EPA Assesses Health Risks from PFAS in Sewage Sludge and Biosolids

January 16, 2025

The U.S. Environmental Protection Agency (EPA) has recently released a draft risk assessment evaluating the potential human health risks associated with per- and polyfluoroalkyl substances (PFAS) in biosolids, commonly known as sewage sludge. This assessment focuses on the toxic “forever chemicals” PFOA and PFOS. These substances have raised significant health concerns due to their persistence in the environment and potential for bioaccumulation.

Overview of PFAS in Biosolids

What Are Biosolids?

Wastewater from households, businesses, and industrial dischargers is treated at wastewater treatment plants (WWTPs). These treatment processes lead to the production of a semi-solid, nutrient-rich product known as “sewage sludge” or “biosolids.” When biosolids meet regulatory standards, they can be repurposed as soil conditioners or fertilizers, benefiting agricultural and non-agricultural lands by promoting plant health and productivity. The application of biosolids on land supports the recycling of essential nutrients, playing a pivotal role in sustainable agriculture.

These biosolids, however, may also contain various contaminants, including PFAS. PFAS are a large group of man-made chemicals used in a wide array of consumer products and industrial applications due to their resistance to heat, water, and oil. Their presence in biosolids poses potential risks as they can transfer from soil to crops and potentially enter the human food chain. The persistence and bioaccumulation properties of PFAS have raised alarms about long-term environmental and health impacts.

Sources of PFAS in Biosolids

PFAS enter sewage sludge primarily through contaminated wastewater flowing into municipal WWTPs. These plants do not intentionally add or use these substances, but they can end up in the sludge through various pathways. PFAS contamination often originates from manufacturers and facilities that have historically used these chemicals in their processes. These industries include textile production, metal plating, and firefighting foam manufacturing.

Additionally, everyday consumer products such as cookware, clothing, cosmetics, and food packaging also contribute to PFAS levels in wastewater. When items like non-stick pans or water-resistant fabrics are washed, small amounts of PFAS are released and eventually reach WWTPs. Due to the widespread use and persistence of PFAS, these chemicals have found their way into the environment on a global scale, necessitating comprehensive regulatory measures to control their presence in biosolids.

Focus of the Draft Risk Assessment

Target Population and Exposure Scenarios

The EPA’s draft risk assessment models hypothetical human health risks for specific populations considered most likely to be exposed to PFOA or PFOS through biosolids. This includes individuals living on or near sites where biosolids are applied or those relying on these sites’ products, such as food crops, animal products, or drinking water. The assessment aims to determine the potential exposure pathways and quantify the associated health risks.

Preliminary findings from the assessment indicate that human health risks from exposure to PFOA or PFOS can exceed EPA’s acceptable thresholds in some scenarios, often by several orders of magnitude. The scenarios include single biosolid applications at 10 dry-metric-tons per hectare and cases involving 40 consecutive years of such applications. Potential risks also emerge from biosolids placed in unlined or clay-lined surface disposal units, where leaching into groundwater can occur.

Key Findings and Risk Levels

The risk assessment revealed that the levels of PFOA and PFOS in biosolids could pose significant health risks under certain conditions. For instance, the risk from applying biosolids at a rate of 10 dry-metric-tons per hectare could exceed acceptable levels, particularly if such applications are repeated over many years. This chronic exposure scenario raises concerns about the cumulative effects of these chemicals on human health over time.

Moreover, the assessment highlighted scenarios where biosolids disposed of in unlined or inadequately lined surface disposal units could leach PFAS into the groundwater, potentially contaminating drinking water sources. The incineration of biosolids was also examined. However, due to significant data gaps, quantifying the risk from this disposal method was not possible. The findings underscore the necessity of continuous monitoring and the implementation of stringent measures to mitigate PFAS exposure.

Factors Affecting Risk Levels

Concentration of PFAS in Biosolids

The concentration of PFAS in biosolids plays a fundamental role in determining the extent of health risks. Higher concentrations of PFAS in biosolids significantly increase the potential for adverse health effects, whereas lower concentrations correspondingly reduce the risks. The variability in concentration levels can be influenced by the sources of wastewater entering WWTPs and the historical usage of PFAS in the region.

Addressing the concentration of PFAS in biosolids requires a comprehensive approach that includes identifying and mitigating sources of contamination. By reducing the input of PFAS into WWTPs through regulatory measures and industrial practices, it is possible to lower the concentrations in the resulting biosolids. This, in turn, minimizes the risks associated with their application on land and potential entry into the human food chain.

Quantity and Frequency of Applications

The quantity and frequency of biosolid applications are critical factors impacting risk levels. Frequent or high-volume applications of biosolids on agricultural land increase the cumulative exposure to PFAS, heightening the associated health risks. Conversely, reduced application rates and less frequent usage can significantly lower the exposure levels and mitigate potential harm.

Long-term applications, as modeled in the assessment with 40 consecutive years of biosolids application, can lead to substantial accumulation of PFAS in the soil. This prolonged exposure period emphasizes the importance of careful management practices and regulatory oversight to ensure that the application of biosolids does not lead to detrimental environmental and health outcomes over time.

Site-Specific Factors

Geographic location, climate, soil conditions, and the types of crops grown are among the site-specific factors that influence risk levels associated with PFAS in biosolids. For instance, the local soil’s ability to retain or degrade PFAS can vary considerably, affecting the extent of contamination and the potential for groundwater leaching. Climate conditions such as rainfall and temperature can also impact the behavior of PFAS in the environment.

The nutrient needs and types of crops cultivated on biosolid-applied land play a role in PFAS uptake. Certain crops may absorb PFAS more readily than others, potentially transferring these chemicals into the human food supply. Understanding these site-specific factors is vital for developing tailored strategies to mitigate risks and ensure safe and sustainable use of biosolids in agriculture.

Impact on Food Supply

General Food Supply

The analysis from the EPA’s draft risk assessment does not suggest that the general food supply is broadly impacted by the use of biosolids containing PFOA or PFOS. Regulatory agencies such as the U.S. Department of Agriculture and the Food and Drug Administration are actively monitoring PFAS levels in the food supply and addressing products that may have elevated levels of these chemicals. These efforts are crucial in ensuring the safety and quality of the national food supply.

Biosolids are used on less than one percent of fertilized agricultural land in the U.S. each year, indicating that while the potential for PFAS contamination exists, it is relatively limited in scope. Nevertheless, it remains essential to continue rigorous monitoring and to identify any emerging risks that may arise from specific applications or regions with higher PFAS concentrations in biosolids.

Hot Spots and Elevated Risks

Despite the broader food supply not being significantly affected, certain “hot spots” where biosolids containing high levels of PFOA or PFOS have been applied may present elevated risks. These hot spots could be areas with specific historical or industrial activities that resulted in higher PFAS levels in the wastewater and subsequently in the biosolids. Identifying and addressing these areas is critical to preventing localized health risks.

Collaboration with impacted operations, stakeholders, and federal agencies is essential to fully understand and mitigate these elevated risks. By working together, it is possible to develop targeted interventions, monitor soil and water quality, and implement best practices to reduce PFAS concentrations in biosolids and mitigate their environmental and health impacts.

Importance of Federal and State Policies

Proactive Measures

The findings from the EPA’s draft risk assessment underscore the need for proactive federal and state policies to control and remove PFAS at their source. The EPA’s PFAS Strategic Roadmap outlines key initiatives aimed at restricting PFAS from entering the environment, holding polluters accountable for cleaning up PFAS contamination, and increasing reviews of new PFAS before they enter commerce. These measures are essential to curbing the overall PFAS burden and protecting public health.

Implementing these proactive measures involves a multi-faceted approach, including regulatory actions, industrial practice changes, and public awareness campaigns. By preventing PFAS from reaching the environment in the first place, the potential for contamination in biosolids and other environmental media can be significantly reduced.

Regulatory Actions

The EPA is working towards setting technology-based limits on discharges from various industrial sectors, including PFAS manufacturers and landfills. These regulatory actions aim to minimize the release of PFAS into wastewater and ultimately into biosolids. States are encouraged to use Clean Water Act permitting authorities and industrial pretreatment programs to mandate that PFAS be removed from waste before it reaches wastewater treatment plants.

Such regulatory actions require close coordination between federal and state agencies, industry stakeholders, and the scientific community. By establishing clear limits and guidelines for PFAS discharge and treatment, it is possible to achieve significant reductions in PFAS contamination and safeguard environmental and public health.

EPA and State Actions on PFAS

Progress Under the PFAS Strategic Roadmap

Significant progress has been made under the EPA’s PFAS Strategic Roadmap to advance the science and establish protective measures against PFAS pollution. Key actions include finalizing the nation’s first drinking water standards for PFAS, holding polluters accountable for contamination, and declaring PFOA and PFOS hazardous substances under the Superfund law. These measures mark crucial milestones in the regulatory control and management of PFAS.

By setting stringent drinking water standards, the EPA aims to ensure that public water systems provide safe, PFAS-free drinking water to communities. Holding polluters accountable creates a deterrent effect, encouraging industries to adopt safer practices and technologies. The designation of PFOA and PFOS as hazardous substances facilitates the cleanup of contaminated sites and the reclamation of affected environments.

Monitoring and Reporting

Several states have begun monitoring PFAS levels in sewage sludge and publicly publishing their reports. This transparency allows stakeholders, including communities, researchers, and policymakers, to access valuable information about PFAS contamination levels and assess the effectiveness of regulatory measures. The draft assessment reviews PFOA and PFOS data from peer-reviewed literature and state reports, providing a comprehensive, data-driven report to inform future regulatory decisions.

The EPA’s draft risk assessment serves as a foundation for further research and policy development. By continuously updating and refining the scientific understanding of PFAS risks, it is possible to develop more effective strategies for managing and mitigating these persistent chemicals. The ongoing efforts by federal and state authorities underscore the commitment to protecting public health and the environment from the impacts of PFAS.

Conclusion

The U.S. Environmental Protection Agency (EPA) has recently issued a draft risk assessment focusing on the potential human health risks linked to per- and polyfluoroalkyl substances (PFAS) found in biosolids, commonly referred to as sewage sludge. The assessment specifically addresses the toxic substances PFOA and PFOS, which are often called “forever chemicals” due to their long-lasting presence in the environment. These chemicals pose significant health concerns because they do not easily break down and have a tendency to accumulate in living organisms over time. The EPA’s evaluation aims to understand the extent of these health risks, given the widespread use of PFAS in various industrial applications and consumer products. Their persistence leads to their pervasive presence in the environment, making it essential to assess and mitigate potential hazards to public health. The draft risk assessment is a critical step in informing regulatory actions and guiding efforts to manage and reduce the impact of these hazardous substances on both human health and the environment.

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