max expiratory flow
rate, because, in Dr. Parker’s view, the mid-max expiratory flow rate
was an unreliable indicator subject to daily variance. Dr. Parker thus
concluded that Williams’s lung injury definitely arose, at least in part,
from coal dust exposure "because he was a coal miner and . . .
because his chest radiograph was not normal." J.A. 179. Ultimately,
Dr. Parker opined that Williams’s breathing impairment would pre-
vent him from returning to his last position as a shop mechanic.

   Fourth, Dr. David M. Rosenberg reviewed the medical reports pre-
pared by Drs. Jaworski, Lebovitz, Devabhaktuni, and Renn, as well
as readings performed by other physicians of an x-ray taken on Octo-
ber 31, 2001. As an initial matter, Dr. Rosenberg determined that the
x-rays did not establish pneumoconiosis. Although Dr. Rosenberg
noted some moderate obstruction in Williams’s airways, he opined
that this condition was due to tobacco smoke, and not coal mine dust
exposure. Finally, because Williams’s maximum voluntary ventilation
(MVV) appeared normal, Dr. Rosenberg concluded that Williams
could return to his previous coal mining position.

   Fifth, Dr. Robert A.C. Cohen reviewed the medical reports pre-
pared by Drs. Devabhaktuni, Renn, Parker, and Rosenberg, and con-
ducted his own x-rays, physical exam, and pulmonary function tests
on July 15, 2003. Dr. Cohen concluded that Williams suffered from
coal worker’s pneumoconiosis based on the following considerations:
(1) Williams’s significant occupational exposure to coal mine dust for
thirty-one years; (2) Williams’s symptoms of chronic lung disease,
which included "progressively worsening shortness of breath and
cough and wheezing" and "sputum production"; (3) pulmonary func-
tion studies indicating moderate obstruction with diffusion impair-
ment; (4) arterial blood gases showing mild hypoxemia; and (5) a
chest x-ray indicating a positive reading for "opacities consistent with
classical pneumoconiosis at a profusion of 1/0." J.A. 223. Dr. Cohen
opined that even setting aside the x-ray evidence, he would still con-
                 CONSOLIDATION COAL CO. v. WILLIAMS                    5
clude that Williams demonstrated clinical and physiological signs of
pneumoconiosis.

   Dr. Cohen asserted that Drs. Renn, Rosenberg, and Jaworksi incor-
rectly concluded that coal mine dust exposure failed to contribute to
Williams’s obstructive lung disease. In citing several academic
studies, Dr. Cohen argued that coal mine dust can cause significant
airflow obstruction. Specifically, Dr. Cohen argued that these studies
established a correlation between coal mine dust exposure and sub-
stantial decreases in lung function, forced vital capacity, forced expir-
atory volume in one second, forced expiratory flow, and carbon
monoxide diffusion capacity. Ultimately, Dr. Cohen concluded that
Williams’s lung impairments would prevent him from performing his
previous job as a shop mechanic.1

   On September 11, 2003, the ALJ held a hearing on Williams’s sec-
ond claim for black lung benefits. Although the parties raised a host
of evidentiary issues, the ALJ expressed its intention to admit the
exhibits in their entirety, note the objections, and permit post-hearing
motions to strike. Williams subsequently presented testimony in sup-
port of his claim. Immediately after the close of Williams’s case,
Consolidation moved for summary judgment, asserting that Wil-
liams’s second claim was barred by the three-year time limitation trig-
gered by Dr. Lebovitz’s report under 20 C.F.R. § 725.308. The ALJ
provisionally denied the motion with leave to renew the motion in
post-hearing submissions.

   The ALJ then addressed Williams’s outstanding motion to compel
with respect to fourteen interrogatories served prior to the hearing.
Upon representation from counsel that Consolidation had disclosed all
of the records relevant to the experts’ diagnoses, Williams withdrew
the motion to compel with respect to interrogatories one through four
(which sought all x-rays, medical reports, and records relevant to Wil-
liams’s case).
  1
   Dr. Rosenberg subsequently responded in a written rebuttal to Dr.
Cohen’s report. In this letter, Dr. Rosenberg attempted to discredit the
scholarly citations provided by Dr. Cohen.
6               CONSOLIDATION COAL CO. v. WILLIAMS
   With respect to the remaining interrogatories, Consolidation argued
that they were irrelevant and overly burdensome. In rejecting Consoli-
dation’s objection to Williams’s interrogatory five, which sought the
number of referrals Consolidation had made to Dr. Renn, the ALJ
opined that it was relevant to "show bias and a number of referrals."
J.A. 401. After Williams agreed to limit the interrogatory to referrals
from Consolidation to its counsel, and to a time period of 1999 to
2002, the ALJ granted the motion to compel.

   With respect to interrogatory six, which sought the number of cases
in which Dr. Renn had found pneumoconiosis, the ALJ and Consoli-
dation became engaged in an increasingly heated exchange. Ulti-
mately, in granting the motion to compel with respect to interrogatory
six, the ALJ specifically stated "[t]his is discovery. I’m not making
any findings." J.A. 410.

   As the ALJ addressed interrogatories seven through fourteen,
which addressed issues of bias for Drs. Renn and Rosenberg, Consoli-
dation again asserted that the information sought was irrelevant to
bias. In granting the motion to compel with respect to these interroga-
tories, the ALJ stressed that the discovery requests were "reasonable."
J.A. 417.

   Following the hearing, the ALJ issued a formal order dated Decem-
ber 9, 2003 explaining its reasons for compelling discovery. In that
order, the ALJ stated that "[b]ased on many years of involvement in
expert testimony as an examiner, cross examiner, and administrative
law judge, I am convinced that doctors are no less biased by money
and by longstanding relations with patients, law firms and the law
firms’ clients than is anyone else." J.A. 458. After noting that Dr.
Renn testified frequently on behalf of coal mine companies for black
lung cases—and specifically, in cases involving Consolidation’s
counsel—the ALJ determined that the probative value of the discov-
ery relating to possible bias outweighed the burden of compliance.
The ALJ reserved decision on Williams’s motion to exclude the
reports of Drs. Renn and Rosenberg.

  After the Board denied Consolidation’s interlocutory appeal of the
ALJ’s December 9, 2003 order, the ALJ issued a second discovery
order dated March 2, 2004, directing Consolidation to release infor-
                 CONSOLIDATION COAL CO. v. WILLIAMS                    7
mation responsive to interrogatories five through fourteen. On April
14, 2004, an en banc panel of the Board denied Consolidation’s
request for reconsideration. Consolidation nevertheless refused to
comply with the discovery orders and did not disclose any of the
requested information.

   On April 16, 2004, the ALJ denied Consolidation’s renewed
motion for summary judgment concerning the timeliness of Wil-
liams’s second claim for black lung benefits, and set a briefing sched-
ule regarding the benefits determination. After considering the
parties’ briefs, the ALJ issued its decision granting Williams black
lung benefits on June 1, 2004. In its opinion, the ALJ resolved several
preliminary matters that are relevant to the present petition for review.
Specifically, the ALJ (1) granted Williams’s motion to strike Dr.
Lebovitz’s report; (2) denied Consolidation’s request to reassign the
case to another judge; (3) denied Consolidation’s third motion for dis-
missal based on the statute of limitations; and (4) declined to strike
the reports of Drs. Renn and Rosenberg as a discovery sanction for
Consolidation’s noncompliance with the ALJ’s December 9, 2003
and March 2, 2004 orders. The ALJ then expressed its intent to treat
the reports proffered by Drs. Renn and Rosenberg "as if [Consolida-
tion] had complied with discovery and as if its responses to that dis-
covery had demonstrated significant bias by both witnesses toward
employers as a class and [its law firm’s] clients as a class." J.A. 490.

   With respect to its merits determination, the ALJ credited the opin-
ions of Drs. Parker and Cohen over the opinions of Drs. Renn and
Rosenberg. In so doing, the ALJ made the following findings of fact:
(1) Dr. Parker had credentials that were superior to those of Drs. Renn
and Rosenberg; (2) the opinions of Drs. Cohen and Parker were more
reasoned and persuasive than the opinions of Drs. Renn and Rosen-
berg; (3) Drs. Renn and Rosenberg did not exhibit a contemporary
knowledge of medical research; and (4) Drs. Renn and Rosenberg
misunderstood the heavy-lifting aspects of Williams’s work.

   On August 8, 2005, the Board affirmed the ALJ’s disposition of the
matter in its entirety. Consolidation has petitioned for review of the
Board’s decision, asserting that (1) Williams’s second claim for bene-
fits was untimely; (2) the ALJ was biased against Consolidation and
coal mine companies in general; (3) the ALJ abused its discretion in
8               CONSOLIDATION COAL CO. v. WILLIAMS
making certain discovery and evidentiary rulings; and (4) the ALJ
improperly credited the opinions of Drs. Cohen and Parker in award-
ing benefits to Williams.

                                  II.

                                  A.

   We apply de novo review to the legal conclusions made by the
Board and the ALJ. Consolidation Coal Co. v. Held, 314 F.3d 184,
186 (4th Cir. 2002). In addition, we engage in an independent review
of the record to determine whether substantial evidence exists to sup-
port the ALJ’s findings of fact. Island Creek Coal Co. v. Compton,
211 F.3d 203, 207 (4th Cir. 2000). Substantial evidence is "‘more
than a mere scintilla.’" Milburn Colliery Co. v. Hicks, 138 F.3d 524,
528 (4th Cir. 1998) (quoting Consol. Edison Co. v. NLRB, 305 U.S.
197, 229 (1938)). Specifically, it is "such relevant evidence as a rea-
sonable mind might accept as adequate to support a conclusion." Id.
at 528 (internal quotation marks and citations omitted).

                                  B.

   Consolidation first contends that Williams’s black lung claim,
which was filed more than three years after he received Dr.
Lebovitz’s diagnosis of totally disabling coal worker’s pneumoconio-
sis, was untimely. Section 932 of Title 30 provides that any claim for
benefits "shall be filed within three years after whichever of the fol-
lowing occurs later—(1) a medical determination of total disability
due to pneumoconiosis; or (2) March 1, 1978." 30 U.S.C. § 932(f).
The implementing regulation, 20 C.F.R. § 725.308, further explains
that the three-year statute of limitations is triggered when the miner
receives a medical determination of total disability arising from pneu-
moconiosis:

    A claim for benefits filed under this part by, or on behalf of,
    a miner shall be filed within three years after a medical
    determination of total disability due to pneumoconiosis
    which has been communicated to the miner or a person
    responsible for the care of the miner, or within three years
                 CONSOLIDATION COAL CO. v. WILLIAMS                    9
      after the date of enactment of the Black Lung Benefits
      Reform Act of 1977, whichever is later.

20 C.F.R. § 725.308(a).

   The facts of this appeal present an unusual situation in which Wil-
liams received Dr. Lebovitz’s diagnosis in 1995, but failed to submit
that diagnosis prior to the DOL’s ultimate denial of his first claim for
black lung benefits in 1996. Thereafter, Williams filed his second
claim for benefits in 2001—six years after he learned of Dr.
Lebovitz’s diagnosis. Thus, we must determine, as a threshold matter,
whether Williams’s receipt of Dr. Lebovitz’s report triggered the
three-year statute of limitations for his second claim.

   This issue of first impression causes us to consider our en banc
decision in Lisa Lee Mines v. Director, Office of Workers’ Compensa-
tion Programs, 86 F.3d 1358 (4th Cir. 1996), which discussed the
appropriate standard applied to a miner’s subsequent claim for black
lung benefits in light of a prior denial of benefits. In Lisa Lee Mines,
we recognized the finality considerations that attach to a prior denial
of black lung benefits. Id. at 1361 (holding that a prior denial of bene-
fits is "‘final’ in a legal sense"). Specifically, the legal conclusion
attendant with a prior denial—i.e., that the miner was not eligible for
benefits at the time of that decision—must be accepted as correct and
"is as off-limits to criticism by the respondent as by the claimant." Id.
This rule of finality, we reasoned, is responsive to the general diffi-
culty in accurately diagnosing pneumoconiosis:

      Accepting the correctness of a final judgment is more than
      legalistic tunnel vision; it is a practical—perhaps the only
      practical—way to discern a concrete form in the mists of the
      past. The ease we might feel at second-guessing this final
      judgment ought not tempt us to overestimate our retrospec-
      tive perspicacity; most black lung claims involve a mixed
      bag of test results and wildly divergent medical opinions.
      The final decision of the ALJ (or BRB or claims examiner)
      on the spot is the best evidence of the truth at the time.

Id.
10               CONSOLIDATION COAL CO. v. WILLIAMS
   Because a prior denial is both final and correct, Lisa Lee Mines
rejected the test articulated by the Seventh Circuit in Sahara Coal Co.
v. Director, Office of Workers’ Compensation Programs, 946 F.2d
554 (7th Cir. 1991), which required the miner to show that he "did
not have black lung disease at the time of the first application but has
since contracted it and become totally disabled by it, or that his dis-
ease has progressed to the point of becoming totally disabling
although it was not at the time of the first application." Id. at 556. In
so doing, we reasoned that Sahara Coal improperly "permit[ted]—in
fact demand[ed]—a plenary review of the evidence behind the first
claim" by forcing the miner to affirmatively prove that each of the
ALJ’s adverse determinations underlying the prior denial was correct.
Lisa Lee Mines, 86 F.3d at 1363. To accommodate the finality consid-
erations that attach to a prior denial, we instead adopted a standard
that presumed that the factual determinations underlying a prior
denial are correct and simply required the miner to disprove the "con-
tinuing validity" of at least one of the elements previously adjudicated
against him in showing a material change in conditions. Id.

   Although Lisa Lee Mines primarily addressed the appropriate test
applied to subsequent claims, the principles of finality expressed
within the decision clearly bear on this appeal. In light of Lisa Lee
Mines, we must accept the DOL’s denial of Williams’s first claim in
1996 as final and correct, regardless of whether the DOL reviewed
Dr. Lebovitz’s diagnosis in adjudicating the claim. For this reason,
the DOL’s legal determination that Williams was not totally disabled
due to coal worker’s pneumoconiosis as of January 11, 1996 neces-
sarily refuted Dr. Lebovitz’s diagnosis that Williams had contracted
the disease by that point. Moreover, because we must treat Dr.
Lebovitz’s diagnosis, for legal purposes, as a misdiagnosis in light of
the denial of Williams’s first claim, we must similarly conclude that
the (mis)diagnosis had no effect on the statute of limitations for his
second claim. See Wyoming Fuel Co. v. Director, Office of Workers’
Comp. Programs, 90 F.3d 1502, 1507 (10th Cir. 1996) ("[A] final
finding by an Office of Workers’ Compensation Program adjudicator
that the claimant is not totally disabled due to pneumoconiosis repudi-
ates any earlier medical determination to the contrary and renders
prior medical advice to the contrary ineffective to trigger the running
of the statute of limitations." (emphasis added)).
                   CONSOLIDATION COAL CO. v. WILLIAMS                       11
   Our conclusion is consistent with the Act’s view of pneumoconio-
sis, its treatment of subsequent claims, and its remedial purpose. First,
the Act explicitly recognizes that pneumoconiosis is a "latent and pro-
gressive disease. . . ." 20 C.F.R. § 718.201(c). Based on this under-
standing of pneumoconiosis, we have acknowledged that "nothing
bars or should bar claimants from filing claims seriatim, and the regu-
lations recognize that many will." Lisa Lee Mines, 86 F.3d at 1362.
See also id. ("The health of a human being is not susceptible to once-
in-a-lifetime adjudication." (citing treatise)); id. at 1364
("[Pneumoconiosis] is a progressive disease, and no rational system
of law or of medicine could stand on the proposition that it can or
must be measured only once."). Although Consolidation relies on cer-
tain dicta expressed in the Sixth Circuit’s decision in Tennessee Con-
solidated Coal Co. v. Kirk, 264 F.3d 602, 608 (6th Cir. 2001), which
suggests that misdiagnoses can trigger the statute of limitations for
subsequent claims,2 the progressive nature of the disease dictates that
"a claimant must be free to reapply for benefits if his first filing was
premature." Sharondale Corp. v. Ross, 42 F.3d 993, 996 (6th Cir.
1994). We see no reason why a miner who has been denied benefits
  2
   Specifically, the Sixth Circuit stated in Tennessee Consolidated Coal:
      The three-year limitations clock begins to tick the first time that
      a miner is told by a physician that he is totally disabled by pneu-
      moconiosis. This clock is not stopped by the resolution of the
      miner’s claim or claims, and . . . the clock may only be turned
      back if the miner returns to the mines after a denial of benefits.
      There is thus a distinction between premature claims that are
      unsupported by a medical determination, like Kirk’s 1979, 1985,
      and 1988 claims, and those claims that come with or acquire
      such support. Medically supported claims, even if ultimately
      deemed "premature" because the weight of the evidence does not
      support the elements of the miner’s claim, are effective to begin
      the statutory period. . . . Three years after such a determination,
      a miner who has not subsequently worked in the mines will be
      unable to file any further claims against his employer, although,
      of course, he may continue to pursue pending claims.
Tennessee Consol. Coal, 264 F.3d at 608 (footnote omitted). A different
panel of the Sixth Circuit later disavowed this dicta in an unpublished
disposition. Peabody Coal Co. v. Director, Office of Workers’ Comp.
Programs, 48 Fed. Appx. 140, 147 (6th Cir. Oct. 2, 2002).
12               CONSOLIDATION COAL CO. v. WILLIAMS
because he presented legally insufficient medical evidence must be
forever barred from bringing a new claim even if he later develops
pneumoconiosis. See Wyoming Fuel, 90 F.3d at 1507 ("[A] claimant
should not be barred from bringing a duplicate claim when his or her
first claim was premature because the claimant’s conditions had not
yet progressed to the point where the claimant met the Act’s defini-
tion of total disability due to pneumoconiosis." (internal citations
omitted)).

   Second, the Act’s treatment of subsequent claims reveals the inher-
ent unfairness in running the statute of limitations based on Dr.
Lebovitz’s diagnosis. In balancing the Act’s view of pneumoconiosis
as a latent and progressive disease with the need for administrative
repose, the duplicate claims regulation, 20 C.F.R. § 725.309(d),
directs that subsequent claims "shall be denied" based on the earlier
denial unless the miner demonstrates a material change in conditions.
Under Lisa Lee Mines’s construction of § 725.309(d), the miner must
"prove, under all of the probative medical evidence of his condition
after the prior denial, at least one of the elements previously adjudi-
cated against him." Lisa Lee Mines, 86 F.3d at 1362.3 Thus, only new
evidence following the denial of the previous claim, rather than evi-
dence predating the denial, can sustain a subsequent claim. Id. See
also Wyoming Fuel, 90 F.3d at 1509 ("In considering whether a
claimant established a material change, the ALJ can consider only
new evidence which relates to the conditions at the time of the second
claim."); Labelle Processing Co. v. Swarrow, 72 F.3d 308, 316 (3d
Cir. 1996) ("If [the miner’s] earlier exposure to coal dust caused his
present disability and pneumoconiosis was merely latent at the time
of his initial application for benefits but has since become manifest,
[the miner] would be entitled to prove that the disease has progressed
to the point of total disability since the filing of his original claim.");
Sharondale, 42 F.3d at 996 ("[T]he claimant cannot prevail on a
duplicate claim unless he shows a ‘material change’ in his condition;
  3
   In light of the fact that subsequent claims measure the miner’s wors-
ened condition after a prior denial, subsequent claims avoid res judicata
issues because "common-law res judicata has no applicability where the
issue is a person’s health at two different times." Lisa Lee Mines, 86 F.3d
at 1362 n.9.
                 CONSOLIDATION COAL CO. v. WILLIAMS                  13
thus, the critical evidence in assessing whether to reopen the claim is
the evidence accruing since the previous denial.").

   In light of the standard articulated in Lisa Lee Mines, we note that
Dr. Lebovitz’s diagnosis, which related solely to Williams’s condition
in 1995, could not have sustained a subsequent claim that his condi-
tion had materially worsened since the initial denial of benefits in
1996. It would be illogical and inequitable to hold that a diagnosis
that could not sustain a subsequent claim could nevertheless trigger
the statute of limitations for such a claim.

   Third, the Act’s remedial nature instructs us to interpret its provi-
sions favorably toward miners. See Labelle, 72 F.3d at 318 ("[C]ourts
should liberally construe remedial legislation, such as the [Act], so as
to include the largest number of claimants within its entitlement pro-
visions."). Keeping the remedial purpose in mind, we recognize that
a rule holding that misdiagnoses could ultimately bar claims for bene-
fits will create a substantial chilling effect discouraging miners from
seeking early examinations and second opinions. See Peabody Coal,
48 Fed. Appx. at 147 ("If a miner knows that a misdiagnosis will ulti-
mately mean that he can never again seek benefits should he eventu-
ally contract this progressive disease, he will be less likely to be
proactive in seeking medical advice during the early stages."). The
health consequences stemming from this chilling effect would be
undoubtedly dire. Moreover, we are cognizant of the difficulty in
accurately diagnosing pneumoconiosis. Thus, the rule we fashion
today simply seeks to reconcile the "mixed bag of test results and
wildly divergent medical opinions" usually attendant with black lung
claims with the Act’s remedial purpose of awarding benefits to
deserving miners. Lisa Lee Mines, 86 F.3d at 1361.

   We therefore hold that a medical determination later deemed to be
a misdiagnosis of pneumoconiosis by virtue of a superseding denial
of benefits cannot trigger the statute of limitations for subsequent
claims. Applying this rule to the facts of this appeal, we find that Dr.
Lebovitz’s diagnosis did not trigger the statute of limitations for Wil-
liams’s second claim. Moreover, having no further objections from
Consolidation, we presume that Williams’s second claim was other-
wise timely. 20 C.F.R. § 725.308(c) (setting forth a rebuttable pre-
14               CONSOLIDATION COAL CO. v. WILLIAMS
sumption that the miner’s claim was timely). Accordingly, we
conclude that Williams’s second claim was timely.

                                    C.

   Having disposed of the timeliness issue, we turn to Consolidation’s
assertion that the Board improperly affirmed the ALJ’s decision
declining to recuse itself from the case. Specifically, Consolidation
argues that the ALJ’s comments at the hearing and within the discov-
ery order demonstrated its bias against coal mine companies. We find
no merit in these contentions.

   The Supreme Court has explained that bias in judicial decision-
making refers to "a favorable or unfavorable disposition or opinion
that is somehow wrongful or inappropriate either because it is unde-
served, . . . rests upon knowledge that the subject ought not to pos-
sess[,] . . . [or] is excessive in degree . . . ." Liteky v. United States,
510 U.S. 540, 550 (1994). In this context, the Court set forth the stan-
dard for finding judicial bias:

     [O]pinions formed by the judge on the basis of facts intro-
     duced or events occurring in the course of the current pro-
     ceedings, or of prior proceedings, do not constitute a basis
     for a bias or partiality motion unless they display a deep-
     seated favoritism or antagonism that would make fair judg-
     ment impossible. Thus, judicial remarks during the course of
     a trial that are critical or disapproving of, or even hostile to,
     counsel, the parties, or their cases, ordinarily do not support
     a bias or partiality challenge. They may do so if they reveal
     an opinion that derives from an extrajudicial source; and
     they will do so if they reveal such a high degree of favorit-
     ism or antagonism as to make fair judgment impossible.

Id. at 555.

  Here, the challenged remarks followed Consolidation’s objection to
Williams’s interrogatory six, which sought the number of cases in
which Dr. Renn had diagnosed pneumoconiosis. The ensuing collo-
quy between Consolidation’s counsel and the ALJ proceeded as fol-
lows:
       CONSOLIDATION COAL CO. v. WILLIAMS               15
COUNSEL:             Judge, that’s impossible for me
                     to determine without doing [sic]
                     back through every client.

JUDGE CAMPBELL:      Well then, you’re going to have
                     to do it.

COUNSEL:             What does that show us? That
                     doesn’t show us anything.

JUDGE CAMPBELL:      It shows bias. Come on, [Coun-
                     sel], you know that.

COUNSEL:             No, it doesn’t.

JUDGE CAMPBELL:      This area of the law is shot
                     through with hacks. And I’m
                     frankly tired of it.

COUNSEL:             Judge, are you calling Dr. Renn
                     a hack?

JUDGE CAMPBELL:      No. But he might be. He per-
                     fectly well might be.

COUNSEL:             No.

JUDGE CAMPBELL:      And this is what we’re trying to
                     find out.

COUNSEL:             No.

JUDGE CAMPBELL:      Stop arguing. I’ve let you go as
                     far as I’m going to let you go.
                     That’s it.

COUNSEL:             Your Honor?

JUDGE CAMPBELL:      No. You’re getting me upset
                     now.
16               CONSOLIDATION COAL CO. v. WILLIAMS
J.A. 408-09 (emphases added). In its written order granting Wil-
liams’s motion to compel, the ALJ expressed its concern that "[b]ased
on many years of involvement in expert testimony as an examiner,
cross examiner, and administrative law judge, I am convinced that
doctors are no less biased by money and by longstanding relations
with patients, law firms and the law firms’ clients than is anyone
else." J.A. 458. After noting that Drs. Renn and Rosenberg testified
frequently on behalf of coal mine companies, see J.A. 458-59,4 the
ALJ determined that Williams’s requested discovery related to bias
was appropriate.

   In our view, the ALJ’s comments express the unremarkable propo-
sition that experts can be biased, and that doctors in coal mine cases
are no less subject to bias than other experts. See Woodward v. Direc-
tor, Office of Workers’ Comp. Programs, 991 F.2d 314, 321 (6th Cir.
1993) ("[E]xperts hired exclusively by either party tend to obfuscate
rather than facilitate a true evaluation of a claimant’s case."). See also
Grizzle v. Picklands Mather and Co./Chisolm Mines, 994 F.2d 1093,
1101 (4th Cir. 1993) (Hall, J., dissenting) ("Disability, or the lack
thereof, seems inevitably in the eye of the paid beholder." (emphasis
added)). Upon representation from counsel, the ALJ properly deter-
mined that the frequency with which Drs. Renn and Rosenberg testi-
fied on behalf of coal mine companies justified discovery concerning
potential bias. See Underwood v. Elkay Mining, Inc., 105 F.3d 946,
951 (4th Cir. 1997) ("[T]he ALJ should consider the qualifications of
the experts, the opinions’ reasoning, their reliance on objectively
determinable symptoms and established science, their detail of analy-
sis, and their freedom from irrelevant distractions and prejudices."
(emphasis added)); id. ("[T]he ALJ should consider whether an opin-
ion was, to any degree, the product of bias in favor of the party retain-
ing the expert and paying the fee.").

   Similarly, the tone and tenor of frustration expressed in the ALJ’s
comments do not, in and of themselves, establish bias against Consol-
idation. Liteky, 510 U.S. at 555-56 ("Not establishing bias or partial-
ity, however, are expressions of impatience, dissatisfaction,
annoyance, and even anger, that are within the bounds of what imper-
  4
   The ALJ also noted that Dr. Renn frequently submitted reports on
behalf of Consolidation’s counsel. J.A. 458.
                 CONSOLIDATION COAL CO. v. WILLIAMS                   17
fect men and women, even after having been confirmed as federal
judges, sometimes display."). At the outset of the hearing, the ALJ
stated that it did not want to resolve the evidentiary issues without
written submissions. Consolidation nevertheless repeatedly raised
outstanding discovery issues, including Williams’s motion to compel
with respect to its interrogatories seeking discovery related to bias.
Throughout the discussion of these interrogatories, Consolidation
interrupted the ALJ, continued to press objections, and reiterated its
position that the requested discovery was not relevant. Given coun-
sel’s behavior, it is not surprising that the ALJ became annoyed.
Liteky, 510 U.S. at 556 ("A judge’s ordinary efforts at courtroom
administration—even a stern and short-tempered judge’s ordinary
efforts at courtroom administration—remain immune.").

   Finally, we note that, to the extent that Consolidation challenges
the discovery order itself as indicative of bias, "judicial rulings alone
almost never constitute a valid basis for a bias or partiality ruling."
Liteky, 510 U.S. at 555 (internal citation omitted). Accordingly, we
affirm the Board’s determination that the ALJ did not demonstrate
bias against Consolidation or coal mine companies in general.

                                   D.

   Consolidation further challenges several discovery and evidentiary
rulings made by the ALJ. Specifically, Consolidation argues that the
ALJ erred by (1) reserving ruling on and later granting Williams’s
discovery requests even though they sought irrelevant information,
imposed burdensome costs, and were untimely; (2) striking Dr.
Lebovitz’s diagnosis from the record and substituting Dr. Cohen’s
report; and (3) applying an adverse inference to the reports submitted
by Drs. Renn and Rosenberg as a discovery sanction and excluding
their supplemental reports. We shall address each contention seriatim.

                                   1.

   Consolidation first contends that the ALJ’s decision to reserve rul-
ing on Williams’s motion to compel deprived it of a meaningful hear-
ing. We disagree. Section 725.455 of Title 20 of the Code of Federal
Regulations provides that "[t]he conduct of the hearing and the order
in which allegations and evidence shall be presented shall be within
18               CONSOLIDATION COAL CO. v. WILLIAMS
the discretion of the administrative law judge and shall afford the par-
ties an opportunity for a fair hearing." 20 C.F.R. § 725.455. No statute
or regulation, however, requires an administrative law judge to rule
on discovery motions prior to the merits hearing. In light of the con-
siderable discretion afforded to administrative law judges in conduct-
ing hearings, we decline to find error in the ALJ’s decision to reserve
ruling on Williams’s motion.

   We similarly find no abuse of discretion with respect to the ALJ’s
decision to grant Williams’s motion to compel. As discussed above,
the ALJ properly determined that discovery concerning potential bias
was relevant to impeaching the credibility of Drs. Renn and Rosen-
berg. Moreover, Consolidation has failed to offer anything more than
conclusory assertions regarding the potentially burdensome aspect of
the discovery requests, despite having numerous opportunities to sub-
stantiate its objections before the ALJ.

   In addition, we reject Consolidation’s remaining argument that the
ALJ could not grant the motion to compel because the requested dis-
covery would be untimely and therefore inadmissible under 20 C.F.R.
§ 725.456(b). Section 725.456(b) provides that where a party seeks to
admit documentary evidence that was not exchanged twenty days
prior to the hearing and cannot establish good cause for its lateness,
the ALJ shall exclude the evidence or remand to the district director
for consideration of the evidence. In this instance, however, Consoli-
dation never disclosed the requested discovery even though Williams
served the interrogatories on July 11, 2003—two months prior to the
hearing. Consolidation’s own recalcitrance in refusing to disclose the
requested discovery therefore created any untimeliness issues.
Accordingly, we conclude that the ALJ properly exercised its discre-
tion in granting Williams’s motion to compel.

                                   2.

   Consolidation next argues that the ALJ abused its discretion by
permitting Williams to substitute Dr. Cohen’s medical report for Dr.
Lebovitz’s medical report. Considering that 20 C.F.R. § 725.414 lim-
its a miner to submitting two medical reports in support of his claim,
we believe that the ALJ properly permitted Williams to designate the
two reports (out of the three filed) he wished to submit in support of
                  CONSOLIDATION COAL CO. v. WILLIAMS                     19
his claim. See Dempsey v. Sewell Coal Co., 23 BLR 1-47 (BRB 2004)
(en banc) (holding that "the administrative law judge acted within his
discretion when he permitted employer to select which two of its
three medical reports employer would submit as its affirmative case").5
We therefore find that the ALJ did not abuse its discretion in striking
Dr. Lebovitz’s report and admitting Dr. Cohen’s report in its place.

                                     3.

   Consolidation further maintains that the ALJ erred in applying an
adverse inference of bias to the reports of Drs. Renn and Rosenberg.
Significantly, however, Consolidation has not challenged the ALJ’s
other reasons for discrediting Drs. Renn and Rosenberg. These rea-
sons were articulated as follows: (1) Dr. Parker had credentials that
were superior to those of Drs. Renn and Rosenberg; (2) the opinions
of Drs. Cohen and Parker were more reasoned and persuasive than the
opinions of Drs. Renn and Rosenberg; (3) Drs. Renn and Rosenberg
did not exhibit a contemporary knowledge of medical research; and
(4) Drs. Renn and Rosenberg misunderstood the heavy-lifting aspects
of Williams’s work. Thus, with or without the application of the
adverse inference, the ALJ had proper reasons for finding that the
reports proffered by Drs. Renn and Rosenberg were unpersuasive.

   In addition, Consolidation has failed to provide any indication that
the supplemental reports proffered by Drs. Renn and Rosenberg
would have cured the defects the ALJ found in their original reports.
Accordingly, we find that any errors concerning the ALJ’s consider-
ation of the reports proffered by Drs. Renn and Rosenberg were harm-
less.6 See Ngarurih v. Ashcroft, 371 F.3d 182, 190 n.8 (4th Cir. 2004)
(reversal of an administrative ruling is unnecessary if the error was
harmless).
  5
    We further note, as the Board pointed out, that because the ALJ
addressed Dr. Lebovitz’s report in connection with the timeliness issue,
Consolidation was not unduly prejudiced by the exclusion of the report.
  6
    In addition, any error arising from the exclusion of x-ray rebuttal evi-
dence is harmless because the ALJ determined that the x-ray evidence
did not establish medical pneumoconiosis.
20               CONSOLIDATION COAL CO. v. WILLIAMS
                                  E.

   Finally, Consolidation raises several challenges to the ALJ’s fac-
tual findings underlying its ultimate award of benefits to Williams.7
These contentions are without merit.

   Consolidation first contends that the ALJ failed to express the
weight afforded to Dr. Devabhaktuni’s opinion. However, the record
demonstrates that the ALJ explicitly discredited Dr. Devabhaktuni’s
opinion because he "seemed to have been testifying in terms of total
disability for purposes of Social Security benefits entitlement . . . ."
J.A. 494. Thus, this argument is unsupported by the record.

   Consolidation next asserts that Dr. Parker’s failure to apportion
Williams’s lung impairment between cigarette smoke and coal mine
dust exposure discredited his medical report. Although Dr. Parker
could not establish the precise percentage of Williams’s lung obstruc-
tion attributable to cigarette smoke and coal mine dust exposure,
"doctors need not make such particularized findings." Freeman
United Coal Mining Co. v. Summers, 272 F.3d 473, 483 (7th Cir.
2001). See also Cornett v. Benham Coal, Inc., 227 F.3d 569, 576 (6th
Cir. 2000) (holding that the miner "was not required to demonstrate
that coal dust was the only cause of his current respiratory prob-
lems"); Consol. Coal Co. v. Swiger, 98 Fed. Appx. 227, 237-38 (4th
Cir. May 11, 2004) (same). Indeed, "[t]he ALJ needs only to be per-
suaded, on the basis of all available evidence, that pneumoconiosis is
a contributing cause of the miner’s disability." Freeman United Coal
Mining, 272 F.3d at 483. See also 20 C.F.R. § 718.201(b) (the miner
is required to show that his lung disease was "significantly related to,
or substantially aggravated by," coal mine dust exposure).

   Although Dr. Parker acknowledged that either cigarette smoking or
coal mine dust could have caused Williams’s airflow obstruction, he
explained that the mid-max expiratory rate, the factor upon which Dr.
Renn relied to rule out coal mine dust as a potential cause of Wil-
liams’s airflow obstruction, was an unreliable variable. In addition,
Dr. Parker supported his view that coal mine dust contributed to Wil-
  7
   Because Williams filed his claim in 2001, his claim is subject to the
permanent regulations set forth in 20 C.F.R. § 718 et seq.
                CONSOLIDATION COAL CO. v. WILLIAMS                  21
liams’s airflow obstruction by citing four types of scientific studies:
(1) studies comparing lung function in miners and non-miners; (2)
studies of the patterns of lung functions and symptoms related to the
miner’s level of coal mine dust exposure; (3) studies of the mortality
rate from chronic obstructive pulmonary disease due to coal mine dust
exposure; and (4) autopsy studies of the relationship between emphy-
sema in coal miners with their previous exposure to coal mine dust.
Dr. Parker further substantiated his conclusion that Williams had suf-
fered totally disabling coal worker’s pneumoconiosis by relying on
the rounded abnormalities apparent on Williams’s x-rays, the pulmo-
nary function studies and diffusion capacity test, and Williams’s
extensive history of coal mine employment.

   We believe that the ALJ properly relied on Dr. Parker’s well-
reasoned report in determining that Williams was entitled to black
lung benefits. Any error arising from the ALJ’s reliance on additional
sources, such as Dr. Cohen’s report, was therefore harmless. Accord-
ingly, we find that the ALJ’s benefits determination is supported by
substantial evidence, and affirm the award.

                                 III.

   We agree with the Board’s determination that the ALJ committed
no errors of law and made findings of fact supported by substantial
evidence. We also conclude that the award of black lung benefits to
Williams was appropriate, and therefore deny Consolidation’s petition
in its entirety.

                                                 PETITION DENIED
