Biosolids are treated sewage sludge, and when they are spread on farmland as fertilizer they can carry PFAS “forever chemicals” onto crops, into grazing livestock, and down into soil and groundwater. Because a large share of the sludge produced at U.S. wastewater plants is applied to land, this practice has become one of the ways PFAS moves from cities into the food and water supply. In January 2025 the U.S. Environmental Protection Agency (EPA) released a draft risk assessment finding that, under some long-term scenarios, PFAS in land-applied sludge may exceed the agency’s health thresholds for people living on or near affected farms.
Key takeaways
– Biosolids are the solid material left after sewage is treated, and roughly half of U.S. sewage sludge is spread on land, much of it on farm fields.
– Because PFAS are not fully removed by standard wastewater treatment, contaminated sludge can pass those chemicals into soil, crops, cattle, and nearby water.
– EPA’s January 2025 draft risk assessment (a draft, not a final rule) found possible health risks near land-application sites, and Maine has already banned the practice.
What are biosolids, and why are they spread on farms?
When wastewater is treated at a sewage plant, the liquid that leaves is cleaned and released, but the solid material that settles out has to go somewhere. After further treatment to reduce pathogens and odor, that solid material is called biosolids. For decades it has been marketed as a low-cost fertilizer and soil conditioner because it is rich in nitrogen and phosphorus. Farmers spread it on fields, and it is also bagged and sold to the public as compost.
The scale is significant. EPA estimates that around four million dry metric tons of sewage sludge is generated each year in the states where the agency is the permitting authority, and based on its 2024 annual reports, roughly 60 percent of that sludge is applied to land. That includes farmland, forests, reclamation sites, and compost sold to home gardeners. So while “sewage on crops” sounds like an edge case, it is a routine and legal part of how the country manages its waste.
How PFAS ends up in the sludge
PFAS are a large family of synthetic chemicals used in nonstick coatings, stain and water repellents, firefighting foam, and many industrial processes. They are often called forever chemicals because their strong carbon-fluorine bonds resist breaking down. If you want the basics, see our guide to what PFAS are.
These chemicals travel down the drain from homes, businesses, and factories and arrive at the wastewater plant. Conventional treatment is designed to remove solids, nutrients, and pathogens, not PFAS, so the chemicals are not destroyed. Instead they concentrate in the leftover sludge. When that sludge is then spread on a field, the PFAS goes with it. In extreme industrial cases the numbers are stark: one Michigan wastewater system was found to contain PFAS in its sludge at 2,150 parts per billion, traced to a single manufacturer discharging into the sewer.
How PFAS moves from sludge to people
Once biosolids are on a field, PFAS does not simply stay put. It can be taken up by plants, eaten by grazing animals, held in the soil for years, and washed into groundwater. The table below shows the main pathways.
| Pathway | Example | Who is most affected |
|---|---|---|
| Crop uptake | Plants draw PFAS from treated soil into leaves and grain | People who eat produce grown on the field |
| Livestock | Cattle eat contaminated feed and forage; PFAS accumulates in meat and milk | Farm families and buyers of that meat or dairy |
| Soil buildup | Repeated applications leave PFAS in the soil for many years | Anyone farming the land later, plus future crops |
| Groundwater | PFAS leaches down into private wells and aquifers | Households drinking from nearby wells |
This is why sludge on one field can matter far beyond that field. If it reaches an aquifer, it can affect drinking water for a whole area. We cover that side of the problem in our guides to PFAS in well water and PFAS in drinking water.
What the documented contamination cases show
The clearest evidence that this is not just theoretical comes from farms that have been shut down. In January 2022, Michigan officials halted operations at Grostic Cattle Company, a century-old farm in Livingston County, after tests found the PFAS chemical PFOS in its beef. The source was traced to contaminated biosolids that had been applied to the farm’s fields, which then moved into the feed crops, soil, and cattle.
Maine has been hit hardest and has done the most testing. State officials there have linked biosolids to contamination on more than 80 farms, and it was the discovery of dozens of contaminated farms that pushed the state to act. In Texas, ranchers who say PFAS-laden fertilizer poisoned their land and killed livestock joined a federal lawsuit against the EPA. One Texas plaintiff reported losing dozens of cattle. A federal court dismissed that suit on jurisdictional grounds in 2025 before the evidence was weighed, so the underlying questions about sludge safety remain open.
What regulators are doing
Maine acted first. In April 2022 Governor Janet Mills signed LD 1911, the first law in the nation to ban the land application of biosolids and the sale of sludge-derived compost, citing PFAS contamination. The law requires the state’s sludge to be landfilled or shipped elsewhere instead of spread on fields.
At the federal level, EPA released its Draft Sewage Sludge Risk Assessment for PFOA and PFOS in January 2025. It is important to be precise here: this is a draft assessment released for public comment, not a final rule. The draft modeled scenarios such as a single sludge application and 40 straight years of applications, and it concluded that even biosolids containing PFOA or PFOS at low concentrations, around 1 part per billion, may exceed the agency’s conservative health thresholds under those long-term scenarios. EPA was careful to note that the population most at risk is narrow: people who live on or very near affected farms, or who rely heavily on food and water from those sites. The agency said it will use the assessment to inform future decisions, which means any binding limits would come later.
What this means for you
For most people, the everyday risk is modest, because the highest exposures fall on households living on or beside affected farmland and drinking from local wells. If that describes you, or if you use bagged compost that may contain biosolids, it is reasonable to ask questions about sourcing and, where wells are involved, to consider testing. Our overview of how to avoid PFAS covers practical steps for water, food, and household products. The larger fix is upstream: keeping PFAS out of the sewer in the first place, so the sludge that returns to farmland is clean.
FAQ
What are biosolids?
Biosolids are the solid material left over after sewage is treated at a wastewater plant, then processed further to reduce pathogens and odor. They are used as fertilizer and soil conditioner on farmland and sold as compost.
How does PFAS get into biosolids?
PFAS travels down drains from homes, businesses, and factories to the wastewater plant. Standard treatment does not destroy it, so the chemicals concentrate in the leftover sludge, which is then spread on land.
How much U.S. sewage sludge is spread on land?
EPA estimates around four million dry metric tons of sludge is generated annually in states it permits, and based on its 2024 reports about 60 percent is land applied, a category that includes farm fields, forests, reclamation sites, and compost sold to the public.
Did EPA ban PFAS in biosolids?
No. In January 2025 EPA released a draft risk assessment finding possible health risks near land-application sites, but it is a draft for comment, not a final rule. Maine, however, banned land application of PFAS-containing sludge under a 2022 state law.
Should I worry about produce or compost?
Most produce sold in stores is not high risk. The greatest concern is for people living on or near affected farms and drinking from nearby wells. If you use bagged compost, you can ask whether it contains biosolids, and well owners in affected areas may want to consider testing.
