UC Davis research finds no uptake of PFAS into oats from fields amended with biosolids
In 2020, Professor Thomas Young and his research team at University of California, Davis (UC Davis) began a study on the uptake of per- and polyfluoroalkyl substances (PFAS) into oats from biosolids-amended soils. The BABC provided partial funding and helped identify agricultural sampling sites for the study. The study was completed in 2023, and the research results were published in January 2025 (https://pubmed.ncbi.nlm.nih.gov/39907451/). This is one of many research projects the BABC has supported in the last decade.
The study evaluated the uptake of 33 PFAS compounds over one growing season in dry-farmed (no irrigation) oats from three agricultural sites in California. All three sites were within 10 miles of each other, with similar environmental characteristics and weather patterns and with the same soil type. Site A had received biosolids since 1978. Site A had received biosolids since 2017. Site C, the control site, was a USDA certified organic site.
Class B biosolids from a Bay Area wastewater treatment plant (WWTP) were applied with lime to Site A and Site B. Site C was split into three subplots: (C1) no amendment, (C2) compost, and (C3) compost with lime. The biosolids were applied at or less than the agronomic rate and incorporated into the soil. Oats were sowed and grown for one growing season. Table 1 provides additional details about the sites.
Soil and crop samples were collected from three locations at each site. The types of samples from each location included:
(1) Soil before application,
(2) Soil at the end of the growing season, and
(3) Oat above ground plant tissue.
Three replicates of the amendment used at each site were also taken.
The soils were analyzed for pH, electroconductivity, organic matter, and texture. Soils at the three sites had little variation in these parameters. 33 PFAS compounds were measured in all the samples. Table 2 and Figure 1 summarize the concentrations of PFAS found in the various samples.
Source: Figure 4 from research paper
Figure 1: Sums of PFAS concentrations in amendments, soil, and oats
Importantly, no PFAS were detected in any of the oat samples. The study authors summarized the environmental significance with this statement:
“Although previous studies have documented the transfer of PFAS from soils to crops, no measurable PFAS uptake occurred in dry farmed oats grown on fields with background PFAS contamination following fresh addition of biosolids. The study provides data critical to delineating the conditions under which PFAS uptake by crops is problematic.”
Previous studies have found PFAS uptake into crops from soils amended with biosolids. However, many of the studies were lab scale studies with spiked soils and relatively few have studied plant uptake in full-scale representative agricultural sites. Studies described as “field-scale” are often performed in lysimeters with spiked soils. One full-scale study found PFAS uptake to roots but not in the stems or leaves. The most directly comparable previous study, by Wen et al. (2014), found uptake of PFAS into wheat from biosolids applied at full-scale agricultural sites. In general, previous studies have found that PFAS uptake into crops varies widely and is highly dependent on the portion of the plant that is measured, type of crop, type of PFAS measured, the amount of PFAS in the soil, soil properties, site characteristics, and growing conditions including irrigation.
The BABC is committed to continuing to advance independent scientific research on the safety and benefits of biosolids. In fact, advancing research is one of our goals, all of which support our vision of a Bay Area where all biosolids are beneficially used.
References:
Black GP, Wong L, Young TM. Uptake of per- and polyfluorinated alkyl substances by dry farmed oats following the agricultural application of biosolids and compost. Environ Sci Process Impacts. 2025 Mar 19;27(3):661-669. doi: 10.1039/d4em00502c. PMID: 39907451.