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[Federal Register Volume 90, Number 9 (Wednesday, January 15, 2025)]
[Notices]
[Pages 3859-3864]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2025-00734]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OW-2024-0504; FRL 12451-01-OW]

Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid 
(PFOA) and Perfluorooctane Sulfonic Acid (PFOS)

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability.

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SUMMARY: As part of the Environmental Protection Agency's (EPA's) 
commitment to safeguarding the environment from per- and 
polyfluoroalkyl substances (PFAS), the agency is announcing the 
availability of the ``Draft Sewage Sludge Risk Assessment for 
Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid 
(PFOS)'' for a 60-day public comment period. This draft risk assessment 
reflects the agency's latest scientific understanding of the potential 
risks to human health and the environment posed by the presence of PFOA 
and PFOS in sewage sludge that is land applied as a soil conditioner or 
fertilizer (on agricultural, forested, and other lands), surface 
disposed, or incinerated. The draft risk assessment focuses on those 
living on or near impacted sites or those that rely primarily on their 
products (e.g., food crops, animal products, drinking water); the draft 
risk assessment does not model risks for the general public. This draft 
risk assessment underwent independent external peer review, and the EPA 
revised the document accordingly. Once finalized, the risk assessment 
will provide information on risk from use or disposal of sewage sludge 
and will inform the EPA's potential future regulatory actions under the 
Clean Water Act (CWA).

DATES: Comments must be received on or before March 17, 2025.

ADDRESSES: The EPA has established a docket for the ``Draft Sewage 
Sludge Risk Assessment for Perfluorooctanoic Acid (PFOA) and 
Perfluorooctane Sulfonic Acid (PFOS)'' action under Docket ID No EPA-
HQ-OW-2024-0504. You may send comments, identified by Docket ID No. 
EPA-HQ-OW-2024-0504, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
     Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Office of Water Docket, Mail Code 28221T, 1200 Pennsylvania 
Avenue NW, Washington, DC 20460.
     Hand Delivery or Courier: EPA Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. 
The Docket Center's hours of operations are 8:30 a.m. to 4:30 p.m., 
Monday through Friday (except Federal Holidays).
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the ``Public Participation--
Written comments'' heading of the SUPPLEMENTARY INFORMATION section of 
this document.

FOR FURTHER INFORMATION CONTACT: David Tobias, Health and Ecological 
Criteria Division, Office of Science and Technology, Office of Water, 
Environmental Protection Agency; email address: 
[email protected].

[[Page 3860]]

SUPPLEMENTARY INFORMATION: 
    This notice of availability is organized as follows:

I. Public Participation--Written Comments
II. Background
    A. Clean Water Act Authorities
    B. What is the purpose of this action?
    C. What is sewage sludge?
    D. What are PFOA and PFOS?
    E. What are the potential sources of PFOA and PFOS to sewage 
sludge?
    F. What is a risk assessment?
III. Description and Preliminary Findings of the EPA's Draft Risk 
Assessment
    A. Scope of the Draft Risk Assessment
    B. Modeling Approaches
    C. Preliminary Findings of the Central Tendency Modeling
IV. Next Steps
    A. Risk Reduction
    B. Related Actions
    C. Final Risk Assessment and Potential Future Actions

I. Public Participation--Written Comments

    The EPA is seeking comments, particularly on scientific and 
technical issues, on its ``Draft Sewage Sludge Risk Assessment for 
Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid 
(PFOS).'' Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2024-0504, on the draft sewage sludge risk assessment at https://www.regulations.gov (our preferred method), or the other methods 
identified in the ADDRESSES section. Once submitted, comments cannot be 
edited or removed from the docket. The EPA may publish any comment 
received to its public docket. Do not submit any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For the full EPA public comment policy, information about CBI 
or multimedia submissions, and general guidance on making effective 
comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.

II. Background

A. Clean Water Act Authorities

    Consistent with CWA section 405(d)(2), 33 U.S.C. 1345(d)(2), the 
EPA periodically reviews its existing regulations for the purpose of 
identifying additional toxic pollutants that may be present in sewage 
sludge and assesses whether those pollutants may adversely affect 
public health or the environment based on their toxicity, persistence, 
concentration, mobility, and potential for exposure. In December 2022, 
the EPA completed its latest review of the sewage sludge regulations as 
published in the EPA's Biennial Review of 40 CFR part 503 To Fulfill 
Clean Water Act Section 405(d)(2)(C), Biosolids Biennial Report No. 9 
(see https://www.epa.gov/biosolids/biennial-report-no-9-reporting-period-2020-2021). This notice of availability for the draft risk 
assessment is in accordance with CWA section 405(g)(1), 33 U.S.C. 
1345(g)(1), which authorizes the EPA to conduct scientific studies and 
provide public information to promote the safe and beneficial 
management or use of sewage sludge.

B. What is the purpose of this action?

    The purpose of this action is to request public comments, 
particularly regarding scientific and technical aspects, on the EPA's 
``Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid (PFOA) 
and Perfluorooctane Sulfonic Acid (PFOS).'' The EPA is most interested 
in receiving comments regarding the draft risk assessment modeling 
(e.g., the scenarios, sewage sludge application rates, environmental 
fate and transport parameters, human exposure assumptions). The draft 
risk assessment reflects the agency's latest scientific understanding 
of the risks to human health and the environment posed by the presence 
of PFOA and PFOS in sewage sludge that is land applied as a soil 
conditioner or fertilizer (on agricultural, forested, and other lands), 
surface disposed (e.g., placed in a sewage sludge-only landfill called 
a monofill), or incinerated. The draft risk assessment focuses on those 
living on or near impacted properties where sewage sludge has been used 
or disposed. The intent of the draft risk assessment is to evaluate 
whether there may be risks to human health or the environment for the 
wide range of possible sewage sludge use and disposal scenarios. Not 
all the scenarios described in the draft risk assessment may be common 
practice or applicable to the general public. The EPA uses sewage 
sludge risk assessments to help evaluate whether risk reduction 
actions, including regulation, are warranted to protect those who may 
experience elevated risks from sewage sludge use or disposal. The draft 
risk assessment reflects external peer review and incorporates 
revisions from the peer review process. The EPA will consider public 
comments and prepare a final risk assessment for publication. The EPA 
will announce the availability of the final risk assessment in the 
Federal Register.

C. What is sewage sludge?

    When domestic sewage is transported and conveyed to a wastewater 
treatment plant (WWTP), it is treated to separate liquids from the 
solids, which produces a semi-solid, nutrient-rich product known as 
sewage sludge. In some instances, industrial wastewater is also 
conveyed to a WWTP and combined with domestic sewage. The terms 
``biosolids'' and ``sewage sludge'' are often used interchangeably by 
the public; however, the EPA typically uses the term ``biosolids'' to 
mean sewage sludge that has been treated to meet the requirements in 
the EPA's regulation entitled, ``Standards for the Use or Disposal of 
Sewage Sludge,'' promulgated at 40 CFR part 503, and intended to be 
applied to land as a soil conditioner or fertilizer. In the U.S., there 
are generally three options for use or disposal of sewage sludge. Based 
on available data, (1) approximately 56 percent of the nation's sewage 
sludge is land applied as a soil conditioner or fertilizer (roughly 31 
percent is applied to agricultural land and 25 percent is applied to 
other lands, such as reclamation sites, home lawns and gardens, or golf 
courses), (2) approximately 27 percent is disposed of in a sewage 
sludge monofill or municipal solid waste (MSW) landfill, and (3) 
approximately 16 percent is incinerated.\1\ Land application of sewage 
sludge can have environmental benefits including improved soil health, 
carbon sequestration, and reduced demand on non-renewable resources 
like phosphorus. Land application also generates reduced emissions of 
greenhouse gases compared to other management practices.
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    \1\ An additional 1 percent of sewage sludge is disposed of 
using other management practices (e.g., deep-well injection).
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D. What are PFOA and PFOS?

    PFOA and PFOS are two chemicals in a large class of synthetic 
chemicals called PFAS. PFOA and PFOS persist in the environment for 
long periods of time and have been linked to a variety of adverse human 
health effects. In 2024, the EPA classified both PFOA and PFOS as 
likely to be carcinogenic to humans and concluded that these chemicals 
are also likely to cause a range of non-cancer effects in humans, 
including hepatic, immunological, cardiovascular, and developmental 
effects, depending

[[Page 3861]]

on exposure conditions (see the EPA's Final Human Health Toxicity 
Assessment for Perfluorooctanoic Acid (PFOA) and Related Salts, 
available at: https://www.epa.gov/sdwa/human-health-toxicity-assessment-perfluorooctanoic-acid-pfoa, and Final Human Health Toxicity 
Assessment for Perfluorooctane Sulfonic Acid (PFOS) and Related Salts, 
available at: https://www.epa.gov/sdwa/human-health-toxicity-assessment-perfluorooctane-sulfonic-acid-pfos).
    PFAS have been manufactured and used by a broad range of industries 
since the 1940s, and there are estimated to be thousands of PFAS 
present in the global marketplace that are used in many consumer, 
commercial, and industrial products. PFOA and PFOS have been widely 
studied, and they were once high production volume chemicals within the 
PFAS chemical class. PFAS manufacturers voluntarily phased out domestic 
manufacturing of PFOS by 2002 and of PFOA by 2015, and the EPA 
restricted their uses by Significant New Use Rules (SNURs) issued under 
section 5(a)(2) of the Toxic Substances Control Act (TSCA), 15 U.S.C. 
2604(a)(2) (see https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/risk-management-and-polyfluoroalkyl-substances-pfas).

E. What are the potential sources of PFOA and PFOS to sewage sludge?

    Although domestic manufacturing of PFOA and PFOS have been phased 
out and their uses restricted, multiple activities still result in 
PFOA, PFOS, and their precursors being released to WWTPs. Current and 
historical activities include industrial releases (e.g., aqueous film-
forming foam, pulp and paper plants), commercial releases (e.g., car 
washes, industrial launderers), and down-the-drain releases from homes 
(e.g., use of consumer products like after-market water resistant 
sprays, ski wax, floor finishes, and laundering of stain or water-
resistant textiles with PFOA or PFOS coatings) (see the Preliminary 
Effluent Guidelines Program Plan 16, available at https://www.epa.gov/eg/preliminary-effluent-guidelines-program-plan, and the Multi-Industry 
Per- and Polyfluoroalkyl Substances (PFAS) Study--2021 Preliminary 
Report, available at https://www.epa.gov/system/files/documents/2021-09/multi-industry-pfas-study_preliminary-2021-report_508_2021.09.08.pdf). If products containing PFOA or PFOS are 
disposed of at a lined MSW landfill, because the most common off-site 
management practice for landfill leachate is to transfer it to a WWTP, 
then that landfill's leachate could be a source of PFOA and PFOS to a 
WWTP. At different WWTPs across the country, any of these release 
mechanisms may play a role in PFOA or PFOS entering the plant and 
contaminating the sewage sludge.
    Statewide surveys have found PFOA and PFOS in sewage sludge 
originating from industrial and non-industrial sources that are 
discharging to WWTPs. Traditional wastewater treatment technology does 
not remove or destroy PFOA or PFOS, and these chemicals typically 
accumulate in the sewage sludge. Appropriate pretreatment solutions at 
industrial dischargers exist, are cost-effective, and have been shown 
to be effective in reducing high concentrations of PFOA and PFOS; 
however, studies have found that PFOA and PFOS are consistently 
detected at varying levels in sewage sludge even at WWTPs that do not 
receive wastewater from industrial users of the chemicals (i.e., they 
only receive wastewater from residential and commercial users).

F. What is a risk assessment?

    Risk assessment is a scientific process that is used to 
characterize the nature and magnitude of health risks to humans (i.e., 
children and adults) and ecological receptors (i.e., aquatic and 
terrestrial plants and wildlife) from pollutants (see https://www.epa.gov/risk/about-risk-assessment#whatisrisk). An environmental 
risk assessment considers three primary factors: (1) presence (i.e., 
how much of a pollutant is present in the environment), (2) exposure 
(i.e., how much contact humans or wildlife have with the pollutant), 
and (3) the toxicity of the pollutant (i.e., the health effects the 
pollutant causes in humans or wildlife).
    The concentration of pollutants found in sewage sludge varies 
across space and time, depending on industrial and other inputs to 
individual WWTPs. The presence of a pollutant in sewage sludge alone 
does not necessarily mean that there is risk to human health or the 
environment from its use or disposal. The EPA estimates potential 
exposures to humans and environmental receptors by modeling the fate 
and transport of a pollutant through the environment, taking into 
account different environmental conditions and exposure scenarios, and 
then estimates risk by comparing those potential exposures to toxicity 
values.

III. Description and Preliminary Findings of the EPA's Draft Risk 
Assessment

A. Scope of the Draft Risk Assessment

    The EPA's draft risk assessment describes the potential human 
health and environmental risks associated with land application, 
surface disposal, and incineration of sewage sludge containing PFOA or 
PFOS, which are the use and disposal practices regulated under CWA 
section 405(d) and the EPA's accompanying regulation at 40 CFR part 
503, Standards for the Use or Disposal of Sewage Sludge. The draft risk 
assessment does not assess human health or environmental risks 
associated with sewage sludge disposal in MSW landfills, a common 
management practice for disposal of sewage sludge, because that 
practice is regulated under the Resource Conservation and Recovery Act 
(RCRA) and the EPA's accompanying regulations at 40 CFR part 258, 
Criteria for Municipal Solid Waste Landfills.
    The draft risk assessment is scoped to model risks to human 
populations because available data indicate that humans are more 
sensitive to PFOA and PFOS exposures than aquatic or terrestrial 
wildlife or livestock. For the land application scenarios, the EPA 
modeled potential PFOA and PFOS exposures and estimated human health 
risks to those living on or near impacted properties under three 
hypothetical scenarios: (1) application to a farm raising dairy cows, 
beef cattle, or chickens (pasture farm scenario), (2) application to a 
farm growing fruits or vegetables (food crop farm scenario),\2\ and (3) 
application to reclaim damaged soils such as an overgrazed pasture 
(reclamation scenario). For the surface disposal scenarios, the EPA 
modeled potential PFOA or PFOS exposures via groundwater to those 
living near a lined or unlined surface disposal site (e.g., sewage 
sludge monofill). For the incineration scenario, the EPA provides a 
qualitative description of the potential risks to communities living 
near a sewage sludge incinerator (SSI). The draft risk assessment does 
not provide quantitative risk estimates for the incineration scenario 
due to significant data gaps related to the extent to which

[[Page 3862]]

incineration in an SSI destroys PFOA and PFOS and the health effects of 
exposure to products of incomplete combustion.\3\
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    \2\ The EPA acknowledges that the majority of food crops grown 
in the United States do not use sewage sludge as a soil conditioner 
or fertilizer and some states have restricted the land application 
of sewage sludge to food crops. However, this practice is not 
consistent across all states. Furthermore, because of the extreme 
persistence of PFOA and PFOS in soils, a property with previous 
sewage sludge land application that has been repurposed as a food or 
feed crop farm could still have multiple relevant human exposure 
pathways.
    \3\ Based on currently available information, sewage sludge 
incinerators may not operate at high enough temperatures and long 
enough residence times to fully destroy PFOA and PFOS in sewage 
sludge (see the Interim Guidance on the Destruction and Disposal of 
Perfluoroalkyl and Polyfluoroalkyl Substances and Materials 
Containing Perfluoroalkyl and Polyfluoroalkyl Substances--Version 2 
(2024), available at: https://www.epa.gov/pfas/interim-guidance-destruction-and-disposal-pfas-and-materials-containing-pfas).
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B. Modeling Approaches

    The EPA first performed a screening-level risk analysis for PFOA 
and PFOS in sewage sludge using a high-end deterministic exposure model 
for a hypothetical farm. This screening approach assumed high starting 
concentrations of PFOA and PFOS in sewage sludge (approximating a 95th 
percentile concentration based on available data), high-end consumption 
rates for each exposure pathway (e.g., 90th percentile consumption 
rates for drinking water intake, milk consumption), and other high-end 
factors. The high-end screening model resulted in risks exceeding the 
EPA's acceptable thresholds for every individual human exposure pathway 
(e.g., drinking water, consumption of fish, milk, beef, vegetables). 
Given that the risk estimates greatly exceeded the agency's acceptable 
thresholds in the screening-level assessment, the EPA next moved on to 
a refined risk assessment. In this assessment, the EPA refined the 
modeling approach and assessed risks under median (i.e., central 
tendency, 50th percentile), rather than high-end exposure conditions, 
to better understand the potential scope and magnitude of risks under 
different use and disposal scenarios. To complete the central tendency 
deterministic modeling steps of the refined risk assessment, the EPA 
(1) identified available fate and transport models to select the best 
models for assessing PFOA and PFOS, and (2) parameterized the models 
with inputs and exposure factors to reflect median U.S. conditions and 
consumption behaviors. For example, when calculating risks from egg 
consumption in the central tendency approach, the model assumes that an 
adult living on a farm consumes, on average, 1 egg per day from the 
impacted property for ten years, which represents the median egg 
consumption rate reported in the EPA's Exposure Factors Handbook for 
households who farm (see https://www.epa.gov/expobox/about-exposure-factors-handbook, Table 13-40). The model further assumes that when the 
adult lives on the impacted farm, they have no sources of PFOA or PFOS 
exposure other than the contaminated eggs and that for the remainder of 
the adult's life, they have no exposure to PFOA or PFOS through any 
pathway.

C. Preliminary Findings of the Central Tendency Modeling

    The findings summarized here and presented in the draft risk 
assessment are preliminary. The EPA expects to publish a final risk 
assessment after reviewing public comments and revising the draft risk 
assessment accordingly. Based on the modeling results of the refined 
risk assessment for the central tendency (median) exposure scenarios, 
the EPA has found that draft risk estimates exceed the agency's 
acceptable human health risk thresholds \4\ for some pasture farm, food 
crop farm, and reclamation scenarios when assuming that the land-
applied sewage sludge contains 1 part per billion (ppb) \5\ of PFOA or 
PFOS. The EPA also finds that there are human health risks associated 
with drinking contaminated groundwater sourced near a surface disposal 
site when sewage sludge containing 1 ppb of PFOA or sewage sludge 
containing 4 to 5 ppb of PFOS is disposed in an unlined or clay-lined 
surface disposal unit.
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    \4\ The risk threshold for non-cancer human health effects is a 
hazard quotient equal to one, i.e., when the exposure is equal to 
the reference dose (RfD). The threshold for cancer effects is a 
lifetime excess cancer risk of 1 x 10-6, i.e., when the 
lifetime average daily dose results in one extra cancer case per 
million people above the background cancer incidence.
    \5\ Though EPA Method 1633 recommends that laboratories develop 
their own limit of quantification (LOQ) and method detection limit 
(MDL) when measuring PFAS in sewage sludge, most laboratories 
running this method achieve LOQs and MDLs of 1 ppb or lower for PFOA 
and PFOS (see https://www.epa.gov/cwa-methods/cwa-analytical-methods-and-polyfluorinated-alkyl-substances-pfas).
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    Not all farms or disposal sites where sewage sludge containing PFOA 
or PFOS have been used or disposed of are expected to pose a risk to 
human health. For example, human health risks are expected to be lower 
when sewage sludge is applied to areas with protected groundwater, 
sites that are distant from surface waters used for fishing or as a 
drinking water source, and when applied to non-food crops, such as 
grain, fuel, or fiber crops. However, the EPA's modeling results from 
the draft risk assessment suggest that under certain scenarios and 
conditions, land-applying or disposing of sewage sludge containing a 
detectable level (i.e., 1 ppb or more) of PFOA or PFOS could result in 
human health risks exceeding the agency's acceptable thresholds for 
cancer and non-cancer effects. At this low level (1 ppb) of PFOA or 
PFOS in sewage sludge, the EPA modeled land application scenarios for 
either a single application at a rate of 50 dry metric tons (dmt) per 
hectare (reclamation scenario) or 40 annual applications at a rate of 
10 dmt per hectare (approximately the median application rate of U.S. 
sewage sludge; used for pasture and food crop farm scenarios). Each of 
these modeled scenarios resulted in exceedances of risk thresholds for 
several exposure pathways (e.g., consumption of drinking water, fish, 
beef, milk, eggs, certain fruits and vegetables). The EPA's modeling 
indicates that, for a subset of the modeled scenarios and pathways, 
there may be potential risks exceeding acceptable levels following a 
single application of sewage sludge contaminated with 1 ppb of PFOA or 
PFOS, applied at a rate of 10 dmt per hectare (median rate).
    The presence and magnitude of human health risks from sewage sludge 
use and disposal to those living on or near impacted properties or 
primarily relying on their products is expected to vary across regions 
and among properties depending on the concentration of PFOA and PFOS in 
sewage sludge; the number of land applications; the volume of sewage 
sludge land applied; the climate, geology, and hydrology at the use or 
disposal site; agronomic practices; human behavioral patterns (e.g., 
drinking water ingestion rates, consumption rate of impacted products); 
and many other site-specific factors.
    Draft risk estimates for the modeled scenarios are presented in the 
risk assessment as cancer risk levels and hazard quotients (HQs). 
Cancer risk levels represent the number of expected excess lifetime 
cancer cases due to exposure to the carcinogenic pollutant in a given 
population size. For example, a cancer risk level of 1 in 1,000 
indicates that lifetime exposure to the carcinogenic pollutant would be 
expected to cause one additional case of cancer for every one thousand 
people in the exposed population. Risk for non-cancer effects are 
expressed as HQs that represent the ratio of the potential exposure to 
a pollutant to the level below which adverse non-cancer effects are not 
expected. In other words, an HQ of less than 1 means adverse non-cancer 
health effects are unlikely and thus risk can be considered negligible; 
an HQ greater than 1 means adverse non-cancer

[[Page 3863]]

effects are possible and thus risk is indicated.
    Modeling for land application scenarios suggests that, when the 
majority of the consumer's dietary intake of a product comes from a 
property impacted by the land application of sewage sludge contaminated 
with PFOA or PFOS, the highest risk pathways include (1) drinking milk 
from pasture-raised cows consuming contaminated forage, soil, and 
water, (2) drinking water sourced from contaminated surface or 
groundwater on or adjacent to the impacted property, (3) eating fish 
from a lake impacted by runoff from the impacted property, and (4) 
eating beef or eggs from majority pasture-raised hens or cattle where 
the pasture has received impacted sewage sludge. The risk calculations 
assume each of these farm products (e.g., milk, beef, eggs) or drinking 
water consumed comes from the impacted property but does not combine 
risks from each of these products. The EPA did not estimate risk 
associated with occasionally consuming products or drinking water 
impacted by land application of contaminated sewage sludge nor foods 
that come from a variety of sources (e.g., milk from a grocery store 
that is sourced from many farms and mixed together before being 
bottled). Additionally, the majority of food produced in the U.S. is 
not grown on fields where sewage sludge is land applied.
    Risk estimates for the highest risk pathways can exceed the EPA's 
acceptable thresholds by several orders of magnitude. For example, for 
the land application scenarios, cancer risk levels associated with 
drinking the modeled amount of contaminated milk (i.e., 32 ounces per 
day for adults) can exceed 1 in 1,000, and HQs for non-cancer effects 
associated with eating the modeled amount of contaminated fish (i.e., 1 
to 2 servings per week for adults) can reach up to 45. For the food 
crop farm scenario, there are limited scientific studies available 
regarding the uptake of PFOA and PFOS from sewage sludge-amended soils 
into certain fruits and vegetables; however, the draft risk assessment 
suggests that cancer risks from consuming the modeled amount of these 
contaminated foods (e.g., 1 serving per day for adults for certain 
categories of fruits and vegetables) can exceed 1 in 100,000 for PFOA. 
Because the draft risk assessment indicates risks associated with 
individual exposure pathways, there may be potential risks to 
populations beyond the farm family (e.g., people living near a use or 
disposal site who use contaminated groundwater as a source of drinking 
water or people who primarily consume produce, dairy, or meat from a 
farm that has applied contaminated sewage sludge under the modeled 
conditions).
    For the surface disposal sites, there are no exceedances of the 
EPA's risk thresholds for PFOA or PFOS in drinking water sourced from 
groundwater near composite-lined surface disposal sites. However, for 
unlined and clay-lined surface disposal sites, there can be exceedances 
of the risk thresholds for the drinking water pathway; for unlined 
sites, the cancer risk levels can exceed 1 in 1,000 and HQs are as high 
as 12; for clay-lined sites, the cancer risk levels can exceed 1 in 
1,000 and HQs are up to 9. As mentioned above, the draft risk 
assessment does not include quantitative risk estimates for 
incineration due to data limitations.
    The draft risk calculations are not conservative estimates because 
they (1) model risks associated with sludge containing 1 ppb of PFOA or 
PFOS, which is on the low end of measured U.S. sewage sludge 
concentrations, (2) reflect median exposure conditions (e.g., 50th 
percentile drinking water intake rates) rather than high exposure 
conditions, (3) do not include non-sewage sludge exposures to PFOA or 
PFOS (e.g., consumer products, other dietary sources), (4) do not 
account for the combined risk of PFOA and PFOS together, and (5) do not 
account for exposures from the transformation of PFOA or PFOS 
precursors. As such, risk estimates that account for multiple dietary 
exposures (e.g., consuming impacted milk, water, and eggs), multiple 
sources of exposure (e.g., exposure to PFOA or PFOS-containing consumer 
products), or exposure to other PFAS would be greater than those 
presented in this draft risk assessment. Further, the EPA's draft risk 
assessment relies on models where risks scale linearly with the 
starting concentration of PFOA or PFOS in sewage sludge. As such, 
sewage sludge containing ten times more PFOA or PFOS (i.e., 10 ppb) 
would yield risk estimates that are ten times greater than those 
presented in the draft risk assessment, assuming all other factors are 
constant.
    The EPA did not complete Monte Carlo probabilistic modeling because 
risks exceeding acceptable thresholds were identified in multiple 
scenarios and pathways in the central tendency deterministic modeling 
results. Further refinement of the draft risk assessment from the 
central tendency deterministic models to Monte Carlo probabilistic 
models would result in an increased risk finding because the EPA's goal 
for a probabilistic assessment is to identify a high-end (e.g., 95th 
percentile) threshold protective of the impacted population (e.g., farm 
families), while a central tendency approach, which the EPA used in 
this case, models a person at the 50th percentile exposure level of the 
impacted population. Since risk is indicated under this central 
tendency scenario, Monte Carlo probabilistic modeling, which would 
examine the entire distribution of potential exposures to PFOA or PFOS 
and report the 95th percentile of the risk distribution, is not 
warranted at this time. For this reason, the EPA is focused on the 
central tendency modeling results and identifying actions that could be 
taken to mitigate risks.

IV. Next Steps

A. Risk Reduction

    The draft risk assessment indicates that there are potential risks 
to human health to those living on or near impacted properties or 
primarily relying on their products from land application and surface 
disposal of sewage sludge containing detectable levels of PFOA or PFOS. 
That risk is dependent on (1) the concentration of PFOA and PFOS in 
sewage sludge, (2) the specific type of management practice (e.g., type 
of farm or presence of a liner in a monofill), (3) the local 
environmental and geological conditions (e.g., climate and distance to 
groundwater), (4) the share of each product (e.g., food crop, drinking 
water) that is sourced exclusively from the impacted property, and 
other factors noted above. Risks are possible, though not quantified 
due to data limitations, from the incineration of PFOA and PFOS-
containing sewage sludge. Site-specific factors should be considered 
when identifying risk mitigation and management practices to reduce 
human exposures associated with PFOA and PFOS in sewage sludge.
    Regardless of the management practice to use or dispose of sewage 
sludge, exposure and risk reduction is possible through pretreatment at 
industrial facilities discharging to a WWTP. By monitoring sewage 
sludge for PFOA and PFOS, WWTPs can identify likely discharges of PFOA 
and PFOS from industrial contributors, require pretreatment, and 
achieve significant reductions in PFOA and PFOS concentrations in their 
sewage sludge. In some state programs, WWTPs with industrial sources 
have achieved a 98 percent reduction in PFOS sewage sludge 
concentrations through industrial pretreatment initiatives. The EPA 
recommends that states, Tribes, and WWTPs monitor sewage sludge for 
PFAS contamination, identify likely

[[Page 3864]]

industrial discharges of PFAS, and implement industrial pretreatment 
requirements, where appropriate. Doing so will help reduce downstream 
PFAS contamination and lower the concentration of PFOA and PFOS in 
sewage sludge (see Section C of the EPA's December 2022 memorandum 
Addressing PFAS Discharges in NPDES Permits and Through the 
Pretreatment Program and Monitoring Programs, available at: https://www.epa.gov/newsreleases/epa-issues-guidance-states-reduce-harmful-pfas-pollution).

B. Related Actions

    The EPA is planning to conduct the next National Sewage Sludge 
Survey (NSSS) in collaboration with the publicly owned treatment works 
(POTW) Influent PFAS Study (see https://www.epa.gov/biosolids/sewage-sludge-surveys). This NSSS will focus on obtaining current national 
occurrence and concentration data on PFAS in sewage sludge. The data 
generated by the NSSS will help inform future risk assessments and risk 
management actions for sewage sludge.
    Additionally, the EPA continues to evaluate opportunities to limit 
PFAS discharges from multiple industrial categories through the 
Effluent Guidelines Program. The specific actions include revising the 
Organic Chemicals, Plastics, and Synthetic Fibers Effluent Limitations 
Guidelines (ELGs) to address wastewater discharge from PFAS 
manufacturing facilities; revising the Metal Finishing and 
Electroplating ELGs to address wastewater discharge from metal 
finishing and electroplating operations focusing on facilities using 
PFAS-based fume suppressants and wetting agents; and revising the 
Landfills ELGs to address PFAS discharges from landfill leachate. The 
upcoming POTW Influent PFAS Study will also help the agency prioritize 
industrial point source categories for future study and, as 
appropriate, ELGs (see https://www.epa.gov/eg/study-pfas-influent-potws).

C. Final Risk Assessment and Potential Future Actions

    After the public comment period has closed, the EPA will consider 
the comments received, revise the draft risk assessment as appropriate, 
and prepare a final risk assessment. The EPA will announce the 
availability of the final risk assessment in the Federal Register. If 
the final risk assessment indicates that there are risks above 
acceptable thresholds when using or disposing of sewage sludge, the EPA 
expects to propose a regulation under CWA section 405 to manage PFOA 
and/or PFOS in sewage sludge to protect public health and the 
environment. The EPA may also consider developing regulations under 
other statutory authorities to further reduce PFAS discharged to WWTPs. 
During the risk management deliberation process, the results of the 
final risk assessment may be integrated with other considerations, such 
as economic costs and treatment feasibility, to reach decisions 
regarding the need for and practicability of implementing various risk 
reduction activities. If the EPA proposes regulatory standards for PFOA 
and/or PFOS in sewage sludge, the public will have an opportunity to 
provide comment.

Bruno Pigott,
Principal Deputy Assistant Administrator.
[FR Doc. 2025-00734 Filed 1-14-25; 8:45 am]
BILLING CODE 6560-50-P
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