U.S. Environmental Protection Agency

Documentation of OMB Review Under Executive Order 12866

Title of Action: !"#$%&'()*+,-.#'/)0%11+(.2")3.&4252%56(%7)8%9.:)04'1.:;,)3',';<')3'=%$2.(&> ?.-2.(&)%-

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Docket#: BC@5!D583E5FGGH5GIJJ FRL#: RIN: FGFK5@@FL

Although this action does not constitute a “rule,” “regulation,” or “regulatory action” within the meaning of Executive Order (E.O.) 

12866, this action was submitted to the Office of Management and Budget (OMB) for review under E.O. 12866, titled Regulatory 

Planning and Review (58 FR 51735, October 4, 1993). Whenever EPA makes publicly available an action that was reviewed under 

E.O. 12866, section 6(a)(3)(E) of the E.O. directs the Agency to also: 

(1) Make available to the public a copy of the information that was provided to OMB’s Office of Information and Regulatory 

Affairs (OIRA) for review under the E.O., i.e., the text of the draft action and, if applicable, an assessment of the potential 

costs and benefits, as well as additional information for those actions that are determined to be economically significant 

under the E.O. (Information requirements are described in sections 6(a)(3)(B) and (C)). 

(2) Identify for the public any substantive changes between the draft submitted to OIRA and the action that was subsequently 

issued, using a method that is complete, clear, and simple. 

(3) Identify for the public those substantive changes made at the suggestion or recommendation of OIRA.

For this action, were substantive changes made to information reviewed under E.O. 12866? [Please check 

the appropriate answer.]

! No. [In the docket, include the information identified in item (1) below.]

! Yes. [In the docket, include the information identified in items (1) – (3) below.]

Accordingly, the Agency has included this form and the following information in the public docket for 

this action: [Please check the appropriate information.]

! (1) A copy of the information that was provided to OIRA for review under the E.O. 

! (2) Documentation of any substantive changes made to the draft text that was submitted to OIRA 

when compared with what was subsequently made publicly available. The documentation is provided 

on the pages following this form. Changes made at the suggestion or recommendation of OIRA, if 

any, are clearly identified through attribution to OIRA. EPA has used one or more of the following 

methods to note changes: [Select the appropriate option(s).]

! (a) Redline-Strikeout – A copy of the draft action submitted, using redline-strikeout to show the 

substantive changes that were made. 

! (b) Hand Markup – A copy of the draft action submitted, using handwritten notes to show the 

substantive changes that were made. 

! (c) Note to the file - A document that identifies the substantive changes that were made, with 

page and paragraph references to the draft action that was submitted.

If you have any questions about this action or this documentation, please call the 

contact:

Name: Daniel Bushman Email: bushman.daniel@epa.gov Phone: 202-566-0743

Revised 06/17/2011
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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 372 

[EPA-HQ-TRI-2009-0844; FRL–XXXX-X] 

RIN 2025-AA27 

Hydrogen Sulfide; Community Right-to-Know Toxic Chemical Release Reporting

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Lifting of Administrative Stay for Hydrogen Sulfide

SUMMARY: EPA is announcing that it is lifting the Administrative Stay of the Emergency 

Planning and Community Right-to-Know Act (EPCRA) section 313 toxic chemical release 

reporting requirements for hydrogen sulfide (Chemical Abstracts Service Number (CAS No.) 

7783-06-4). Hydrogen sulfide was added to the EPCRA section 313 list of toxic chemicals in a 

final rule published in the Federal Register on December 1, 1993. However, on August 22, 

1994, EPA issued an Administrative Stay of the reporting requirements for hydrogen sulfide in 

order to evaluate issues brought to the Agency’s attention after promulgation of the final rule 

concerning the human health effect basis for the listing and the Agency’s use of exposure 

analysis in EPCRA section 313 listing decisions. Although the final rule listing hydrogen sulfide 

under section 313 of EPCRA remained in force, the stay deferred the reporting requirements for 

hydrogen sulfide while EPA completed this further evaluation. EPA completed its further 

evaluation of additional information that has become available since the stay was put in place 

regarding the human health and environmental effects of hydrogen sulfide, and the Agency 

published a position that the stay should be lifted in the in the February 26, 2010, Federal 

Register document “Intent to Consider Lifting Administrative Stay; Opportunity for Public 

Comment.” Based on EPA’s further evaluation and the consideration of the public comments 
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received on the notice of intent, EPA continues to believe that the Administrative Stay should be 

lifted. By this current action, EPA is not revisiting the original listing decision, which was 

accomplished by final rule on December 1, 1993. Rather, EPA is lifting the Administrative Stay 

of the reporting requirements for hydrogen sulfide.

DATES: This action is effective on November 30, 2010. 

ADDRESSES: EPA has established a docket for this action under Docket ID No. EPA-HQTRI-2009-0844. All documents in the docket are listed in the www.regulations.gov index. 

Although listed in the index, some information is not publicly available, e.g., CBI or other 

information whose disclosure is restricted by statute. Certain other material, such as copyrighted 

material, will be publicly available only in hard copy. Publicly available docket materials are 

available either electronically in www.regulations.gov or in hard copy at the OEI Docket, 

EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC. This Docket 

Facility is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. 

The telephone number for the Public Reading Room is (202) 566-1744, and the telephone 

number for the OEI Docket is (202) 566-1752. 

FOR FURTHER INFORMATION CONTACT: Daniel R. Bushman, Environmental Analysis 

Division, Office of Information Analysis and Access (2842T), Environmental Protection 

Agency, 1200 Pennsylvania Ave., NW, Washington, DC 20460; telephone number: 202-566-

0743; fax number: 202-566-0677; e-mail: bushman.daniel@epa.gov, for specific information on 

this document. For general information on EPCRA section 313, contact the Emergency Planning 

and Community Right-to-Know Hotline, toll free at (800) 424-9346 or (703) 412-9810 in 

Virginia and Alaska or toll free, TDD (800) 553-7672, http://www.epa.gov/epaoswer/hotline/. 

SUPPLEMENTARY INFORMATION: 
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I. General Information

A. Does this Action Apply to Me?

You may be potentially affected by this action if you manufacture, process, or otherwise 

use hydrogen sulfide. Potentially affected categories and entities may include, but are not 

limited to:

Category Examples of Potentially Affected Entities

Industry Facilities included in the following NAICS manufacturing codes 

(corresponding to SIC codes 20 through 39): 311*, 312*, 313*, 314*, 

315*, 316, 321, 322, 323*, 324, 325*, 326*, 327, 331, 332, 333, 334*, 

335*, 336, 337*, 339*, 111998*, 211112*, 212324*, 212325*, 212393*, 

212399*, 488390*, 511110, 511120, 511130, 511140*, 511191, 511199, 

512220, 512230*, 519130*, 541712*, or 811490*.

*Exceptions and/or limitations exist for these NAICS codes.

Facilities included in the following NAICS codes (corresponding to SIC 

codes other than SIC codes 20 through 39): 212111, 212112, 212113 

(correspond to SIC 12, Coal Mining (except 1241)); or 212221, 212222, 

212231, 212234, 212299 (correspond to SIC 10, Metal Mining (except 

1011, 1081, and 1094)); or 221111, 221112, 221113, 221119, 221121, 

221122, 221330 (Limited to facilities that combust coal and/or oil for the 

purpose of generating power for distribution in commerce) (correspond to 

SIC 4911, 4931, and 4939, Electric Utilities); or 424690, 425110, 425120 

(Limited to facilities previously classified in SIC 5169, Chemicals and 

Allied Products, Not Elsewhere Classified); or 424710 (corresponds to 

SIC 5171, Petroleum Bulk Terminals and Plants); or 562112 (Limited to 

facilities primarily engaged in solvent recovery services on a contract or 

fee basis (previously classified under SIC 7389, Business Services, 

NEC)); or 562211, 562212, 562213, 562219, 562920 (Limited to facilities 

regulated under the Resource Conservation and Recovery Act, subtitle C, 

42 U.S.C. 6921 et seq.) (correspond to SIC 4953, Refuse Systems).

Federal 

Government

Federal facilities

This table is not intended to be exhaustive, but rather provides a guide for readers 

regarding entities likely to be affected by this action. Some of the entities listed in the table have 
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exemptions and/or limitations regarding coverage, and other types of entities not listed in the 

table could also be affected. To determine whether your facility would be affected by this action, 

you should carefully examine the applicability criteria in part 372 subpart B of Title 40 of the 

Code of Federal Regulations. If you have questions regarding the applicability of this action to a 

particular entity, consult the person listed in the preceding "FOR FURTHER INFORMATION 

CONTACT" section.

II. Introduction

Section 313 of EPCRA, 42 U.S.C. 11023, requires certain facilities that manufacture, 

process, or otherwise use listed toxic chemicals in amounts above reporting threshold levels to 

report their environmental releases and other waste management quantities of such chemicals 

annually. These facilities must also report pollution prevention and recycling data for such 

chemicals, pursuant to section 6607 of the Pollution Prevention Act (PPA), 42 U.S.C. 13106. 

EPCRA section 313 established an initial list of toxic chemicals composed of more than 300 

chemicals and 20 chemical categories. 

EPCRA section 313(d) authorizes EPA to add or delete chemicals from the list and sets 

forth criteria for these actions. Specifically, EPCRA section 313(d)(2) states that EPA may add a 

chemical to the list if “there is sufficient evidence to establish any one” of the listing criteria. 

Therefore, to add a chemical, EPA must demonstrate that at least one criterion is met, but need 

not determine whether any other criterion is met. Conversely, EPCRA section 313(d)(3) states 

that to remove a chemical from the list, EPA must determine that “there is not sufficient 

evidence to establish any” of the Section 313(d)(2) criteria. Therefore, to remove a chemical, 

EPA must demonstrate that none of the criteria are met. The EPCRA section 313(d)(2) criteria 

are:
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(A) The chemical is known to cause or can reasonably be anticipated to cause significant 

adverse acute human health effects at concentration levels that are reasonably likely to 

exist beyond facility site boundaries as a result of continuous, or frequently recurring, 

releases.

(B) The chemical is known to cause or can reasonably be anticipated to cause in humans–

(i) cancer or teratogenic effects, or

(ii) serious or irreversible–

(I) reproductive dysfunctions,

(II) neurological disorders,

(III) heritable genetic mutations, or

(IV) other chronic health effects.

(C) The chemical is known to cause or can be reasonably anticipated to cause, because of

(i) its toxicity,

(ii) its toxicity and persistence in the environment, or

(iii) its toxicity and tendency to bioaccumulate in the environment,

a significant adverse effect on the environment of sufficient seriousness, in the judgment 

of the Administrator, to warrant reporting under this section.

EPA often refers to the section 313(d)(2)(A) criterion as the “acute human health effects 

criterion;” the section 313(d)(2)(B) criterion as the “chronic human health effects criterion;” and 

the section 313(d)(2)(C) criterion as the “environmental effects criterion.”

Under EPCRA section 313(e)(1), any person may petition EPA to add chemicals to or 

delete chemicals from the list. EPA issued a statement of petition policy and guidance in the 

Federal Register of February 4, 1987 (52 FR 3479) to provide guidance regarding the 
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recommended content and format for submitting petitions under EPCRA section 313(e). EPA 

also issued guidance in the Federal Register of May 23, 1991 (56 FR 23703) regarding the 

recommended content of petitions to delete individual members of the section 313 metal 

compound categories. In addition, EPA published in the Federal Register of November 30, 

1994 (59 FR 61432) a statement clarifying its interpretation of the section 313(d)(2) and (d)(3) 

criteria for modifying the section 313 list of toxic chemicals.

III. Background Information

A. What is the History of the Listing of Hydrogen Sulfide Under EPCRA section 313?

In response to a petition from the Natural Resources Defense Council and the Governor 

of New York, hydrogen sulfide, along with 20 other chemicals and two chemical categories, was 

added to the EPCRA section 313 list of toxic chemicals as part of a 1993 final rule (December 1, 

1993, 58 FR 63500). Hydrogen sulfide was listed under the criteria of EPCRA section 

313(d)(2)(B) (chronic human health effects) based on chronic neurotoxic effects in humans and

under EPCRA section 313(d)(2)(C) (environmental effects) based on acute aquatic toxicity. 

However, on August 22, 1994 (59 FR 43048), EPA issued an Administrative Stay of the EPCRA 

section 313 reporting requirements for hydrogen sulfide. Although the final rule listing 

hydrogen sulfide under section 313 of EPCRA remained in force, the stay deferred the reporting 

requirements for hydrogen sulfide. On February 26, 2010, EPA issued a document in the 

Federal Register entitled “Intent to Consider Lifting Administrative Stay; Opportunity for 

Public Comment” (75 FR 8889). That document provided the public with the opportunity to 

comment on EPA’s review of the currently available data on the human health and 

environmental effects of hydrogen sulfide – specifically, chronic respiratory effects, chronic 
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neurotoxic effects, and acute, chronic and early-life stage aquatic toxicity – and EPA’s belief that 

the Administrative Stay should be lifted based on that data.

B. What was the Basis for the Administrative Stay?

After the final rule was issued adding hydrogen sulfide to the EPCRA section 313 list of 

toxic chemicals, some members of the regulated community expressed a concern that the 

“chronic human health effects” basis for listing hydrogen sulfide under EPCRA section 

313(d)(2)(B) had changed between the proposed rule (September 8, 1992, 57 FR 41020) and the 

final rule (December 1, 1993, 58 FR 63500), and that commenters on the proposed rule therefore 

did not have an opportunity to comment on that individual basis for the listing. Specifically, 

although the Agency cited the same acute aquatic toxicity as an “environmental effects” basis for 

the listing under EPCRA section 313(d)(2)(C) in both the proposed and final rules, the Agency 

also cited chronic respiratory effects as a “chronic human health effects” basis under EPCRA 

section 313(d)(2)(B) in the proposed rule, but chronic neurotoxic effects as a “chronic human 

health effects” basis under that same provision in the final rule. In addition, after issuance of the 

final rule, some members of the regulated community expressed concern that EPA’s decision not 

to include an exposure analysis in deciding to list hydrogen sulfide on the basis of chronic human 

health effects was inconsistent with past Agency practice.

Although EPA did not agree that it had been inconsistent in its use of exposure analyses, 

and notwithstanding the fact that the listing decision was dictated by the acute aquatic toxicity 

finding alone under EPCRA section 313(d)(2)(C), the Agency issued an Administrative Stay of 

the reporting requirements for hydrogen sulfide in order to review the concerns raised after 

issuance of the final rule by some members of the regulated community.

C. What is EPA’s Rationale for Lifting the Administrative Stay for Hydrogen Sulfide?
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EPA’s technical evaluation of hydrogen sulfide, as discussed in detail in the February 26, 

2010 Federal Register document (75 FR 8889), shows that it can reasonably be anticipated to 

cause chronic health effects in humans. The chronic health effects have been observed in 

laboratory animals at concentrations as low as 28 milligrams per cubic meter (mg/m3) (20 parts 

per million (ppm)) and 41.7 mg/m3 (30 ppm). In addition, EPA’s technical evaluation of 

hydrogen sulfide also shows that it can reasonably be anticipated to cause, because of its toxicity, 

significant adverse effects in aquatic organisms. Examples of hydrogen sulfide’s ecological 

toxicity include acute toxicity (96-hour LC50 (i.e., the concentration that is lethal to 50% of test 

organisms)) values for freshwater fish that ranged from 0.0149 milligrams per liter (mg/L) 

(fathead minnow) to 0.0448 mg/L (bluegill), indicating high aquatic toxicity. Examples of 

hydrogen sulfide’s chronic ecological toxicity include freshwater fish values that ranged from a 

6-week lowest-observed-effect-concentration (LOEC) (growth rate) of 0.0005 mg/L in a tropical 

fish (Mystus nemurus) to a 430-day LOEC (final weight) of 0.009 mg/L for goldfish, also 

indicating high aquatic toxicity. 

Based on the above findings, EPA believes that there is no basis for continuing the 

Administrative Stay of the reporting requirements for hydrogen sulfide, and that the 

Administrative Stay should therefore be lifted. As an aside, EPA notes also that it believes that 

the above findings clearly demonstrate the correctness of the Agency’s final decision in 

December 1993 to list hydrogen sulfide on the EPCRA section 313 toxic chemicals list based on 

the listing criteria in EPCRA sections 313(d)(2)(B) and (C). 

Finally, in accordance with EPA’s stated policy on the use of exposure assessments (59 

FR 61432), EPA does not believe that an exposure assessment is appropriate for determining 
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whether hydrogen sulfide meets the criteria of EPCRA section 313(d)(2)(B) or (C), and therefore 

the Administrative Stay should not be continued for lack of an exposure analysis. 

D. What is the Purpose of This Document?

The purpose of this document is to respond to the public comments received on EPA’s 

February 26, 2010 Federal Register document “Intent to Consider Lifting Administrative Stay; 

Opportunity for Public Comment” (75 FR 8889), and to give notice that EPA is lifting the 

Administrative Stay of the EPCRA section 313 toxic chemical release reporting requirements for 

hydrogen sulfide. With the lifting of this stay, pursuant to Section 313 of EPCRA, certain 

facilities that manufacture, process, or otherwise use hydrogen sulfide in amounts above 

reporting threshold levels must now comply with the reporting requirements that have been in 

place since hydrogen sulfide was added to the EPCRA section 313 list in 1993.

IV. What Comments Did EPA Receive on the Intent to Consider Lifting the Administrative 

Stay and What Are EPA’s Responses to Those Comments?

EPA received fifteen comments on the Federal Register document “Intent to Consider 

Lifting Administrative Stay; Opportunity for Public Comment” (75 FR 8889). The comments 

represented 6 individuals, 32 environmental groups, one state agency, and 10 industry groups. 

Environmental groups that commented included the Food & Water Watch, National Association 

of Clean Water Agencies, Natural Resources Defense Council, Waterkeeper Alliance and one 

comment submitted by 28 other environmental organizations. The comments from the 

individuals, environmental groups, and state agency were supportive of EPA’s intent to lift the 

administrative stay. Many of these groups provided additional information to support EPA’s 

action as well as requesting other actions such as listing additional industry sectors that have 

significant releases of hydrogen sulfide. The most extensive comments came from the Hydrogen 
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Sulfide Consortium, whose members are: American Coke and Coal Chemicals Institute, 

American Forest and Paper Association, American Petroleum Institute, Asphalt Institute, Carbon 

Disulfide Coalition, Corn Refiners Association, National Petrochemical and Refiners 

Association, and The Sulphur Institute. The most significant opposing comments are 

summarized and responded to below. The complete set of comments and EPA’s responses can 

be found in the response to comment document in the docket for this action (Ref. 1).

A. Comments from the Hydrogen Sulfide Consortium

1. Scope of Comments. Commenters claim that “EPA cannot properly limit comments to 

whether or not EPA should lift its administrative stay of EPCRA section 313 reporting 

requirements,” but rather must revisit the original listing decision accomplished by final rule in 

1993. In support of this argument, commenters assert that: 1) EPA stated, when it issued the 

administrative stay in 1994, that it would revisit the original listing decision; 2) EPA cited 

chronic respiratory effects as one of the bases for listing under EPCRA section 313(d)(2)(B) in 

the proposed rule, but chronic neurotoxic effects as a basis under that same provision in the final 

rule; 3) EPA adopted its current policy regarding exposure analyses subsequent to the 1993 

listing of hydrogen sulfide; and 4) EPA “must make a new listing determination before it may lift 

[the stay].”

For the reasons stated below, EPA disagrees with commenters that EPA must revisit the 

original listing decision in the context of EPA’s consideration of lifting the administrative stay of 

the EPCRA reporting requirements for hydrogen sulfide. Before addressing each of these 

arguments in turn, however, a brief reiteration of the factual background is useful.

As described in detail below, EPCRA section 313(d)(2) states that EPA may add a 

chemical to the list if “there is sufficient evidence to establish any one” (emphasis added) of the 
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listing criteria specified in section 313(d)(2). Therefore, to add a chemical, EPA must 

demonstrate that at least one criterion is met, but need not determine whether any other criterion 

is met.

EPA proposed to add hydrogen sulfide to the EPCRA section 313 list of toxic chemicals 

on September 8, 1992 (57 FR 41020) based on a determination that there was sufficient evidence 

establishing both chronic human health effects per EPCRA section 313(d)(2)(B) (specifically, 

chronic respiratory effects) and environmental effects per EPCRA section 313(d)(2)(C) 

(specifically, acute aquatic toxicity). On December 1, 1993, EPA promulgated a final rule 

adding hydrogen sulfide to the EPCRA section 313 list of toxic chemicals (58 FR 63500) 

(effective January 1, 1994). In the final rule, the listing decision was based on a determination 

that there was sufficient evidence establishing environmental effects per EPCRA section 

313(d)(2)(C) (specifically, the same acute aquatic toxicity as identified in the proposed rule) and 

chronic human health effects per EPCRA section 313(d)(2)(B). In the final rule, however, the 

chronic human health effects finding was based on chronic neurotoxic effects, instead of chronic 

respiratory effects as stated in the proposed rule.

After the final rule was issued adding hydrogen sulfide to the EPCRA section 313 list, 

and notwithstanding the fact that the Agency cited the same acute aquatic toxicity as an 

“environmental effects” basis for the listing under EPCRA section 313(d)(2)(C) in both the 

proposed rule and the final rule, some members of the regulated community expressed a concern 

that the Agency cited chronic respiratory effects as a “chronic human health effects” basis under 

EPCRA section 313(d)(2)(B) in the proposed rule, but chronic neurotoxic effects as a “chronic 

human health effects” basis under that same provision in the final rule. In addition, after 

issuance of the final rule, some members of the regulated community expressed concern that 
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EPA’s decision not to include an exposure analysis in deciding to list hydrogen sulfide on the 

basis of chronic human health effects was inconsistent with past Agency practice. Notably, 

however, the final rule adding hydrogen sulfide to the EPCRA section 313 list was never 

administratively or judicially challenged.

In response to the post-promulgation comments and concerns raised by some in the 

regulated community, and notwithstanding the fact that the listing decision was dictated by the 

acute aquatic toxicity finding alone under EPCRA section 313(d)(2)(C), EPA issued an 

administrative stay of the EPCRA section 313 reporting requirements for hydrogen sulfide on 

August 22, 1994 (59 FR 43048) in order to review those post-promulgation comments and 

concerns. 

The stay issued on August 22, 1994 made clear that: “The effect of this stay is to defer 

reporting on [hydrogen sulfide] while the Agency reviews new data and information made 

available subsequent to the promulgation of the final rule” (59 FR 43048 (Aug. 22, 1994) 

(emphasis added)). As a result, while the subsequent stay deferred reporting requirements, the 

stay did not remove hydrogen sulfide from the EPCRA section 313 list or alter that final listing 

determination, which remained in effect as of January 1, 1994.

On February 26, 2010, EPA issued a notice announcing its “Intent to consider lifting [the 

hydrogen sulfide] administrative stay; opportunity for public comment.” 75 FR 8889 

(hereinafter Intent to Lift the Stay). That document stated: “The purpose of this document is to 

provide the public with the opportunity to comment on EPA’s review of the currently available 

data on the human health and environmental effects of hydrogen sulfide ... and EPA’s belief that 

the Administrative Stay should be lifted based on that data.... In addition, this document 

addresses the concerns raised regarding use of exposure analyses.” Id. at 8891. The Intent to Lift 
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the Stay notice clearly explained: “By this current action, EPA is not revisiting the original 

listing decision, which was accomplished by final rule on December 1, 1993. Rather, EPA is 

merely presenting its rationale for why the Administrative Stay of the reporting requirements for 

hydrogen sulfide should be lifted.” Id. at 8889 (emphasis added). Again, the final rule of 

December 1, 1993 adding hydrogen sulfide to the EPCRA section 313 list of toxic chemicals was 

never administratively or judicially challenged.

a. EPA Statements when Issuing the Stay. Commenters first argue that EPA cannot now 

limit comment to whether or not to lift the stay because the Agency stated, when it issued the 

administrative stay in 1994, that it intended, at some point in the future, to “seek comment on the 

Agency’s initial determination for [hydrogen sulfide].” 59 FR at 43049. Specifically, the 

administrative stay stated:

[T]he Agency will be issuing a forthcoming Federal Register notice which will 

seek comment on the Agency’s initial determination for [hydrogen sulfide], ... 

procedural issues concerning the initial final rule, and generally, comments (and 

any supporting data) on whether the Agency should either propose to delete 

[hydrogen sulfide] or affirm its initial determination and dissolve today’s 

Administrative Stay. (59 FR at 43049).

Commenters have pointed to no authority which requires the Agency to revisit a final 

EPCRA section 313 listing determination in order to lift a subsequently issued stay of the 

reporting requirements that flow from that listing determination, regardless of the potential issues 

that the Agency may have anticipated as requiring future consideration when it issued the stay. 

The Notice announcing the stay was not a proposed or final rule or a regulation formulated 

through notice and comment rulemaking, and it changed no regulatory text. See, e.g., 59 FR at 
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43050 (“. . . the Agency does not regard today’s action as a rule. . . .”). Furthermore, even if the 

stay were a proposed or final rule, which it is not, the statements at issue would constitute 

nothing more than preamble statements and, “[w]hile preamble statements may in some unique 

cases constitute binding, final agency action susceptible to judicial review, this is not the norm. 

Agency statements ‘having general applicability and legal effect’ are to be published in the Code 

of Federal Regulations.” Natural Resources Defence Council v. EPA, 559 F.3d 561, 564–65 

(D.C. Cir. 2009) (citations omitted). As such, the statements on which the commenters are

focused simply are not binding on the Agency or outside parties.

Hydrogen sulfide was listed under section 313 of EPCRA by final rule on December 1, 

1993. The stay did not remove hydrogen sulfide from the EPCRA section 313 list or alter that 

final listing determination, which was never administratively or judicially challenged. The 1993 

listing decision was dictated by the acute aquatic toxicity finding alone under EPCRA section 

313(d)(2)(C), which was included in both the proposed and final rules and never challenged. 

Therefore, EPA does not believe it is necessary or appropriate to revisit the 1993 final listing of 

hydrogen sulfide in order to lift the stay of reporting requirements. 

Further, the Agency believes that its action in taking comment on its intent to lift the stay 

is substantially in accord with the course of action it described in issuing the stay in 1994. In the 

Intent to Lift the Stay notice, the Agency invited comment on the data underlying its 

consideration of the matter. As described in the Intent to Lift the Stay notice, that intent is based 

on EPA’s review of the currently available data, which clearly demonstrate both chronic health 

effects in humans (upper respiratory tract toxicity and neurotoxicity) and significant adverse 

effects in aquatic organisms (acute, chronic, and early life stage). Based on these findings, EPA 

believes that there is no basis for continuing the administrative stay of the reporting requirements 
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for hydrogen sulfide, and that the administrative stay should therefore be lifted. Moreover, these 

findings also demonstrate that there is no basis to even consider delisting hydrogen sulfide. 

EPCRA section 313(d)(3) states that to remove a chemical from the list, EPA must determine 

that “there is not sufficient evidence to establish any” of the Section 313(d)(2) criteria (emphasis 

added). Therefore, to remove a chemical, EPA must demonstrate that none of the criteria are 

met. As EPA’s review of the currently available data in the context of its consideration of lifting 

the administrative stay demonstrate, EPA cannot show that none of the criteria are met.

b. Proposed and Final Chronic Human Health Effects. Second, commenters argue that 

EPA cannot now limit comment to whether or not to lift the stay because EPA cited chronic 

respiratory effects as one of the bases for listing under EPCRA section 313(d)(2)(B) in the 

proposed rule, but chronic neurotoxic effects as a basis under that same provision in the final 

rule.

EPCRA section 313(d) authorizes EPA to add or delete chemicals from the list and sets 

forth criteria for these actions. The EPCRA section 313(d)(2) criteria are:

(A) The chemical is known to cause or can reasonably be anticipated to 

cause significant adverse acute human health effects at concentration levels that 

are reasonably likely to exist beyond facility site boundaries as a result of 

continuous, or frequently recurring, releases.

(B) The chemical is known to cause or can reasonably be anticipated to 

cause in humans-

(i) Cancer or teratogenic effects, or

(ii) Serious or irreversible-

(I) Reproductive dysfunctions,
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(II) Neurological disorders,

(III) Heritable genetic mutations, or

(IV) Other chronic health effects.

(C) The chemical is known to cause or can be reasonably anticipated to 

cause, because of

(i) Its toxicity,

(ii) Its toxicity and persistence in the environment, or

(iii) Its toxicity and tendency to bioaccumulate in the environment, 

a significant adverse effect on the environment of sufficient seriousness, in the

judgment of the Administrator, to warrant reporting under this section.

EPA often refers to the section 313(d)(2)(A) criterion as the “acute human health effects 

criterion;” the section 313(d)(2)(B) criterion as the “chronic human health effects criterion;” and 

the section 313(d)(2)(C) criterion as the “environmental effects criterion.”

While it is true that the Agency cited chronic respiratory effects as a “chronic human 

health effects” basis under EPCRA section 313(d)(2)(B) in the proposed rule, but chronic 

neurotoxic effects as a “chronic human health effects” basis under that same provision in the 

final rule, it bears emphasizing once again that the Agency also separately cited the same acute 

aquatic toxicity as an “environmental effects” basis for the listing under EPCRA section 

313(d)(2)(C) in both the proposed and final rules. As a result, and in light of the fact that 

EPCRA section 313(d)(2) expressly allows EPA to add a chemical to the list if “there is 

sufficient evidence to establish any one” of the listing criteria (emphasis added), the 1993 listing 

decision was dictated by the acute aquatic toxicity finding alone under EPCRA section 

313(d)(2)(C). That basis for the listing was never challenged and was and continues to be 
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Page 17 of 56

supported by the data. Any procedural error that may have occurred regarding the section 

313(d)(2)(B) “chronic human health effects” finding was harmless in light of the unchallenged 

section 313(d)(2)(C) “environmental effects” finding presented in both the proposed and final

rules.

EPA is currently lifting the stay of hydrogen sulfide reporting requirements – a substance 

that has been and remains listed under EPCRA since promulgation of the final rule on December 

1, 1993 – based on EPA’s review of the currently available data, which clearly demonstrate both 

chronic health effects in humans (upper respiratory tract toxicity and neurotoxicity) and 

significant adverse effects in aquatic organisms (acute, chronic, and early life stage). EPA is not 

revisiting the original listing determination, and comments on the original listing decision are 

beyond the scope of this action.

c. EPA’s Exposure Policy. Third, commenters argue that EPA cannot now limit 

comment to whether or not to lift the stay because EPA adopted its current policy regarding 

exposure analysis subsequent to the 1993 listing of hydrogen sulfide.

EPA did not “adopt a new policy” on its use of exposure analysis for listing chemicals 

under EPCRA section 313 subsequent to the listing of hydrogen sulfide in 1993. Instead, the 

Agency’s then-existing position on the use of exposure analyses in listing decisions under 

EPCRA section 313 was presented in a proposed rule in the Federal Register of January 12, 

1994 (59 FR 1788). That proposed rule provided the public with the opportunity to comment on 

the Agency’s then-existing interpretation of the statutory listing criteria as it relates to the use of 

exposure considerations. After considering the comments received, EPA published in the 

Federal Register of November 30, 1994 (59 FR 61432) a “chemical expansion” final rule, 

including a statement clarifying its interpretation of the statutory requirements regarding how 
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exposure is considered in listing decisions. Subsequent to that final rule, EPA’s interpretation of 

the statutory listing criteria as it relates to the consideration of exposure was upheld in National 

Oilseed Processors Ass’n. v. Browner, 924 F. Supp. 1193 (D.D.C. 1996), aff’d in part & 

remanded in part, Troy Corp. v. Browner, 120 F.3d 277 (D.C. Cir. 1997).

As stated in the chemical expansion final rule:

Through this rulemaking, EPA is clarifying its position regarding the use 

of hazard, exposure, and risk in listing decisions under EPCRA section 313. EPA 

will consider exposure factors when making determinations under section 

313(d)(2)(A) (acute human toxicity). In addition, EPA has discretion to consider 

exposure factors where appropriate for determinations under sections

313(d)(2)(B) (chronic human toxicity) and (C) (environmental toxicity), and that 

there is a broader range of circumstances in which exposure will be considered 

under section 313(d)(2)(C) than under (B).

EPA has reviewed its past listing decisions in light of this clarification, 

and believes that its prior listing determinations have been consistent in the 

consideration of exposure in 31 of the 32 listing/delisting determinations previous 

to this action....(59 FR 61442 (Nov. 30, 1994) (emphasis added)).

In Troy Corp. v. Browner, the D.C. Circuit agreed with EPA, finding:

Were the EPA to abandon a long-held exposure policy and take a new direction 

we would, as urged, require a thorough explanation of its reasons for doing so. 

Yet, the EPA’s pronouncement in its preamble of its exposure policy is not a 

change in course. With one exception, the EPA has consistently stated, as it does 

in this rulemaking, that it will consider exposure under subsection (B) only when 
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the chemical was of “low to moderately low” toxicity. ... [T]he agency has long 

maintained that it would consider exposure under subheading (B) only for low 

toxicity chemicals. The inorganic fluorides petition was denied over ten years 

ago. Since that time, the agency has made several dozen listing and delisting 

decisions under EPCRA. The inorganic fluorides case was the only instance in 

which the agency articulated a policy contrary to the one explicated in this 

rulemaking. Under these circumstances we cannot say that the agency has 

departed from prior practice in a way that requires more explanation than was 

provided. (Troy Corp. v. Browner, 120 F.3d at 287 (emphasis added) (citation 

omitted)).

Thus, EPA did not subsequently adopt a new exposure policy as Commenters suggest. 

Rather, the Agency simply clarified the existing exposure policy. Further, the 31 of 32 previous 

cases, noted by the court in Troy Corp., in which the Agency had been consistent with this 

exposure policy included the listing of hydrogen sulfide. Therefore, EPA had applied this same 

exposure policy to the listing of hydrogen sulfide, and need not, as Commenters suggest, provide 

a new notice and opportunity to comment on the use of exposure analyses in listing hydrogen 

sulfide under section 313 of EPCRA. 

As EPA explained in the Intent to Lift the Stay:

EPA has determined that hydrogen sulfide can reasonably be anticipated to cause serious 

or irreversible chronic human health effects at relatively low doses and thus is considered 

to have moderately high to high chronic toxicity. EPA does not believe that it is 

appropriate to consider exposure for chemicals that are moderately high to highly toxic 

based on a hazard assessment when determining if a chemical can be listed for chronic 
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Page 20 of 56

effects pursuant to EPCRA section 313(d)(2)(B) (see 59 FR 61432, 61433, 61440-

61442). Hydrogen sulfide has also been determined to cause ecotoxicity at relatively low 

concentrations, and thus is considered to have high ecotoxicity. EPA believes that 

chemicals that induce death or serious adverse effects in aquatic organisms at relatively 

low concentrations (i.e., they have high ecotoxicity) have the potential to cause 

significant changes in the population of fish and other aquatic organisms, and can 

therefore reasonably be anticipated to cause a significant adverse effect on the 

environment of sufficient seriousness to warrant reporting. EPA does not believe that it 

is required to consider exposure for chemicals that have high ecotoxicity based on a 

hazard assessment when determining if a chemical can be listed for effects pursuant to 

EPCRA section 313(d)(2)(C) (see 59 FR 61432, 61433, 61440-61442). (75 FR 8889, 

8893 (Feb. 26, 2010)).

d. EPA Must Make a New Listing Determination. Finally, Commenters argue that EPA 

cannot now limit comment to whether or not to lift the stay because EPA “must make a new 

listing determination before it may lift [the stay].”

This argument merely restates Commenters’ first three arguments in support of 

Commenters’ ultimate position that EPA must revisit the 1993 listing decision. For the reasons 

already discussed above, the Agency disagrees with Commenters’ arguments.

2. Implementation of EPA’s Exposure Policy. Commenters state that EPA may not 

implement its policy on the use of exposure analysis in EPCRA section 313 listing decisions in 

an arbitrary manner. Commenters claim that EPA has not identified the specific criteria it 

utilizes in determining whether a substance causes chronic human health effects at relatively low 

doses or ecotoxicity at relatively low concentrations. Commenters noted that EPA stated in its 
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intent to lift the administrative stay that it is applying the interpretation of the statutory listing 

criteria and the policy on the use of exposure analyses adopted by the EPA in its November 30, 

1994, final rule listing other substances. Commenters cited EPA’s statements from the rule that 

exposure considerations are appropriate in making listing determination under EPCRA section 

313(d)(2)(B) for chemicals with low to moderately low toxicity based on hazard assessment and 

under EPCRA section 313(d)(2)(C) for chemicals that are low or moderately ecotoxic. 

Commenters claim that they were unable to identify or locate in the docket for this action any 

objective criteria that EPA uses in making a determination of whether a substance may cause 

“serious or irreversible chronic health effects” or has “low to moderately low toxicity.” 

Commenters state that they were unable to find any explanation of the criteria that EPA uses in 

deciding whether a substance has “low to moderately low ecotoxicity.” Commenters noted that 

EPA stated that its interpretation of the statutory listing criteria that supports the 1994 policy 

statement was sustained during subsequent judicial review. 

Commenters state that even if EPA has discretion to select a policy concerning the 

circumstances in which exposure analysis will be part of the EPCRA section 313(d)(2) listing 

decision, it does not mean the EPA has unfettered discretion to apply that policy in an arbitrary 

manner. Commenters state that if EPA is to have a rational policy that can be applied in a fair 

and equitable manner, the scientists conducting a hazard assessment under EPCRA section 

313(d)(2) should not be permitted to make qualitative judgments concerning potential toxicity in 

the absence of objective criteria or guidance concerning what these terms mean.

EPA has identified the criteria that it uses in making a determination of whether a 

substance that may cause “serious or irreversible chronic health effects” has “low to moderately 

low toxicity,” and has not applied its policy on the use of exposure analysis in EPCRA section 
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Page 22 of 56

313 listing determinations in an arbitrary manner. To the contrary, in the preamble to the 1994 

chemical expansion final rule, EPA explained that two types of chemicals are considered to 

exhibit moderately high to high toxicity:

• Where a review of the scientific data provides a high level of confidence that the 

chemical causes an adverse effect at relatively low dose levels, and

• Where a review of the scientific data indicates that the chemical will cause various 

adverse effects at moderate dose levels.

(59 FR 61432, 61433 (Nov. 30, 1994). 

Thus, EPA has in fact articulated criteria for its determination whether or not exposure 

considerations will be taken into account in its chemical listing decisions.

More specifically, EPA has provided guidance concerning how it evaluates chemicals to 

determine whether they meet the EPCRA section 313 listing criteria, including information on 

the factors EPA considers in determining whether a chemical is sufficiently toxic that exposure 

need not be considered in the listing decision. The specific criteria EPA uses to determine 

whether a chemical has moderately high or high toxicity, and thus does not have low to 

moderately low toxicity, was explained in detail in the 1994 chemical expansion rule:

3. Hazard evaluation. After completing the screening phase, EPA conducted a thorough 

hazard assessment for each of the addition candidates that resulted from the above 

analyses and determined based on the weight-of-the evidence if there was sufficient 

evidence to establish that the candidate chemical met the statutory criteria for addition to 

EPCRA section 313. To make this determination, EPA senior scientists reviewed readily 

available toxicity information on each chemical for each of the following effect areas: 

acute human health effects; cancer; other chronic human effects; and environmental 
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Page 23 of 56

effects. In addition, EPA reviewed, where appropriate, information on the environmental 

fate of the chemical. 

The hazard assessment was conducted in accordance with relevant EPA 

guidelines for each adverse human health or environmental effect (e.g., the appropriate 

guidelines for hazard evaluation of chemical carcinogens and for the type of evidence 

required to substantiate a determination of carcinogenicity are the Assessment Guidelines 

for Carcinogen Risk (Ref. 4)). During this assessment the number, severity, and 

significance of the effects induced by the chemical, the dose level causing the effect, and 

the quality and quantity of the available data, including the nature of the data (e.g., 

human epidemiological, laboratory animal, field or workplace studies) and confidence 

level in the existing data base, were all considered. Where a careful review of the 

scientific data for a particular chemical results in a high level of confidence that the 

chemical causes an adverse effect at relatively low dose levels, EPA believes that this 

evidence is sufficient for listing the chemical under section 313. EPA also believes that 

where a review of the scientific data indicates that the chemical will cause various 

adverse effects at moderate dose levels, the total weight-of-the-evidence indicates that 

there is sufficient evidence for listing the chemical under EPCRA section 313. EPA 

believes that both types of chemicals described above exhibit moderately high to high 

toxicity based on a hazard assessment.

 EPA also conducted an analysis of exposure for each chemical or chemical 

category proposed for listing under EPCRA section 313(d)(2)(A) (i.e., based on adverse 

acute human health effects), and, where appropriate, under section 313(d)(2)(C) (i.e., 

based on adverse ecological effects). For chemicals listed under EPCRA section 
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Page 24 of 56

313(d)(2)(A), this analysis included estimated concentrations of the chemical at or 

beyond the facility site boundary through the use of estimated releases and modelling 

techniques. EPA did not conduct an analysis of exposure for the chemicals proposed for 

listing under section 313(d)(2)(B) because these chemicals exhibit moderately high to 

high toxicity based on a hazard assessment (see Unit IV.B. for a discussion of the use of 

exposure). As discussed more thoroughly in Unit IV.B. of this preamble, EPA does not 

believe that it is appropriate to factor exposure into the listing decisions for the chemicals 

being listed pursuant to section 313(d)(2)(B) in this rulemaking. 

 Following a review and analysis of the information available about each chemical 

in this final rule (including information provided through public comment) by senior 

Agency scientists, the Agency concludes that for each of the chemicals listed one or more 

of the EPCRA section 313 listing criteria are met. Moreover, the adverse effects 

associated with each of the chemicals being listed today are serious and significant. In 

some cases the effects are extreme, such as cancer or death. In others, the effects are 

serious and lasting, including, for example, impairment of a fetus' or an offspring's 

physical development, neurological effects inhibiting motor abilities or mental processes 

or impairing the ability to reproduce, or the sustainability of a fragile ecosystem such as 

an estuary. For a number of chemicals in the final rule, there is more than one adverse 

effect. 

 It is important to understand that although an adverse effect is known or can be 

reasonably anticipated to be caused by a chemical on the section 313 list, a release of a 

chemical into a community does not necessarily mean that the effect will occur. 

Exposure and dose are also important factors in determining whether an adverse effect 
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Page 25 of 56

occurs and how serious the manifestation will be. The listing of a chemical on the 

section 313 list does not mean that a particular community will experience these adverse 

effects. Instead the purpose for listing a chemical is to ensure that the public gets 

information about releases of such chemicals. Thus, EPA believes that for chemicals that 

typically do not affect solely one or two species but rather affect changes across a whole 

ecosystem and for which there is well-documented evidence supporting the adverse 

effects, that their addition to the EPCRA section 313 list is warranted even though the 

severity of the adverse effects that they induce will be dependent upon site-specific 

characteristics. Once EPA makes release data available through TRI, the community 

may then make its own determination on the importance of these releases (and their 

potential adverse effects). (59 FR at 61433, 11/30/1994 (emphasis added)). 

EPA went on to state in the chemical expansion rule that:

Through this rulemaking, EPA is clarifying its position regarding the use of hazard, 

exposure, and risk in listing decisions under EPCRA section 313. EPA will consider 

exposure factors when making determinations under section 313(d)(2)(A) (acute human 

toxicity). In addition, EPA has discretion to consider exposure factors where appropriate 

for determinations under sections 313(d)(2)(B) (chronic human toxicity) and (C) 

(environmental toxicity), and that there is a broader range of circumstances in which 

exposure will be considered under section 313(d)(2)(C) than under (B). 

EPA has reviewed its past listing decisions in light of this clarification, and believes that 

its prior listing determinations have been consistent in the consideration of exposure in 31 

of the 32 listing/delisting determinations previous to this action, including a number of 

deletions of low toxicity chemicals that Congress placed on the initial EPCRA section 
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Page 26 of 56

313 list. EPA is currently reviewing the one exception, inorganic fluorides, to determine 

if additional action is warranted. EPA will continue to evaluate petitions according to 

this clarification and will delete chemicals that do not meet the statutory criteria. (59 FR 

at 61442, 11/30/1994).

In National Oilseed Processors Ass’n. v. Browner, 924 F. Supp. 1193 (D.D.C. 1996), 

aff’d in part & remanded in part, Troy Corp. v. Browner, 120 F.3d 277 (D.C. Cir. 1997), the 

court held:

The Agency ... adequately explained and documented its decision making 

process in the administrative record. EPA made a finding that all of the chemicals 

that were being listed under Section 313(d)(2)(B) in this rulemaking were of high 

or moderately high toxicity, and that consideration of exposure was therefore not 

appropriate for these chemicals. See 59 Fed.Reg. 61,442.... What is significant is 

that EPA stated what its policy for consideration of exposure would be, and then 

described its application to the chemicals considered in this rulemaking.

Plaintiffs here have failed to show that EPA was unreasonable or arbitrary 

in exercising its discretion. Because EPA’s decision to not consider exposure in 

this rulemaking was consistent with its policy of using exposure data only in 

particular circumstances, i.e., where chemicals are of low toxicity, the Court 

concludes that the Agency was not arbitrary and capricious. (National Oilseed 

Processors, 924 F. Supp. at 1203-1204 (footnote omitted)).

As with the chemicals in the 1994 chemical expansion rule and all other EPA listing 

actions, EPA conducted a hazard assessment of the human health and ecological effects of 

hydrogen sulfide. Based on the data from the hazard assessment, as presented in the Federal 
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Page 27 of 56

Register notice and supporting documents, EPA determined that hydrogen sulfide is moderately 

high to highly toxic to humans and highly toxic to aquatic organisms. EPA discussed these 

determinations in detail in the notice of Intent to Lift the Stay in the Federal Register (75 FR 

8889, 2/26/2010). Human health toxicity was discussed in detail beginning on page 8891, with 

references, and ecological effects were discussed in detail beginning on page 8893, with 

references. The determinations that hydrogen sulfide has moderately high to high human 

toxicity and high ecotoxicity were based on these hazard assessments, just as EPA did in the 

1994 chemical expansion rule and other previous listing decisions.

In the section of the Federal Register document that discussed the rationale for lifting 

the stay, EPA provided the following summary of the hazard data:

EPA’s technical evaluation of hydrogen sulfide shows that it can reasonably be 

anticipated to cause chronic health effects in humans. The chronic health effects have 

been observed in laboratory animals at concentrations as low as 28 mg/m3 (20 ppm) and 

41.7 mg/m3 (30 ppm). In addition, EPA’s technical evaluation of hydrogen sulfide also 

shows that it can reasonably be anticipated to cause, because of its toxicity, significant 

adverse effects in aquatic organisms. Examples of hydrogen sulfide’s ecological toxicity 

include acute toxicity (96-hour LC50) values for freshwater fish that ranged from 0.0149 

mg/L (fathead minnow) to 0.0448 mg/L (bluegill), indicating high aquatic toxicity. 

Examples of hydrogen sulfide’s chronic ecological toxicity include freshwater fish values 

that ranged from a 6-week LOEC (growth rate) of 0.0005 mg/L in a tropical fish (Mystus 

nemurus) to a 430-day LOEC (final weight) of 0.009 mg/L for goldfish, also indicating 

high aquatic toxicity. (75 FR 8893, 2/26/2010).

As the language above clearly shows, EPA did identify the information and the rationale 
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Page 28 of 56

for why hydrogen sulfide was determined to have moderately high to high human toxicity and 

high ecotoxicity.

3. EPA’s Rationale for Hydrogen Sulfide’s Toxicity Level. Commenters claim that EPA 

has not given its rationale for why hydrogen sulfide causes chronic human health effects at 

relatively low levels and ecotoxicity at relatively low concentrations. Commenters contend that 

EPA has not provided any rationale for the determinations that no exposure assessment is needed 

for hydrogen sulfide. Commenters noted that EPA provided a description of the chronic human 

health effects and ecological toxicity of hydrogen sulfide. Commenters also noted that EPA 

asserted that it had made the requisite determinations concerning the relative magnitude of the 

toxicity of hydrogen sulfide for both human health and ecological effects. Commenters contend, 

however, that EPA’s statements are wholly conclusory and that the docket does not appear to 

contain any explanations of the relation between the hazard assessments prepared by EPA 

scientists and these determinations. Commenters state that they do not believe that the effect 

levels cited by EPA will be caused by the releases reportable under EPCRA section 313. 

Commenters state that they believe that the effect levels cited by EPA as “relatively low” are 

actually very high. Commenters stated that the chronic health effect levels cited by EPA are 

2,000 to 3,000 times greater than the odor detection threshold (10 parts per billion (ppb)) for 

hydrogen sulfide. Commenters claim that while releases may result in ambient hydrogen sulfide 

concentrations that exceed the odor detection threshold, the concentrations will always be far 

below the lowest levels for chronic effects in animals cited by EPA. Commenters cited a 1990 

EPA study on oil and natural gas extraction and a 1999 Public Health Service study for one city 

near hydrogen sulfide sources as evidence that hydrogen sulfide levels are low. Commenters 
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Page 29 of 56

also cited established state air standards that range from 83 to 200 ppb noting that these are 100 

to 150 times less than the lowest levels EPA cited for chronic effects in animals.

In discussing the data EPA cited as supporting its evaluation that hydrogen sulfide is 

toxic to aquatic organisms at relatively low concentrations, the commenters stated that while the 

levels may seem relatively low in the abstract, they believe they are actually quite high when 

viewed in the context of data that clearly establish that hydrogen sulfide will rapidly oxidize to 

less toxic chemical forms when released to surface waters. Commenters cited the EPA Water 

Quality Criteria Gold Book as support for their position:

The fact that H2S is oxidized in well-aerated water by natural biological systems to 

sulfates or is biologically oxidized to elemental sulfur has caused investigators to 

minimize the toxic effects of H2S on fish and other aquatic life. (EPA Gold Book, May 

1, 1986, page 268 (Ref. 2)).

As discussed in the previous response, EPA has provided guidance on how it determines 

whether a chemical has moderately high to high human toxicity and high ecotoxicity. In its 

notice of Intent to Lift the Stay, EPA provided a detailed hazard assessment of both the human 

health effects and the ecological effects of hydrogen sulfide. This assessment included both the 

effects caused by hydrogen sulfide and the doses/concentrations that caused those effects. This 

information was discussed in the Federal Register (75 FR 8889, 2/26/2010), and the details 

were contained in the hazard assessments and other references cited by EPA. Specifically, at 75 

FR 8889, 8891-8893 (Feb. 26, 2010), EPA’s lengthy and detailed technical review of hydrogen 

sulfide (Part IV. of the Federal Register notice, entitled “What is EPA’s Technical Review of 

Hydrogen Sulfide?”), including references, can be found (and need not be reiterated here). EPA 

then concluded, based on the hazard assessment:
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EPA has determined that hydrogen sulfide can reasonably be anticipated to cause serious 

or irreversible chronic human health effects at relatively low doses and thus is considered 

to have moderately high to high chronic toxicity.... Hydrogen sulfide has also been 

determined to cause ecotoxicity at relatively low concentrations, and thus is considered to 

have high ecotoxicity. EPA believes that chemicals that induce death or serious adverse 

effects in aquatic organisms at relatively low concentrations (i.e., they have high 

ecotoxicity) have the potential to cause significant changes in the population of fish and 

other aquatic organisms, and can therefore reasonably be anticipated to cause a 

significant adverse effect on the environment of sufficient seriousness to warrant 

reporting. (75 FR 8893, 2/26/2010). 

In the section of the Federal Register document that discussed the rationale for lifting 

the stay, EPA provided the following summary of the hazard data:

EPA’s technical evaluation of hydrogen sulfide shows that it can reasonably be 

anticipated to cause chronic health effects in humans. The chronic health effects have 

been observed in laboratory animals at concentrations as low as 28 mg/m3 (20 ppm) and 

41.7 mg/m3 (30 ppm). In addition, EPA’s technical evaluation of hydrogen sulfide also 

shows that it can reasonably be anticipated to cause, because of its toxicity, significant 

adverse effects in aquatic organisms. Examples of hydrogen sulfide’s ecological toxicity 

include acute toxicity (96-hour LC50) values for freshwater fish that ranged from 0.0149 

mg/L (fathead minnow) to 0.0448 mg/L (bluegill), indicating high aquatic toxicity. 

Examples of hydrogen sulfide’s chronic ecological toxicity include freshwater fish values 

that ranged from a 6-week LOEC (growth rate) of 0.0005 mg/L in a tropical fish (Mystus 

nemurus) to a 430-day LOEC (final weight) of 0.009 mg/L for goldfish, also indicating 
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Page 31 of 56

high aquatic toxicity. (75 FR 8893, 2/26/2010).

The above determinations are based on the human health effects and ecological effects 

caused by hydrogen sulfide and the doses/concentrations that caused those effects. EPA clearly 

stated why the hazard assessment supports a finding of moderately high to high human toxicity 

and high ecotoxicity. Therefore, EPA has clearly stated how the hazard assessment data supports 

a conclusion that hydrogen sulfide has moderately high to high human toxicity and high 

ecological toxicity.

Regarding the information that the commenter provided on previous exposure 

assessments, air standards, etc., none of that information is relevant to a determination that 

hydrogen sulfide has moderately high to high human toxicity or high ecological toxicity. The 

toxicity of a chemical is separate from whether exposures to that chemical occur or not. In 

addition, the information provided by the commenter does not demonstrate that releases of 

hydrogen sulfide could not reach a level of concern from all the types of facilities that report 

under EPCRA section 313. EPA notes that the examples of the very low air standards for 

hydrogen sulfide of 83 – 200 parts per billion support EPA’s determination that hydrogen sulfide 

is highly toxic. 

The commenter’s statement that the cited toxic effects of hydrogen sulfide are 2,000 to 

3,000 times greater than the odor detection threshold for hydrogen sulfide of 10 ppb is not a basis 

for discounting the toxic effects of hydrogen sulfide. As EPA has stated:

“Recent reviews of the health hazards associated with H2S exposure and subsequent 

treatment include Milby and Baselt (1999a) and Guidotti (1996). Earlier reviews of the 

health effects were provided by Glass (1990), Reiffenstein et al. (1992), and Mehlman 

(1994). Exposure to H2S has been reported to be an important cause of morbidity and 
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Page 32 of 56

mortality in the workplace (Snyder et al., 1995) and olfactory dysfunction (Hirsch and 

Zavala, 1999). These reviews indicate that the typical “rotten-egg odor” of H2S is an 

inadequate warning indicator of exposure since levels in the range of 100-200 ppm (140-

280 mg/m3) can lead to loss of smell followed by olfactory paralysis (Reiffenstein et al., 

1992).” (IRIS, 2003, page 10 (Ref. 3)). 

In addition, simply because someone can smell hydrogen sulfide does not mean they will 

automatically remove themselves from that exposure. Individuals that are frequently exposed to 

hydrogen sulfide may become less sensitive to the smell and, as indicated in the IRIS 

assessment, it is possible to have loss of smell from hydrogen sulfide exposure.

Commenters further state that:

EPA bases its evaluation that H2S is ecotoxic at “relatively low concentrations” 

exclusively on potential effects on aquatic life, noting that toxicity values for aquatic 

species include “numerous values that are well below 1 milligram per liter (mg/L).” 

While the levels cited by EPA may seem “relatively low” in the abstract, they are actually 

quite high when viewed in the context of data that clearly establish that H2S will be 

rapidly oxidized to less toxic chemical forms when released to surface waters. The EPA 

Water Quality Criteria Gold Book makes a similar observation: 

The fact that H2S is oxidized in well-aerated water by natural 

biological systems to sulfates or is biologically oxidized to 

elemental sulfur has caused investigators to minimize the toxic 

effects of H2S on fish and other aquatic life. 

(Footnotes omitted)

The quote from the water quality criteria document that “[t]he fact that H2S is oxidized in 
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Page 33 of 56

well-aerated water by natural biological systems to sulfates or is biologically oxidized to 

elemental sulfur has caused investigators to minimize the toxic effects of H2S on fish and other 

aquatic life” is from the introductory paragraph of the water quality criteria for hydrogen sulfide. 

This statement simply explains what has caused some investigators in the past to minimize the 

toxic effects of hydrogen sulfide. However, in the rationale section, the document goes on to 

discuss the toxicity of hydrogen sulfide to aquatic life in detail and does not dismiss the potential 

impacts hydrogen sulfide may have on aquatic life. In fact, the document presents the rationale 

for setting a water quality criterion of just 2 micrograms per liter (!g/L) undissociated hydrogen 

sulfide for fish and other aquatic life in both fresh and marine water. Concerning oxidation, the 

EPA Gold Book states:

The degree of hazard exhibited by sulfide to aquatic animal life is dependent on the 

temperature, pH, and dissolved oxygen. At lower pH values a greater proportion is in the 

form of the toxic undissociated H2S. In winter when the pH is neutral or below or when 

dissolved oxygen levels are low but not lethal to fish, the hazard from sulfide is 

exacerbated. (EPA Gold Book, May 1, 1986, page 268, (Ref. 2)). 

The criteria document also states that:

Many past data on the toxicity of hydrogen sulfide to fish and other aquatic life have been 

based on extremely short exposure periods. Consequently, these early data have 

indicated that concentrations between 0.3 and 0.4 mg/L permit fish to survive (Van Horn 

1958, Boon and Follie 1967, Theede et al., 1969). Recent long-term data, both in field 

situations and under controlled laboratory conditions, demonstrate hydrogen sulfide 

toxicity at lower concentrations. (EPA Gold Book, May 1, 1986, page 268, (Ref. 2)). 

and concludes that:
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“Available data indicate that water containing concentrations of 2.0 !g/L undissociated 

H2S would not be hazardous to most fish and other aquatic wildlife, but concentrations in 

excess of 2.0 !g/L would constitute a long-term hazard.” (EPA Gold Book, May 1, 1986, 

page 270 (emphasis added) (Ref. 2)).

The conclusion that a concentration of hydrogen sulfide in excess of just 2.0 !g/L would 

constitute a long-term hazard to aquatic life supports a determination that hydrogen sulfide is 

clearly highly toxic and a potential hazard to aquatic life despite its fate under certain 

environmental conditions. If hydrogen sulfide were not highly toxic to fish and other aquatic 

life, then there would be no need for such a very low water quality criteria value.

Regarding the two references cited by the commenters concerning oxidation of hydrogen 

sulfide in seawater and aqueous solutions (i.e., Millero, F.J., Hubinger, Fernandez and Garnett 

(1987). Oxidation of H2S in Seawater as a Function of Temperature, pH and Ionic Strength. Env. 

Sci. Tech. 21:439-443; Obrien, D.J. and Birkner, F.B. (1977). Kinetics of Oxygenation of 

Reduced Sulfur Species in Aqueous Solutions. Env. Sci. Tech. 11:1114-1120.), the Millero 

reference was cited in EPA’s hazard assessment (page 8) and the Obrien reference was cited in 

the Millero reference (see U.S. Environmental Protection Agency, Technical Review of 

Hydrogen Sulfide: Chemistry, Environmental Fate and Ecological Toxicity, CAS Registry 

Number 7783–06–4; Office of Environmental Information, Office of Information Access and 

Analysis, Environmental Analysis Division, Analytical Support Branch; June 22, 2009, in the 

docket). EPA is thus familiar with the issue of oxidation of hydrogen sulfide and discussed the 

topic in its hazard assessment on page 8 and again on page 17. However, the fact that hydrogen 

sulfide can be oxidized under certain environmental conditions does not mean that it is not 

highly toxic. As was cited above, the EPA Gold Book stated:
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The degree of hazard exhibited by sulfide to aquatic animal life is dependent on the 

temperature, pH, and dissolved oxygen. At lower pH values a greater proportion is in the 

form of the toxic undissociated H2S. In winter when the pH is neutral or below or when 

dissolved oxygen levels are low but not lethal to fish, the hazard from sulfide is 

exacerbated. (EPA Gold Book, May 1, 1986, page 268 (Ref. 2)).

If hydrogen sulfide were rapidly oxidized to harmless chemicals under all environmental 

conditions, then that would have an impact on EPA’s assessment, but that is certainly not the 

case. How much damage a particular release of hydrogen sulfide will cause can depend on a 

number of factors including the amount of the release, whether the release is continuous or 

infrequent, the pH of the water, the temperature of the water, the type of water (fresh or 

seawater), the time of year, velocity of the body of water, etc. These factors would be 

considered in site specific exposure and risk assessments. While hydrogen sulfide may be 

oxidized under certain environmental conditions, there are many common environmental 

conditions under which oxidation will not be significant and thus will not lessen the impact of a 

release of hydrogen sulfide. As the aquatic toxicity data shows, hydrogen sulfide is toxic to 

many different aquatic species and at several stages of life with some toxicity values at or below 

one part in a billion. Thus, it takes very little hydrogen sulfide to have an impact on aquatic life. 

Even under favorable oxidation conditions, the experimental half-life of hydrogen sulfide is 50 

hours in fresh water and 26 hours in seawater. Considering how low the 48 and 96 hour LC50

values are for hydrogen sulfide, hydrogen sulfide toxicity is still a concern even under favorable 

oxidation conditions. The potential oxidation of hydrogen sulfide does not lessen the inherent 

toxicity of hydrogen sulfide. 

EPA notes that, other than the single quote from the water quality criteria document and 
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two references concerning oxidation of hydrogen sulfide in water, the commenters have not 

questioned or tried to refute in any way the aquatic toxicity information provided in EPA’s 

hazard assessment. The summary table of the aquatic toxicity values presented in the hazard 

assessment provided over 90 toxicity values from more than a dozen sources. If the commenters 

did not believe that all this information supports a finding that hydrogen sulfide is highly toxic to 

aquatic organisms, then it would have been helpful if they could have provided specific 

comments on why those data should not be considered sufficient to support EPA’s conclusions.

With regard to the commenters’ statements concerning criteria or guidance for 

determining whether a chemical has moderately high to high human toxicity or high ecological 

toxicity, the commenters appear to have been looking for some type of bright-line numerical 

criteria. The comments regarding criteria or guidance for determining whether a chemical has 

moderately high to high human toxicity or high ecological toxicity, have been addressed in 

EPA’s other responses to the commenters. With regard to possible numerical criteria, EPA 

would not agree that bright-line numerical criteria should be or need to be established in order to 

determine whether a chemical has moderately high to high human toxicity or high ecological 

toxicity. As EPA explained in the chemical expansion rule in 1994:

The hazard assessment was conducted in accordance with relevant EPA guidelines for 

each adverse human health or environmental effect (e.g., the appropriate guidelines for 

hazard evaluation of chemical carcinogens and for the type of evidence required to 

substantiate a determination of carcinogenicity are the Assessment Guidelines for 

Carcinogen Risk (Ref. 4)). During this assessment the number, severity, and significance 

of the effects induced by the chemical, the dose level causing the effect, and the quality 

and quantity of the available data, including the nature of the data (e.g., human 
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epidemiological, laboratory animal, field or workplace studies) and confidence level in 

the existing data base, were all considered. Where a careful review of the scientific data 

for a particular chemical results in a high level of confidence that the chemical causes an 

adverse effect at relatively low dose levels, EPA believes that this evidence is sufficient 

for listing the chemical under section 313. EPA also believes that where a review of the 

scientific data indicates that the chemical will cause various adverse effects at moderate 

dose levels, the total weight-of-the-evidence indicates that there is sufficient evidence for 

listing the chemical under EPCRA section 313. EPA believes that both types of 

chemicals described above exhibit moderately high to high toxicity based on a hazard 

assessment. (59 FR 61433, 11/30/1994).

EPA provided a hazard assessment that presented the information used to support the 

finding that hydrogen sulfide has moderately high to high human toxicity and high ecotoxicity. 

As in the 1994 rulemaking, and subsequent rulemakings, the data presented in the hazard 

assessments addressed issues such as the number, severity, and significance of the effects 

induced by the chemical, the dose level causing the effect, and the quality and quantity of the 

available data, including the nature of the data (e.g., human epidemiological, laboratory animal, 

field or workplace studies) and confidence level in the existing data base. All commenters had 

the opportunity to comment on whether these data support EPA’s determinations regarding the 

toxicity of hydrogen sulfide in response to EPA’s notice of Intent to Lift the Stay of the reporting 

requirements for hydrogen sulfide. Establishing a bright-line numerical criteria would limit 

EPA’s ability to consider other factors that might increase or decrease the concern for the 

toxicity of a chemical. For example, if one chemical causes one serious effect at 100 milligrams 

per kilogram per day (mg/kg/day) and another chemical causes multiple serious effects across 
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multiple organ systems but at 300 mg/kg/day it would not make sense to discount the latter if 

there were some arbitrary numerical cutoff of 200 mg/kg/day. EPA does not believe that would 

be the correct way to evaluate chemicals for listing. Rather, EPA considers all of the toxicity 

data, including the doses/concentrations causing the toxic effects, in making determinations 

about the toxicity of a chemical. EPA provided this information in the hazard assessment for 

hydrogen sulfide and provided its rationale for lifting the stay based on this information.

While EPA has not set bright-line numerical criteria, a quick review of the chemicals 

included in the 1994 chemical expansion rule (59 FR 61432, 11/30/1994), the Persistent, 

Bioaccumulative, and Toxic (PBT) rule (64 FR 693, 1/5/1999), and other actions shows that the 

doses and concentrations that cause adverse effects for hydrogen sulfide are well within those of 

chemicals that EPA has previously determined to have moderately high to high human toxicity 

and high ecotoxicity. In fact, with regard to ecotoxicity, some of the levels at which hydrogen 

sulfide causes toxicity are among the lowest that EPA has evaluated. Even if EPA were to 

establish a bright-line numerical criteria, based on EPA’s previous listing determinations the 

levels at which hydrogen sulfide causes toxicity would be well below any such numerical 

criteria.

EPA notes that other programs within the Agency that have numerical criteria for aquatic 

organisms have set numerical criteria that are consistent with the kind of toxicity concentrations 

that EPA has identified has being highly toxic in EPCRA section 313 evaluations. For example, 

the Office of Pesticide Programs cites the following:

Aquatic Organisms: Acute

Concentration (ppm) Toxicity Category

<0.1 very highly toxic

0.1 – 1 highly toxic

>1 – 10 moderately toxic

>10 – 100 slightly toxic
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>100 practically nontoxic

(http://www.epa.gov/oppefed1/ecorisk_ders/toera_analysis_eco.htm#Ecotox).

Under the above numerical criteria, not only would hydrogen sulfide be considered highly toxic, 

but most of the available data would support a classification of very highly toxic.

4. Qualitative Judgment on Exposure Levels. Commenters stated that the lack of any 

objective rationale for EPA’s determination that hydrogen sulfide causes health and ecological 

effects at relatively low levels suggests that EPA made a qualitative judgment about the 

magnitude of the potential exposure without preparing any supporting exposure analysis. 

Commenters restated their position that EPA has not provided any objective criteria for its 

determination that hydrogen sulfide causes human health effects and ecological effects at 

relatively low levels. Commenters assert that one possibility is that EPA scientists have simply 

made a qualitative judgment concerning the plausibility that hydrogen sulfide exposure might 

occur at the levels in question. Commenters stated that such a judgment would be intrinsically 

arbitrary when it is possible to do a proper and defensible exposure analysis. Commenters claim 

that if an exposure analysis were conducted they are confident it would show that exposure 

levels are below the levels that EPA has identified for human health effects and ecological 

effects.

As discussed in a previous response to this commenter, EPA has provided the 

information it used to determine that hydrogen sulfide has moderately high to high human 

toxicity and high ecotoxicity and has explained the methodology by which EPA makes such 

determinations. Therefore, EPA disagrees with the commenter’s statement that EPA did not 

provide an objective rationale for its determinations.

Commenter asserts that:

“One possibility is that EPA scientists have simply made a qualitative judgment 
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concerning the plausibility that H2S exposure might occur at the levels in question. Such 

a judgment would be intrinsically arbitrary when it is possible to do a proper and 

defensible exposure analysis.”

There is nothing in the materials that EPA has provided that even suggests that EPA made a 

qualitative judgment about hydrogen sulfide exposure levels. The determination as to whether or 

not a chemical has moderately high to high human toxicity or high ecotoxicity is separate from 

any consideration of potential exposures. EPA did not consider or evaluate the potential 

exposures to hydrogen sulfide in making its finding that hydrogen sulfide has moderately high to 

high toxicity to humans and is highly toxic to aquatic organisms. The toxicity of a chemical is 

an intrinsic property of the chemical; it is not based on exposure levels. Unlike the intrinsic 

toxicity of a chemical, exposure levels can change depending on many factors such as release 

quantities, type of release, changes in weather patters, etc. As EPA has stated:

It is important to understand that although an adverse effect is known or can be 

reasonably anticipated to be caused by a chemical on the section 313 list, a release of a 

chemical into a community does not necessarily mean that the effect will occur. 

Exposure and dose are also important factors in determining whether an adverse effect 

occurs and how serious the manifestation will be. The listing of a chemical on the 

section 313 list does not mean that a particular community will experience these adverse 

effects. Instead the purpose for listing a chemical is to ensure that the public gets 

information about releases of such chemicals. Thus, EPA believes that for chemicals that 

typically do not affect solely one or two species but rather affect changes across a whole 

ecosystem and for which there is well-documented evidence supporting the adverse 

effects, that their addition to the EPCRA section 313 list is warranted even though the 
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severity of the adverse effects that they induce will be dependent upon site-specific 

characteristics. Once EPA makes release data available through TRI, the community 

may then make its own determination on the importance of these releases (and their 

potential adverse effects). (59 FR 61433, 11/30/1994).

The U.S. Court of Appeals for the District of Columbia Circuit, in upholding EPA’s 

interpretation of EPCRA section 313 listing decisions as it relates to the use of exposure 

provided a very good example of the difference between the toxicity of a chemical and exposure 

to that chemical:

It is not the case that the congressional language mandating listing of a chemical that ‘is 

known to cause or can reasonably be anticipated to cause in humans’ the enumerated 

adverse effects unambiguously incorporates the likelihood of contact between humans 

and the chemical. A simple analogy quickly refutes NPG's argument that the language is 

unambiguous. Consider a herpetologist and a student contemplating a reptile imprisoned 

in a glass cage. The student asks, ‘Can that snake's bite reasonably be anticipated to 

cause death in humans?’ The scientist replies, ‘Yes.’ The scientist is not commenting on 

the likelihood of the serpent's escape, only the toxicity of its venom. Concededly, his 

answer could be taken to mean, ‘Yes, it is likely that this creature will escape, bite 

someone, and kill them.’ But that is certainly not the unambiguous purport of his words. 

Even so is the statutory language of Congress. It is conceivable that Congress may have 

contemplated release in its phrasing of the standard, but that is certainly not 

unambiguously the case. (Troy Corp. v. Browner, 120 F.3d 277, 285 (D.C. Cir. 1997)).

The example of a snake in a glass cage provides a perfect illustration of the difference 

between exposure and toxicity. Just as the containment of the snake in a glass cage does not 
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change the fact that the snake’s venom is highly toxic, lack of exposure does not lessen the 

intrinsic toxicity of a chemical. Lack of exposure addresses the issue of the level of risk, not the 

level of toxicity.

5. Use of Best Available Science. Commenters claim that EPA did not properly consider 

the best available scientific evidence concerning hydrogen sulfide toxicity and exposure. 

Commenters cited to one clinical study of potential neurological effects of hydrogen sulfide 

exposure in humans that EPA did not consider. Commenters stated that in the Fieldler et al.

study (Ref. 4), 74 healthy male and female volunteers participated in a clinical study designed to 

evaluate neurobehavioral effects of 2-hour controlled chamber exposures to hydrogen sulfide. 

Commenters state that neurobehavioral effects were evaluated using a battery of established tests 

immediately prior to, and immediately following, exposure to 0.05, 0.5, and 5.0 ppm hydrogen 

sulfide in separate sessions approximately one week apart. Commenters state that the sequence 

of exposures was randomly assigned to each subject and that the investigators reported that no 

significant changes were found between pre- and post-exposure performance, and that no doseresponse was found in any of the neurobehavioral or neurosensory data sets. Commenters 

contend that although the exposures studied in the Fiedler et al. study did not constitute chronic 

exposure, the study is highly relevant in establishing the levels at which humans might 

experience neurological effects from hydrogen sulfide exposure. Commenters claim that the 

neurobehavioral endpoints that were evaluated in this study are likely to be much more effective 

in capturing subtle neurological impairments that could not be detected in animal studies. 

Commenters provided an additional primary literature resource for the evaluation of 

hydrogen sulfide human health effects. However, the commenters mistakenly reported no 

significant changes between pre- and post-exposure performance. This is inaccurate as the 
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authors identified significant impairment of verbal learning in all exposure groups (p ! 0.0003). 

Although the response was not dose dependent, the authors offer several explanations for this 

finding including a threshold effect for hydrogen sulfide as low as 0.05 ppm. 

EPA’s Federal Register notice of Intent to Lift the Stay of the hydrogen sulfide 

reporting requirements specifically states that the human health concern for hydrogen sulfide is 

chronic human health effects (both upper respiratory and neurotoxic effects) (75 FR 8893, 

February 26, 2010). As the commenters correctly pointed out, the Fiedler et al. study “Sensory 

and Cognitive Effects of Acute Exposure to Hydrogen Sulfide” evaluated only acute exposures –

not chronic exposures. The study evaluated subjects exposed to hydrogen sulfide for ! 2 hours. 

Therefore, the study in question is not relevant to the chronic human health effects or the 

environmental effects that form the basis of EPA’s cited concerns for hydrogen sulfide.

While the Fiedler et al. study may be relevant in establishing the levels at which humans 

might experience neurological effects from acute hydrogen sulfide exposure, the Agency does

not support the extension to chronic neurological effects. The Fiedler et al. study was designed 

to evaluate cognitive endpoints shown to be responsive in acute studies. As detailed in the 

Federal Register (75 FR 8891, February 26, 2010), hydrogen sulfide neurotoxicity is thought to 

occur due to hypoxia induced neuronal cell death. This pathology would not be evidenced in the 

short-term human study conducted by Fiedler et al. because the exposures were acute not 

chronic. Therefore, we would also conclude that the neurobehavioral endpoints that were used in 

the Fiedler et al. study are not, as the commenters suggests, “likely to be much more effective in 

capturing subtle neurological impairments that could not be detected in animal studies” since the 

effects of chronic exposure would not be observed. The ability to sacrifice animals to study 

neurotransmitters and brain chemistry provides a powerful molecular tool that is not available in 
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human studies. These technologies provide powerful quantitative data, as evidenced in Skrajny 

et al. (1992) (Ref. 5).

It should also be noted that the hydrogen sulfide inhalation exposure in the Fiedler et al.

study ranged from 0.05 to 5.0 ppm. This is far below the lowest observed adverse effect levels 

(LOAELs) seen in the animal studies of neurotoxicity cited in EPA’s notice of Intent to Lift the 

Stay and support materials. The Fiedler et al. study may indicate that hydrogen sulfide can cause 

adverse effects in humans at exposure levels (at least acute exposure levels) much lower than 

previously expected.

6. New Hydrogen Sulfide Dosimetry Data. Commenters state that EPA has not 

considered new information on tissue dosimetry in determining the no observed adverse effect 

levels for chronic inhalation exposure to hydrogen sulfide. Commenters cited two studies that, in 

combination with the Fiedler et al. study, they contend demonstrate that the chronic human 

health effects are not likely at hydrogen sulfide concentrations of 5 ppm or below. Commenters 

cited the 2006 Schroeter et al. study (Ref. 6), in which the authors used computational fluid 

dynamics (CFD) modeling to quantitatively correlate hydrogen sulfide tissue dosimetry in rat 

and human nasal passages. Commenters state that assuming that equivalent hydrogen sulfide 

flux values will induce similar responses in the olfactory regions of rats and humans, the no 

observed adverse effect level-human equivalent concentration (NOAEL-HEC) was estimated to 

be 5 ppm. Commenters also cited a 2010 Schroeter et al. study (Ref. 7) in which the authors 

investigated interhuman variability of hydrogen sulfide nasal dosimetry using anatomically 

accurate CFD models of the nasal passages of five adults and two children generated from 

magnetic resonance imaging (MRI) or computed tomography (CT) scan data. Commenters state 

that using allometrically equivalent breathing rates, the authors simulated steady-state inspiratory 
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airflow and hydrogen sulfide uptake. Approximate locations of olfactory epithelium were 

mapped in each model to compare air:tissue flux in the olfactory region among individuals. The 

fraction of total airflow to the olfactory region ranged from 2 percent to 16 percent. Despite this 

wide range in olfactory airflow, hydrogen sulfide dosimetry in the olfactory region was predicted 

to be similar among individuals. Differences in the 99th percentile and average flux values were 

<1.2-fold at inhaled concentrations of 1, 5, and 10 ppm. Commenters contend that these 

preliminary results suggest that differences in nasal anatomy and ventilation among adults and 

children do not have a significant effect on hydrogen sulfide dosimetry in the olfactory region. 

The Agency would like to thank the commenters for bringing additional primary research 

studies to our attention, enabling us to make decisions using all available resources. EPA agrees 

with the commenters in regard to consideration of the dosimetry information presented in both 

papers by Schroeter et al. This type of pharmacokinetic modeling and the results presented 

represent the current state-of-the-science for inhalation dosimetry and are being reviewed by 

EPA for its utility in addressing our current reference concentration (RfC) derivation methods 

(see http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=212131). However, it is important to 

note that the purpose of the papers by Schroeter et al. was to provide a model-based NOAELHEC (5 ppm), not an alternative final RfC which incorporates the application of uncertainty 

factors. Thus, the only part of the EPA’s methods in deriving a value that is addressed is the 

calculation of an HEC extrapolated from animal data. No judgment is made by these authors 

that 5 ppm represents a replacement or alternative RfC or serves to replace or reduce the 

application of uncertainty factors. EPA's human health hazard assessment for hydrogen sulfide 

is based on the Agency’s current IRIS toxicological profile (Ref. 3), and while this new 

dosimetry information and resulting NOAEL-HEC might be considered in a revaluation of the 
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current RfC, it does not impact EPA’s assessment of the potential for hydrogen sulfide to cause 

chronic toxicity.

The Agency does not concur with the commenter’s conclusion that the Fiedler and 

Shroeter studies demonstrate that chronic human health effects are not likely at hydrogen sulfide 

concentrations of 5 ppm or below. As noted, the Fiedler study addresses solely acute exposures 

and is not relevant to chronic effects. Further, the Schroeter reports only provide data for use in 

calculating the NOEAL-HEC based on pharmacokinetic modeling. Therefore, the commenter’s 

conclusions regarding chronic human health effects of hydrogen sulfide are not supported by the 

studies presented.

7. No Need for TRI Reporting. Commenters contend that there is no need to include 

hydrogen sulfide on the Toxics Release Inventory. Commenters restated their claim that 

emissions of hydrogen sulfide reported under EPCRA section 313 cannot be reasonably 

anticipated to cause any of the chronic health effects covered by EPCRA section 313(d)(2)(B). 

Commenters state that although accidental releases of hydrogen sulfide can result in serious 

adverse effects, such releases are subject to the emergency notification requirements of EPCRA 

section 304 and by the Comprehensive Environmental Response, Compensation, and Liability 

Act (CERCLA) section 103. Commenters state that such accidental releases are expressly

regulated pursuant to Clean Air Act (CAA) Section 112(r) and hydrogen sulfide is among the 

substances that were specifically identified for such regulation by Congress in Section 112(r). 

Commenters also claim that since there is no evidence that suggests that routine releases of 

hydrogen sulfide pose any risk, nothing would be achieved by adding reporting requirements 

under EPCRA section 313. Commenters contend that since emissions of hydrogen sulfide that 

would typically be reported under EPCRA Section 313 are irrelevant to potential chronic health 
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effects of the type addressed by EPCRA Section 313(d)(2)(B), and accidental releases of 

hydrogen sulfide that might be expected to present a potential hazard are well regulated, 

reporting under EPCRA Section 313 serves no purpose. Commenters claim that even if EPA has 

properly determined that hydrogen sulfide has “moderately high to high chronic toxicity,” EPA 

is not required to list hydrogen sulfide in these circumstances.

Commenters state that in announcing its policy concerning use of exposure analyses in 

listing determinations under EPCRA Section 313(d)(2), EPA stated: 

The statute is silent on the issue of exposure considerations for the section 313(d)(2)(B) 

and (C) criteria. The language of section 313 does not prohibit EPA from considering 

exposure factors when making a finding under either section 313(d)(2)(B) or section 

313(d)(2)(C). (59 FR 61441-61442).

Commenters state that the reviewing court that reviewed this construction expressly affirmed this 

conclusion, stating that “chemicals of moderate or high toxicity are not necessarily added [to the 

list] because of it.” Troy Corp. v. Browner, 120 F.3d at 287.

Commenters claim that EPA has not cited any adverse consequence from the 

administrative stay of reporting requirements under EPCRA Section 313 that has been in place 

for over 15 years and that EPA should exercise its discretion to consider exposure factors in 

making a new listing determination for hydrogen sulfide and then rescind its prior listing 

determination.

As EPA stated in response to the commenter’s previous comments on the releases of 

hydrogen sulfide, EPA does not agree that the commenters have shown that releases of hydrogen 

sulfide will not cause the kinds of health and environmental effects that EPA cited as support for 

listing hydrogen sulfide. Most importantly, EPA is not required to show that the effects that 
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hydrogen sulfide can cause are actually occurring in order to list it on EPCRA section 313. EPA 

notes that other commenters have provided comments alleging that they have experienced 

adverse health effects from hydrogen sulfide releases (see for example: EPA-HQ-TRI-2009-

0844-0076, EPA-HQ-TRI-2009-0844-0081 in the docket for this action).

Regarding the fact that accidental releases of hydrogen sulfide that may cause serious 

adverse health effects including death are covered by other statutes, this has no impact on the 

listing of a chemical under EPCRA section 313. Listing of a chemical under EPCRA section 

313 is separate and apart from any other regulatory actions. EPCRA section 313 is focused on a 

community’s right-to-know about releases of toxic chemicals, not emergency reporting 

requirements for industrial accidents.

With regard to the commenter’s statements that listing hydrogen sulfide on EPCRA 

section 313 serves no purpose, the Agency disagrees. As EPA has stated:

It is important to understand that although an adverse effect is known or can be 

reasonably anticipated to be caused by a chemical on the section 313 list, a release of a 

chemical into a community does not necessarily mean that the effect will occur. 

Exposure and dose are also important factors in determining whether an adverse effect 

occurs and how serious the manifestation will be. The listing of a chemical on the 

section 313 list does not mean that a particular community will experience these adverse 

effects. Instead the purpose for listing a chemical is to ensure that the public gets 

information about releases of such chemicals. Thus, EPA believes that for chemicals that 

typically do not affect solely one or two species but rather affect changes across a whole 

ecosystem and for which there is well-documented evidence supporting the adverse 

effects, that their addition to the EPCRA section 313 list is warranted even though the 
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Page 49 of 56

severity of the adverse effects that they induce will be dependent upon site-specific 

characteristics. Once EPA makes release data available through TRI, the community 

may then make its own determination on the importance of these releases (and their 

potential adverse effects). (59 FR 61433, 11/30/1994 (emphasis added)).

Listing a chemical under EPCRA section 313 allows the public and governments to track 

and assess the impacts of chemical releases and make determinations as to whether or not a risk 

exists. Without release data, the public is limited in its ability to determine whether or not 

releases of a toxic chemical are impacting their health and/or environment. Even if releases are 

low and no adverse impacts are expected, that information is still of value to the public. 

The listing of hydrogen sulfide on EPCRA section 313 is consistent with EPA’s stated 

policy on the use of exposure assessments, which does not include the use of exposure for 

chemicals such as hydrogen sulfide that have moderately high to high human toxicity and high 

ecotoxicity. The commenter suggests that EPA should exercise its discretion with regard to the 

consideration of exposure, citing Troy Corp v. Browner for the proposition that “chemicals of 

moderate or high toxicity are not necessarily added [to the list] because of it.” Placed in greater 

context, that quotation is as follows:

The EPA's exposure policy merely informed the public that the agency would 

exercise its discretion by considering exposure only for low toxicity chemicals. 

The EPA did not thereby curtail this discretion; it did nothing more than clarify its 

own position. The policy does not impose rights or obligations or bind the 

agency to a particular result. Chemicals of low toxicity may be added despite the 

policy, just as chemicals of moderate or high toxicity are not necessarily added 

because of it. (Troy Corp. v. Browner, 120 F.3d at 287).
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As the D.C. Circuit noted, EPA stated that it would exercise its discretion by considering 

exposure only for low toxicity chemicals. If EPA were to consider exposure for hydrogen 

sulfide it would be inconsistent with the Agency’s stated policy on the use of exposure 

assessments in EPCRA section 313 listing decisions. While EPA does have discretion to deviate 

from its policy, the Agency does not believe that there is any reason to consider exposure in its 

listing decision for hydrogen sulfide and thus has no reason to deviate from its stated exposure 

policy. 

B. Comments from the National Renderers Association.

The commenter stated that they do not support listing hydrogen sulfide emissions from 

rendering plants under EPCRA section 313 because of what they claim are extremely low levels 

of hydrogen sulfide potentially emitted from such facilities. The commenter stated that they 

agreed with EPA that, at certain concentration levels, exposure to hydrogen sulfide can cause 

significant adverse acute and chronic human health effects and adverse impacts to the 

environment. The commenters contend that these potentially harmful concentrations are well 

understood, published, and regulated under the Occupational Safety and Health Administration 

(OSHA) and the National Institute for Occupational Safety and Health (NIOSH) standards with 

which their facilities comply. The commenter stated that there are safe levels of hydrogen 

sulfide exposure and that the fence-line concentration of hydrogen sulfide at a typical rendering 

plant would be expected to be well below these safe levels. The commenter recommended that 

EPA take into account the “concentration levels that are reasonably likely to exist beyond facility 

site boundaries as a result of continuous, or frequently recurring, releases,” as required under 

EPCRA section 313(d)(2)(A), and exempt the reporting of hydrogen sulfide as a by-product of 

rendering operations.
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The commenter provided information on the natural sources of hydrogen sulfide and 

information that hydrogen sulfide degrades rapidly in the environment. The commenter stated 

that the typical rendering plant might emit roughly 400 pounds of hydrogen sulfide per year. 

The commenter stated that hydrogen sulfide can be found in very low concentrations throughout 

the rendering industry supply and processing chain as a by-product related to the recycling, 

collecting, handling and processing of animal byproduct and used cooking oil. The commenter 

claims that hydrogen sulfide releases in the rendering facility workplace environment tend to be 

fugitive in nature, inconsistent in concentration, and irregularly present. The commenter stated 

that the presence of hydrogen sulfide, if any, depends on the age of the raw materials, moisture 

content, temperature, state of anaerobic bacterial decay, and other factors. The commenter 

claimed that “[h]ydrogen sulfide concentration emissions from a typical rendering plant likely 

result in air concentrations off-site that would be several orders of magnitude below 

concentrations that are potentially hazardous to human health and the environment.” The 

commenter claims that as a result of these characteristics, the hydrogen sulfide that may be 

present in a rendering facility is not likely to reach site boundaries at any measurable or reliably 

quantifiable concentration. The commenters claim that through their years of studying potential 

hydrogen sulfide emissions in rendering operations, they know that it is difficult to quantify and 

report the low levels of emissions that may occur at their facilities. The commenter suggested 

that the addition of hydrogen sulfide to TRI listing must, at a minimum, allow for no TRI 

requirements for de minimums sources such as facilities in the rendering supply and processing 

chain.

As EPA discussed in the Notice of Intent to Lift the Stay (75 FR 8893, 8889, February 

26, 2010), exposure consideration is not appropriate for chemicals that have moderately high to 
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high chronic human health toxicity or high environmental toxicity. Hydrogen sulfide meets both 

of these criteria, therefore exposure (or the potential for exposure) is not a factor in the listing 

decision. Regarding EPCRA section 313(d)(2)(A), hydrogen sulfide is not listed under that 

criteria, but rather the criteria of EPCRA sections 313(d)(2)(B) and (C).

It is well known that hydrogen sulfide is a byproduct of the rendering process (Ref. 8). 

EPA has published emission factors for at least one stage of the rendering process (Ref. 9). The 

commenter believes that reporting would be difficult for hydrogen sulfide, yet they provide an 

estimate of 400 pounds of releases per year, thus it appears that these facilities could make at 

least a reasonable estimate of releases as required under EPCRA section 313. EPA notes that 

rendering plants must already report their release of ammonia, another gas with variations in 

production and release. Regarding whether or not “emissions from a typical rendering plant 

likely result in air concentrations off-site that would be several orders of magnitude below 

concentrations that are potentially hazardous to human health and the environment,” unless the 

release data is made available the local communities and governments will not be able to confirm 

this conclusion. EPCRA section 313 contains no provisions for de minimis sources other than 

the fact that facilities must exceed the reporting thresholds (25,000 pounds for manufacture and 

processing and 10,000 pounds for otherwise use). It appears that rendering plants do not use 

hydrogen sulfide, thus they would have to manufacture or process 25,000 pounds before they 

would have to file a report. 

C. Comments from the American Meat Institute.

The commenters stated that they agree with the comments submitted by the National 

Renderers Association. The commenter stated that in their members’ plants hydrogen sulfide is 

released primarily in rendering and waste treatment processes and that the releases are fugitive, 
Internal Draft Document Only; Do Not Cite, Quote or Release.

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can be widespread and are in concentrations that are irregular and inconsistent. The commenter 

stated that to comply with EPCRA Section 313, their members will have to estimate their 

releases to determine if the reporting thresholds are met. The commenter claimed that because of 

the ephemeral nature of the releases, standard field and even more sophisticated laboratory grade 

measurement devices are inadequate and unreliable. The commenter claimed that the releases 

disperse rapidly, resulting in concentrations below the measurement capability of some devices 

and, regardless of the measurement device, the measurements are not easily replicated. The 

commenter stated that meat packing and processing plants do not have a reliable method for 

determining compliance. The commenter stated that because of this they have significant 

concerns regarding how to implement EPCRA section 313 with respect to hydrogen sulfide and 

contend EPA should consider such practical issues before lifting the stay. 

EPA notes that the ability of any one particular industry to be able to report releases is 

not a factor in determining whether a chemical meets the EPCRA section 313 listing criteria. It 

is well known that hydrogen sulfide is a byproduct of the rendering process (Ref. 8). EPA has 

published emission factors for at least one stage of the rendering process (Ref. 9). The 

commenter believes that reporting would be difficult for hydrogen sulfide, yet the National 

Renderers Association provided an estimate of 400 pounds of releases per year, thus it appears 

that these facilities could make at least a reasonable estimate of releases as required under 

EPCRA section 313. EPA notes that rendering plants as well as meat packing and processing 

plants must already report their release of ammonia, another gas that is also likely to have 

variations in production and release as it is also produced from the decay of organic matter. 

While EPA would like to collect the most accurate information possible, EPCRA section 313 

only requires that facilities report a reasonable estimate of releases. EPA sees no reason why 
Internal Draft Document Only; Do Not Cite, Quote or Release.

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meat packing and processing plants should not be able to make at least reasonable estimates of 

the amounts of hydrogen sulfide manufactured and released.

VI. What are the References Cited in This Document?

EPA has established an official public docket for this action under Docket ID No. EPAHQ-TRI-2009-0844. The public docket includes information considered by EPA in developing 

this action, including the documents listed below, which are electronically or physically located 

in the docket. In addition, interested parties should consult documents that are referenced in the 

documents that EPA has placed in the docket, regardless of whether these referenced documents 

are electronically or physically located in the docket. For assistance in locating documents that 

are referenced in documents that EPA has placed in the docket, but that are not electronically or 

physically located in the docket, please consult the person listed in the above FOR FURTHER 

INFORMATION CONTACT section. 

1. USEPA, OEI. Response to Comments Received on the February 26, 2010, Federal Register 

Document (75 FR 8889): Hydrogen Sulfide; Community Right-to-Know Toxic Chemical 

Release Reporting; Intent to consider lifting the administrative stay; opportunity for public 

comment. U.S. Environmental Protection Agency, Office of Environmental Information, Office 

of Information Analysis and Access. September 30, 2010.

2. USEPA, Office of Water Regulations and Standards, Quality Criteria for Water, EPA 440/5-

86-001 (May 1, 1986) (EPA Gold Book), page 268.

3. U.S. Environmental Protection Agency. “Toxicological Review of Hydrogen sulfide, (CAS 

No. 7783-06-4), In Support of Summary Information on the Integrated Risk Information 

System.” Washington, DC: Integrated Risk Information System. U.S. Environmental Protection 

Agency. June, 2003. http://www.epa.gov/ncea/iris/toxreviews/0061-tr.pdf Integrated Risk 
Internal Draft Document Only; Do Not Cite, Quote or Release.

Page 55 of 56

Information Summary for Hydrogen Sulfide available at: 

http://www.epa.gov/ncea/iris/subst/0061.htm

4. Fiedler N., Kipen H., Ohman-Strickland P., Zhang J., Weisel C., Laumbach R., Kelly-McNeil 

K., Olejeme K., and Lioy P., “Sensory and Cognitive Effects of Acute Exposure to Hydrogen 

Sulfide.” Env. Health Persp. v. 116(1), (2008), pp. 78-85.

5. Skrajny, B., Hannah, R.S., Roth, S.H., “Low concentrations of hydrogen sulphide alter 

monoamine levels in the developing rat central nervous system.” Can. J. Physiol. Pharmacol. v. 

70(11), (1992), pp. 1515-1518.

6. Schroeter J.D., Kimbell J.S., Andersen M.E., and Dorman D.C., “Use of a pharmacokineticdriven computational fluid dynamics model to predict nasal extraction of hydrogen sulfide in rats 

and humans.” Toxicol. Sci. v. 94(2), (2006), pp. 359-367. 

7. Schroeter J.D., Garcia G.J. M., and Kimbell, J.S., “A computational fluid dynamics approach 

to assess interhuman variability in hydrogen sulfide nasal dosimetry.” Inhalation Toxicol. v. 

22(4), (2010), pp. 277-286. 

8. Emission Factor Documentation for AP-42 Section 9.5.3 Meat Rendering Plants Final Report. 

Prepared by Midwest Research Institute (MRI) for the Office of Air Quality

Planning and Standards (OAQPS), U. S. Environmental Protection Agency (EPA), under EPA 

Contract No. 68-D2-0159. September 1995.

9. AP 42, Fifth Edition, January 1995. Compilation of Air Pollutant Emission Factors, Volume I: 

Stationary Point and Area Sources. Chapter 9: Food and Agricultural Industries section 9.5.3 

Meat Rendering Plants. Office of Air Quality Planning and Standards (OAQPS), Office of Air 

and Radiation, U. S. Environmental Protection Agency (EPA).

List of Subjects in 40 CFR Part 372
Internal Draft Document Only; Do Not Cite, Quote or Release.

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Environmental protection, Community right-to-know, Reporting and recordkeeping 

requirements, and Toxic chemicals

Dated:_ XXX.. XX, 2010.__________________

_____________________________________

Lisa P. Jackson, 

Administrator.

[FR Doc. 00–?????? Filed ??–??–00; 8:45 am] 

BILLING CODE 6560–50–F