Top: Recent PFAS-related journal papers focused on municipal wastewater and solids. Design by Doug Pinkerton

Sally Brown

Read all about it! Forever chemicals found in soil and water where biosolids have been applied. Those are likely what the headlines would be based on several new publications in the scientific literature. As always though, the devil is in the details or, in certain cases their absence. Let me explain.

Pennsylvania Farm Fields

Oviedo-Vargas et al (2025) sampled soils on farms in Pennsylvania. They sampled 10 fields that had been applied with biosolids and partner fields that hadn’t received biosolids. There was more PFAS in the fields that had gotten the biosolids than in the fields that hadn’t. They also sampled water from streams on two of the farms and found PFAS.

Those are your headlines. What is missing here is information on the source of the biosolids and the total amount applied. Two of the farms sampled had a lot more PFAS than the other eight. One appears to have had two applications of biosolids each year for 19 years but no dry application rate. The biosolids that were at the farm at the time of the sampling appear to be pretty conventional stuff — higher than average but far from the worst. The other had four years of applications and no details about the loading rate or what the biosolids looked like.

The stream data is less helpful. The authors say that the majority of the water in the streams comes from groundwater. The PFOS in one of the streams tested had higher levels than the source biosolids, suggesting that the source wasn’t the biosolids. The authors also point out that the PFAS they found was higher than in many studies and much lower than in others. They note that there is PFAS in streams in Pennsylvania without any biosolids applied in the vicinity. Same for soils in Sweden. So yes — the headline holds true but is far from the whole story.

Biosolids application on cropland. Photo courtesy Casella Organics

Surface And Groundwater In Indiana

The headline from the next article is much the same except that the authors didn’t sample soils. Peter and Lee (2025) sampled surface and groundwater in an agricultural county in Indiana where biosolids are regularly used to fertilize farm fields. They found PFAS in both surface water and groundwater. There is your headline.

First important detail that doesn’t make the headline is that there was no indication that what went on in the surface soil or water had any impact on the groundwater. The PFAS in the groundwater, while present in 84% of those sampled, was less than 5 ng/L in 90% of the 103 private wells that were sampled. Most of the groundwater in this study is under a clay layer, meaning that it is generally protected from surface water. The PFAS in the groundwater did not come from the biosolids, rather the PFAS originated somewhere long ago and in a place far, far away. As far as the surface water sampling went, of the 168 surface sights sampled, the water in the more urbanized portion of the county fared far worse than the vast majority of the biosolids amended sites. Of the sites with the biosolids — one in particular and two to a limited extent — showed any real impact of the biosolids. These three sites have gotten biosolids since 1980 with annual application since about 2000. No information on application rates or source of the biosolids is provided.

Soils And Plants In California

The next article (Black et al., 2025) likely won’t make any headlines. The authors sampled soils and plants on fields in California with a history of biosolids applications. They used an organically managed farm down the road as a control. Yes, there was measurable PFAS in the soil. The problem was there was no PFAS in the plants. “Nothing happened!! Read all about it.” The PFOA and PFOS in the soils were similar to those in many of the soils sampled in the Pennsylvania study. In this study, the biosolids had been applied at one site since 1978 every one to five years at application rates ranging from 3 to 35 tons/acre. That counts as a lot of cake. At the second site biosolids had been applied every year since 2017 at 10 to 12 tons/acre. The other part of this research that should make headlines but won’t is that the biosolids from both treatment plants started out in people’s toilets and sinks. Both plants treated wastewater that was >96% from domestic sources.

Speaking Of Domestic Sources

That leads me to the last article in this research update. Although published in 2024, I think that it merits inclusion. Lin et al (2024) looked at flows into several treatment plants in the San Francisco area. They tracked PFAS into and out of the plant measuring concentrations in influent, effluent and the biosolids (see more details in this Connections column). Their primary conclusion, mentioned directly (Black et al., 2025) and implied (via biosolids, soil and water PFAS concentrations) in the other two studies, is that the PFAS comes from people’s houses. As with all of the other studies, there was PFAS in the biosolids.

But rather than potential exposure through a lengthy detour via soils to water coming off of farmer’s fields or not being taken up into plants, the take home and headline here is that “It comes from us.” Requiring industries to treat their wastewater before discharging into municipal systems is a terrific option and should be required nationwide. But for the majority of treatment plants, the primary source of PFAS is people’s homes. Unless we stop putting PFAS in just about everything (including toilet paper) it will show up in soils, it will show up in water and most importantly, it will show up in us. Biosolids or no biosolids.

Sally Brown, BioCycle Senior Advisor, is a Research Professor at the University of Washington in the College of the Environment.