PFAS, Biosolids and Yuma: What the Evidence Actually Shows

PFAS can turn up in municipal biosolids. Researchers have also found these persistent chemicals in soils where biosolids have been applied. EPA information and published research support both findings.

But finding PFAS in biosolids is one thing. Establishing that a particular company contaminated a Yuma groundwater well or agricultural crop is another. The difference matters, especially when concerns about AgTech's operations have become part of the local debate over biosolids disposal.

Finding PFAS Is Not the Same as Identifying Its Source

Scientists have to answer several questions before connecting contamination to a particular operation.

First, is the chemical present? Laboratory testing can establish whether PFAS was detected in a sample and at what concentration.

Next comes exposure. How might that chemical reach groundwater, crops, animals or people?

Then comes the difficult part: determining where it originated.

A 2021 study abstract examined soils where both biosolids and irrigation water were relevant potential sources of PFAS. That distinction is particularly important in an agricultural region such as Yuma, where irrigation is central to farming.

The study provides a reason to investigate more than one possible pathway. It does not establish that AgTech introduced PFAS into a particular Yuma field or groundwater source.

Identifying the source would require samples from the relevant materials and locations, collected under conditions that allow meaningful comparisons.

What National Research Tells Us

Research on PFAS movement through soil offers useful evidence, although the results depend on the conditions being studied.

One national study reported that PFAS concentrations generally decreased with soil depth across its sampled locations. That finding helps researchers understand how these chemicals behave underground.

It does not mean every soil or groundwater system behaves the same way. Differences in soil composition, irrigation, application history and local hydrology can affect what happens after PFAS reaches the ground.

The study also was not a measurement of Yuma groundwater.

Federal regulators have been examining the issue more closely.

On January 14, 2025, the Environmental Protection Agency released a draft risk assessment for PFOA and PFOS in sewage sludge. Both chemicals belong to the broader PFAS family.

The assessment modeled possible exposures associated with different sewage-sludge management practices, including agricultural land application. Its scenarios included concentrations of 1 part per billion.

That number deserves context. It was used in the agency's modeling, not established as a universal dividing line between safe and unsafe conditions at every property.

The assessment did not involve sampling an AgTech site in Yuma County.

EPA subsequently took a different approach.

A separate draft guidance memorandum dated June 29, 2026 proposed voluntary measures for reducing risks associated with PFOA and PFOS in biosolids.

In its July 1 announcement, EPA criticized assumptions used in the earlier assessment and described a new opportunity for public comment.

The agency questioned whether some earlier modeling assumptions adequately reflected real-world conditions. Its newer guidance addressed practices such as avoiding land application near waterways and limiting uses that could present greater exposure risks.

Both documents were issued as drafts. Neither establishes a nationwide prohibition on applying biosolids to agricultural land. Neither determines whether AgTech's operations have contaminated groundwater or crops in Yuma.

And neither settles the broader scientific questions simply because EPA changed its proposed approach.

What About PFAS Already Detected Around Yuma?

There is local information worth examining, but the locations matter.

The Arizona Department of Environmental Quality maintains cleanup information concerning Marine Corps Air Station Yuma. That is a separately identified site with its own environmental history.

The presence of PFAS in records associated with the air station cannot, by itself, establish a connection to AgTech's biosolids operations.

Yuma County has also addressed the subject publicly.

On its biosolids information page, under the question "What about PFAS and groundwater?", the County says Naval Facilities provided results from well testing outside Marine Corps Air Station Yuma.

According to the County, PFAS compounds were detected, but the reported concentrations were below current regulatory thresholds.

That is useful information. It also leaves some basic questions unanswered.

The County's summary does not identify the individual wells, sample dates, chemicals detected or measured concentrations. The underlying laboratory results would be needed to examine those details and determine which regulatory thresholds apply.

Nor does the summary identify AgTech as the source.

Connecting those detections to biosolids operations would require evidence establishing the relevant locations, timing, groundwater movement and likely sources. A shared geographic label is not enough.

The Evidence Still Missing

The central question for Yuma is straightforward: Is there measurable PFAS contamination connected to AgTech's biosolids operations, and has it reached groundwater or agricultural crops?

The records reviewed here do not answer that question.

A defensible investigation would need comparable measurements from AgTech's source materials, receiving soils at different depths, irrigation water, groundwater and potentially affected crops.

Those results would also need enough supporting information to determine whether the measurements can be trusted and compared. That includes sampling methods, laboratory detection limits, quality-control results, chain-of-custody documentation and appropriate comparison samples.

Even a laboratory report showing no detectable PFAS requires careful reading. A nondetect means the substance was not detected under the method's reporting conditions. It does not necessarily mean the substance was entirely absent.

Without those records, it would be premature to assign responsibility for a particular contamination finding.

It would be equally premature to declare that no contamination exists.

Yuma Informed has published two related claim checks:

• Has AgTech contaminated Yuma groundwater with PFAS?
• Has AgTech contaminated lettuce grown in Yuma?

Both remain unverified.

National research demonstrates that PFAS in biosolids and agricultural soils is a legitimate environmental concern. EPA's work explains why potential exposure deserves scrutiny. The County's account establishes that PFAS detections have been reported in wells outside the air station, although the underlying measurements are not reproduced here.

What is missing is the evidence connecting AgTech's material to a particular Yuma groundwater well or crop.

Until that connection can be documented, neither a contamination allegation nor a declaration of safety should be presented as a settled finding.

The available evidence supports investigating the question. It does not support pretending the investigation has already answered it.

Clarification: This article distinguishes EPA's January 2025 draft risk assessment from its June 2026 draft guidance, identifies the County's well-testing account as separate from AgTech's operations, and reflects the published, unverified status of the two local claim checks.