 United States Court of Appeals
          FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued September 24, 2014             Decided October 24, 2014

                          No. 12-1228

   NATIONAL OILSEED PROCESSORS ASSOCIATION, ET AL.,
                     PETITIONERS

                                v.

OCCUPATIONAL SAFETY & HEALTH ADMINISTRATION, ET AL.,
                   RESPONDENTS

      AMERICAN FEED INDUSTRY ASSOCIATION, ET AL.,
                     INTERVENORS


        On Petition for Review of a Final Rule of the
        Occupational Safety & Health Administration


     Donald C. McLean argued the cause for petitioners and
intervenor for petitioners. With him on the briefs were Marc L.
Fleischaker and Valerie N. Butera. Philip C. Olsson, Gary H.
Baise, and Anson M. Keller Sr. entered appearances.

     Louise M. Betts, Attorney, Occupational Safety & Health
Administration, argued the cause for respondents. On the briefs
were Joseph M. Woodward, Associate Solicitor for
Occupational Safety and Health, at the time the briefs were filed,
Ann Rosenthal, Acting Associate Solicitor for Occupational
Safety and Health, Heather R. Phillips, Counsel for Appellate
Litigation, and Edmund C. Baird, Attorney. Anne R. Ryder,
                               2

Attorney, U.S. Department of Labor, entered an appearance.

     Randy S. Rabinowitz and Stephen A. Yokich were on the
brief for intervenors Change to Win, et al. in support of
respondents. Steven H. Wodka entered an appearance.

    Before: HENDERSON, ROGERS and GRIFFITH, Circuit
Judges.

    Opinion for the Court filed by Circuit Judge ROGERS.

     Rogers, Circuit Judge: Responding to international efforts
to harmonize the requirements for identification and labeling of
hazardous chemicals, the Occupational Safety and Health
Administration (“OSHA”) revised its Hazard Communication
Standard in 2012. See Hazard Communication, 77 Fed. Reg.
17,574 (Mar. 26, 2012) (“Final Rule”). That standard requires
employers across industries to develop a program for classifying
the dangers of workplace chemicals and conveying those
dangers to their employees. See 29 C.F.R. § 1910.1200.
Petitioners (and intervenor for petitioners), whose members
include numerous businesses that handle and process grain and
other agricultural products, seek vacatur of the Final Rule as it
applies to combustible dust. For the following reasons, we deny
the petition for review.

                               I.

     The Occupational Safety and Health Act of 1970 authorizes
the Secretary of Labor to promulgate workplace safety or health
standards, 29 U.S.C. § 655(b), including prescribing the use of
labels or other warnings “to insure that employees are apprised
of all hazards to which they are exposed.” Id. § 655(b)(7). Two
longstanding OSHA standards and an ongoing rulemaking are
relevant here.
                               3

      The Hazard Communication Standard was promulgated in
1983 and initially applied only to manufacturers. See 48 Fed.
Reg. 53,280 (Nov. 25, 1983) (codified at 29 C.F.R.
§ 1910.1200). In 1987, OSHA made the Standard applicable to
all employers with employees exposed to hazardous chemicals
in the workplace. See 52 Fed. Reg. 31,852 (Aug. 24, 1987).
The Standard is designed to “address comprehensively the issue
of classifying the potential hazards of chemicals, and
communicating information concerning hazards and appropriate
protective measures to employees.”                  29 C.F.R.
§ 1910.1200(a)(2). “Rather than attempting to identify every
hazardous chemical, the [Hazard Communication Standard]
‘places primary responsibility for determining which products
are hazardous on the chemical manufacturer or importer.’”
Nat’l Ass’n of Mfrs. v. OSHA, 485 F.3d 1201, 1202 (D.C. Cir.
2007) (quoting United Steelworkers of Am., AFL-CIO-CLC v.
Auchter, 763 F.2d 728, 739 (3d Cir. 1985)). Manufacturers and
importers must evaluate and classify each chemical they produce
or import to determine whether it is a “hazardous chemical.”
See 29 C.F.R. §§ 1910.1200(c), (d). They must ensure that
hazardous chemicals are labeled for downstream users and
create material safety data sheets that explain the hazard and
applicable safety procedures in detail. Id. §§ 1910.1200(f), (g).
Employers must develop, implement, and maintain “a written
hazard communication program” to inform employees about
hazardous chemicals present in the workplace through labels and
safety data sheets, and they must train employees on the
detection of hazardous chemical releases, safe handling
methods, and emergency procedures. Id. §§ 1910.1200(b)(1),
(e), (h).

    OSHA also promulgated a safety standard for grain
handling in 1987. See Grain Handling Facilities, 52 Fed. Reg.
49,592 (Dec. 31, 1987) (codified at 29 C.F.R. § 1910.272)
(“Grain Handling Standard”). It sets workplace “requirements
                                 4

for the control of grain dust fires and explosions, and certain
other safety hazards associated with grain handling facilities,”
and applies to “grain elevators, feed mills, flour mills, rice mills,
dust pelletizing plants, dry corn mills, soybean flaking
operations, and the dry grinding operations of soycake.” 29
C.F.R. §§ 1910.272(a), (b)(1). Employers are to control
“fugitive grain dust,” which is defined as “combustible dust
particles” of a certain size. Id. §§ 1910.272(c), (j).

    In 2006, OSHA issued an advanced notice of proposed
rulemaking requesting comments on revisions to the Hazard
Communication Standard to implement the Globally
Harmonized System. See 71 Fed. Reg. 53,617 (Sept. 12, 2006).
This is a uniform international chemical labeling system, which
OSHA had been involved in developing, adopted by the United
Nations Committee of Experts on the Transport of Dangerous
Goods and the Globally Harmonized System of Classification
and Labelling of Chemicals, and endorsed by the Economic and
Social Council of the United Nations.            The Globally
Harmonized System, unlike the Hazard Communication
Standard, designates hazard classes (e.g., carcinogens,
explosives) and categories of specific hazards within most
hazard classes, and provides standardized labels and safety data
sheet formats for employers to use for each class and category
of hazard.

     In 2009, OSHA published a notice of proposed rulemaking
stating it was considering modifying the Hazard Communication
Standard to conform with the Globally Harmonized System. See
74 Fed. Reg. 50,280 (Sept. 30, 2009) (“NPRM”). As relevant,
OSHA proposed to include combustible dust as an “unclassified
hazard” subject to the Standard’s general labeling, data sheet,
and training requirements, even though the Globally
Harmonized System had not yet classified or defined
“combustible dust.”        OSHA proposed a definition for
                                 5

“unclassified hazards” to ensure all hazards currently covered or
hazards identified in the future were included in the scope of the
revised Hazard Communication Standard “until such time as
specific criteria for the effect are added to the [Globally
Harmonized System] and subsequently adopted by OSHA.” Id.
at 50,282. OSHA inquired: “Will this approach provide
sufficient interim coverage for hazards such as combustible
dust?” Id. OSHA noted its “longstanding position” that the
general obligation to determine whether chemicals were
hazardous extended to “dusts known to be subject to
deflagration and subsequent explosion, i.e., combustible dusts.”
Id. at 50,395.

     The Final Rule designated combustible dust as a “hazardous
chemical,” 77 Fed. Reg. at 17,704, by defining “hazardous
chemical” as “any chemical which is classified as a physical
hazard or a health hazard, a . . . combustible dust . . . , or hazard
not otherwise classified.” 29 C.F.R. § 1910.1200(c). OSHA did
not include a definition of combustible dust in the Final Rule,
but noted that it had “already provided considerable guidance on
the nature and definition of combustible dust in a variety of
materials,” 77 Fed. Reg. at 17,704, referring specifically to
OSHA, 3371-08, Hazard Communication Guidance for
Combustible Dusts (2009) (“2009 Guidance”), and OSHA, CPL
03-00-008, Combustible Dust National Emphasis Program
Directive (Mar. 11, 2008) (“National Emphasis Program”). 77
Fed. Reg. At 17,704. Acknowledging commenters had urged
clarity through inclusion of a definition of combustible dust,
OSHA noted the delay in the global effort to develop a
definition and explained that it did not want to eliminate
safeguards that long had been in place, highlighting its 1986
interpretation that the Hazard Communication Standard already
covered combustible dusts as a flammable solid and an
explosive hazard. Id. at 17,704-705.
                                6

     OSHA provided further guidance in December 2013,
advising that regulated parties should classify materials as
combustible dust in light of any past experience of explosions
involving their workplace materials and testing data, and if such
information was unavailable, particle size or published
information about similar materials. See Memorandum to
Regional Administrators from Thomas Galassi, Director,
Directorate of Enforcement Programs, Classification of
Combustible Dusts under the Revised Hazard Communication
Standard (Dec. 27, 2013) (“2013 Guidance”). When using
particle size standards to determine whether a product
constituted combustible dust, parties could use either of two
particle sizes as well as other reliable methods of classification.
Id.

     Separate and apart from the Hazard Communication
Standard rulemaking, in 2009 OSHA issued an advanced notice
of proposed rulemaking on combustible dust, with the intent of
creating a substantive standard that would address the hazards
of combustible dust from a wide variety of materials, see
Combustible Dust, 74 Fed. Reg. 54,334, 54,334-335 (Oct. 21,
2009). Although OSHA has received some comments, it has not
yet issued a notice of proposed rulemaking.

                                II.

     Petitioners challenge the Final Rule on procedural,
statutory, and constitutional grounds. The Occupational Safety
and Health Act incorporates the notice and opportunity
requirements for general rulemaking of the Administrative
Procedure Act, see 29 U.S.C. § 655(b)(2); 5 U.S.C. § 553(b)(3);
Resp’t’s Br. 25, and adopts the substantial evidence test for
judicial review, see 29 U.S.C. § 655(f). This court has
acknowledged the difficulties of applying the substantial
evidence test “to regulations which are essentially legislative
                                7

and rooted in inferences from complex scientific and factual
data, and which often necessarily involve highly speculative
projections of technological development in areas wholly
lacking in scientific and economic certainty.”              United
Steelworkers of Am., AFL-CIO-CLC v. Marshall, 647 F.2d 1189,
1206-07 (D.C. Cir. 1980). The reviewing court’s task, then, is
to ensure the agency has acted within the scope of its authority,
followed the statutory and regulatory procedures, explicated the
bases of its decision, and adduced substantial evidence in the
record to support its determinations. Id. at 1206. This includes
“requiring the agency to identify relevant factual evidence, to
explain the logic and the policies underlying any legislative
choice, to state candidly any assumptions on which it relies, and
to present its reasons for rejecting significant contrary evidence
and argument.” Id. at 1207 (citation and quotation omitted); see
also Nat’l Maritime Safety Ass’n v. OSHA, 649 F.3d 743, 751-52
(D.C. Cir. 2011). Although the “substantial evidence” standard
demands more stringent review of OSHA rules than would the
APA’s arbitrary and capricious standard, see AFL-CIO v. OSHA,
965 F.2d 962, 970 (11th Cir. 1992); Nat’l Grain & Feed Ass’n
v. OSHA, 866 F.2d 717, 728 (5th Cir. 1989); AFL-CIO v.
Marshall, 617 F.2d 636, 649 (D.C. Cir. 1979), this court has
cautioned, in view of an “‘emerging consensus’ of the Courts of
Appeals,” that the difference between the two standards should
not be “exaggerate[d].” United Steelworkers, 647 F.2d at 1213
n.23 (citing Pac. Legal Found. v. DOT, 593 F.2d 1338, 1343
n.35 (D.C. Cir. 1979)). Petitioners’ constitutional challenge is
subject to de novo review. C-SPAN v. FCC, 545 F.3d 1051,
1054 (D.C. Cir. 2008); Rural Tel. Coal. v. FCC, 838 F.2d 1307,
1313 (D.C. Cir. 1988); see also 5 U.S.C. § 706(2)(B).

                            A.
    Petitioners contend that they were not provided notice of
and an opportunity to comment on the possible inclusion of
combustible dust from grain in the Hazard Communication
                               8

Standard.     The advanced notice did not mention that
combustible dust might be regulated as a hazardous chemical,
and the proposed rule, in discussing combustible dust, did not
explicitly indicate that grain dust would be considered
combustible dust. Further, petitioners maintain, although notice
is adequate when an interested party could have reasonably
anticipated the final rulemaking from the proposed rule, see
Nat’l Mining Ass’n v. MSHA, 116 F.3d 520, 531 (D.C. Cir.
1997), the grain industry could not have anticipated that the
Hazard Communication Standard revisions would address grain
dust because grain dust has been regulated since 1987 by the
Grain Handling Standard. Petitioners also maintain they lacked
notice that the Final Rule would require their members to
consider dangers from downstream uses (rather than the initial
manufacturing of the product) and to provide downstream users
with material safety data sheets and labeling for combustible
dust.

     The NPRM confirms that OSHA gave adequate notice that
combustible dust would be regulated under the Hazard
Communication Standard when it proposed treating combustible
dust as an “unclassified hazard” subject to the Standard’s
requirements. Significantly, OSHA expressly requested and
received comment on whether such treatment of combustible
dust would be adequate. See NPRM, 74 Fed. Reg. at 50,282.
Relevant as background to this question, OSHA issued
interpretive letters in 1986 and 1987 confirming that the
Standard covered agricultural products – including grain –
presenting dust explosion hazards. More particularly, in 1994,
OSHA rejected the grain industry’s position that the Hazard
Communication Standard should not cover grain dust. Citing
evidence that grain dust presents physical and health hazards,
OSHA responded that its “position . . . remain[ed] the same —
grain dust meets the definition of a hazardous chemical under
the [Hazard Communication Standard].”                   Hazard
                                 9

Communication, 59 Fed. Reg. 6,126, 6,154 (Feb. 9, 1994).
Grain elevators thus had the responsibility to develop a grain
dust safety data sheet and provide it to the elevators’ workers as
well as downstream users. See id. at 6,154-155. Additionally,
as referenced in the NPRM, OSHA’s 2008 National Emphasis
Program explicitly noted that the agricultural industry handles
combustible dusts, see National Emphasis Program § I & apps.
D-1, D-2, and the 2009 Guidance included flour and sugar as
examples of products that could cause combustible dust
explosions. While petitioners suggest that they had no reason to
expect that grain would be considered a “hazardous chemical”
because food products had long been exempted from the Hazard
Communication Standard, see Pet’rs’ Br. 9 (citing 29 C.F.R. §
1910.1200(b)(5)(iii)), they acknowledge that the Standard
covers respiratory hazards posed by grain dust, see id. 22, 39-40,
45. Moreover, the exemption for food products is only a partial
one. See 29 C.F.R. § 1910.1200(b)(5).

     Petitioners still suggest that the Final Rule was not a logical
outgrowth of the proposed rule, which they contend
contemplated regulating only inhalation hazards from grain
dusts, while the Final Rule included “combustible dust” as a
hazardous chemical subject to all provisions of the Hazard
Communication Standard. In their view, the Final Rule was “an
unforeseeable change of course.” Pet’rs’ Br. 46. In fact, both
the proposed and final rules subjected combustible dust to the
Hazard Communication Standard requirements for labeling, use
of safety data sheets, and training. Compare NPRM, 74 Fed.
Reg. at 50,395, 50,441, 50,540, with Final Rule, 77 Fed. Reg. at
17,704, 17,883. The proposed rule also mentions that employers
must consider the potential hazards from downstream uses of a
chemical. See NPRM, 74 Fed. Reg. at 50,395. In citing a
Chemical Safety Board report recommending that the Hazard
Communication Standard be amended to address combustible
dust as evidence that the regulated community was not on notice
                               10

that the Standard would apply to grain dust hazards, petitioners
overlook that the report was referenced in the NPRM, 74 Fed.
Reg. at 50,395, and so cannot be evidence that OSHA’s
treatment of combustible dust changed between the proposed
rule and the Final Rule. Although the Final Rule does treat
combustible dust as a specific category of hazard, see Final
Rule, 77 Fed. Reg. at 17,703-705, rather than as an “unclassified
hazard” as proposed, see NPRM, 74 Fed. Reg. at 50,390, OSHA
indicated in the proposed rule that it was contemplating
continuing to treat combustible dust as a hazardous chemical,
see id. In any event, OSHA stated that its proposal “would
require the chemicals posing unclassified hazards” – including
combustible dust – “to be treated as hazardous chemicals under
the rule.” Id. Petitioners thus had express notice that
combustible dust, however labeled, would be subject to the
relevant requirements in the Final Rule.

                                B.
     Petitioners also contend that OSHA’s decision to forgo
establishing a uniform definition for combustible dust in the
Final Rule, and to incorporate a definition from its ongoing
combustible dust enforcement program, was unreasonable and
unsupported by substantial evidence, in violation of section 6(f)
of the Act, 29 U.S.C. § 655(f). In petitioners’ view, rather than
regulate combustible dust under the Hazard Communication
Standard, OSHA should have addressed combustible dust in the
pending Combustible Dust rulemaking, because there is no
clear, consistent definition of “combustible dust” and existing
OSHA and private standards are inconsistent and have not been
evaluated through rulemaking.

    Contrary to petitioners’ characterization of the rulemaking,
OSHA neither failed to provide any definition of nor adopted a
multiplicity of wide-ranging approaches to classifying
combustible dust: OSHA pointed regulated entities to an
                                  11

“operative definition” of combustible dust in the National
Emphasis Program, and then noted that commenters had
suggested that certain industry consensus standards provided
“further guidance.” Final Rule, 77 Fed. Reg. at 17,705. The
various government and industry definitions of combustible dust
are not as different as petitioners suggest: each definition, with
varying phrasing, refers similarly to particles that may explode
under certain conditions.1 The main substantive difference
between the standards is whether they rely on a maximum
particle size and if so, what that size is. Additionally, the 1987
Grain Handling Standard defines “fugitive grain dust” by
reference to “combustible dust,” and, although referring to a
particle size, does not further define combustible dust. See 29
C.F.R. § 1910.272(c) (“Fugitive grain dust means combustible
dust particles . . . of such size as will pass through a U.S.
Standard 40 mesh sieve (425 microns or less).”). Yet there is no
indication that the grain industry has struggled to understand
what “fugitive grain dust” means. Because preexisting OSHA
definitions and voluntary standards reflect a general consensus


        1
            Compare, e.g., National Emphasis Program § VIII.B
(defining combustible dust as “[a] combustible particulate solid that
presents a fire or deflagration hazard when suspended in air or some
other oxidizing medium over a range of concentrations, regardless of
particle size or shape”), with Nat’l Fire Protection Ass’n, Standard for
the Prevention of Fires and Dust Explosions in Agricultural and Food
Processing Facilities § 3.3.1 (2013) (defining agricultural dust as
“[a]ny finely divided solid agricultural material 420 microns or
smaller in diameter . . . that presents a fire or explosion hazard when
dispersed and ignited in air”), and Nat’l Fire Protection Ass’n,
Standard for the Prevention of Fire and Dust Explosions from the
Manufacturing, Processing, and Handling of Combustible Particulate
Solids § 3.3.5 (2013) (defining combustible dust as “[a] finely divided
combustible particulate solid that presents a flash fire hazard or
explosion hazard when suspended in air or the process-specific
oxidizing medium over a range of concentrations”).
                              12

on the meaning of combustible dust, OSHA could reasonably
conclude that it was unnecessary to articulate a single, uniform
definition in the Final Rule.

     In the Final Rule, OSHA explained that regulating
combustible dust as a specific hazard, rather than as an
“unclassified hazard” as originally proposed, was needed
because of the urgency of the combustible dust hazards in
workplaces: OSHA noted the “important nature of the issue, a
number of public comments, and the need to provide clarity
sooner than the United Nations Sub-committee will complete its
work.” Final Rule, 77 Fed. Reg. at 17,705. Responding to the
suggestion that OSHA address combustible dust only in the
separate and specific Combustible Dust rulemaking, OSHA
noted that it had consistently viewed combustible dust as within
the scope of the Hazard Communication Standard and that
excluding combustible dust from the Standard’s coverage would
eliminate longstanding protections. “[G]iven ongoing activities
in the [Combustible Dust] rulemaking, as well as in the UN Sub-
committee,” OSHA decided to provide an interim definition by
reference to the National Emphasis Program. See id. OSHA
explained as well that the Combustible Dust rulemaking and the
Hazard Communication Standard serve separate functions: “The
rulemaking on combustible dust is a much broader approach to
the issue, and will likely establish methods to control and
address such dusts in the workplace.              The [Hazard
Communication Standard] is an information transmittal
standard.” Id.

    Given OSHA’s conclusion that the industry had shown only
minor disagreement on the meaning of combustible dust, and the
importance it attributed to maintaining existing protection
against combustible dust, there was substantial evidence and an
adequate explanation in support of OSHA’s decision to
incorporate an interim definition and guidance until a more
                                13

precise definition is implemented in another rulemaking – even
if that process takes several years. See United Steelworkers, 647
F.2d at 1207. To the extent petitioners object that OSHA
guidance and voluntary industry standards have not been
evaluated under the “best available evidence” as required by 29
U.S.C. § 655(b)(5), or undergone required feasibility analyses,
absent elucidation or meaningful citation, by mentioning this
claim only in a cursory manner, petitioners have forfeited it. See
Schneider v. Kissinger, 412 F.3d 190, 200 n.1 (D.C. Cir. 2005).

                               C.
     Finally, petitioners contend that OSHA violated the Due
Process Clause because the Final Rule, for lack of a definition
of combustible dust, is unconstitutionally vague on its face.
They maintain their members lack notice of whether and how
they must comply, and are concerned that the lack of a clear
definition will encourage discriminatory enforcement. See
Pet’rs’ Br. 55-59 (citing, e.g., Flynn Decl. ¶¶ 6-7 (Feb. 10,
2014)). OSHA responds this claim is not ripe, and in any event,
petitioners’ facial vagueness claim fails on the merits.

     The ripeness inquiry requires courts “to evaluate both the
fitness of the issues for judicial decision and the hardship to the
parties of withholding court consideration.” Abbott Labs. v.
Gardner, 387 U.S. 136, 149 (1967). The “fitness” factor takes
into account “whether the issue ‘is purely legal, whether
consideration of the issue would benefit from a more concrete
setting, and whether the agency’s action is sufficiently final.’”
Clean Air Implementation Project v. EPA, 150 F.3d 1200, 1204
(D.C. Cir. 1998) (quoting Natural Res. Def. Council, Inc. v.
EPA, 22 F.3d 1125, 1133 (D.C. Cir. 1994)). OSHA disputes
only the second element of the fitness inquiry, maintaining that
the court could better evaluate the vagueness claim in the
concrete setting of an enforcement action. Relying on Village
of Hoffman Estates v. Flipside, Hoffman Estates, Inc., 455 U.S.
                               14

489, 497 (1982), and Natural Resources Defense Council, Inc.
v. EPA, 194 F.3d 130, 138 (D.C. Cir. 1999) (“NRDC”), OSHA
maintains that petitioners must – but cannot here – show that
the law is incapable of any valid application. See Resp’t’s Br.
52. Further, OSHA maintains, petitioners have not established
the requisite hardship.

     We conclude petitioners’ facial vagueness challenge is ripe
for review. It presents a legal question where OSHA’s relevant
factual determinations are relatively undisputed and further
factual development would not provide the court with a
significantly richer record. See Sabre, Inc. v. DOT, 429 F.3d
1113, 1119-20 (D.C. Cir. 2005); Vill. of Bensenville v. FAA, 376
F.3d 1114, 1120 (D.C. Cir. 2004). Unlike the petitioner in
NRDC, 194 F.3d at 138, petitioners contend that the failure of
notice regarding grain dust renders the combustible dust
provisions invalid in all their applications. See Pet’rs’ Br. 56-
58; Pet’rs’ Reply Br. 19-21. Indeed, the Final Rule has already
had an immediate impact on the grain industry’s ability to make
decisions, even if some provisions will not take effect until
2015. See EPA v. Nat’l Crushed Stone Ass’n, 449 U.S. 64, 72
n.12 (1980); Abbott Labs., 387 U.S. at 153-54; Reckitt Benckiser
Inc. v. EPA, 613 F.3d 1131, 1137-38 (D.C. Cir. 2010); Sabre,
429 F.3d at 1117, 1120. The training provisions in the Final
Rule became effective in 2013.              See 29 C.F.R. §
1910.1200(j)(1); Pet’rs’ Br. 56. Faced with not knowing
whether they were required to provide training by December 1,
2013, much less the measure to use to determine if their
products could create combustible dust downstream, petitioners’
members claim they incurred costs and administrative burdens
to ensure compliance at the risk of potentially more costly
enforcement and sanctions. See, e.g., Gordon Decl. ¶ 8 (Feb. 11,
2014); Rowe Decl. ¶¶ 6-9 (Feb. 19, 2014). OSHA offers no
plausible reasons why it has an institutional interest in
postponing review beyond generally referring to its desire to
                                15

remain free from judicial interference until the effects of its rule
have been felt in a concrete way, which has already occurred.
Moreover, 29 U.S.C. § 655(f) expressly authorizes pre-
enforcement review of OSHA standards, and because this
provision imposes a sixty-day time limit, “[p]ostponing review
. . . could burden [petitioners] by preventing [them] from
bringing a [pre-enforcement] challenge at all,” Vill. of
Bensenville, 376 F.3d at 1120.

     On the merits, petitioners’ vagueness claim fails, however.
The Final Rule satisfies Due Process because the term
“combustible dust” is clear enough to provide fair warning of
enforcement, and OSHA has provided additional guidance on
how the revised Hazard Communication Standard will be
enforced. “If, by reviewing the regulations and other public
statements issued by the agency, a regulated party acting in good
faith would be able to identify, with ‘ascertainable certainty,’ the
standards with which the agency expects parties to conform,
then the agency has fairly notified a petitioner of the agency’s
interpretation.” Gen. Elec. Co. v. EPA, 53 F.3d 1324, 1329
(D.C. Cir. 1995) (quoting Diamond Roofing Co. v. OSHRC, 528
F.2d 645, 649 (5th Cir. 1976)); see also Aeronautical Repair
Station Ass’n, Inc. v. FAA, 494 F.3d 161, 174 (D.C. Cir. 2007).
Contrary to petitioners’ reading of the Final Rule and the 2013
Guidance, the relevant documents lay out reasonably consistent
and clear instructions on how employers should determine
whether products in their workplaces may pose a combustible
dust hazard.

     First, “combustible dust” is part of the definition of
“fugitive grain dust” in the Grain Handling Standard yet is not
further defined by that regulation, see 29 C.F.R. § 1910.272(c),
and petitioners have not suggested that the term is vague in that
context. Just as the Grain Handling Standard provides a clear
“action level” by forbidding the accumulation of more than 1/8
                               16

inch of fugitive grain dust on surfaces, the Hazard
Communication Standard provides clear action requirements,
such as labeling and training; the obligations imposed when
combustible dust is present do not affect the clarity of the term
“combustible dust.” Second, the Final Rule indicates that the
National Emphasis Program provides an “operative definition”
of “combustible dust.” 77 Fed. Reg. at 17,705. That Program
defines combustible dust as “[a] combustible particulate solid
that presents a fire or deflagration hazard when suspended in air
or some other oxidizing medium over a range of concentrations,
regardless of particle size or shape.” National Emphasis
Program § VIII.B. The Emphasis Program describes the
necessary criteria for evaluating the risk of an explosion and
discusses various testing methods to assess combustibility. See
id. § IX.E & app. E. The 2013 Guidance advises that previous
incidents of explosion will be the best indication of a
combustible dust hazard, but employers may use alternative
classification methods depending on the available information
from laboratory testing, published test results, or particle size,
using either of two size standards. In other words, the employer
may choose the method of classification: If test data are
unavailable and an employer is classifying by particle size, there
is an express particle size below which dust capable of burning
should be deemed combustible, but an employer may use a more
protective standard that would classify larger dust particles as
combustible.

     The combustible dust provisions in the Final Rule are, thus,
not vague in all their applications. A grain elevator company
that had previous experience with dust explosions would know
that its products presumptively pose a combustible dust hazard,
unless it had evidence that the explosion was due to abnormal or
unforeseeable conditions. Employers looking to the 2013
Guidance would know that they should consider available
laboratory test data, but if such data are unavailable, they may
                                 17

rely on other methods. Indeed, the Guidance appears to be
written so that any vagueness in the Final Rule should inure to
the benefit, not the detriment, of regulated parties. Petitioners
maintain, however, that the 2013 Guidance is excessively
confusing because it “could easily be interpreted as instructing
enforcement now for provisions of the Final Rule that do not go
into effect until 2015 or 2016.” Petr’s’ Br. 43. Even assuming
the Guidance is unclear about when enforcement should
commence, this would have no bearing on whether the definition
of “combustible dust” is unconstitutionally vague.

     With regard to petitioners’ concern about possible
discriminatory enforcement, the absence of clear criteria in the
Final Rule for evaluating a party’s chosen alternative methods
is not fatal. The 2013 Guidance indicates that in many cases
OSHA expects that previous experience, laboratory testing, and
published test results will adequately allow employers to classify
combustible dust hazards. OSHA has explained why petitioners
overstate the importance of OSHA’s recognition of two different
particle size standards: It means only that when an employer
has chosen to classify combustible dust hazards by particle size
(which is not the preferred method when test data are available),
they may use the more protective of the two standards if they
wish. That employers can use alternative methods if those
methods are reliable does not undermine the Guidance’s clear
priority of methods by which employers should classify
combustible dust hazards. Although a particular employer
might pursue an as-applied vagueness challenge in future
enforcement proceedings, the combustible dust provision of the
Final Rule is not void for vagueness on its face.

     In a footnote to their reply brief, petitioners contend that the
Final Rule affects their First Amendment rights by compelling
them to communicate the hazards of combustible dust, and thus
strict scrutiny applies. But the court generally declines to
                               18

consider an argument if a party buries it in a footnote and raises
it in only a conclusory fashion, CTS Corp. v. EPA, 759 F.3d 52,
64 (D.C. Cir. 2014), and on that basis we will not entertain
petitioners’ contention here.

    Accordingly, we deny the petition for review.
