Across rural stretches of the Northeast and California’s agricultural valleys, a quiet farming practice may be seeding the air, water, and soil with “forever chemicals.” Federal researchers and university scientists have spent the past two years tracing PFAS, the synthetic compounds linked to cancer, thyroid disease, and immune suppression, back to an unlikely source: treated sewage sludge spread on cropland as fertilizer.
The practice is not obscure. According to EPA estimates, roughly half of all biosolids produced at U.S. wastewater treatment plants are applied to agricultural land each year. Biosolids are nutrient-rich and cheap, making them attractive to farmers. But a convergence of studies published between 2024 and early 2026 now shows that those biosolids carry measurable loads of PFAS, and that the chemicals do not stay where they are spread.
PFAS confirmed in soil and water near treated fields
A peer-reviewed study published in Scientific Reports examined agricultural soils at ten northeastern farms that had received biosolids applications. Researchers found PFAS concentrations in treated fields were significantly elevated compared with untreated control plots, and the data suggested that repeated applications over multiple years compounded the contamination. The chemicals persisted in topsoil rather than breaking down or leaching away quickly, consistent with what scientists expect from compounds engineered to resist degradation.
A separate U.S. Geological Survey study looked at water rather than soil. USGS researchers sampled 10 streams in two Northern California agricultural valleys during pesticide application periods in May and July 2024, screening for 183 pesticides and 57 PFAS compounds. They found that PFAS co-occurred with pesticides in 80% of samples. The seasonal timing of the sampling, during active fieldwork when soil is disturbed and irrigation water flows across treated land, pointed to farming operations as the mechanism pushing PFAS into surrounding waterways.
Together, these studies establish a pattern: PFAS deposited through biosolids do not remain locked in place. They migrate through soil profiles and wash into streams, creating exposure pathways that extend well beyond the fields where sludge was originally spread.
Atmospheric detection adds a new dimension
The most provocative piece of the puzzle involves air. Researchers led by Katz and colleagues published a 2025 analysis in ACS Environmental Au drawing on atmospheric data collected through the Department of Energy’s Atmospheric Radiation Measurement (ARM) User Facility. The ARM network, originally designed to study cloud and radiation processes, captures detailed atmospheric measurements at sites across the country, and the dataset is publicly accessible for independent verification.
The Katz team’s analysis detected PFAS in air samples and identified temporal patterns that aligned with regional agricultural activity. That correlation is suggestive but not conclusive. No published study has yet traced the full chain from a specific biosolids application event, through volatilization or dust generation, to elevated PFAS concentrations in downwind air using a controlled, field-scale design.
The plausible mechanisms are well understood in atmospheric science. Tilling breaks up soil and lofts fine particles. Wind erosion carries dust from bare or recently worked fields. Warm temperatures can volatilize certain PFAS compounds from the soil surface. All three processes peak during the same agricultural seasons when biosolids are most commonly applied, creating conditions that could move soil-bound PFAS into breathable air. What remains unmeasured is how much PFAS actually travels this route and at what concentrations.
EPA signals concern but has not set new rules
The Environmental Protection Agency has taken a formal step that reflects the weight of this accumulating evidence. In its draft risk assessment for PFOA and PFOS in biosolids, the agency recognized land-applied sewage sludge as a significant PFAS exposure pathway, serious enough to warrant dedicated assessment resources. That designation signals regulatory attention, but as of May 2026, it has not translated into new federal limits on PFAS concentrations in biosolids or restrictions on how they are applied.
Some states have moved faster. Maine banned the land application of biosolids entirely in 2022 after PFAS contamination was discovered on farms that had used the material for years. Michigan and other states have introduced testing requirements or voluntary guidelines. But most of the country still operates under the EPA’s existing biosolids framework, which was designed decades before PFAS contamination became a recognized concern.
Farmers who rely on biosolids as a low-cost alternative to commercial fertilizer currently face no new federal compliance requirements. That could change if the EPA finalizes its risk assessment and moves toward rulemaking, a process that typically takes years. In the meantime, the gap between scientific evidence and regulatory action leaves communities near treated fields in a gray zone: enough data to raise serious questions, not enough regulation to compel answers.
What the science can and cannot tell us yet
The strongest evidence in this body of research comes from direct, peer-reviewed field measurements. The USGS stream sampling and the Scientific Reports soil study both report specific PFAS concentrations found at specific locations using standardized analytical methods. These are not modeled estimates or extrapolations; they are measurements of what is actually in the ground and water near farms that use biosolids.
The atmospheric data occupies a different evidentiary tier. The ARM dataset is real, publicly archived, and was used in a peer-reviewed publication. But the connection between PFAS detected in air and biosolids applied to nearby fields remains an inference drawn from geographic and seasonal correlations, not from a study designed to isolate that specific source. Industrial emissions, consumer products, and long-range atmospheric transport all contribute PFAS to ambient air, and no study has yet apportioned how much of the airborne burden near agricultural areas comes from fertilizer versus these other sources.
For people living near fields where biosolids are spread, the distinction between confirmed contamination in soil and water and probable but unquantified contamination in air is not academic. It shapes what protective steps make sense right now. Residents and local officials can request records on whether biosolids are being applied on nearby land and what PFAS testing, if any, is performed on those materials before use. Farmers can weigh the cost savings of biosolids against the possibility that future regulations or liability exposure could follow if contamination is traced to their fields.
Filling the gaps will require boots on the ground
The research published through early 2026 paints a consistent picture: biosolids are a meaningful source of PFAS in soil and water, and a plausible contributor to PFAS measured in the atmosphere. What is missing is the quantitative bridge. How much PFAS moves from a treated field into the air column above it? Under what weather and soil conditions does that transfer peak? And what does that mean for the health of farmworkers spending hours in those fields or families living a quarter-mile downwind?
Answering those questions will require coordinated field campaigns that follow PFAS from the wastewater treatment plant to the spreading truck to the field surface to the fence line air monitor. Several research groups have signaled interest in exactly this kind of source-to-receptor study, but as of spring 2026, no published results from such a campaign are available. Until they are, the science supports a posture of informed caution: the chemicals are there, they are moving, and the air pathway, while not yet proven at field scale, fits everything researchers already know about how PFAS behave in the environment.
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*This article was researched with the help of AI, with human editors creating the final content.
