Unpacking the PFAS Risk in Biosolids 

Biosolids, or sewage sludge, are the organic by-products left over from treating wastewater. In the U.S., roughly 51% of biosolids are land applied. Over half of those go onto agricultural fields as a soil amendment and fertilizer because they contain nutrients like nitrogen and phosphorus and micronutrients that can improve soil pH and structure. The remainder are applied to land for the purpose of disposal due to limited alternatives and high costs. 

There is growing concern about the presence of per- and polyfluoroalkyl substances (PFAS) in biosolids—even in Class A biosolids, which receive the highest level of treatment under current EPA guidelines. PFAS, or “forever chemicals,” is catchall term for related compounds like PFOA and PFOS that are used in a wide range of everyday goods, from non-stick cookware to waterproof clothing. PFAS ends up in humans, and then in our waste. Most wastewater treatment infrastructure was not designed to address PFAS, which means many of these compounds pass through conventional processes and remain intact in high concentrations in biosolids. 

Recent EPA guidance recognizes deep injection wells like Vaulted’s as a reliable disposal pathway for biosolids that keeps PFAS out of local environments. This blog explores key findings from the latest evidence on PFAS in biosolids, including the implications for human health and environmental management. 

PFAS are common in treated biosolids at unsafe levels  

Municipal wastewater treatment plants are designed to remove solids, pathogens, and nutrients—but not PFAS. Despite sewage sludge undergoing intensive processing, PFAS tend to persist through every stage of treatment and typically become more concentrated in biosolids by the end of the process as other precursor chemicals biodegrade into PFAS. 

PFAS are widespread in Class B and Class A biosolids. Recent EPA modeling found that there may be human health risks to those living nearby when land-applying sewage sludge with just 1 parts per billion (ppb) of PFOA or PFOS. Compounding the issue, some PFAS found in wastewater start out as precursor compounds that biodegrade into PFAS during treatment. As a result, the treatment process itself can increase total PFAS concentrations by as much as 54%. 

Land application can introduce PFAS into soils and groundwater 

PFAS can migrate more than 30 feet below the surface soils. Research has found that soils where biosolids have been land applied can contain 10x to 100x more PFAS than background soils. In some cases, PFAS concentrations in underlying groundwater were another 10 to 100 times higher than the soils above—showing how PFAS can accumulate as it moves through the environment. A 2025 study of 10 U.S. farms found PFAS concentrations in soils receiving biosolids were 2–10x higher than global background levels, and in some cases 100x higher than adjacent control plots. 

Land application is a direct way that PFAS gets introduced into the food chain. Despite this, biosolids are still approved for fertilizer use.  

PFAS makes its way into what we eat and drink, posing health risks 

PFAS are long-lasting compounds that bind to protein-rich tissues and remain in the human body for extended periods. The CDC’s National Health and Nutrition Examination Survey estimates that 98% of the U.S. population has measurable PFAS in their bodies. 

Persistent PFAS exposure has been associated with a range of health effects, including kidney and testicular cancer, high cholesterol and cardiovascular disease, reproductive issues, and metabolic disorders like obesity and Type II diabetes. 

Eating crops or drinking water from PFAS-contaminated areas is one contributor to this exposure and can increase health risks. The FDA found PFAS present in about 3% of tested fresh and processed food products, with seafood being a primary source. Screening of rivers nationwide found that 92% of sampled fish from the rivers contained PFAS levels that are associated with increased risk of non-cancerous health issues. Elevated PFAS levels in soil have been suspected as a factor in livestock illness and death. 

Other international studies have identified PFAS in eggs from chickens raised on contaminated feed and in milk from dairy cows exposed to PFAS-contaminated forage. For example, a Danish study concluded that children consuming more than 2.5 organic eggs per week could exceed safe exposure limits set by the European Food Safety Authority. 

State-by-state rules vary for PFAS in biosolids 

While the EPA regulates pathogens in land-applied biosolids, there is no federal PFAS standard for biosolids disposal or reuse. Only six U.S. states currently require PFAS monitoring in biosolids. Where monitoring exists, levels can vary widely based on industrial activity and local treatment practices. For example, Maine and New Hampshire reported average PFAS concentrations of 19.3 ppb and 8 ppb, respectively, in monitored biosolids (2-20x higher than EPA’s advisory levels). 

Many states want more robust monitoring plans but cite high lab testing costs and limited technical capacity as barriers to broader regulation and testing. 

Disposal options are limited 

The lack of disposal options is a major barrier to managing PFAS in biosolids and reducing associated health risks. A national survey of state environmental agencies found that “limited disposal options and disposal capacity” ranked as the top concern in biosolids management. Some regions face landfill capacity constraints and prioritize other waste streams like municipal solid waste. Landfills may decline to accept biosolids or charge high tipping fees due to their moisture content that can contribute to leachate and their potential to introduce pathogens—factors that complicate landfill operations. 

Land application remains the dominant disposal method for biosolids, but it’s increasingly under scrutiny from the public and regulators. New guidance from the EPA points to deep well injection as a promising alternative solution. 

Looking ahead 

Managing PFAS in biosolids is a complex challenge. With few scalable disposal alternatives, many communities must navigate tradeoffs between cost and risk. Solutions that can safely remove or contain PFAS at scale—without burdening land, water, or community health—will be essential as awareness and regulation continue to evolve. Vaulted is working with municipalities like Derby, Kansas to use deep geologic infrastructure as a safe, permanent disposal pathway for biosolids and PFAS.