Advocacy Alert

EPA released its Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid (PFOA) and Perfluorooctanoic Sulfonic Acid (PFOS) on January 14, with a request for comments published in the Federal Register on January 15. Along with the Draft Risk Assessment, EPA posted Fact Sheets and related information aimed at key stakeholders, including one for wastewater treatment plants, and other supporting documents on its website. Comments are due on March 17, 2025, and NACWA will be seeking member input on its comment effort at the appropriate time.

This Advocacy Alert provides a summary of the risk assessment, next steps and new resources provided by NACWA to help utilities respond to the assessment.

In the Draft Risk Assessment, EPA evaluated risk for a “farm family” for various scenarios of biosolids land application and surface disposal. The scenarios evaluated likely do not apply to any real-life farm family and do not represent the general public. EPA found in certain scenarios, its risk thresholds were exceeded for biosolids containing 1 part per billion (ppb) or more of PFOA and PFOS. But the Agency emphasized that the nation’s food supply is safe and that there is no risk to the general public.

It is critical to note that the Draft Risk Assessment does not create any new regulatory requirements or standards or require any new action on the part of clean water utilities. However, it is likely to spark interest among the media and an array of stakeholders. As such, NACWA has provided resources on its website to assist utilities in communicating about the Draft Risk Assessment with the public and the press. NACWA will be providing extensive comments to EPA on the Draft Risk Assessment by the comment deadline.

Summary of Draft Risk Assessment

EPA completed the Draft Risk Assessment as part of its authority under Clean Water Act Section 405 to conduct scientific studies and provide public information to promote the safe and beneficial management of biosolids. EPA uses risk assessments to determine if regulations or other actions are necessary to protect public health or the environment. This Draft Risk Assessment for PFOA and PFOS is the first time that EPA has released a sewage sludge risk assessment without a corresponding proposal to amend the Part 503 sewage sludge regulations.

Methodology for Draft Risk Assessment

EPA evaluated risk for the following scenarios:

• Land application – modeled exposures and estimated human health risks to those living on or near impacted properties for:
  • Pasture farm scenario – application to a farm raising pasture-raised dairy cows, beef cattle, or chickens.
  • Food crop farm scenario – application to a farm growing fruits or vegetables.
  • Reclamation scenario – application to reclaim damaged soils, such as on an overgrazed pasture.
• Surface disposal (i.e., sewage sludge monofill) – modeled exposures via groundwater to those living near a lined or unlined surface disposal site.
• Incineration – EPA did not model this scenario due to insufficient data related to this potential exposure scenario but provided a qualitative description of the potential risks to communities living near a sewage sludge incinerator (SSI).

Landfill disposal was not evaluated since this biosolids management method is managed pursuant to the requirements of the Resource Conservation and Recovery Act (RCRA).

EPA modeled the land application scenarios with biosolids containing 1 ppb of PFOA or PFOS. The biosolids application rate was 40 annual applications of 10 dry metric tons (dmt) per hectare for the pasture and food crop farm scenarios, or a single application of 50 dry metric tons (dmt) per hectare for the reclamation scenario, for a period of 40 years.

The exposure pathways included consumption of drinking water, fish, beef, milk, eggs, and certain fruits and vegetables. Each PFAS chemical and pathway was modeled individually, and the risks were evaluated separately, so the risk was assessed for one method of consumption for either PFOA or PFOS. Risks for multiple consumption methods were not modeled, nor were risks of biosolids containing both PFOA and PFOS. EPA modeled exposure to a hypothetical “farm family” that only consumed groundwater-sourced drinking water and food derived from their property for a period of 10 years which had land-applied biosolids at the rates noted above.

EPA evaluated both cancer and non-cancer effects in the Draft Risk Assessment. Cancer risk levels represent the number of expected excess lifetime cancer cases due to exposure to the carcinogenic pollutant. For example, a cancer risk level of 1 x 10^-3 (1 in 1,000) means 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. EPA generally targets a cancer risk level of less than 1 x 10^-6 (1 in a million).

Hazard quotients (HQs) for non-cancer effects represent the ratio of the potential exposure to a pollutant to the level below which adverse non-cancer effects are not expected. An HQ less than 1 means adverse non-cancer health effects are unlikely, while an HQ greater than 1 means adverse non-cancer effects are possible.

Results of Draft Risk Assessment

EPA found that its acceptable human health risk thresholds were exceeded for some of the pasture farm, food crop farm, and reclamation exposure scenarios. Specifically, these include:

• Pasture farm scenario—cancer risks for milk consumption can exceed 1 x 10^-3, and cancer risks for consumption of drinking water, fish, beef, and eggs can exceed 1 x 10^-4. The HQ for consuming fish is 45 for children and 39 for adults.
• Food crop farm scenario—cancer risks for consumption of drinking water and fish can exceed 1 x 10^-4, while risks for consumption of fruits and vegetables can exceed 1 x 10^-5. The HQ for fish consumption is 25 for children and 21 for adults.
• Reclamation scenario – cancer risk for consumption of milk, fish, and eggs can exceed 1 x 10^-4.

For the surface disposal scenario, EPA evaluated risk for biosolids containing 1 ppb of PFOA and 4 to 5 ppb of PFOS disposed of in unlined, clay-lined, and composite-lined surface disposal units. EPA found there are human health risks associated with drinking groundwater sourced near an unlined or clay-lined surface disposal unit including a cancer risk exceeding 1 x 10^-3, but did not find risk from drinking groundwater sourced near composite-lined units.

EPA did not quantify risks for incineration due to data limitations. However, EPA states that there is some risk associated with incineration, since sewage sludge incinerators (SSIs) may not operate at temperatures high enough to completely destroy PFOA and PFAS.

The models used by EPA for the Draft Risk Assessment scale risk linearly with the starting concentration of PFOA or PFOS in sewage sludge. Therefore, biosolids containing 10 ppb of PFOA or PFOS, which is ten times the amount modeled, would have a risk estimate that is ten times greater than the risk found with EPA’s Draft Risk Assessment.

Limitations of the Draft Risk Assessment

Although EPA found risks for a family living at or near a site with land application or surface disposal of PFOA- or PFOS- containing biosolids under the conditions that were modeled, these conditions are unlikely to be seen by the general public. As EPA points out, the risk to the general public may be lower because:

• EPA did not estimate risk associated with occasionally consuming products or drinking water impacted by land application of biosolids;
• The majority of food produced in the U.S. is not grown on fields where sewage sludge is land applied;
• Food sold to the public often comes from a variety of sources (e.g., milk from a grocery store is sourced from many farms and mixed together before bottling).

EPA also points out that the draft risk calculations may not be conservative estimates because they:

• 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;
• Reflect median exposure conditions (e.g., 50th percentile drinking water intake rates) rather than high exposure conditions;
• Do not include non-sewage sludge exposures to PFOA or PFOS (e.g., consumer products, other dietary sources);
• Do not account for the combined risk of PFOA and PFOS; and
• Do not account for exposures from the transformation of PFOA or PFOS precursors.

However, NACWA disagrees with EPA’s statement that the assessment does not use conservative estimates. The “farm family” that EPA used as the centerpiece of its Draft Risk Assessment is not a typical control group and generally is not a viable lens through which to make health risk assessments.

To ensure that any risk-based decisions made using the new risk levels were protective of any individuals exposed to biosolids containing PFOA or PFOS, EPA created a hypothetical farm family that would simulate exposure to PFOA and PFOS. The draft assessment assumes that the family, including adults and children, lives on a farm that uses municipal biosolids as its fertilizer. The assessment further assumes that, for ten years, all of the family’s food comes only from food grown and produced on the farm and that they only drink water from a well on the farm. The assessment also assumes the family’s children eat dirt from the farm that has been exposed to biosolids. Within each of these assumptions about the family’s way of life, EPA has further built in layers of conservative assumptions regarding exposure from each potential pathway.

These assumptions are extremely conservative and do not reflect real world conditions. In fact, the Agency’s own Science Advisory Board (SAB) took issue with the conservative nature of EPA’s approach when it reviewed the framework for the risk assessment, noting that the assumptions used by EPA are “well outside the norm of present-day family farms.” The SAB also noted that “the vast majority of biosolids applications are made to lands that are not used for producing food directly consumed by humans but rather to lands used for producing animal feed, fiber and/or fuel.”¹

The draft assessment also suffers from a significant flaw in that, despite requests from NACWA and other clean water sector advocates, EPA declined to include risk information associated with exposure to PFOA and PFOS from other fertilizers, such as synthetic fertilizers and manure, which might be used as alternatives by the farm family. EPA also declined to assess other exposure pathways, such as consumption of food wrapped in fast food wrappers or other food containers coated in PFAS chemicals.

Additionally, the assessment does not examine relative risk between ingestion of PFOA and PFOS versus other exposure pathways present in people’s everyday lives, such as dermal exposure via products such as makeup, cosmetic products, and contact lenses – just to name a few.

The lack of comparative risk information between biosolids and these other substances and exposure pathways means that the draft risk assessment does not provide any way to determine the relative risk associated with PFAS exposure from biosolids versus these other substances and pathways. Without this additional context, the results from the Draft Risk Assessment could easily be misconstrued to imply that the risk from biosolids is greater than these other pathways, when biosolids could present a significantly lower risk.

Notably for the clean water utility community, the Federal Register notice for the Draft Risk Assessment contains language overstating the ability of utility pretreatment programs to reduce sources of PFAS:

“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 [wastewater treatment plant]. 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 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.”

This statement ignores the fact that EPA has not yet developed pretreatment standards for any industrial category, and although its recent Effluent Limitations Guidelines Plan 16 outlines planned rulemakings for some industrial categories, it will still be many years before utilities have federal pretreatment standards for industrial categories that may be discharging PFAS to the sewer system.

In addition, studies from states such as California have shown that domestic discharges of PFAS can be the majority of the PFAS received at a publicly owned treatment works (POTW). Utilities have no authority to regulate discharges from domestic sources. While pretreatment programs will have an important role in limiting industrial sources of PFAS, domestic discharges will still be a problem until PFAS are removed from the multitude of household products that contain these chemicals. Even then, PFAS will likely continue to be released from households to the POTW for years as long as durable goods such as cookware and textiles produced with PFAS remain in use.

Next Steps

In its release, EPA stresses that the Draft Risk Assessment is only in draft form and is non-regulatory in nature. EPA intends to review the public comments received and then may finalize the draft risk assessment, which NACWA estimates could occur by the end of 2025.

EPA notes that it is specifically interested in receiving comments regarding the modeling approach utilized (e.g., the scenarios, sewage sludge application rates, environmental fate and transport parameters, human exposure assumption). NACWA has initiated an in-depth scientific review and will be preparing detailed comments for EPA.

However, with the transition between the outgoing Biden Administration and the incoming Trump Administration, the new administration has the power to withdraw the risk assessment entirely because it has only been issued in draft form. That would allow the new administration to review the basis of the assessment and decide if it wants to continue working to finalize the risk assessment, potentially make changes to it, or to not proceed. It is not known at this time how the new Trump EPA team plans to proceed on this issue.

If the risk assessment is finalized and indicates there are risks above acceptable thresholds associated with sewage sludge reuse or disposal, EPA could propose regulations under CWA section 405 to manage PFOA and/or PFOS in sewage sludge. That regulatory process will likely take several years to complete.

Communications Resources for Utilities

NACWA has created multiple resources to assist utilities in communicating with the public and the press about the draft risk assessment and about biosolids in general, including the beneficial reuse of biosolids through land application. Today marks the launch of biosolidsexplained.org, the hub for information and resources about biosolids.

The site features an overview of the wastewater treatment process and contains frequently asked questions to help dispel myths and misinformation about biosolids, including a specific FAQ document and suggested talking points related to the Draft Risk Assessment. NACWA's utility-focused resources are also available on site, and includes fact sheets, talking points and customizable templates for writing a letter to the editor or op-ed.

Three key themes emerge in the resources:

• Biosolids are beneficial
• Clean water utilities are passive receivers of PFAS
• Polluters should ultimately be responsible for PFAS remediation and removal

NACWA has also developed a media guidance document that includes best practices when dealing with the news media. The resources may be used as-is or can be modified to supplement existing communications materials.

The documents and resources being provided by NACWA related to biosolids are intended to be iterative and will be updated as needed and additional information is available. NACWA welcomes any comments or input that members have on these resources.

Members with questions or comments on the Draft Risk Assessment and NACWA’s communications resources can contact Cynthia Finley, NACWA’s Director of Regulatory Affairs, or Rahkia Nance, NACWA’s Director of Communications.