Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Proposed Rules 91299 

safety, marine or other environmental 

resources, and access to ports. 

2. Does the recommended Portland 

Eastern Approach Fairway provide a 

safe and efficient route for vessels 

transiting to and from the Eastern 

Approach TSS? Why or why not? If not, 

what would you recommend instead? 

3. Would the recommended Portland 

Eastern Approach Fairway have any 

positive or negative environmental 

impacts? 

4. Would the recommended Portland 

Eastern Approach Fairway have any 

positive or negative tribal impacts? 

C. Gulf of Maine Fairway 

The Coast Guard is proposing a Gulf 

of Maine Fairway to meet the needs of 

vessel traffic primarily proceeding 

between Boston, Massachusetts, and the 

Bay of Fundy. The Coast Guard may 

consider design alternatives to the 

recommended Gulf of Maine Fairway to 

ensure safe transit for vessels, while 

providing ocean space for wind energy 

leasing. 

1. Are there any positive or negative 

economic impacts from the 

recommended Gulf of Maine Fairway? 

2. Is the recommended Gulf of Maine 

Fairway necessary to provide safe and 

efficient routes for vessels transiting to 

and from domestic and international 

ports? Why or why not? If not, what 

would you recommend instead? 

3. What are the positive or negative 

vessel transit impacts to altering the 

recommended fairway’s design, 

location, and characteristics, such as 

narrower width and change in cardinal 

direction? Please explain your answer, 

including specific comments on how 

any changes to this recommended 

fairway would affect maritime traffic 

patterns, navigational safety, marine or 

other environmental resources, and 

access to ports. 

4. What other offshore uses may be 

positively or negatively impacted by 

alteration to this recommended fairway 

design, location, and characteristics, 

such as narrower width and change in 

cardinal direction? Please include 

specific locations, potential impact, and 

associated costs or benefits. Please also 

describe the safety significance of 

alterations to this recommended fairway 

on other offshore use activity. 

5. If this fairway is established as 

recommended, what persons, entities, or 

organizations would be positively or 

negatively impacted? In other words, 

which groups of people, businesses, or 

industries (maritime and non-maritime) 

would be positively or negatively 

impacted by this recommended fairway? 

6. Would the recommended Gulf of 

Maine Fairway have any positive or 

negative environmental impacts? 

7. Would the recommended Gulf of 

Maine Fairway have any positive or 

negative tribal impacts? 

Linda L. Fagan, 

Admiral, U.S. Coast Guard, Commandant. 

[FR Doc. 2024–26830 Filed 11–18–24; 8:45 am] 

BILLING CODE 9110–04–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 751 

[EPA–HQ–OPPT–2024–0403; FRL–11628– 

01–OCSPP] 

RIN 2070–AL16 

N-(1,3-Dimethylbutyl)-N′-phenyl-pphenylenediamine (6PPD) and its 

Transformation Product, 6PPDquinone; Regulatory Investigation 

Under the Toxic Substances Control 

Act (TSCA) 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Advance notice of proposed 

rulemaking (ANPRM). 

SUMMARY: In granting a petition filed 

under the Toxic Substances Control Act 

(TSCA) by Earthjustice on behalf of the 

Yurok Tribe, the Port Gamble S’Klallam 

Tribe, and the Puyallup Tribe of 

Indians, the Environmental Protection 

Agency (EPA or Agency) committed to 

pursuing an action to solicit and collect 

information from the public on the 

potential risks associated with N-(1,3- 

Dimethylbutyl)-N′-phenyl-pphenylenediamine (6PPD) (CASRN 793– 

24–8, DTXSID 9025114) and its 

transformation product, 6PPD-quinone 

(CASRN 2754428–18–5, DTXSID 

301034849). With this document, EPA is 

soliciting that information, along with 

information about potential alternatives 

and regulatory options to help inform 

the Agency’s consideration of potential 

future regulatory actions under TSCA. 

DATES: Comments must be received on 

or before January 21, 2025. 

ADDRESSES: Submit your comments, 

identified by docket identification (ID) 

number EPA–HQ–OPPT–2024–0403, 

through https://www.regulations.gov. 

Follow the online instructions for 

submitting comments. Do not submit 

electronically any information you 

consider to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Additional instructions on commenting 

and visiting the docket, along with more 

information about dockets generally, is 

available at https://www.epa.gov/ 

dockets. 

FOR FURTHER INFORMATION CONTACT: 

For technical information: Wyn 

Zenni, Existing Chemicals Risk 

Management Division (7404M), Office of 

Pollution Prevention and Toxics, 

Environmental Protection Agency, 1200 

Pennsylvania Ave. NW, Washington, DC 

20460–0001; telephone number: (202) 

565–6294; email address: zenni.wyn@

epa.gov. 

For general information on TSCA: The 

TSCA Hotline, ABVI-Goodwill, 422 

South Clinton Ave., Rochester, NY 

14620; telephone number: (202) 554– 

1404; email address: TSCA-Hotline@

epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. Executive Summary 

A. Does this action apply to me? 

You may be potentially affected by 

this action if you manufacture 

(including import), process (including 

recycling), distribute in commerce, 

dispose of, or use 6PPD and/or 6PPDquinone. The following list of North 

American Industry Classification 

System (NAICS) codes is not intended 

to be exhaustive, but rather provides a 

guide to help readers determine whether 

this document applies to them. 

Potentially affected entities may 

include: 

• 325130 Synthetic Dye and Pigment 

Manufacturing; 

• 325199 All Other Basic Organic 

Chemical Manufacturing ; 

• 325212 Synthetic Rubber 

Manufacturing; 

• 325998 All Other Miscellaneous 

Chemical Product and Preparation 

Manufacturing; 

• 326211 Tire Manufacturing (Except 

Retreading); 

• 326291 Rubber Product 

Manufacturing for Mechanical Use; 

• 336999 All Other Transportation 

Equipment Manufacturing; and 

• 424690 Other Chemical and Allied 

Products Merchant Wholesalers. 

If you have any questions regarding 

the applicability of this action to you, 

please consult the technical information 

contact listed under FOR FURTHER

INFORMATION CONTACT. 

B. What is the Agency’s authority for 

taking this action? 

This action is being taken under the 

Toxic Substances Control Act (TSCA), 

15 U.S.C. 2601 et seq. 

TSCA section 21 allows any person to 

petition EPA to initiate a rulemaking 

proceeding for the issuance, 

amendment, or repeal of a rule under 


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TSCA sections 4, 6, or 8 or an order 

under TSCA sections 4, 5(e) or (f). If 

EPA grants the petition, the Agency 

must promptly commence an 

appropriate proceeding. 

Under TSCA section 6(a), if EPA 

determines that the manufacture, 

processing, distribution in commerce, 

use, or disposal of a chemical substance 

presents an unreasonable risk to human 

health or the environment, it must 

‘‘apply one or more of the [TSCA 

section 6(a)] requirements . . . to the 

extent necessary so that the chemical 

substance . . . no longer presents such 

risk,’’ which may range from prohibiting 

or otherwise restricting the 

manufacturing, processing, or 

distribution in commerce of the 

chemical substance (or a particular use), 

to commercial use requirements or 

disposal restrictions, to labeling and 

recordkeeping. 

C. What action is the Agency taking? 

EPA is seeking public comment on all 

of the information included in and 

referenced by this ANPRM. EPA also 

seeks any additional information 

relevant to 6PPD, 6PPD-quinone, and 

potential 6PPD substitutes that could 

help inform potential future 

rulemakings. Topics in this ANPRM 

include but are not limited to: 

Information on the chemicals’ 

environmental effects on aquatic and 

terrestrial ecosystems, potential human 

health effects, environmental fate and 

transport, exposure pathways, 

persistence and bioaccumulation, 

additional uses of 6PPD, and releases 

from consumer products (e.g., sneakers, 

playgrounds, rubber-modified asphalt, 

reused tire or other rubber products, 

etc). EPA is also seeking comment and 

information related to alternatives to 

6PPD, as well as potential chemical 

transformation products associated with 

potential alternatives. 

When submitting information, the 

Agency is interested in receiving 

quantitative information, data and/or 

case examples, including peer-reviewed 

studies, statistical analyses, and 

industry, scientific, or technical reports 

describing datasets or syntheses of 

environmental or human health impacts 

of 6PPD, 6PPD-quinone, or potential 

alternatives for 6PPD. 

D. What are the incremental costs and 

benefits of this action? 

This action does not propose or 

impose any requirements, and instead 

seeks comments and suggestions that 

will help inform the Agency’s 

consideration of potential future actions 

for 6PPD and/or 6PPD-quinone. As 

such, there are no incremental costs or 

benefits associated with this ANPRM. 

Should the Agency pursue a rulemaking 

in the future, EPA will conduct the 

appropriate assessments of the potential 

costs and benefits associated with the 

proposed action. 

E. What should I consider as I prepare 

my comments for EPA? 

1. Submitting CBI 

Do not submit CBI to EPA through 

https://www.regulations.gov or email. If 

you wish to include CBI in your 

comment, please follow the applicable 

instructions at https://www.epa.gov/ 

dockets/commenting-epa-dockets#rules 

and clearly mark the information that 

you claim to be CBI. Information so 

marked will not be disclosed except in 

accordance with procedures set forth in 

40 CFR parts 2 and 703. 

2. Tips for Preparing Your Comments 

When preparing and submitting your 

comments, see the commenting tips at 

https://www.epa.gov/dockets/ 

commenting-epa-dockets.html. 

II. Background 

A. What was requested in the TSCA 

section 21 petition for 6PPD? 

On August 1, 2023, Earthjustice, on 

behalf of the Yurok Tribe, the Port 

Gamble S’Klallam Tribe, and the 

Puyallup Tribe of Indians, filed a TSCA 

section 21 petition requesting that EPA 

establish regulations prohibiting the 

manufacturing, processing, use, and 

distribution of 6PPD (CASRN 793–24–8, 

DTXSID 9025114) in and for tires under 

EPA’s TSCA section 6(a) authority, 15 

U.S.C. 2605(a). The petitioners 

requested that such regulation take 

effect as soon as practicable to eliminate 

the unreasonable risk 6PPD in tires 

presents to the environment (Ref. 1). 

In the petition, concerns were raised 

that the chemical 6PPD, which has been 

used in tires since the 1960s to prevent 

tire degradation (Ref. 2), poses 

unreasonable risk to the environment 

due to the acute toxicity of its 

transformation product, 6PPD-quinone 

(CASRN 2754428–18–5, DTXSID 

301034849), to coho salmon 

(Oncorhynchus kisutch) and other fish 

species. The petition described that the 

presence of 6PPD-quinone in 

stormwater runoff and urban watersheds 

are at levels that can kill coho salmon 

(O. kisutch), steelhead trout 

(Oncorhynchus mykiss), and other 

aquatic organisms. The petition also 

referenced the presence of 6PPDquinone in sediments and soils, road 

and household dust, and the urine of 

pregnant women, with emerging science 

pointing to potential risks to human 

health and to a larger extent, toxicity in 

mammals (Ref. 1). 

On November 2, 2023, EPA granted 

the petition, stating that the petition, 

along with information reasonably 

available to EPA, set forth facts 

establishing that it was appropriate to 

initiate a TSCA section 6(a) proceeding 

to address risks to the environment from 

6PPD and its transformation product, 

6PPD-quinone (Ref. 3 [3]). Specifically, 

EPA committed to: (a) Issuing an 

ANPRM for 6PPD and 6PPD-quinone 

under TSCA section 6(a) by fall 2024; 

and (b) Finalizing a TSCA section 8(d) 

rulemaking by the end of 2024 that 

would require persons who manufacture 

(including import) 6PPD to submit lists 

or copies of unpublished health and 

safety studies to EPA. With this action, 

the Agency has promptly commenced 

an appropriate proceeding. The 

expected information resulting from this 

action will inform the Agency’s 

consideration of future potential action 

though, as noted in the petition 

response, EPA cannot commit to a 

specific timeframe or outcome (Ref. 3). 

B. What is 6PPD? 

1. Physical and Chemical Use Properties 

6PPD is the organic compound N-(1,3- 

dimethylbutyl)-N′-phenyl-pphenylenediamine (CASRN 793–24–8, 

DTXSID 9025114), which is added to 

tires and other rubber products to 

prevent degradation. As a solid, 6PPD is 

dark brown with violet flakes and is 

generally sold as pellets, pastilles, or in 

liquid form (Refs. 4 and 5). 6PPD can 

diffuse easily to the surface of a rubber 

product and quickly react with ozone 

(O3) to protect the rubber polymers from 

oxidation (Ref. 5). This chain of events 

occurs quickly enough to effectively 

protect the rubber but slowly enough to 

last for the lifetime of the product, 

which has made 6PPD a useful 

antidegradant for use in rubber products 

(Ref. 6). 

2. 6PPD’s Use in Tires 

6PPD has been used globally since the 

1960s as an antidegradant and 

antiozonant to prevent automobile tire 

degradation caused by exposure to 

ozone, oxygen, and temperature 

fluctuations (Refs. 2 and 7). By 

continuously migrating to the surface of 

the tire to fill microcracks and react 

with oxygen and ambient ozone in the 

environment, 6PPD protects the tire’s 

rubber polymers from becoming brittle 

and cracked over time (Ref. 4). In doing 

so, 6PPD increases tire longevity, safety, 

and performance due to its ability to 

protect tires from premature degradation 

(Ref. 4). 


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Products that use recycled tire crumbs 

or pieces such as rubber-modified 

asphalt, playgrounds (rubber mulch), 

artificial turf, and sneakers may also 

contain 6PPD (Refs. 8 and 9). 

3. 6PPD’s Use in Other Products 

6PPD is also used as an additive in 

other rubber goods (e.g., conveyor and 

transmission belts, hoses, and gaskets), 

other automotive parts (e.g., engine 

mounts, grommets, bushings, and seals), 

polymers, lubricants, dyes, and other 

house-hold or recycled rubber products 

(Refs. 4, 10, and 11). Little information 

on the release of 6PPD and/or 6PPDquinone from these non-tire products 

currently exists. 

4. Environmental Fate and Transport of 

6PPD 

Although more information is needed 

on the environmental fate and transport 

of 6PPD, one source of 6PPD in the 

environment occurs through the release 

of tire wear particles (TWP) from tires 

containing 6PPD (Refs. 12, 13, 14, and 

15). Though limited data suggest 6PPD 

has a short half-life (hours to several 

days) in aqueous solutions (Ref. 16), 

TWP are continuously being emitted 

into the environment, especially as cars 

brake, accelerate, or turn (Refs. 17, 18, 

and 19). It is believed that TWP reach 

soils and aquatic media close to 

roadways, with a small fraction emitted 

into the atmosphere or sorbed to 

sediments (Refs. 4 and 19). During 

rainfall events, TWP can be mobilized 

from roads and road dust into nearby 

waterbodies (Ref. 20). For example, one 

study in Denmark investigating the 

annual TWP generated in a local road 

network and released into the aquatic 

environment found that 8–40 percent of 

the TWP from the roads reached surface 

waters after storm events depending on 

the stormwater treatment system (Ref. 

21). 

Once TWP containing 6PPD enter the 

environment, it is hypothesized that the 

environmental transformation of 6PPD 

primarily occurs through hydrolysis 

(water breaking down chemical bonds) 

or by reaction with oxygen and ozone 

and photodegradation from exposure to 

sunlight and air (Ref. 4). The more 

frequent detection of 6PPD in 

extractions from TWP but not road 

runoff suggests that these reactions 

occur on the surface of the tire or road 

and/or that 6PPD rapidly transforms 

once released from the tire (Ref. 4). 

However, fully understanding these 

processes since 6PPD is such a reactive 

compound remains an information gap. 

Abiotic degradation of 6PPD occurs in 

water and the atmosphere. In water, 

6PPD is highly reactive and can be 

affected by the water’s pH, temperature, 

available sunlight, and other 

constituents in water such as metals 

(Ref. 4). Reported half-lives in water 

have ranged between 3.4 hours to less 

than a day, with warmer waters 

containing more heavy metals leading to 

a shorter half-life of 6PPD (Refs. 4 and 

16). In the atmosphere, 6PPD can 

degrade quickly via indirect 

photodegradation, with a half-life in air 

between 1–2 hours, further limiting the 

gas phase dispersal of the unreacted 

chemical (Ref. 22). Direct entry into the 

environment in the gas phase is likely 

limited given the low vapor pressure of 

6PPD (Ref. 22). 

As for 6PPD’s degradation in 

sediments, very little is known. Initial 

indications suggest that 6PPD is likely 

to adsorb to organic matter such as soil, 

sediments, and suspended particulate 

matter once released into the 

environment. This suggests that it may 

persist in aquatic and terrestrial 

sediments unless it undergoes 

photodegradation and hydrolysis 

through resuspension (Ref. 4). There are 

no available data on how 6PPD adheres 

to and binds to soil under different 

environmental conditions, but leaching 

of 6PPD through soil to groundwater is 

anticipated to be unlikely (Ref. 4). EPA’s 

Estimation Program Interface (EPI) Suite 

estimates 6PPD’s half-life to be 75 days 

in soil with photodegradation likely 

being the main process in which it is 

lost in surface soils (Refs. 4 and 23). 

5. 6PPD’s Transformation Products 

Both in tires and in TWP, 6PPD reacts 

at the rubber’s surface with ambient 

ozone (O3) and possibly secondary O3- 

related oxidants (e.g., OH-). 6PPD has 

less reactivity with molecular oxygen 

(O2) and other ambient air constituents 

(Refs. 18 and 22). 6PPD’s high reactivity 

with ozone triggers chemical reactions, 

resulting in the formation of 

transformation products (TPs) as the 

chemical undergoes structural changes 

and/or the formation of degradants as 

the chemical breaks down into smaller 

molecules (Refs. 18 and 24). The 

resulting transformation products can be 

more or less mobile and more or less 

toxic in the environment than their 

parent compound, with 6PPD-quinone 

generally being more toxic to fish, more 

stable, and more mobile than 6PPD 

according to available data (Refs. 18, 25, 

and 24). Studies have identified 25–38 

ozonation transformation products for 

6PPD that form depending on the 

environmental conditions, but more 

research on the hazard traits and 

behaviors of these transformation 

products is needed as data are still 

insufficient (Refs. 18 and 26). One 

recent study identified four of 6PPD’s 

most abundant transformation products, 

including 6PPD-quinone, as the most 

environmentally relevant because they 

were observed in roadway runoff, 

indicating that they may be ubiquitous 

contaminants in roadway-impacted 

environments and need further 

investigation (Ref. 26). 

C. What is 6PPD-quinone? 

1. Physical and Chemical Properties 

One of 6PPD’s transformation 

products is 6PPD-quinone, or 2-anilino5-(4-methylpentan-2-ylamino) 

cyclohexa-2,5-diene-1,4-dione (CASRN 

2754428–18–5, DTXSID 301034849). 

Due to 6PPD’s highly reactive nature, it 

is thought that 6PPD is continually 

reacting with ozone at the surface of 

tires to form 6PPD-quinone (Refs. 6 and 

27). As 6PPD-quinone forms on the 

surface of the tire, it adds to the 

protective film that 6PPD naturally 

creates, providing further protection 

from cracking of the tire rubber (Refs. 6, 

27, and 28). However, this also means 

that 6PPD-quinone and 6PPD are likely 

present in most TWP that are common 

in the environment (Refs. 12, 29, and 

30). 

2. Environmental Fate and Transport 

There are currently little data 

available to describe the environmental 

fate and transport of 6PPD-quinone, but 

data from several monitoring studies 

suggest that it persists longer in the 

environment than 6PPD (Ref. 31). One 

study found that 6PPD-quinone had a 

half-life of 33 hours in dechlorinated tap 

water compared to 5 hours for 6PPD 

(Ref. 16). The longer persistence of 

6PPD-quinone in water indicates more 

potential exposure time to induce toxic 

effects in aquatic life (Ref. 16). Another 

study found that leachate from TWP 

remained toxic after exposure to 

extreme heat (80 °C) for 72 hours, 

suggesting that 6PPD-quinone is stable 

under extreme heat conditions (Ref. 32). 

It is also likely that the polar carbonyl 

groups (added oxygen atoms from 

oxidation) may make 6PPD-quinone 

more mobile in the environment than 

6PPD (Ref. 33). 

D. What are the ecological effects 

caused by 6PPD and 6PPD-quinone? 

1. Aquatic Ecosystem Effects 

The number of studies on 6PPD and/ 

or 6PPD-quinone’s impacts on aquatic 

ecosystems has increased since 6PPDquinone from TWPs was identified in 

2020 as the likely causative agent for 

urban runoff mortality syndrome 

(URMS) (Ref. 32). URMS has been 

occurring in the Pacific Northwest at 


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least since it was first reported between 

1999–2001, and refers to the death of 

adult fish (particularly coho salmon) 

that return to urban waterways to spawn 

(Refs. 32 and 34). However, much is still 

unknown about the chemicals’ effects 

on aquatic life generally. As of 

December 2023, there were 16 available 

studies on the hazard effects of 6PPD on 

aquatic species and 26 available studies 

on the hazard effects of 6PPD-quinone 

that were identified by and included in 

the EPA’s ECOTOX Knowledgebase 

(Ref. 35). Those studies along with 

additional online publications (as of 

July 2024) have primarily evaluated 

6PPD-quinone’s acute mortality impacts 

on aquatic species (i.e., lethal 

concentration (LC) values) due to its 

higher reported toxicity, with the 

majority focusing on fish species, 

compared to aquatic invertebrates and 

plant species. 

For the hazard effects of 6PPD on 

aquatic species, there are acute toxicity 

data for nine freshwater species as of 

December 2023. The following acute 

toxicity data includes both the authorreported mortality values (LC50) and the 

EPA-adjusted values (if needed) to 

account for observed chemical loss in 

studies that only measured exposure 

concentrations at the beginning of the 

study or not at all (Ref. 36). Of the nine 

studied species, Medaka (Oryzias 

latipes) (author-reported LC50 of 28 mg/ 

L after 96 hours of exposure), rare 

minnows (Gobiocypris rarus) (authorreported LC50 of 162 mg/L after 96 hours 

of exposure; EPA-adjusted LC50 of 94.94 

mg/L), coho salmon (Oncorhynchus 

kisutch) (author-reported juvenile LC50

of 251 mg/L after 24 hours of exposure; 

EPA-adjusted LC50 of 143.7 mg/L), and 

amphipods (Hyalella azteca) (authorreported juvenile LC50 of 250 mg/L after 

96 hours of exposure; EPA-adjusted 

LC50 of 159.7 mg/L) were the most 

sensitive aquatic species to acute 6PPD 

exposure (Refs. 16, 37, 38, 39, and 40). 

As for 6PPD’s chronic effects on aquatic 

species, data are available for only two 

aquatic species: Medaka (Oryzias) 

(author-reported lowest observed effect 

concentration (LOEC) of 11 mg/L after an 

early-life stage test of unknown 

duration) and fathead minnows 

(Pimephales) (author-reported LC50 of 

150 mg/L after 28 days of exposure) 

(Refs. 37 and 41). Although additional 

research on the chronic effects of 6PPD 

will be important, acute toxicity is 

expected to be a more important driver 

for aquatic risk compared to chronic 

toxicity given the quick degradation of 

6PPD. In addition, studies on 6PPD’s 

effects on estuarine and marine species, 

as well as algae and vascular plants, are 

extremely limited. 

For the hazard effects of 6PPDquinone on aquatic species, coho 

salmon (O. kisutch) are the most 

sensitive species to acute 6PPD-quinone 

exposure identified to date, with an 

author-reported lethal concentration 

(LC50; the concentration that is lethal to 

50 percent of tested organisms) value of 

0.041 mg/L for juveniles in less than 24 

hours (EPA-adjusted LC50 of 0.036 mg/L) 

(Refs. 42 and 43) and up to 0.095 mg/L 

for adults after 24 hours (EPA-adjusted 

LC50 of 0.092 mg/L) (Refs. 43 and 44), 

indicating potential age-related 

differences in sensitivity. Other 

identified fish species that are acutely 

sensitive to 6PPD-quinone include: lake 

trout (Salvelinus namaycush) (LC50 of 

0.5 mg/L after 24 hours of exposure; 

EPA-adjusted LC50 of 0.5186 mg/L) (Ref. 

45), white-spotted char (Salvelinus 

leucomaenis pluvius) (<1 year juvenile 

LC50 of 0.80 mg/L after 24 hours; EPAadjusted LC50 of 0.5709 mg/L) (Refs. 43 

and 46), brook trout (Salvelinus 

fontinalis) (∼1 year juvenile LC50 of 0.59 

mg/L after 24 hours) (Ref. 47), rainbow 

trout (Oncorhynchus mykiss) (∼2 month 

juvenile LC50 of 0.64 mg/L; EPA-adjusted 

LC50 of 0.2961 mg/L) (∼2 year juvenile 

LC50 of 1.00 mg/L after 96 hours) (Refs. 

38, 43, and 47), and chinook salmon 

(Oncorhynchus tshawytscha) (582-day 

old LC50 of 82.1 mg/L after 24 hours; 

EPA-adjusted LC50 of 65.68 mg/L) (Refs. 

43 and 48). 

These LC50 values for both chemicals 

were also used to support EPA’s 

published screening values for acute 

6PPD and 6PPD-quinone exposure for 

freshwater fish species (published June 

2024) which are 8.9 and 0.011 mg/L, 

respectively (Refs. 36 and 43). EPA’s 

acute screening values (published under 

Clean Water Act Section 304(a)(2)) are 

the maximum concentrations of 6PPD 

and 6PPD-quinone (not in mixtures) 

with associated frequency and duration 

specifications that are expected to 

support protection of aquatic life from 

acute effects in freshwaters based on 

currently available scientific data (Refs. 

36 and 43). For comparison, one study 

that measured the concentration of 

6PPD-quinone in roadway runoff, 

stormwater-affected creeks, and 

watersheds throughout the U.S. west 

coast found a widespread occurrence of 

6PPD-quinone at concentrations ranging 

from 0.3–19 mg/L following storm 

events, which exceeds EPA’s published 

acute screening value for 6PPD-quinone 

(Refs. 32 and 43). Overall, although 

there is available information on the 

acute LC50 values and impacts on 

multiple fish species, more studies 

identifying the concentrations of 6PPD 

and 6PPD-quinone measured in U.S. 

waterbodies, the sublethal and chronic 

effects of 6PPD and 6PPD-quinone 

exposure, and additional toxicity data 

on other aquatic species are important. 

Studies have also identified that 

certain fish species appear to be 

significantly more sensitive to 6PPDquinone exposure than other species. 

For example, studies show that coho, 

steelhead, and chinook salmon are 

sensitive to 6PPD-quinone exposure; 

however, sockeye and chum salmon 

lacked a similar response and were not 

significantly affected by 6PPD-quinone 

(Refs. 12 and 49). The modes of action 

driving the large variation in the toxicity 

of 6PPD-quinone across species remains 

unknown, but one study suggests that a 

tissue-specific disruption of 

mitochondrial respiration is involved. 

Increased ventilation and gasping of 

sensitive species (coho salmon, brook 

trout, rainbow trout) was observed after 

exposure, suggesting that 6PPD-quinone 

exposure (5–80 mg/L) impacts cellular 

respiration and the oxygen consumption 

rate (Ref. 50). Another study found that 

the large increases in hematocrit 

commonly associated with coho salmon 

mortality after being exposed to 

roadway runoff could be due to a 

disruption in the blood-brain barrier 

since plasma leakage from the 

cerebrovasculature was observed (Ref. 

51). This early research indicates that 

neurologic, metabolic, and 

mitochondrial disruption may be 

involved (Refs. 50, 51, and 52), but more 

research and tests are needed to confirm 

the specific modes of action for 6PPDquinone and why it is acutely toxic to 

certain species. The mode of action 

driving 6PPD’s toxicity may be different 

from 6PPD-quinone’s, as 6PPD is toxic 

to many tested aquatic organisms but 

never reaches the high toxicity exerted 

by 6PPD-quinone to selected species. 

Further, although EPA’s published 

acute screening values for 6PPD and 

6PPD-quinone in freshwater provided 

critical concentrations for protecting 

aquatic life from the two chemicals, the 

reports suggest that additional research 

will be important to fully characterize 

the toxicity of 6PPD-quinone and other 

key transformation products and 

degradants of 6PPD to aquatic life (Refs. 

36 and 43). For example, the reports 

indicated that additional research that 

includes analytical confirmation of 

6PPD-quinone is needed, as some of the 

available studies lacked analytical 

measurements of 6PPD-quinone at the 

end of the tests, which is important 

given the uncertainty of 6PPD-quinone’s 

fate in lab water. In addition, the 

screening value reports noted that most 

of the available aquatic species’ tests on 


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acute toxicity were run for only 24 

hours (standard test duration for acute 

toxicity tests are 96 hours) and 

occasionally in overcrowded fish tanks 

(Refs. 36 and 43). 

For these reasons, additional acute 

and chronic toxicity studies that include 

full analytical measurements at 

appropriate intervals across the study 

duration that are conducted using 

standard toxicity test guidelines would 

be useful. Additionally, the completion 

of tests on a broader range of aquatic 

taxa would provide a broader 

understanding of how these chemicals 

are impacting fish and other aquatic 

species (Refs. 36 and 43). 

2. Terrestrial Ecosystem Effects 

There are very limited data publicly 

available on how 6PPD and/or 6PPDquinone may impact terrestrial 

ecosystems. As of December 2023, there 

was one available terrestrial study on 

the hazard effects of 6PPD on chicken 

embryos (Gallus gallus) and five 

available studies on the hazard effects of 

6PPD-quinone on nematodes 

(Caenorhabditis elegans) and springtails 

(Folsomia candida) that passed EPA’s 

ECOTOX screening. (Ref. 35). 

In the one terrestrial study focused on 

the hazard effects of 6PPD, 3-day old 

chicken embryos were exposed to 80 

different rubber tire chemicals in either 

acetone or water (Ref. 53). Exposure to 

6PPD resulted in deaths and 

malformations (EC50 of 1.5 umol 11 

days post-exposure), but the authors 

reported an incomplete, irregular or flat 

dose-response curve for early death and 

malformations (Ref. 53). Given the 

incomplete dose-response 

characterization, more information on 

avian species and other terrestrial 

organisms will be important to further 

characterize the potential hazard effects 

of 6PPD. 

Of the five other studies on the hazard 

effects of 6PPD-quinone on terrestrial 

organisms, four studies investigated the 

chronic effects of 6PPD-quinone 

exposure on nematodes (an 

invertebrate). One study on nematodes 

found that prolonged exposure to 6PPDquinone at 1–10 mg/L shortened lifespan 

by up to 27.4 percent due to insulin 

signaling pathway dysfunction, 

decreased the amount of fertilized eggs 

due to DNA and signaling pathway 

damage, and decreased pharyngeal 

pumping and locomotion behavior (Ref. 

54). Another study by the same authors 

found that after exposing nematodes to 

environmentally relevant concentrations 

of 6PPD-quinone (0.1–100 mg/L) for 4.5 

days (from the larval to adult stage), 

several forms of abnormal locomotion 

behavior and neurodegeneration was 

observed, with exposure to 100 mg/L 

causing 5 percent lethality (Ref. 55). A 

similar study on nematodes found that 

6PPD-quinone exposure negatively 

affected their digestive systems and 

lipid metabolism, with evidence of lipid 

accumulation and fatty acid deposition 

(Ref. 56) and that plastic nanoparticles 

in the environment enhanced the 

neurotoxicity and accumulation of 

6PPD-quinone in nematodes (Ref. 57). In 

springtails, a soil organism, one study 

found that 6PPD-quinone exposure 

impaired the survival of the organisms, 

with a LC50 of 16.31 mg/kg after 28 days 

of exposure (Ref. 58). The studies 

meeting inclusion requirements for the 

EPA’s ECOTOX knowledgebase 

primarily focus on the impacts of 6PPDquinone on invertebrates such as 

nematodes and springtails; however, 

published data in rodents that are 

commonly used to inform human health 

hazards and are summarized in Unit 

II.E.2 may also be informative of the 

ecological effects on mammalian species 

(Ref. 35). Overall, the limited studies 

available indicate that prolonged 

exposure to environmentally relevant 

concentrations of 6PPD-quinone 

induces a multisystem toxic response, 

including neurotoxicity, reproductive 

risks, intestinal damage, and 

dysfunctions in lipid metabolism with 

bioaccumulation concerns in at least 

terrestrial invertebrates (Refs. 54, 55, 

and 57). However, more studies on the 

effects of 6PPD and/or 6PPD-quinone on 

terrestrial organisms and ecosystems 

would provide a more comprehensive 

understanding of the impacts of these 

chemicals across the environment. 

E. What are the potential exposures to 

and human health effects of 6PPD and 

6PPD-quinone? 

There are limited data on the 

exposure pathways of 6PPD and 6PPDquinone, however several recent studies 

in Asia have predicted potential 

exposure through dust inhalation and 

ingestion. For example, one study in 

Hangzhou, China measured 6PPD and 

6PPD-quinone levels in indoor dust and 

estimated the daily intake of 6PPD and 

6PPD-quinone for children based on 

expected ingestion and inhalation rates 

for indoor dust (Ref. 59). The study 

found 6PPD and 6PPD-quinone to be the 

predominant phenylene diamine (PPD) 

and PPD-q in indoor dust and that 

children, especially infants, were 

potentially ingesting 6PPD and 6PPDquinone through indoor dust based on 

the measured concentrations and daily 

intake estimations (Ref. 59). A similar 

study measured 6PPD-quinone levels in 

outdoor dust near roads, homes, and 

kindergartens in Guiyu, an e-wasteexposed area, and in Haojiang, a 

reference area, from 2019–2021 (Ref. 

60). The study found that 6PPD-quinone 

levels were significantly higher in home 

and kindergarten classroom dust within 

the e-waste-exposed area compared to 

the reference area, indicating that dust 

may be an exposure pathway for 

humans and that e-waste may be 

another potential source of 6PPDquinone in the environment (Ref. 60). 

Using the measured concentrations of 

6PPD-quinone in dust, the study also 

estimated that higher daily intakes of 

6PPD-quinone from kindergarten 

classroom dust could be associated with 

lower body mass indexes and higher 

incidences of influenza and diarrhea in 

kindergarten children, although these 

data are potentially confounded by 

other environmental stressors and 

chemicals that may be found within ewaste-exposed areas (Ref. 60). Another 

study in Hong Kong that measured the 

environmental occurrence of 6PPD and 

6PPD-quinone in road dust to estimate 

potential pathways of human exposure 

found that exposure levels for 

contaminated road dust were higher for 

6PPD-quinone than for 6PPD (Ref. 61). 

Although these studies were primarily 

done in Asia and under unique 

exposure scenarios (i.e., near an e-waste 

recycling facility), these studies indicate 

environmental occurrence of 6PPD and 

6PPD-quinone in indoor and outdoor 

dust, suggesting that human exposure to 

6PPD and 6PPD-quinone is plausible 

and may be occurring through dust 

ingestion, inhalation, and dermal 

absorption, with potential effects on 

body mass index (Refs. 7, 59, 60, and 

61). 

A limited number of biomonitoring 

studies in Asia identified 6PPD-quinone 

in human samples, some of which also 

monitored for 6PPD. However, it is 

important to note that many of these 

studies had a small sample size. In one 

study, after 6PPD-quinone levels were 

recorded in the cerebrospinal fluid 

(CSF) of 13 patients with Parkinson’s 

disease (PD) and 11 control participants, 

researchers found that 6PPD-quinone 

levels were twice as high in PD patients 

compared to controls and confirmed 

through immunostaining assays that 

6PPD-quinone at environmentally 

relevant concentrations exacerbated the 

formation of Lewy neurites and 

impaired mitochondrial activity (Ref. 

62). Four other studies detecting PPDs 

and PPD-qs in human urine and blood 

found that the median concentrations of 

6PPD and 6PPD-quinone were 

significantly higher than other PPD and 

PPD-qs measured in the study, 

especially in pregnant women and 

people with liver disease which may 


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indicate lipid oxidative damage (Refs. 7, 

63, 64, and 65). Additional 

biomonitoring studies with larger 

sample sizes and in different locations 

are needed since factors influencing 

exposures can vary by region and be 

influenced by other environmental 

stressors. 

Although there are limited data 

available on the potential human health 

effects of 6PPD and/or 6PPD-quinone, 

the health effects of 6PPD are better 

characterized than 6PPD-quinone in the 

scientific literature (Refs. 4, 25, and 66). 

6PPD is a known skin-sensitizer that can 

lead to contact dermatitis in sensitized 

individuals and is listed as a category 

1B reproductive toxicant by the 

European Chemicals Agency (Ref. 67). 

Preliminary toxicity studies in 

rodents may also inform human health 

effects. For example, one study found 

that 6PPD and 6PPD-quinone 

bioaccumulate in the liver, with higher 

doses of both chemicals potentially 

causing an inflammatory response, 

altered hepatic metabolism, and 

hepatotoxicity in mice (Ref. 62) while 

another study identified that repeated 

exposure over 4 weeks to 6PPD-quinone 

(4 mg/kg) caused multiple organ injury 

in male BALB mice (Ref. 68). These 

early mammalian toxicity studies 

indicate that repeated exposure to 6PPD 

and 6PPD-quinone may affect organ 

function, metabolism, bioaccumulation, 

and inflammation in humans, but more 

studies are needed on 6PPD and 6PPDquinone’s impacts on human health. 

As for bioaccumulation potential, one 

study found that when lettuce plants 

were exposed to TWP-derived 6PPD and 

6PPD-quinone (among other TWP 

compounds) in hydroponic solutions 

over 14 days in a lab, the chemicals 

were taken up and metabolized by the 

lettuce with concentrations of 6PPD and 

6PPD-quinone found in the plant’s 

roots, leaves, and nutrient solution (Ref. 

69). Other limited studies that reported 

bioaccumulative potential of 6PPDquinone in aquatic species predicted 

that although there is potential for 

uptake, the data suggests that 6PPDquinone does not significantly 

accumulate in fish tissues and instead 

metabolizes rapidly in vivo (Refs. 38 and 

70). Further, the predicted 

bioconcentration factors (BCF) for 6PPD 

and 6PPD-quinone are currently below 

1,000, suggesting a low to moderate 

bioaccumulative potential based on EPA 

policy, which identifies chemicals with 

BCFs above 1,000 as bioaccumulative 

(Refs. 4, 38, 70, and 71). That said, 

additional data and field studies are 

needed on the potential for 

bioaccumulation in plant and animal 

species as well as on the potential for 

6PPD to metabolize to 6PPD-quinone 

within humans. 

Overall, more research on the effects, 

characteristics, relevant exposure 

pathways, and dose-response data are 

needed to identify the potential human 

health impacts from exposure to 6PPD 

and 6PPD-quinone. This is of particular 

importance for pregnant women and 

children, communities and workers near 

roadways, people with existing medical 

conditions, populations that participate 

in subsistence activities (i.e., fishing, 

hunting), and communities with 

environmental justice concerns. 

F. What are the potential impacts on 

Tribal Nations? 

In their petition, the Yurok Tribe, the 

Port Gamble S’Klallam Tribe, and the 

Puyallup Tribe of Indians present many 

potential impacts of 6PPD’s 

transformation product, 6PPD-quinone, 

on their resources. They explain that 

their health, wellbeing, and culture are 

intimately connected to the health of 

their waters and ecosystems. The 

petition states that many Tribes share an 

important connection with their 

waterbodies, rendering them culturally 

significant and protected resources. The 

petitioners, along with additional Tribes 

that EPA engaged with related to this 

action, all emphasized that thriving 

shellfish and abundant salmonids are 

essential for their subsistence, cultural, 

and economic lifeways and has been 

one of their most important resources 

since time immemorial (Refs.1, 72, and 

73). 

The petition further explains that 

‘‘exposure to 6PPD-q[uinone] can kill a 

coho salmon within hours, and the 

chemical is responsible for ‘urban runoff 

mortality syndrome,’ which kills up to 

100% of coho returning to spawn in 

urban streams’’ (Refs. 1 and 32). 

Petitioners state that the decline of coho 

salmon has negatively impacted their 

access to commercial fishing income, 

food security, health, and wellbeing and 

has affected their ability to pass on 

traditional ceremonial and ecological 

knowledge to future generations. 

Decreased fish populations and 

diminished water quality have also 

meant a loss of cultural identity and 

have led to increased reliance on 

expensive, less-healthy food sources, 

especially in rural, low-income 

communities (Refs. 1, 72, and 73). 

Petitioners also assert that Tribal 

Treaty Rights, such as the Treaty of 

Point No Point, ‘‘guarantees the Tribe[s] 

access to salmon . . . and that any 

action that reduces the number of 

salmon available for harvest by Tribal 

members is a violation of its rights 

under this treaty.’’ 

The Tribes also conclude that, 

‘‘salmon and steelhead populations, 

central to the ecosystems, Tribal 

cultures, and economies of the West 

Coast, have already declined 

dramatically, due in part to exposure to 

6PPD-q[uinone], and they cannot 

recover without its removal from the 

environment . . . We therefore call on 

EPA to exercise its authority under 

TSCA to protect the environment from 

the unreasonable risk presented by the 

use of 6PPD in tires’’ (Ref. 1). 

G. What are the potential sources and 

geographic extent of 6PPD and/or 6PPDquinone contamination in the 

environment? 

Studies have shown that one source of 

6PPD and 6PPD-quinone contamination 

in the environment is from TWP that are 

constantly entering the environment as 

tires roll across the road’s surface (Ref. 

30). These chemicals can also enter the 

environment from tire rubber if tires are 

disposed of in or near waterways. Tires 

and tire pieces are sometimes used as 

parts of dams, embankments, and 

erosion-control infrastructure, but little 

is known about whether 6PPD and 

6PPD-quinone leach from these 

structures into the environment (Ref. 

74). E-waste recycling and rubbermodified asphalt have been identified as 

other potential sources (Refs. 60 and 

75). For example, a recent study found 

that rubber-modified asphalt containing 

6PPD was acting as a sorbent for tirederived 6PPD-quinone that released 

6PPD-quinone into the environment 

after simulated rainfall events, with 

0.0015–0.0049 mg/L of 6PPD-quinone 

recorded in the rainfall runoff (Refs. 76 

and 77). 

Additionally, although 6PPD has been 

identified in other non-tire rubber 

products (described in Unit II.B.3.) 

(Refs. 78, 79, and 80), more research is 

needed to determine the full suite of 

products that may contain 6PPD and the 

extent to which these products may be 

contributing to environmental 

contamination and exposure. 

Monitoring studies have measured 

both 6PPD and 6PPD-quinone in air 

(Refs. 61 and 81), water (Ref. 61), 

outdoor and indoor dust (Refs. 82 and 

59), sediments, and soil (Ref. 61), 

indicating that 6PPD and 6PPD-quinone 

contamination is widespread across 

multiple media (Ref. 83). Overall, 6PPD 

and 6PPD-quinone have been measured 

in environmental media around the 

world and a limited number of studies 

have shown both chemicals in human 

biomonitoring samples (Refs. 62, 63, 64, 

and 65). 


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H. What actions can be taken under 

TSCA section 6? 

TSCA section 6 requires EPA to take 

action to address unreasonable risks of 

injury to human health or the 

environment from a chemical substance 

or mixture to the extent necessary so 

that the chemical substance or mixture 

no longer presents such risk. If EPA 

determines that a chemical substance 

presents unreasonable risk to health or 

the environment, it must promulgate 

requirements under TSCA section 6(a) 

that can include one or more of the 

following actions, alone or in 

combination, to the extent necessary 

such that the chemical no longer 

presents the unreasonable risk: 

• Prohibit or otherwise restrict the 

manufacturing (including import), 

processing, or distribution in commerce 

of the substance, or limit the amount of 

such substance or mixture which may 

be manufactured, processed, or 

distributed in commerce (TSCA section 

6(a)(1)). 

• Prohibit or otherwise restrict the 

manufacturing, processing, or 

distribution in commerce of the 

substance for a particular use or above 

a specific concentration for a particular 

use (TSCA section 6(a)(2)). 

• Limit the amount of the substance 

which may be manufactured, processed, 

or distributed in commerce for a 

particular use or above a specific 

concentration for a particular use (TSCA 

section 6(a)(2)). 

• Require clear and adequate 

minimum warning and instructions 

with respect to the substance, 

distribution in commerce, or disposal, 

or any combination of those activities, 

to be marked on or accompanying the 

substance (TSCA section 6(a)(3)). 

• Require manufacturers and 

processors of the substance to make and 

retain certain records or conduct certain 

monitoring or testing (TSCA section 

6(a)(4)). 

• Prohibit or otherwise regulate any 

manner or method of commercial use of 

the substance (TSCA section 6(a)(5)). 

• Prohibit or otherwise regulate any 

manner or method of disposal of the 

substance, or any article containing 

such substance, by its manufacturer or 

processor or by any person who uses or 

disposes of it for commercial purposes 

(TSCA section 6(a)(6)), and 

• Direct manufacturers or processors 

of the substance to give notice of the 

unreasonable risk determination to 

distributors, certain other persons, and 

the public, and to replace or repurchase 

the substance (TSCA section 6(a)(7)). 

Per TSCA section 6(c)(2)(B), in 

selecting among prohibitions and other 

restrictions, EPA must factor in, to the 

extent practicable, the effects of the 

substance on human health and the 

environment, any benefits of uses of the 

substance, and the reasonably 

ascertainable economic consequences of 

the rule. 

In addition, TSCA section 6(g) allows 

EPA to grant an exemption from a 

requirement of a TSCA section 6(a) rule 

for a specific condition of use of a 

chemical substance or mixture, if the 

Administrator finds that: the specific 

condition of use is a critical or essential 

use for which no technically and 

economically feasible safer alternative is 

available; compliance with the 

requirement, as applied with respect to 

the specific condition of use, would 

significantly disrupt the national 

economy, national security, or critical 

infrastructure; or the specific condition 

of use of the chemical substance or 

mixture, as compared to reasonably 

available alternatives, provides a 

substantial benefit to health, the 

environment, or public safety. 

I. What are the alternatives to 6PPD for 

use in tires? 

At this time, an effective alternative to 

6PPD’s use in tires has not been 

identified, but multiple researchers, 

states, and tire manufacturers are 

studying potential replacements. For 

example, in October 2023, California’s 

Department of Toxic Substances Control 

(DTSC) listed tires containing 6PPD as 

a Priority Product under the Safer 

Consumer Products Regulations (SCPR, 

Cal. Code Regs. Tit. 22, § 69511.7). 

Manufacturers of tires which contain 

6PPD and are entered into the stream of 

commerce in California have submitted 

Preliminary Alternatives Analysis 

Reports to California DTSC, including a 

submission from the United States Tire 

Manufacturers Association’s (USTMA) 

consortium of over 30 tire 

manufacturers (Refs. 2 and 84). Many of 

the identified potential alternatives in 

phase I of USTMA’s alternatives 

analysis were other PPDs or non-PPD 

alternatives, including: 7PPD (CASRN 

3081–01–4; DTXSID 5027516), IPPD 

(CASRN 101–72–4; DTXSID 1025485), 

77PD (CASRN 3081–14–9; DTXSID 

2024618), CCPD (CASRN 4175–38–6; 

DTXSID 8063335), and NA (an 

unnamed, specialized graphene nanoplatelet). According to the report, early 

data suggests that these potential 

alternatives would have reduced 

impacts on salmonids and overall 

hazard relative to 6PPD based on 

screening level performance data and 

acceptable physical and chemical 

properties indicative of exposure 

potential (Ref. 2). California has granted 

a Notice of Compliance for the 

Preliminary (Stage 1) Alternatives 

Analysis report, and manufacturers will 

proceed with a Stage 2 Alternatives 

Analysis to confirm their list of possible 

alternatives, assess the potential impacts 

of these options, and initiate a more 

detailed review of the chemicals’ 

potential hazards and exposure-related 

properties (Ref. 85). 

Similarly, Washington State’s 

Department of Ecology recently 

published a 6PPD Alternatives 

Assessment Hazard Criteria and an 

Alternatives Assessment (AA) Guide for 

them and other businesses to use when 

conducting an AA for 6PPD in tires (Ref. 

86). The State of Washington also 

included 6PPD as a proposed priority 

chemical under their Safer Products of 

Washington law which will result in a 

list of products containing 6PPD in 2025 

(Ref. 87). 

Efforts are also underway to analyze 

other potential alternatives. For 

example, researchers are investigating 

gallates (antioxidant food preservative), 

lignins (plant-based polymer), 

Durazone-37 (another existing rubber 

antiozonant), Graphene, and N,N′- 

dicyclohexyl-1,4-phenylene diamine 

(CCPD) as potential replacements for 

6PPD in tires (Ref. 88). USTMA and the 

U.S. Geological Survey are testing the 

toxicity of potential 6PPD alternatives 

and refining methods for evaluating 

potential alternatives, including the 

ones identified in USTMA’s alternatives 

analysis report in California (Ref. 89). 

The U.S. Department of Agriculture’s 

Western Regional Research Center and 

Flexsys are collaborating to explore a 

bio-based alternative to 6PPD (Ref. 90). 

EPA is funding multiple research efforts 

to test and identify potential 

alternatives, including EPA-funded 

Small Business Innovation Research 

(SBIR) grants (Ref. 91). Efforts are also 

underway to identify other potential 

solutions to reducing the risks posed by 

6PPD and 6PPD-quinone, including 

reformulating tires using natural rubbers 

without 6PPD or modifying 6PPD 

molecules to avoid transformation into 

6PPD-quinone (Ref. 88). 

III. Specific Requests for Comment, 

Data, and Information 

EPA is seeking public comment on all 

information included or referenced in 

this ANPRM and is also seeking any 

other information relevant to 6PPD and/ 

or 6PPD-quinone. The Agency is 

particularly interested in receiving 

quantitative information, data and/or 

case examples (e.g., peer-reviewed 

studies and industry scientific and 

technical reports describing datasets 

and/or syntheses of environmental and 


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human health impacts that include 

statistical analyses) addressing the 

following topics and questions. To 

avoid duplicative submissions, studies 

that have already been cited in this 

ANPRM or that have been submitted 

through another regulatory reporting 

requirement are not being requested via 

this ANPRM. 

A. What information is the Agency 

requesting on environmental effects of 

6PPD and/or 6PPD-quinone on aquatic 

ecosystems? 

EPA is interested in all information 

regarding 6PPD and/or 6PPD-quinone’s 

effects on aquatic ecosystems (such as 

aquatic toxicity data). Adherence to 

standard guidelines or laboratory 

practices (e.g., EPA’s 850 Ecological 

Effects Test Guidelines, American 

Society for Testing and Materials 

(ASTM) methods, or Organization for 

Economic Co-operation and 

Development (OECD) methods) is 

preferred but not required. Note that 

high-quality analytical measurements 

throughout toxicity tests are important 

because of the instability of 6PPD and 

6PPD-quinone under conditions 

relevant to aquatic environments. 

1. To ensure that EPA has robust, 

reasonably available data and 

information that is consistent with the 

best available science, EPA requests 

monitoring data reporting 6PPD and/or 

6PPD-quinone concentrations and 

detection frequency in groundwater, 

surface waters, wastewater, saltwater, or 

estuaries across the United States. 

Specifically, EPA is requesting 

information and data on the volumes, 

locations, sources, dates/timeframes, 

and types of 6PPD and/or 6PPD-quinone 

contamination in impacted surface 

waters and sediments (e.g., through 

TWP or direct contact with the tire), 

including the concentration, field 

methods/SOPs for collection of the data, 

and analytical methods used to detect 

the chemicals (including quantification 

limits and other quality assurance 

details) when available. 

2. EPA is interested in information 

and data concerning the acute exposure 

hazard effects of 6PPD and/or 6PPDquinone on a broader range of aquatic 

species than are discussed in Unit II.D.1 

of this ANPRM, as well as chronic 

effects on all aquatic taxa. Even for 

species and effects that have been 

investigated previously, repeated highquality tests with analytical 

measurements following testing 

guidelines are desired. Such hazard 

information includes, but it is not 

limited to, mortality (lethal 

concentrations), growth, developmental, 

behavioral, reproductive, hormonal, 

immunological, neurological, 

cardiovascular, respiratory, and renal 

effects from the cellular level to the 

organismal and population levels that 

might inform lethal and sub-lethal 

physiological, histological, and 

accumulative effects as well as any 

other hazard information that may be 

relevant to 6PPD and/or 6PPD-quinone. 

EPA seeks hazard effects information for 

any aquatic species, including but not 

limited to: 

• Fish species (e.g., Salmonidae, 

Cyprinidae, Centrarchidae, Serranidae, 

Percidae, Ictaluridae, Acipenseridae, 

etc.); 

• Aquatic studies done using new 

approach methodologies such as fish 

cell line assays or in vitro methods; 

• Species of Tribal or cultural 

significance such as lamprey and 

mussels; 

• Aquatic plants (including vascular 

and non-vascular (algae) species); 

• Aquatic invertebrates (including 

benthic species); 

• Aquatic and aquatic-dependent 

vertebrates other than fish (e.g., 

mammals, amphibians, reptiles, birds); 

• Bacteria/microbiome; and 

• Any other potentially sensitive 

species. 

3. EPA is requesting information and 

data concerning known concentrations 

of 6PPD and/or 6PPD-quinone found in 

aquatic animal and plant tissue that may 

indicate the bioaccumulation of 6PPD 

and/or 6PPD-quinone in these species, 

particularly in species which are 

culturally significant to Tribes or 

subsistence fisher populations. This 

information may have important 

implications for potential exposure 

through the consumption of affected 

plant and animal species. 

B. What information is the Agency 

requesting on environmental effects of 

6PPD and/or 6PPD-quinone on 

terrestrial ecosystems? 

EPA is interested in all information 

regarding 6PPD and/or 6PPD-quinone’s 

effects on terrestrial ecosystems (such as 

terrestrial toxicity data). Data collected 

by any means is requested. Adherence 

to standard guidelines or laboratory 

practices (e.g., EPA’s 850 Ecological 

Effects Test Guidelines, American 

Society for Testing and Materials 

(ASTM) methods, or Organization for 

Economic Co-operation and 

Development (OECD) methods) is 

preferred but not required. 

1. To ensure that EPA has robust, 

reasonably available data and 

information that is consistent with the 

best available science, EPA requests 

monitoring information and data 

reporting for 6PPD and/or 6PPDquinone concentrations and detection 

frequency in air, soil, and other 

terrestrial media. Specifically, EPA is 

requesting information and data on the 

volumes, locations, sources, dates/ 

timeframes/pollutographs, and types of 

6PPD and/or 6PPD-quinone 

contamination (e.g., through TWP or 

direct contact with the tire) in terrestrial 

environments, including the 

concentration and field methods and 

analytical methods used to detect the 

chemicals (including quantification 

limits) when available. 

2. EPA is also interested in 

information and data concerning the 

hazard effects of 6PPD and/or 6PPDquinone on a broader range of terrestrial 

species than are discussed in Unit II.D.2 

of this ANPRM. Such hazard 

information includes, but it is not 

limited to, data on mortality (lethal 

concentrations), growth, development, 

genetics, behavior, and reproduction as 

well as data on the cellular, hormonal, 

immunological, neurological, 

accumulative, histological, and 

physiological effects of 6PPD and/or 

6PPD-quinone and any other hazard 

information. EPA seeks hazard effects 

information for any terrestrial species, 

including: 

• Terrestrial vertebrates (e.g., 

mammals, birds, reptiles, amphibians); 

• Soil fauna (e.g., worms, microbes, 

nematodes) with an emphasis on 

roadside soil fauna; 

• Land invertebrates (e.g., insects, 

worms, slugs, snails, spiders); 

• Terrestrial plants (including 

nonvascular plants such as moss and 

lichen) with an emphasis on roadside 

plants; 

• Fungi; 

• Bacteria/microbiome; and 

• Potentially sensitive species. 

3. EPA is requesting information and 

data concerning known concentrations 

of 6PPD and/or 6PPD-quinone found in 

terrestrial animal and plant tissue that 

may indicate the bioaccumulation of 

6PPD and/or 6PPD-quinone in these 

species, particularly in species which 

are culturally significant to Tribes or 

subsistence fisher populations. This 

information may have important 

implications for potential exposure 

through the consumption of affected 

species. 

4. EPA is requesting information and 

data on any used methods of detection 

of 6PPD and/or 6PPD-quinone in biota, 

sediments, and soils. 

C. What are the potential human health 

and Tribal effects of 6PPD and/or 6PPDquinone? 

1. As discussed in Unit II.E. of this 

ANPRM, there are limited data on the 


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human health effects of 6PPD and/or 

6PPD-quinone, including toxicity 

studies (in vivo and in vitro) on 

carcinogenicity, reproductive and 

developmental effects, genotoxicity, 

neurotoxicity, immunotoxicity, 

endocrine effects, and other systemic 

toxicity and toxicokinetics (absorption, 

distribution, metabolism, or 

elimination), including modelling 

studies in humans. To ensure that EPA 

has robust, reasonably available data 

and information that are consistent with 

the best available science, EPA requests 

information and data on the human 

health effects of 6PPD and/or 6PPDquinone on the general population, and 

on specific subpopulations including 

the following: 

• Pregnant women and children; 

• Workers, including roadway 

workers, auto repair workers, racetrack 

maintenance crews, tire manufacturers 

or recyclers, and others who may be 

more frequently exposed to tires, TWP, 

vehicle dust, and road dust that may 

contain 6PPD and/or 6PPD-quinone; 

and 

• Other potentially exposed or 

susceptible subpopulations (PESS), 

which may include: 

—Communities that engage in 

subsistence fishing and/or gathering 

activities (e.g., Tribal communities and 

other populations engaging in fishing in 

urban or semi-urban waterways); 

—Near-roadway communities that 

may be more frequently exposed to tires, 

TWP, vehicle dust, and road dust that 

may contain 6PPD and/or 6PPDquinone; 

—Communities living near goodsmovement facilities, such as seaports, 

inland ports, land ports of entry, 

intermodal facilities and warehouse 

distribution centers; 

—Populations with existing 

disabilities or medical conditions whose 

inhalation or ingestion of 6PPD and/or 

6PPD-quinone may exacerbate existing 

medical concerns; and 

—Populations that are otherwise 

vulnerable or experiencing multiple 

environmental stressors; and 

• Studies showing the composition 

and purity of test substances should be 

reported, if available. 

2. As discussed in Unit II.E. of this 

ANPRM, there is also limited data on 

relevant human exposure pathways (the 

ways a person can be exposed to 6PPD 

and/or 6PPD-quinone), including 

inhalation, ingestion, or direct contact 

with the chemicals in media such as air, 

water, soil, and dust. To ensure that 

EPA has robust, reasonably available 

data and information that is consistent 

with the best available science, EPA 

requests information and data on human 

exposure pathways of 6PPD and/or 

6PPD-quinone on the general 

population, and especially for the 

following: 

• Pregnant women and children; 

• Disproportionately affected 

workers, including roadway workers, 

auto repair workers, and others who 

may be more frequently exposed to tires, 

TWP, vehicle dust, and road dust that 

may contain 6PPD and/or 6PPDquinone; and 

• Other potentially exposed or 

susceptible subpopulations (PESS), 

which may include: 

—Communities that engage in 

subsistence fishing and/or gathering 

activities (e.g., Tribal communities and 

other populations engaging in fishing in 

urban or semi-urban waterways); 

—Near-roadway communities that 

may be more frequently exposed to tires, 

TWP, vehicle dust, and road dust that 

may contain 6PPD and/or 6PPDquinone; 

—Populations with existing 

disabilities or medical conditions whose 

inhalation or ingestion of 6PPD and/or 

6PPD-quinone may exacerbate existing 

medical concerns; and 

—Populations that are otherwise 

vulnerable or experiencing multiple 

environmental stressors. 

3. EPA is requesting information on 

the cultural, political, economic, and 

environmental justice impacts of 6PPD 

and 6PPD-quinone contamination on 

Tribes. 

4. EPA is requesting information and 

data on the detection of 6PPD and/or 

6PPD-quinone contamination in 

drinking water. Specifically, EPA is 

requesting information on the volumes, 

locations, sources, and types of 6PPD 

and/or 6PPD-quinone contamination in 

drinking water, including the 

concentration and analytical method 

used to detect the chemicals (including 

quantification and detection limits) 

when available. 

D. What is 6PPD’s use in tires, releases 

of 6PPD and/or 6PPD-quinone into the 

environment, and remediation 

technologies? 

1. To help inform EPA’s 

understanding of how 6PPD from tires 

and/or TWP enters the environment, 

EPA is requesting information on the 

use of 6PPD in tires, including quantity 

and concentration. For example, this 

information includes but is not limited 

to the following: 

• How many and what types of 

businesses are engaged in importing, 

manufacturing, processing, distributing 

in commerce, using, and disposing of 

6PPD? 

• What percent by weight of 6PPD 

meets the minimum criteria for the 

chemical’s function within tires? Since 

the concentration of 6PPD in tires is not 

necessarily equivalent to the 

concentration that is released by tires, 

due to varying tire structures and 

designs, the amount and production of 

6PPD’s transformation products such as 

6PPD-quinone and other degradants 

may be among the considerations for 

this response. 

• What concentration of 6PPD is 

currently used during the tire 

manufacturing process? How does this 

vary across tire manufacturing 

companies and processes, as well as 

across different types of tire use (e.g., 

cars vs. large trucks, electric vehicles vs. 

gas powered)? 

• What is the rate of release of 6PPD 

and 6PPD-quinone from tires on electric 

vehicles vs. gas-powered vehicles? 

• What is the concentration of 6PPD 

in the finished tire and where in the tire 

is 6PPD present (i.e., in the sidewalls, 

tread, inner liner, etc)? Include the 

different concentrations for different 

types of tires, if applicable. 

• How does the concentration of 

6PPD in the tire change over time 

during normal wear and tear—after one 

year of use, versus after 5 years, etc over 

the normal lifespan of a tire? Does the 

6PPD concentration decrease steadily, 

or are there seasonal or other variations? 

• Whether, and if so how, 6PPD 

content in tires has changed over the 

last several decades. Specifically, has 

6PPD content changed on a per-pound 

basis? Or has it changed on a per-tire 

basis given that tire size and 

formulation can vary for light versus 

heavy duty vehicles? 

• Has the trend toward increased 

specialization in light duty vehicle tires 

altered 6PPD use/content in tires? In 

particular, has the use of highperformance summer tires, winter tires, 

and tires with off-road capability 

increased over time? 

• What are the water discharges from 

tire manufacturing facilities, including 

wastewater from processing and 

stormwater originating from these sites? 

Are monitoring data from near such 

sites available? 

• What are the water discharges from 

other aquatic and terrestrial sites that 

use or reuse tires, including but not 

limited to artificial reefs, playgrounds 

that use crumb rubber or artificial turf, 

and/or tire dumps? Are monitoring data 

from near such sites available? 

2. EPA is requesting data and 

information concerning the contribution 

of tire disposal, tire recycling, and tire 

reuse on environmental releases of, and 


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wildlife exposures to 6PPD and 6PPDquinone. 

3. For EPA to better understand the 

fate and transport of 6PPD and 6PPDquinone, EPA is requesting data and 

information on 6PPD as it moves from 

tires into the environment, reacts with 

ozone, and evolves into multiple 

transformation products, such as 6PPDquinone. EPA is requesting information 

and data regarding the fate and transport 

of 6PPD and/or 6PPD-quinone in and for 

use in tires, as well as the fate and 

transport of TWP containing 6PPD and/ 

or 6PPD-quinone. For example, EPA is 

requesting information on, but not 

limited to, the following: 

• What factors influence the 

transformation of 6PPD to 6PPDquinone and other transformation 

products (e.g., how does the 

concentration of ozone in ambient air 

impact the reaction rate of 6PPD to 

6PPD-quinone and other products)? 

• What are the degradation and 

transformation products of 6PPD, how 

do they move through the environment 

(e.g., via TWP, road dust, etc), and how 

are they absorbed in aqueous media, air, 

and soil/sediments? For aqueous fate 

and transport, conditions of interest 

under variable water quality conditions 

could include but are not limited to a 

broad range of pH (5–9), dissolved 

oxygen (2–10 mg/L), conductivity (0– 

50,000 mS/cm), and temperature (0– 

30C). 

• How do 6PPD and 6PPD-quinone 

react with water quality sampling 

equipment (i.e., water grab and passive 

samplers) such as resins, filtration 

media with plastic or silica-based tubs, 

caulking, or tubing 

(polytetrafluoroethylene—lined and 

others), deployment times, or flow rate 

meters? 

4. To gain a better understanding of 

6PPD’s uses, EPA is requesting 

information and data regarding other 

products that contain 6PPD and the 

potential for 6PPD and/or 6PPD-quinone 

contamination from these other sources, 

some of which are mentioned in Unit 

II.G. (sneakers, plumbing seals, elastics, 

etc). 

5. EPA is requesting information and 

data on successful water, air, soil, or 

sediment remediation and mitigation 

technologies that help reduce 6PPD 

and/or 6PPD-quinone exposure, such as 

green infrastructure, bioinfiltration 

basins, or technologies that capture 

TWP before they enter the environment, 

including methods that reduce 6PPD 

and/or 6PPD-quinone bound to airborne 

particulate matter. EPA is interested in 

information on remediation 

technologies once 6PPD and/or 6PPDquinone has entered the environment 

and the scalability and feasibility of 

implementing those remediation 

approaches for reducing 6PPD and/or 

6PPD-quinone in the environment. 

6. EPA is requesting information and 

data regarding the cost and efficacy of 

technologies for remediating water 

sources that have been contaminated 

with 6PPD and/or 6PPD-quinone. EPA 

is particularly interested in examples or 

case studies of remediation efforts that 

have addressed 6PPD and/or 6PPDquinone contamination, and cost and 

efficacy comparisons with other 

remediation efforts. 

E. What are the alternatives to 6PPD’s 

use in tires? 

1. There are multiple efforts 

underway investigating potential 

alternatives to 6PPD in tires, many of 

which are summarized in Unit IV of this 

ANPRM. EPA is requesting information 

and data on potential alternatives and 

their associated transformation or 

degradation products, including those 

not identified in this ANPRM, that may 

replace 6PPD as an antiozonant in tires. 

In addition to identifying potential 

alternatives, EPA is requesting 

information and data on the following: 

• What concentration of the potential 

alternative would be used during the 

tire manufacturing process and what 

concentration would be present in the 

finished tire? How would this vary 

across different types of tire use (e.g., 

car tires vs. large truck tires)? 

• What are the degradation and 

transformation products of the potential 

alternative, how do they move through 

the environment (e.g., via TWP, road 

dust, etc.), and how are they absorbed 

in aqueous media, air, and soil/ 

sediments once they’re in the 

environment? 

• What are the risks posed by 

potential alternatives to 6PPD on human 

health and the environment, including 

but not limited to hazard and toxicity 

effects of the parent and/or its 

transformation and degradation 

products on humans, aquatic and 

terrestrial species and ecosystems, and 

on air quality, greenhouse gas 

emissions, and potential disposal; 

• What are relevant considerations to 

include when evaluating an alternative 

that might replace 6PPD in tires (e.g., 

the standards used to assess the efficacy 

of potential alternatives); • What is the 

durability of the alternative (how long 

would it last as an antidegradant in the 

tire) and what is its ability to protect 

tires from degradation compared to 

6PPD; 

• Are there any potential nonchemical alternatives to 6PPD, such as, 

but not limited to, bio-based 

alternatives, self-healing polymers, or 

making physical changes to the tire or 

6PPD molecule that could result in less 

release into the environment of 6PPD or 

TWP; and 

• Any other exposure information, 

properties, or considerations of the 

potential alternatives. 

2. More generally, EPA is requesting 

information and data on the potential 

challenges and timelines of 

transitioning to using an alternative to 

6PPD as a tire antiozonant, such as: 

• What is a timeframe for finding an 

alternative that presents no/less hazards 

than 6PPD? 

• Once an alternative is identified, 

how long would it take for the 

alternative to be screened for feasibility 

in terms of its use in tires (e.g. ability 

to incorporate into manufacturing 

processes at large scale, ability to 

protect the tires from degradation)? 

• What safety testing and approval 

processes need to occur on the 

alternative to ensure it passes federal 

highway safety regulations? What are 

the relevant timeframes for completing 

those processes? 

• Once there is a feasible alternative 

that has passed initial safety screenings 

and is scalable, how might an extended 

phaseout be implemented to replace 

tires currently in use that contain 6PPD 

with the new tires? 

• How much time would be necessary 

for tire and rubber manufacturers to 

phase out and/or replace 6PPD as an 

antiozonant from their production cycle 

once a safe and feasible alternative was 

ready to be implemented? 

• What is a reasonable timeframe to 

phase out existing stocks of 6PPD that 

have already been produced for use in 

tires? Can existing stocks of 6PPD that 

have not been added to tires yet be 

safely disposed of (include associated 

methodologies)? 

• What is a reasonable timeframe to 

phase out existing stocks of 6PPDcontaining tires? 

• How can 6PPD-containing tires be 

disposed of or repurposed (include 

associated methodologies) and what are 

the potential impacts of such actions? 

• What is a reasonable timeframe to 

phase out the need for further 

introduction into commerce of 6PPDcontaining tires? 

• What transition periods (e.g., 3, 5, 

10 years) would be necessary and what 

would the likely associated impact be 

on the price or supply of tires and 

rubber products? 

• If a ban on the use of 6PPD in tires 

were in place, how long would it take 

to replace all tires currently in use given 

the expected lifespan of current tires (7– 

10 years)? EPA is requesting information 


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and data regarding impacts on human 

health or the environment that might 

result from the phase out or restricted 

use of 6PPD as a tire additive and 

antiozonant (e.g., reduced tire safety, 

disposal issues due to more frequent 

changing of tires). 

3. EPA is requesting information and 

data on the economic considerations 

and tradeoffs of removing 6PPD from 

tires and switching to an alternative 

formulation, process, or chemical. 

4. EPA is requesting information and 

data based on actual releases to the 

environment of potential alternatives 

and their associated transformation 

products and degradants; including 

degree of contamination, and the cost 

and efficacy of the technologies 

available to remediate such 

contamination. Specifically, EPA is 

requesting, to the extent possible, 

information on the volumes, 

concentrations, locations, sources, and 

types of contamination from potential 

alternatives in water, soil, and air. 

F. What actions could the Agency take 

under TSCA? 

As explained in this ANPRM, EPA is 

gathering information on a potential 

rulemaking. EPA requests comment on: 

1. If the Agency moves forward with 

a proposed rule after the ANPRM is 

published, what potential actions could 

EPA take under TSCA section 6(a)? 

Potential options include: 

• Regulate the manufacturing, 

processing, or distribution in commerce 

of the chemical, including a complete 

ban of any such activity or limiting the 

amounts of the chemical manufactured, 

distributed, and/or included in tires; 

• Regulate the manufacturing, 

processing, or distribution in commerce 

of the chemical for particular uses, 

including banning any such activity for 

a particular use; limiting the 

concentration of the chemical that may 

be used; or limiting the amounts of the 

chemical for particular uses; 

• Require warning statements and/or 

instructions for use with respect to the 

chemical’s use in tires and non-tire 

materials (e.g., rubber modified asphalt, 

sneakers, elastics, etc.), distribution in 

commerce, and/or disposal of the 

chemical or products containing the 

chemical; 

• Require manufacturers/processors 

to make and retain such records of the 

manufacturing process and/or monitor 

or conduct tests to ensure compliance 

with a TSCA section 6 rule; 

• Prohibiting or regulating any 

manner or method of commercial use of 

the chemical; 

• Prohibit or regulate the disposal of 

the chemical; and 

• Require manufacturers/processors 

to provide warnings to distributors or 

users and to replace or repurchase the 

chemical. 

2. TSCA provides EPA authority to 

select a combination of TSCA section 

6(a) actions and limit the geographic 

application of a rule under TSCA 

section 6(a). EPA is requesting comment 

on whether, and if so, where EPA 

should consider limits to the 

geographical scope of any potential 

action under TSCA section 6(a)? 

3. TSCA section 9 provides that the 

EPA Administrator shall consult and 

coordinate with the heads of other 

appropriate federal executive 

departments or agencies to achieve 

maximum enforcement of TSCA, while 

imposing the least burden of duplicative 

requirements. The Administrator is also 

directed to coordinate actions taken 

under TSCA with actions taken under 

other federal laws administered by the 

EPA, such as the Resource Conservation 

and Recovery Act, the Clean Air Act and 

the Clean Water Act. Are there other 

statutory authorities administered by 

EPA that could be used to eliminate or 

reduce to a sufficient extent any risk 

identified? 

4. As discussed in Unit II.H., TSCA 

section 6(g) allows EPA to grant an 

exemption from a requirement of a 

TSCA section 6(a) rule for a specific 

condition of use of a chemical substance 

or mixture, if the Administrator finds 

that: the specific condition of use is a 

critical or essential use for which no 

technically and economically feasible 

safer alternative is available; compliance 

with the requirement, as applied with 

respect to the specific condition of use, 

would significantly disrupt the national 

economy, national security, or critical 

infrastructure; or the specific condition 

of use of the chemical substance or 

mixture, as compared to reasonably 

available alternatives, provides a 

substantial benefit to health, the 

environment, or public safety. What 

should EPA consider regarding a 

potential TSCA section 6(g) exemption 

for 6PPD use in tires? If so, what 

conditions may be necessary to protect 

health and the environment while 

achieving the purposes of an 

exemption? 

IV. References 

The following is a list of the 

documents that are specifically 

referenced in this document. The docket 

includes these documents and other 

information considered by EPA, 

including documents that are referenced 

within the documents that are included 

in the docket, even if the referenced 

document is not physically located in 

the docket. For assistance in locating 

these other documents, please consult 

the technical person listed under FOR

FURTHER INFORMATION CONTACT. 

1. Earthjustice, ‘‘Citizen Petition under TSCA 

section 21 to Prohibit 6PPD in Tires,’’ 

August 1, 2023. [Online]. Available: 

https://www.epa.gov/system/files/ 

documents/2023-08/ 

TSCA%20Section%20

21%20Petition%20to%20

EPA%20re%206PPD%20in%20tires.pdf. 

2. U.S. Tire Manufacturers Association 

(USTMA), ‘‘Preliminary (Stage 1) 

Alternatives Analysis Report Motor 

Vehicle Tires Containing N-(1,3- 

dimethylbutyl)-N′-phenyl-pphenylenediamine (6PPD),’’ March 25, 

2024. [Online]. Available: https://

www.ustires.org/sites/default/files/2024- 

03/USTMA%20

Consortium%206PPD%20

AA%20Preliminary%20Report_3-25- 

24.pdf. 

3. U.S. EPA, ‘‘Final EPA Response to Section 

21 Petition Regarding N-(1,3- 

Dimethylbutyl)-N′-phenyl-pphenylenediamine (CASRN 793–24–8, 

aka 6PPD) in Tires,’’ November 2, 2023. 

[Online]. Available: https://

www.epa.gov/system/files/documents/ 

2023-11/pet-001845_tsca-21_petition_

6ppd_decision_letter_

esigned2023.11.2.pdf. 

4. Oslo and Paris Convention (OSPAR) 

Commission, ‘‘Hazardous Substances 

Series 4- 

(dimethylbutylamino)diphenylamine 

(6PPD),’’ 2005 (2006 Update). [Online]. 

Available: https://www.ospar.org/ 

documents?v=7029. 

5. PubChem, ‘‘N-(1,3-Dimethylbutyl)-N′- 

phenyl-p-phenylenediamine (6PPD) 

Compound Summary,’’ [Online]. 

Available: https://

pubchem.ncbi.nlm.nih.gov/compound/ 

13101. [Accessed July 2024]. 

6. P. Lewis, ‘‘Effect of ozone on rubbers: 

Countermeasures and unsolved 

problems,’’ Polymer Degradation and 

Stability, vol. 15, no. 1, pp. 33–66, 1986. 

7. Y. Jiang, C. Wang, L. Ma, T. Gao and Y. 

Wa ̄ng, ‘‘Environmental profiles, hazard 

identification, and toxicological 

hallmarks of emerging tire rubber-related 

contaminants 6PPD and 6PPD-q,’’ 

Environment International, vol. 187, 

May 2024. 

8. M. Llompart, L. Sanchez-Prado, J.P. Lamas, 

C. Garcia-Jares, E. Roca and T. Dagnac, 

‘‘Hazardous organic chemicals in rubber 

recycled tire playgrounds and pavers,’’ 

Chemosphere, vol. 90, no. 2, pp. 423– 

431, August 22, 2012. 

9. R. Massey and Z. Tian, ‘‘6PPD in Tires: A 

concern for playgrounds, artificial turf, 

and more,’’ Collaborative for Health and 

Environment, October 9, 2023. [Online]. 

Available: https://

www.healthandenvironment.org/join-us/ 

blog/6ppd-in-tires-a-concern-forplaygrounds-artificial-turf-and-more. 

10. Joined Fortune Chemical, ‘‘6PPD Rubber 

Antioxidant: Characteristics, 

Applications, Combinations, and 


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91310 Federal Register / Vol. 89, No. 223 / Tuesday, November 19, 2024 / Proposed Rules 

Considerations for Commercial 

Procurement,’’ June 25, 2023. [Online]. 

Available: https://

joinedfortunechemical.com/blogs/new/ 

6ppd-rubber-antioxidant-characteristicsapplications-combinations-andconsiderations-for-commercialprocurement. 

11. S. Varshney, A.H. Gora, P. 

Siriyappagouder, V. Kiron and P.A. 

Olsvik, ‘‘Toxicological effects of 6PPD 

and 6PPD q in zebrafish larvae,’’ Journal 

of Hazardous Materials, vol. 424, no. 

Part C, p. 127623, February 15, 2022. 

12. J.K. McIntyre, J. Prat, J. Cameron, J. 

Wetzel, E. Mudrock, K.T. Peter, Z. Tian, 

C. Mackenzie, J. Lundin, J.D. Stark, K. 

King, J.W. Davis, E.P. Kolodziej and N.L. 

Scholz, ‘‘Treading Water: Tire Wear 

Particle Leachate Recreates an Urban 

Runoff Mortality Syndrome in Coho but 

Not Chum Salmon,’’ Environmental 

Science and Technology, vol. 55, no. 17, 

p. 11767–11774, August 19, 2021. 

13. X. Chen, T. He, X. Yang, Y. Gan, X. Qing, 

J. Wang and Y. Huang, ‘‘Analysis, 

environmental occurrence, fate and 

potential toxicity of tire wear 

compounds 6PPD and 6PPD-quinone,’’ 

Journal of Hazardous Materials, vol. 452, 

no. 2023, p. 131245, June 15, 2023. 

14. S. Wagner, T. Hu ̈ffer, P. Klo ̈ckner, M. 

Wehrhahn, T. Hofmann and T. 

Reemtsma, ‘‘Tire wear particles in the 

aquatic environment—A review on 

generation, analysis, occurrence, fate and 

effects,’’ Water Research, vol. 139, no. 

2018, pp. 83–100, August 1, 2018. 

15. Y.J. Zhang, T.T. Xu, D.M. Ye, Z.Z. Lin, 

F. Wang and Y. Guo, ‘‘Widespread N- 

(1,3-Dimethylbutyl)-N′-phenyl-pphenylenediamine Quinone in SizeFractioned Atmospheric Particles and 

Dust of Different Indoor Environments,’’ 

Environmental Science & Technology 

Letters, vol. 9, no. 5, pp. 420–425, April 

25, 2022. 

16. K. Hiki, K. Asahina, K. Kato, T. 

Yamagishi, R. Omagari, Y. Iwasaki, H. 

Watanabe and H. Yamamoto, ‘‘Acute 

Toxicity of a Tire Rubber-Derived 

Chemical, 6PPD Quinone, to Freshwater 

Fish and Crustacean Species,’’ 

Environmental Science & Technology 

Letters, vol. 8, no. 9, p. 779–784, August 

10, 2021. 

17. K. Hiki and H. Yamamoto, 

‘‘Concentration and leachability of N- 

(1,3-dimethylbutyl)-N′-phenyl-pphenylenediamine (6PPD) and its 

quinone transformation product (6PPD– 

Q) in road dust collected in Tokyo, 

Japan,’’ Environmental Pollution, vol. 

302, p. 119082, June 1, 2022. 

18. B. Seiwert, M. Nihemaiti, M. Troussier, 

S. Weyrauch and T. Reemtsma, ‘‘Abiotic 

oxidative transformation of 6–PPD and 

6–PPD quinone from tires and 

occurrence of their products in snow 

from urban roads and in municipal 

wastewater,’’ Water Research, vol. 212, 

p. 118122, April 1, 2022. 

19. B. Baensch-Baltruschat, B. Kocher, F. 

Stock and G. Reifferscheid, ‘‘Tyre and 

road wear particles (TRWP)—A review of 

generation, properties, emissions, human 

health risk, ecotoxicity, and fate in the 

environment,’’ Science of the Total 

Environment, vol. 733, p. 137823, 

September 1, 2020. 

20. J. Blok, ‘‘Environmental exposure of road 

borders to zinc,’’ Science of The Total 

Environment, vol. 348, no. 1–3, pp. 173– 

190, September 15, 2005. 

21. C. Lassen, S.F. Hansen, K. Magnusson, 

N.B. Hartmann, P.R. Jensen, T.G. Nielsen 

and A. Brinch, ‘‘Microplastics: 

Occurrence, effects and sources of 

releases to the environment in 

Denmark,’’ The Danish Environmental 

Protection Agency, 2015. 

22. X. Hu, H.N. Zhao, Z. Tian, K.T. Peter, 

M.C. Dodd and E.P. Kolodziej, 

‘‘Transformation Product Formation 

upon Heterogeneous Ozonation of the 

Tire Rubber Antioxidant 6PPD (N (1,3-,′′ 

Environmental Science and Technology 

Letters, vol. 9, no. 5, pp. 413–419, April 

12, 2022. 

23. U.S. EPA, ‘‘Estimation Programs Interface 

SuiteTM for Microsoft® Windows, v 

4.11,’’ [Online]. Available: https://

www.epa.gov/tsca-screening-tools/episuitetm-estimation-program-interface. 

24. C. Theodorakis and T. Walker, 

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V. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and executive orders can be 

found at https://www.epa.gov/ 

regulations/laws-and-executive-orders. 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

This action is not a significant 

regulatory action as defined in 

Executive Order 12866 (58 FR 51735, 

October 4, 1993), as amended by 

Executive Order 14094 (88 FR 21879, 

April 11, 2023), and was therefore not 

subject to a requirement for Executive 

Order 12866 review. 

B. Other Regulatory Assessment 

Requirements 

Because this action does not impose 

or propose any requirements, the 

various other review requirements in 

statutes and Executive Orders that apply 

when an agency imposes or proposes 

requirements do not apply to this 

ANPRM. Should EPA subsequently 

determine to pursue a rulemaking, EPA 

will address the requirements in the 

statutes and executive orders as 

applicable to that rulemaking. 

List of Subjects in 40 CFR Part 751 

Chemicals, Environmental protection, 

Exports, Hazardous substances, Imports, 

Reporting and recordkeeping 

requirements. 

Michael S. Regan, 

Administrator. 

[FR Doc. 2024–26894 Filed 11–18–24; 8:45 am] 

BILLING CODE P 


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