United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued January 9, 2007 Decided February 9, 2007

No. 01-1046

KENNECOTT GREENS CREEK MINING COMPANY,

PETITIONER

v.

MINE SAFETY AND HEALTH ADMINISTRATION AND

SECRETARY OF LABOR,

RESPONDENTS

UNITED STEEL, PAPER AND FORESTRY, RUBBER,

MANUFACTURING, ENERGY, ALLIED INDUSTRIAL AND

SERVICE WORKERS INTERNATIONAL UNION, AFL-CIO, ET AL.,

INTERVENORS

Consolidated with

01-1124, 01-1146,

 05-1255, 05-1291, 05-1296, 05-1312, 05-1314,

 06-1184, 06-1194, 06-1204, 06-1205, 06-1223, 06-1225

On Petitions for Review of Final Standards of the

Federal Mine Safety and Health Administration

Henry Chajet and Thomas C. Means argued the causes for

petitioners. With them on the briefs were Edward M. Green,

David Farber, Harold P. Quinn, Jr., Laura E. Beverage, John
2

K. McDonald, Michael T. Heenan, Margaret S. Lopez, and

William K. Doran. Kurt E. Blase entered an appearance.

Edward D. Sieger, Senior Appellate Attorney, U.S.

Department of Labor, argued the cause for respondent. With

him on the brief was Nathaniel I. Spiller, Assistant Deputy

Solicitor. Allen H. Feldman, Attorney, entered an appearance.

Daniel M. Kovalik and Randy S. Rabinowitz were on the

brief for intervenor United Steel, Paper and Forestry, Rubber,

Manufacturing, Energy, Allied Industrial and Service Workers

International Union.

Before: GINSBURG, Chief Judge; SENTELLE,Circuit Judge;

and EDWARDS, Senior Circuit Judge.

Opinion for the Court filed by Circuit Judge SENTELLE.

SENTELLE, Circuit Judge: Several mining industry groups

and mine operators petition for review of three Mine Safety and

Health Administration (“MSHA”) rules that regulate diesel

particulate matter (“DPM”) in underground metal and non-metal

mines. Petitioners contend that MSHA did not have sufficient

evidence that DPM presents a risk to miners’ health, that MSHA

unreasonably chose to regulate other substances as surrogates

for DPM, and that the DPM exposure limits in the new rules

cannot feasibly be achieved by mine operators. Petitioners also

assert that MSHA unlawfully granted medical evaluation and

transfer rights to workers who are required to wear respirators,

and that MSHA’s final implementation timetable was not a

logical outgrowth of the proposed rules. We find these

arguments to be without merit, and we deny the petitions for

review.
3

1

In 2001, MSHA also promulgated rules regulating diesel

engine exhaust in coal mines. See Diesel Particulate Matter Exposure

of Underground Coal Miners, 66 Fed. Reg. 5526 (2001) (codified at

30 C.F.R. pt. 72). Those rules were not challenged, and have been in

force since 2001.

I.

Diesel exhaust is comprised of both gasses and particulate

matter. The challenged rules regulate only the particulate

components of diesel exhaust. Other provisions of MSHA rules,

not at issue in this case, regulate exposure to diesel exhaust

gasses. See 30 C.F.R. § 57.5001.

On January 19, 2001, MSHA promulgated rules setting

concentration limits for diesel particulate matter in underground

metal and non-metal mines.1 Diesel Particulate Matter

Exposure, 66 Fed. Reg. 5706 (2001) (“2001 Rules”). First,

MSHA conducted a risk assessment for DPM. The agency

determined that miners were exposed to very high levels of

DPM, and that this exposure can cause numerous adverse health

effects, including eye irritation, respiratory problems, and lung

cancer. Id. at 5752-5855. MSHA concluded that it was

necessary to regulate DPM exposure to protect miners from

these risks. Id. at 5855. Second, the agency determined that

there was no reliable way to measure DPM directly for

compliance purposes. Id. at 5718. Therefore, MSHA chose to

regulate total carbon (“TC”) as a surrogate for DPM. Id. at

5726-27. Total carbon was deemed to be a reliable surrogate

because there was evidence in the record that TC makes up

approximately 80-85% of DPM, and that this is a consistent

relationship. Id. In the 2001 Rules, MSHA set concentration

limits of 400 micrograms of TC (effective July 2002) and 160
4

2

All exposure limits in MSHA’s rulemakings are expressed in

terms of micrograms per cubic meter. For simplicity, we will refer to

the limits only in terms of the exposure limit and the substance being

regulated (i.e. 160 TC instead of 160 TC μg/m3

 ).

micrograms of TC (effective January 2006).2 Id. at 5706-07.

During the rulemaking, several commenters argued that TC was

an unreliable surrogate for DPM because it was susceptible to

interference from other organic carbon compounds, such as

tobacco smoke and oil mist. However, MSHA concluded that

it could avoid these problems by collecting samples a sufficient

distance away from possible sources of interference. Id. at

5726-30. Lastly, in its 2001 Rules, MSHA determined that mine

operators could feasibly comply with the new DPM exposure

limits. Id. at 5884-90. The agency identified numerous control

technologies that could be used to reduce DPM emissions,

including exhaust filters, environmental cabs, low-emission

engines, improved ventilation systems, low sulfur fuels, and

better training and maintenance. Id. at 5888-90.

Several parties petitioned for review of the 2001 Rules.

MSHA conceded that there were problems with the rules –

especially regarding the use of TC as a surrogate for DPM – and

agreed to conduct further research to address the problem of

interference with TC sampling. After a study of 31 mines,

MSHA, the miners’ unions, and the industry groups agreed to

several changes to the 2001 Rules. The effective date for the

400 TC interim limit was postponed until July 2003. Diesel

Particulate Matter Exposure, 67 Fed. Reg. 47,296, 47,298-99

(2002). Also, MSHA concluded that TC was an unreliable

proxy for DPM in certain circumstances, and promised to

initiate an expedited rulemaking to change the DPM surrogate

from total carbon to elemental carbon (“EC”). Id.
5

In a rulemaking completed in June 2005, MSHA made

several changes to its 2001 Rules. Diesel Particulate Matter

Exposure, 70 Fed. Reg. 32,868 (2005) (“2005 Rules”). Most

importantly, MSHA converted the interim DPM limit from 400

TC to 308 EC, based on a TC-to-EC conversion factor of 1.3 to

1. Id. at 32,944. This conversion factor was calculated based on

data from samples in the 31-mine study. Id. The agency

expressed confidence that this sampling and conversion

methodology “produces a reasonable estimate of TC without

interferences.” Id. However, the agency did not convert the

final limit from EC to TC – it kept that limit at 160 TC, pending

further rulemaking. Id. at 32,870. In the 2005 Rules, MSHA

also made two key changes with respect to feasibility. First, the

rules state that mine operators must require miners to wear

respirators if “controls do not reduce a miner’s exposure to the

DPM limit, controls are infeasible, or controls do not produce

significant reductions in DPM exposures.” Id. at 32,915-16.

Second, MSHA permitted mine operators to seek a one-year

renewable extension of the compliance deadline if they could

show that they were unable to meet the DPM exposure limits.

Id. at 32,951-53.

In September 2005, MSHA sought comments on several

more proposed changes to the DPM rules. Diesel Particulate

Matter Exposure, 70 Fed. Reg. 53,280 (2005) (“2005 Proposed

Rules”). The agency noted that mine operators were having

some difficulties with new filter and engine technologies, and

thus proposed extending the effective date for the final limit of

160 TC to 2011 (with a five-year graduated phase-in period).

Id. at 53,282-84, 53,288. It also proposed adding medical

evaluation and transfer rights for miners who would be forced

to wear respirators because their employers were not in

compliance with the DPM exposure limits. Id. at 53,289-90.
6

In May 2006, MSHA once again amended the DPM rules.

Diesel Particulate Matter Exposure, 71 Fed. Reg. 28,924 (2006)

(“2006 Rules”). The 2006 Rules departed from MSHA’s 2005

proposal by postponing the effective date for the 160 TC final

limit for only two years to May 2008. They also set a new

interim limit of 350 TC, effective January 2007. Id. at 28,977-

78. MSHA promised to initiate a separate rulemaking to convert

these final limits from TC to the more reliable EC. Id. at

28,983. With respect to feasibility, the agency determined that

several types of DPM control technologies were becoming more

readily available, and that mine operators could use these

technologies to meet the DPM exposure limits. Id. at 28,933-40.

The 2006 Rules also adopted the agency’s proposal to grant

medical evaluation and transfer rights to miners who must wear

respirators because the mines in which they work are not in

compliance with the DPM exposure limits. Id. at 28,986-91.

The National Mine Association, the National Stone, Sand

& Gravel Association, and several mine operators petitioned for

review of MSHA’s 2001, 2005, and 2006 rules, alleging that the

rules are arbitrary and capricious and contrary to law. The

United Steelworkers Union intervened on behalf of MSHA in

defense of the DPM rules.

II.

Petitioners first challenge MSHA’s risk assessment for

diesel particulate matter. In particular, they argue that: (1)

MSHA failed to demonstrate that DPM presents a substantial

risk to miners’ health; (2) MSHA failed to consider whether preexisting regulations on diesel exhaust gasses are sufficient to

protect miners from the risks of DPM; and (3) MSHA

disregarded the fact that newer engines might increase the

number of harmful “nanoparticles” in mines. We review

MSHA’s risk assessment under the Administrative Procedure
7

Act, which states that reviewing courts shall “hold unlawful and

set aside” any agency action that is “arbitrary, capricious, an

abuse of discretion, or otherwise not in accordance with law.”

5 U.S.C. § 706(2)(A). Under the arbitrary and capricious test,

we must ensure that the agency has “examine[d] the relevant

data and articulate[d] a satisfactory explanation for its action

including a rational connection between the facts found and the

choice made.” Motor Vehicle Mfrs. Ass’n v. State Farm Mut.

Auto. Ins. Co., 463 U.S. 29, 43 (1983) (internal quotation marks

omitted).

The Mine Act states that MSHA shall “develop,

promulgate, and revise as may be appropriate, improved

mandatory health or safety standards for the protection of life

and prevention of injuries in coal or other mines.” 30 U.S.C. §

811(a). Moreover, the Act states:

The Secretary, in promulgating mandatory standards

dealing with toxic materials or harmful physical agents

under this subsection, shall set standards which most

adequately assure on the basis of the best available evidence

that no miner will suffer material impairment of health or

functional capacity even if such miner has regular exposure

to the hazards dealt with by such standard for the period of

his working life. Development of mandatory standards

under this subsection shall be based upon research,

demonstrations, experiments, and such other information as

may be appropriate.

Id. § 811(a)(6)(A). Thus, before promulgating a health or safety

standard under the Mine Act, MSHA must show that the

substance being regulated presents a risk of “material

impairment of health or functional capacity” for miners who are

regularly exposed to the substance. Under the applicable

standard, courts extend deference to MSHA’s determinations as
8

to which substances present such a risk. In a case involving

MSHA’s regulation of oxygen levels in mines, we noted that

“[a]t most . . . the agency was required to identify a significant

risk associated with having no oxygen standard at all.” Nat’l

Mining Ass’n v. MSHA, 116 F.3d 520, 528 (D.C. Cir. 1997).

Moreover, we emphasized that “the Secretary was entitled to err

on the side of overprotection by setting a fully adequate margin

of safety.” Id. (internal quotation marks omitted).

Here, MSHA has adequately demonstrated that DPM

presents a significant risk to the health and safety of miners. In

the 2001 Rules, MSHA conducted an exhaustive risk assessment

that was based upon an analysis of the relevant data and

scientific literature. 66 Fed. Reg. at 5752-5855. First, the

agency cited several studies that showed that miners were

exposed to DPM at much higher levels than workers in other

occupations. Id. at 5753-64. More specifically, MSHA

determined that “median dpm concentrations observed in some

underground mines are up to 200 times as high as mean

environmental exposures in the most heavily polluted urban

areas, and up to 10 times as high as median exposures estimated

for the most heavily exposed workers in other occupational

groups.” Id. at 5764.

Next, MSHA determined that numerous adverse health

effects are causally related to heightened DPM exposure. Id. at

5764-5822. The agency identified several studies that found

links between DPM exposure and acute health effects, such as

eye irritation, decreases in pulmonary function, and bronchial

inflammation. Id. at 5767-70. More significantly, MSHA

concluded that miners who are regularly exposed to DPM will

face a heightened risk of developing lung cancer. In reaching

this conclusion, MSHA analyzed 47 epidemiological studies

(from 1957 to 1999) as well as two “meta-analyses” that

aggregated the data from the earlier studies. Id. at 5773-82.
9

“Some degree of association between occupational dpm

exposure and an excess prevalence of lung cancer was reported

in 41 of the 47 studies reviewed by MSHA.” Id. at 5775.

Moreover, the agency reasonably explained why it discounted

the findings of the six studies that did not find a causal link

between DPM exposure and lung cancer risk. Three of these

studies did not allow for a sufficiently long latency period

between exposure and evaluation, and a fourth study used too

small of a cohort. Id. at 5783. And five of the six “negative”

studies did not have statistically significant results, whereas 25

of the 41 “positive” studies did find a statistically significant

link between DPM exposure and lung cancer risk. Id. at 5785.

MSHA concluded that:

Although no epidemiologic study is flawless, studies of

both cohort and case-control design have quite consistently

shown that chronic exposure to diesel exhaust, in a variety

of occupational circumstances, is associated with an

increased risk of lung cancer. . . . With only rare

exceptions, involving too few workers and/or observation

periods too short to have a good chance of detecting excess

cancer risk, the human studies have shown a greater risk of

lung cancer among exposed workers than among

comparable unexposed workers.

Id. at 5825. We hold that MSHA corralled more than enough

evidence in support of its risk assessment, and that the agency

reasonably explained why it did not rely on the studies that cut

against its conclusions.

Petitioners argue that MSHA’s risk assessment was flawed

because the agency failed to consider whether pre-existing

limitations on diesel exhaust gasses might also provide adequate

protection against exposure to diesel particulate matter.

However, this argument ignores the fact that DPM presents
10

health risks independent of the risks posed by diesel exhaust

gasses. MSHA’s risk assessment in the 2001 Rules focused only

on the specific risks caused by exposure to diesel particulate

matter. See 66 Fed. Reg. at 5764 (noting that MSHA’s risk

assessment “reviews the various health effects . . . that may be

associated with dpm exposures”) (emphasis added). As

explained above, the agency reasonably determined that DPM

is a “toxic material or harmful physical agent” that poses a

significant risk to the health of miners. Accordingly, MSHA

was authorized by the Mine Act to promulgate exposure limits

for DPM independent of the agency’s pre-existing rules

regulating diesel exhaust gasses. See 30 U.S.C. § 811(a)(6).

Indeed, the agency emphasized that “MSHA will, of course,

continue to enforce the limits applicable to diesel gasses, but this

enforcement will be separate from the enforcement of the dpm

concentration limits under the final dpm rule.” 2001 Rules, 66

Fed. Reg. at 5856. Thus, we hold that MSHA reasonably chose

to promulgate separate rules for diesel particulate matter based

upon the agency’s determination that DPM – in its own right –

presents significant risks to the health and safety of miners that

are distinct from the health risks posed by diesel exhaust gasses.

Petitioners also assert that MSHA’s risk analysis was

flawed because it failed to take into consideration the effects of

“confounders” such as miners’ use of tobacco products.

However, in the 2001 Rules, MSHA specifically identified

eighteen published epidemiological studies that controlled for

tobacco use, five of which also controlled for asbestos exposure.

Id. at 5787. Even controlling for tobacco use, “[a]ll but one of

these 18 studies reported some degree of excess risk associated

with occupational exposure to diesel particulate, with

statistically significant results reported in eight.” Id.

Finally, petitioners contend that MSHA’s risk assessment

was arbitrary and capricious because it disregarded the fact that
11

newer, cleaner engines – which are often necessary to reduce

DPM exposure – may increase the number of dangerous

“nanoparticles” in mines. We disagree. As explained above, a

substantial body of scientific evidence has identified a

statistically significant causal connection between DPM

exposure and lung cancer risk. In contrast, the risks from

nanoparticles are currently speculative at best – in the 2001

rulemaking, MSHA noted that nanoparticles “may” be more

harmful than larger particles, but that “much more medical

research and diesel emission studies are needed to fully

characterize diesel nanoparticles emissions and their impact on

human health.” Id. at 5738. MSHA’s actions in the face of this

evidence were entirely reasonable. The agency chose to

promulgate rules immediately to regulate the known risks from

DPM, while conducting further research into the potential health

effects of nanoparticles. We cannot hold that this course of

action was arbitrary and capricious.

Under the Mine Act, MSHA is given a significant degree of

deference in its identification of substances that present

significant risks to the health and safety of miners. See Nat’l

Mining Ass’n, 116 F.3d at 527-28. Here, MSHA conducted an

exhaustive survey of the relevant evidence and concluded that

exposure to diesel particulate matter may place miners at a

heightened risk of developing lung cancer and other health

problems. We see no reason to disrupt this conclusion, and thus

we deny the petitions for review with respect to MSHA’s

threshold risk assessment.

III.

In its rulemakings, MSHA concluded that it did not have a

reliable method of measuring DPM directly at low concentration

levels. See 2001 Rules, 66 Fed. Reg. at 5718. Accordingly, the

agency chose to regulate total carbon (“TC”) and elemental
12

carbon (“EC”) as surrogates for DPM. Petitioners raise several

challenges to MSHA’s use of these surrogates. In particular,

petitioners argue that TC and EC are flawed proxies for DPM

because TC is sensitive to interference from other carbon-based

sources, and because there is no reliable and consistent method

for converting DPM to EC and TC. We agree with the

petitioners that TC and EC are not perfect substitutes for DPM.

But our standard of review under the arbitrary and capricious

test is only reasonableness, not perfection. See State Farm, 463

U.S. at 43 (requiring the agency to “articulate a satisfactory

explanation for its action including a rational connection

between the facts found and the choice made”). Additionally,

“we will give an extreme degree of deference to the agency

when it ‘is evaluating scientific data within its technical

expertise.’” Hüls Am., Inc. v. Browner, 83 F.3d 445, 452 (D.C.

Cir. 1996) (quoting Int’l Fabricare Inst. v. EPA, 972 F.2d 384,

389 (D.C. Cir. 1992)). On the record before us, we cannot hold

that MSHA acted arbitrarily and capriciously by using TC and

EC as surrogates for DPM.

At the outset, we note that there is nothing inherently

problematic with an agency regulating one substance as a

surrogate for another substance. In other areas of environmental

law, this Court has held that “[t]he EPA may use a surrogate to

regulate hazardous pollutants if it is ‘reasonable’ to do so.”

Nat’l Lime Ass’n v. EPA, 233 F.3d 625, 637 (D.C. Cir. 2000).

For example, we have upheld the EPA’s use of hydrocarbons

(“HC”) as a surrogate for fine particulate matter (“PM”),

explaining that:

EPA regulated HC emissions as a means of controlling fine

PM emissions and pollution. The Agency reasonably

determined that regulating HC would control PM pollution

both because HC itself contributes to such pollution, and

because HC provides a good proxy for regulating fine PM
13

emissions.

Bluewater Network v. EPA, 370 F.3d 1, 18 (D.C. Cir. 2004).

See also Sierra Club v. EPA, 353 F.3d 976, 985 (D.C. Cir. 2004)

(upholding the EPA’s regulation of particulate matter as a

surrogate for hazardous air particles because there were

“[s]trong direct correlations” between the surrogate and the

target substance).

In the instant case, MSHA reasonably chose to use TC as a

surrogate for DPM. Based on the results of several studies,

MSHA determined that TC “accounts for 80-85% of the total

dpm concentration when low sulfur fuel is used.” 2001 Rules,

66 Fed. Reg. at 5719. The agency also noted that the “NIOSH

5040” method of analysis measures TC with “the accuracy,

precision, and sensitivity necessary to use in compliance

sampling for dpm.” Id. at 5719-22 (noting that samples taken

pursuant to the NIOSH 5040 method meet NIOSH’s “accuracy

criterion” because they “come within 25 percent of the true TC

concentration at least 95 percent of the time”). Given that TC

and DPM were tightly correlated, and that MSHA had a reliable

method for determining the amount of TC in a sample, it was

not per se unreasonable for MSHA to use TC as a surrogate for

DPM.

However, as MSHA recognized in its 2001 Rules, TC is not

always a perfect surrogate for DPM because TC measurements

can be sensitive to interferences from other carbon-based

sources, such as oil mist and tobacco smoke. Id. at 5726-30.

Accordingly, in the 2005 Rules, MSHA converted one of the

interim DPM exposure limits from total carbon to elemental

carbon (“EC”), another surrogate for DPM that is less sensitive

to interference. See 70 Fed. Reg. at 32,871 (noting that “using

EC would impose fewer restrictions or caveats on sampling

strategy (locations and durations), would produce a
14

measurement much less subject to questions, and inherently

would be more precise”). MSHA reviewed the relevant

evidence and concluded that EC was a reliable proxy for DPM

because NIOSH research and MSHA’s laboratory tests “indicate

that DPM, on average, is approximately 60 to 80% elemental

carbon.” Id. Also, using the results of the 31-mine study,

MSHA was able to establish a TC:EC conversion factor of 1.3.

See id. at 32,889-99. MSHA obtained the 1.3 conversion factor

by taking the median of the ratios observed during sampling.

Moreover, in making these calculations, the agency only focused

on valid samples – it omitted samples that were subject to

interference. Id. at 32,944. Petitioners assert that the TC:EC

conversion ratio used by MSHA is arbitrary and capricious

because the correlation between TC and EC varies in a

statistically significant manner. However, after analyzing over

1,000 samples from various mines, MSHA found that measuring

TC directly or measuring EC and multiplying by the conversion

factor of 1.3 made no difference to finding compliance with the

400 TC limit in 93.6% of the samples. Id. at 32,876.

Obviously, the conversion factor is not perfect, and there is still

some variability in the TC:EC ratio. However, MSHA’s

decision to use the median ratio from valid samples in the 31-

mine study as the conversion factor was well within the scope of

the agency’s discretion. And MSHA’s sampling confirms that

the 1.3 conversion factor – although not perfect – is a relatively

accurate way of converting EC to TC. We cannot hold that it

was arbitrary and capricious for the agency to use EC as a

surrogate for DPM.

Finally, petitioners assert that the current interim limit of

350 TC and the final limit of 160 TC are arbitrary and capricious

because MSHA did not convert these limits from TC to EC,

even though the agency had acknowledged that TC can be an

unreliable measure of DPM. We disagree. Although MSHA

has recognized that TC is sensitive to interferences, the agency
15

3

MSHA did not apply the 1.3 conversion factor to the final

limit out of concern that the TC to EC ratio may be different at the

lower level. It has, however, indicated that it will apply the 1.3

conversion factor as a check to samples measured for compliance with

the 350 TC interim limit if the rulemaking has not been completed by

that time.

has not entirely written off TC as a proxy for DPM. Indeed,

MSHA has clearly stated in its rules that TC can still serve as a

consistent and reliable surrogate for DPM as long as samples are

taken in areas away from tobacco smoke and oil mist. See 2001

Rules, 66 Fed. Reg. at 5719 (noting that cigarette smoke is

“under the control” of mine operators, and therefore it can be

prohibited during sampling periods); id. at 5729 (noting that

samples should be taken “upwind” of drilling that produces oil

mist). Moreover, MSHA has stated that it will initiate a new

rulemaking to convert the final limits from TC to EC.3 2006

Rule, 71 Fed. Reg. at 28,983. In sum, MSHA has concluded

that EC is a better proxy for DPM than TC, but this does not

automatically render the use of TC to be arbitrary and

capricious. Even though TC sampling is more difficult than EC

sampling, MSHA has reasonably determined that TC can still be

a reliable proxy for DPM as long as samples are taken in the

proper manner. In any event, MSHA’s rulemaking suggests that

it has no intention of using TC as a stand alone proxy.

Although total carbon and elemental carbon are not perfect

surrogates for DPM, MSHA reasonably concluded based on

evidence in the record that TC and EC are sufficiently wellcorrelated with DPM that they can serve as reliable proxies.

These determinations are given “an extreme degree of

deference” given that they involve complex judgments about

sampling methodology and data analysis that are “within [the

agency’s] technical expertise.” Hüls Am., 83 F.3d at 452.

Accordingly, we deny the petitions for review with respect to
16

the use of total carbon and elemental carbon as surrogates for

diesel particulate matter. 

IV.

Petitioners argue that the DPM exposure limits violate the

Mine Act because they cannot feasibly be achieved by mine

operators within the time period established by MSHA’s rules.

Petitioners also contend that MSHA was too optimistic about the

efficacy of various DPM control technologies, and that the

agency changed its feasibility determinations without a reasoned

explanation. We find these arguments to be without merit.

Under the Mine Act, MSHA “shall set standards which

most adequately assure on the basis of the best available

evidence that no miner will suffer material impairment of health

or functional capacity even if such miner has regular exposure

to the hazards dealt with by such standard for the period of his

working life.” 30 U.S.C. § 811(a)(6)(A). Moreover, the Act

states:

In addition to the attainment of the highest degree of health

and safety protection for the miner, other considerations

shall be the latest available scientific data in the field, the

feasibility of the standards, and experience gained under

this and other health and safety laws.

Id. This Court has not yet analyzed the precise role of feasibility

in a Mine Act rulemaking. However, many other environmental

and worker protection statutes contain feasibility requirements,

and we can look to cases interpreting those statutes to inform

our analysis. See, e.g., 29 U.S.C. § 655(b)(5) (“Occupational

Safety and Health Act”) (stating that the Secretary of Labor shall

“set the standard which most adequately assures, to the extent

feasible, on the basis of the best available evidence, that no
17

employee will suffer material impairment of health”).

The Supreme Court has interpreted “feasible” in the OSH

Act as meaning “capable of being done, executed, or effected,”

both technologically and economically. Am. Textile Mfrs. Inst.

v. Donovan, 452 U.S. 490, 508-09 (1981). In order for its rules

to be deemed feasible, an agency must establish “a reasonable

possibility that the typical firm will be able to develop and

install engineering and work practice controls that can meet the

[permissible exposure limit] in most of its operations.” Am. Iron

& Steel Inst. v. OSHA, 939 F.2d 975, 980 (D.C. Cir. 1991)

(“AISI”) (citation omitted). Given that feasibility determinations

involve complex judgments about science and technology, our

standard of review is deferential: the agency is “not obliged to

provide detailed solutions to every engineering problem,” but

only to “give plausible reasons for its belief that the industry

will be able to solve those problems in the time remaining.”

Nat’l Petrochemical & Refiners Ass’n v. EPA, 287 F.3d 1130,

1136 (D.C. Cir. 2002). The fact that “a few isolated operations

within an industry” will not be able to comply with the standard

does not undermine a showing that the standard is generally

feasible. AISI, 939 F.2d at 980. Moreover, MSHA has

emphasized that its DPM rules are intended to be “technology

forcing,” and the industry petitioners have conceded in their

brief that MSHA has authority to promulgate technology-forcing

rules. See 2005 Proposed Rules, 70 Fed. Reg. at 53,283 (“When

we established the 2001 final limit, we were expecting some

mine operators to encounter difficulties implementing control

technology because the rule was technology forcing.”); Reply

Br. of Petitioners at 33. When a statute is technology-forcing,

the agency “can impose a standard which only the most

technologically advanced plants in an industry have been able to

achieve – even if only in some of their operations some of the

time.” United Steelworks of Am. v. Marshall, 647 F.2d 1189,

1264 (D.C. Cir. 1980) (quoting AISI v. OSHA, 577 F.2d 825,
18

832-35 (3d Cir. 1978)).

Petitioners assert that the implementation timetable

established by the 2006 Rules is not feasible, and that many

mine operators will be unable to meet the final exposure limits.

To the contrary, MSHA provided more than enough evidence to

justify its conclusion that the timetable is feasible. See 2006

Rules, 71 Fed. Reg. at 28,933-75 (summarizing evidence in

support of feasibility determinations). In the 2006 Rules,

MSHA determined that several types of DPM control

technologies were more widely available than the agency had

previously thought. For example, the agency noted that by

2005, several mines were using biodiesel fuel, which reduces

DPM emissions from diesel engines. Id. at 28,936. Similarly,

MSHA acknowledged that mine operators had problems using

filters in the past, but the agency emphasized that filters are a

highly effective tool for controlling DPM if they are properly

selected, installed, and maintained. Id. at 28,944-46. MSHA

extensively discussed the pros and cons of all currently-available

filtering technologies, and it determined that several newer

models of filters “are not subject to many of the difficult

implementation issues that have slowed the adoption of some

DPM controls.” Id. at 28,944. Moreover, MSHA stated that it

will continue to provide “extensive information” to mine

operators about the proper procedures for selecting, installing,

and maintaining their filtration systems. Id. at 28,946. In sum,

the agency concluded that “the mining industry as a whole can

reduce DPM levels to the 2001 final limit of 160 TC μg/m3

 by

May 20, 2008.” Id. at 28,978. MSHA offered an abundance of

evidence in support of its feasibility determinations, and we

cannot hold that the agency’s conclusions were arbitrary and

capricious.

Petitioners also challenge MSHA’s findings about several

specific types of control technologies, especially “environmental
19

cabs” and improved mine ventilation. They argue that these

control technologies should not have been considered in

MSHA’s feasibility analysis because they have important

limitations or are only useful in certain types of mines. These

arguments misinterpret the meaning of “feasibility.” For its

rules to be upheld, MSHA does not need to show that every

technology can be used in every mine. The agency must only

demonstrate a “reasonable possibility” that a “typical firm” can

meet the permissible exposure limits in “most of its operations.”

AISI, 939 F.2d at 980. In the 2006 Rules, MSHA explained that:

As we have maintained throughout this rulemaking, mine

operators should determine the control or combination of

controls that will be best suited to their mine-specific

circumstances and conditions, and that controls need to be

evaluated, selected, and implemented on a case-by-case and

application-by-application basis.

71 Fed. Reg. at 28,942. Thus, the fact that some of the specific

control technologies identified by MSHA cannot be used in

every mine does not undermine the overall reasonableness of the

agency’s feasibility determinations. This also undercuts

petitioners’ argument that MSHA should have engaged in a

feasibility analysis for each specific type of mine. MSHA has

never suggested that there is a one-size-fits-all approach for

every mine to meet the DPM exposure limits. Rather, the

agency has reasonably concluded that many different

technologies can be effective in reducing DPM exposure, and it

is up to each individual mine operator to choose the best mix of

controls for that particular mine. Nothing in the Mine Act or the

APA requires an agency to describe in detail how every single

regulated party will be able to comply with the agency’s rules.

See, e.g., Nat’l Petrochemical & Refiners Ass’n, 287 F.3d at

1136 (noting that an agency must “identify the major steps for

improvement” but need not provide “detailed solutions to every
20

engineering problem”) (citation omitted).

MSHA’s feasibility determinations are buttressed by the

agency’s statistical findings that many mines are already in

compliance with the DPM exposure limits. In the 2006 Rules,

MSHA provided data from its prior enforcement sampling,

which revealed that 82% of samples were in compliance with

the 308 EC interim limit, 78% of samples were in compliance

with the 350 TC interim limit, and 46% of samples were in

compliance with the 160 TC final limit. 71 Fed. Reg. at 28,961.

Furthermore, the data indicated that of the mines sampled, 54%

were in compliance with the 308 EC interim limit, 45% were in

compliance with the 350 TC interim limit, and 18% were in

compliance with the 160 TC final limit. Id. Moreover, this

sampling focused on mines that were likely to have the highest

DPM exposure levels; thus, the actual industry-wide compliance

rates are likely to be higher than the compliance rates for these

samples. Id. Focusing upon the percentage of sampled mines

in compliance, petitioners contend the data demonstrates that the

imposed limits are infeasible. On the contrary, we agree with

MSHA that the data supports the agency’s conclusion that the

limits are feasible. It is not arbitrary or capricious to consider

feasible an interim limit with which half of all sampled mines

are already in compliance. And given that – in the 2006 Rules

– MSHA extended the effective date for the final limit until May

2008, mines that are not yet in compliance will still have almost

a year and a half to achieve compliance with the final limits.

Additionally, this Court has held that “[a]ny risk that the

standard may prove to be infeasible in practice is

counterbalanced by flexibility in the standard’s enforcement.”

AISI, 939 F.2d at 980. Here, MSHA’s rules allow mine

operators to seek an extension of the compliance deadline if they

are having difficulty achieving the DPM exposure limits. A

mine that “requires additional time to come into compliance”
21

because of “technological or economic constraints” may seek a

renewable one-year extension of the deadline. 30 C.F.R. §

57.5060(c). See also 2005 Rules, 70 Fed. Reg. at 32,951-53.

We also noted in AISI that an agency’s burden of proving

feasibility is “greatly ease[d]” if employers are permitted to

require employees to use respirators if the exposure limits

cannot be met by other means. 939 F.2d at 980. MSHA’s 2005

Rules contain precisely that requirement – if a mine operator is

unable to comply with the DPM exposure limits, it must provide

“respiratory protection” to miners. See 30 C.F.R. § 57.5060(d).

See also 2006 Rules, 71 Fed. Reg. at 28,986-91; 2005 Rules, 70

Fed. Reg. at 32,953-58. Thus, if any mine operators experience

difficulty complying with the DPM exposure limits, they will be

able to apply for an extension of the deadline and require their

employees to wear respirators. This “flexibility in the standard’s

enforcement” only reinforces our conclusion that MSHA’s

feasibility determinations were reasonable. See AISI, 939 F.2d

at 980.

Finally, petitioners contend that MSHA’s feasibility

determinations are arbitrary and capricious because the agency

reversed itself several times without reasoned explanation.

Contrary to petitioners’ assertions, however, MSHA did not

change its feasibility determinations between the 2005

rulemaking and the 2006 rulemaking. After promulgating the

2005 Rules, MSHA issued a set of proposed rules that would

have changed the effective date for the DPM final limit. See

2005 Proposed Rules, 70 Fed. Reg. at 53,280-93. In the

proposed rules, MSHA noted that some of its feasibility

determinations were being “questioned” and that some of its

assumptions “may not” have been valid; the agency sought

comments from the public about these issues. Id. at 53,283.

However, none of these statements can be deemed a “reversal”

of the agency’s feasibility determinations. Indeed, in the same

set of proposed rules, MSHA also stated that the final limit of
22

160 TC might still be feasible because of mine operators’ “wider

use of alternative fuels and filter technology.” Id. Thus, the

2005 Proposed Rules sought new comments from the public

about certain feasibility issues, but did not actually change any

of the agency’s feasibility determinations. It cannot be said that

the agency changed its position on these matters without

reasoned explanation.

In sum, we deny the petitions for review with respect to

MSHA’s feasibility determinations. The agency identified

several types of control technologies that are effective at

reducing DPM exposure, and it offered evidence that a

substantial number of mines are already in compliance with the

DPM limits. We see no reason to second-guess MSHA’s

conclusion that its DPM exposure limits are feasible.

V.

Petitioners also challenge MSHA’s inclusion in the DPM

rules of medical evaluation and transfer rights for workers who

are required to wear respirators. See 2006 Rules, 71 Fed. Reg.

at 28,986-91. First, petitioners assert that MSHA included these

provisions in its final rules without giving adequate notice to the

regulated parties. This argument is flatly contradicted by the

2005 Proposed Rules, in which MSHA stated:

We are interested in comments from the mining community

on whether we should include in the final rule, pursuant to

Section 101(a)(7) of the Mine Act, a provision requiring a

medical evaluation to determine a miner’s ability to use a

respirator before the miner is fit tested or required to work

in an area of the mine where respiratory protection must be

used under the final limits. In addition, we are seeking

comments on whether the final rule should contain a

requirement for transfer of a miner to an area of the mine
23

where respiratory protection is not required if a medical

professional has determined in the medical evaluation that

the miner is unable to wear a respirator for medical reasons.

70 Fed. Reg. at 53,289. MSHA also included the full text of the

proposed rules regarding medical evaluation and transfer rights.

Id. Thus, the petitioners’ contention that MSHA pulled a

“surprise switcheroo” by including these provisions in the 2006

Rules is groundless.

Petitioners also contend that MSHA lacked statutory

authority to adopt the medical evaluation and transfer

requirements. The Mine Act expressly permits MSHA to

require medical evaluations and transfers “where appropriate.”

30 U.S.C. § 811(a)(7). In the 2006 Rules, MSHA reasonably

concluded that such provisions were “appropriate.” With

respect to medical evaluations, MSHA relied upon an OSHA

study that found that “use of a respirator may place a

physiological burden on a worker while wearing such a device.”

71 Fed. Reg. at 28,986. Given that respirators could potentially

cause “illness, injury, and in some instances, even death,”

MSHA reasonably concluded that miners should be provided

with medical examinations before they are required to wear

respirators. Id. at 28,986-87. Similarly, MSHA determined that

it was “appropriate” to require transfers with pay protection for

workers who are physically unable to wear respirators (but only

to an “existing” job, not a new position). Id. at 28,987-91. If

the rules did not provide transfer rights, miners might attempt to

wear respirators – despite the risks of doing so – in order to

protect their jobs. Id. at 28,990. MSHA reasonably concluded

that the transfer rights would “remove the fear of reprisals” for

such workers. Id. Petitioners argue that MSHA was required to

do a full cost-benefit analysis before it could grant medical

evaluation and transfer rights. However, the Mine Act contains

no such requirement – it only requires that these provisions be
24

“appropriate.” MSHA easily met its burden of showing the

appropriateness of these provisions.

* * *

Finally, petitioners argue that in the 2006 Rules MSHA

impermissibly reduced the length of the phase-in period for the

final exposure limits from what was proposed in 2005. We find

this contention to be without merit because MSHA’s final

implementation timetable was a “logical outgrowth” of the

proposed rules. At the time the proposed rules were issued in

2005, the final DPM limit of 160 TC was scheduled to go into

effect in January 2006. In the proposed rules, MSHA sought

comments about whether the agency should “stagger the

effective dates for implementation of the final DPM limit,

phased-in over a five year period” between 2006 and 2011. 70

Fed. Reg. at 53,288. The proposed rules also stated:

We request comments on whether five years is the correct

timeframe for reducing miners’ exposures to the 160

micrograms of TC as originally established in the 2001

standard and to have been effective in January 2006.

Id. In the 2006 Rules, MSHA ultimately chose an effective date

of May 2008 for the final limit. 71 Fed. Reg. at 28,978. This

choice essentially splits the difference between the original

effective date (January 2006) and the proposed effective date

(January 2011). This Court has found the “logical outgrowth”

test to be satisfied in similar circumstances. In Husqvarna v.

EPA, 254 F.3d 195, 203 (D.C. Cir. 2001), we held that a fouryear phase-in period for certain EPA rules was “a logical

outgrowth of the proposed five-year implementation schedule.”

Just so here. We hold that the final two-year phase in period for

the 160 TC final limit was a logical outgrowth of the proposed

five-year phase in period.
25

VI.

For the aforementioned reasons, we deny the petitions for

review in their entirety. MSHA’s risk assessment was based

upon evidence in the record that workers who are exposed to

high levels of DPM face increased risks of lung cancer and other

adverse health effects. The agency’s selection of total carbon

and elemental carbon as surrogates for DPM was based upon

evidence that TC and EC are closely correlated with DPM and

that there are reliable conversion ratios between DPM, TC, and

EC. And MSHA offered more than enough evidence in support

of its conclusion that mine operators can feasibly comply with

the DPM exposure limits. Our standard of review is deferential,

and we can find nothing in the administrative record that would

justify second-guessing the agency’s conclusions. The petitions

for review are therefore

Denied.