[Federal Register Volume 89, Number 223 (Tuesday, November 19, 2024)]
[Proposed Rules]
[Pages 91299-91312]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-26894]
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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-p-phenylenediamine (6PPD) and its
Transformation Product, 6PPD-quinone; Regulatory Investigation Under
the Toxic Substances Control Act (TSCA)
AGENCY: Environmental Protection Agency (EPA).
ACTION: Advance notice of proposed rulemaking (ANPRM).
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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-p-
phenylenediamine (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:
[email protected].
For general information on TSCA: The TSCA Hotline, ABVI-Goodwill,
422 South Clinton Ave., Rochester, NY 14620; telephone number: (202)
554-1404; email address: [email protected].
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 6PPD-quinone. 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
[[Page 91300]]
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
6PPD-quinone 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-p-
phenylenediamine (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).
[[Page 91301]]
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
6PPD-quinone 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-
anilino-5-(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 [deg]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 6PPD-quinone 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
[[Page 91302]]
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 author-reported
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 [mu]g/L after 96 hours of
exposure), rare minnows (Gobiocypris rarus) (author-reported
LC50 of 162 [mu]g/L after 96 hours of exposure; EPA-adjusted
LC50 of 94.94 [mu]g/L), coho salmon (Oncorhynchus kisutch)
(author-reported juvenile LC50 of 251 [mu]g/L after 24 hours
of exposure; EPA-adjusted LC50 of 143.7 [mu]g/L), and
amphipods (Hyalella azteca) (author-reported juvenile LC50
of 250 [mu]g/L after 96 hours of exposure; EPA-adjusted LC50
of 159.7 [mu]g/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 [mu]g/L after an early-life stage test of unknown
duration) and fathead minnows (Pimephales) (author-reported
LC50 of 150 [mu]g/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 6PPD-quinone 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 [mu]g/L for juveniles in
less than 24 hours (EPA-adjusted LC50 of 0.036 [mu]g/L)
(Refs. 42 and 43) and up to 0.095 [mu]g/L for adults after 24 hours
(EPA-adjusted LC50 of 0.092 [mu]g/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
[mu]g/L after 24 hours of exposure; EPA-adjusted LC50 of
0.5186 [mu]g/L) (Ref. 45), white-spotted char (Salvelinus leucomaenis
pluvius) (<1 year juvenile LC50 of 0.80 [mu]g/L after 24
hours; EPA-adjusted LC50 of 0.5709 [mu]g/L) (Refs. 43 and
46), brook trout (Salvelinus fontinalis) (~1 year juvenile
LC50 of 0.59 [mu]g/L after 24 hours) (Ref. 47), rainbow
trout (Oncorhynchus mykiss) (~2 month juvenile LC50 of 0.64
[mu]g/L; EPA-adjusted LC50 of 0.2961 [mu]g/L) (~2 year
juvenile LC50 of 1.00 [mu]g/L after 96 hours) (Refs. 38, 43,
and 47), and chinook salmon (Oncorhynchus tshawytscha) (582-day old
LC50 of 82.1 [mu]g/L after 24 hours; EPA-adjusted
LC50 of 65.68 [mu]g/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 [mu]g/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 [mu]g/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 6PPD-quinone 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 [mu]g/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 6PPD-quinone 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
[[Page 91303]]
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
6PPD-quinone 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 6PPD-quinone at 1-10 [mu]g/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 [mu]g/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 [mu]g/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 [mu]g/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 6PPD-
quinone 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 6PPD-
quinone, 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 6PPD-
quinone 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-waste-exposed 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 6PPD-quinone 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 e-waste-
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
[[Page 91304]]
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 6PPD-quinone'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 6PPD-quinone in aquatic species
predicted that although there is potential for uptake, the data
suggests that 6PPD-quinone 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
6PPD-quinone 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 rubber-modified 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 tire-derived 6PPD-quinone that released 6PPD-quinone into the
environment after simulated rainfall events, with 0.0015-0.0049 [mu]g/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).
[[Page 91305]]
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,
Sec. 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
nano-platelet). 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
[[Page 91306]]
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 6PPD-quinone 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 high-quality
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
6PPD-quinone 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 6PPD-quinone 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 6PPD-quinone?
1. As discussed in Unit II.E. of this ANPRM, there are limited data
on the
[[Page 91307]]
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 6PPD-quinone 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
6PPD-quinone;
--Communities living near goods-movement 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 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
6PPD-quinone;
--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 high-performance 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
[[Page 91308]]
wildlife exposures to 6PPD and 6PPD-quinone.
3. For EPA to better understand the fate and transport of 6PPD and
6PPD-quinone, 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 6PPD-quinone. 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 6PPD-
quinone 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 [micro]S/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 6PPD-quinone
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 6PPD-quinone 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 non-chemical 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 6PPD-containing 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 6PPD-containing 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
[[Page 91309]]
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.
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2. U.S. Tire Manufacturers Association (USTMA), ``Preliminary (Stage
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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]
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