Environmental Forensic Investigation of PFAS in Biosolids, Agricultural Soil Contamination, Groundwater Migration, and Food-Chain Exposure
Project Overview
This investigation involved a comprehensive environmental forensic evaluation of the occurrence, transport, and potential exposure pathways of per- and polyfluoroalkyl substances (PFAS) associated with the land application of municipal biosolids. The reviewed materials included laboratory analytical reports, wastewater treatment facility monitoring data, statewide biosolids management information, Geographic Information System (GIS) datasets, scientific literature, regulatory guidance, and technical evaluations concerning the production, transport, application, and environmental fate of biosolids. Collectively, these materials were evaluated to determine how PFAS originating from municipal wastewater treatment systems may migrate through soils, groundwater, surface water, agricultural systems, livestock, and food products following biosolids land application. Unlike investigations focused on a single contaminated property, this project evaluated regional environmental processes affecting numerous agricultural areas where biosolids have historically been used as soil amendments.
The investigation incorporated multiple technical disciplines, including environmental chemistry, environmental forensics, hydrogeology, soil science, agricultural engineering, GIS analysis, laboratory analytical chemistry, environmental toxicology, contaminant fate and transport, and exposure assessment. Particular emphasis was placed on identifying potential pathways by which PFAS present in biosolids may enter agricultural ecosystems through direct soil application, migration into groundwater and surface water, uptake by crops, accumulation within livestock, and subsequent transfer into human food supplies. In addition to evaluating environmental transport mechanisms, the investigation reviewed wastewater treatment plant monitoring programs, biosolids management practices, and laboratory analytical methodologies used to quantify PFAS concentrations in environmental media. This multidisciplinary approach provided a scientifically rigorous framework for evaluating potential environmental and agricultural impacts associated with long-term biosolids land application.
A significant component of the investigation involved evaluating the relationship between municipal wastewater treatment facilities and downstream agricultural land application practices. Statewide biosolids management records demonstrated that a substantial proportion of wastewater solids generated by municipal treatment plants are beneficially reused through agricultural land application rather than disposal. The reviewed materials also identified numerous agricultural regions where biosolids have historically been applied and documented efforts to identify livestock operations and farms located near those application sites. Laboratory reports prepared using EPA Method 1633 further demonstrated the application of current analytical techniques for quantifying PFAS in environmental solids, while additional technical materials evaluated emerging treatment technologies—including high-temperature pyrolysis—for reducing PFAS concentrations within biosolids before land application. Together, these materials illustrate how modern environmental forensic investigations integrate laboratory science, GIS analysis, environmental engineering, hydrogeology, agricultural research, and contaminant transport evaluations to assess complex environmental exposure pathways involving persistent contaminants such as PFAS.
Chemicals of Concern
The primary chemicals of concern evaluated during this investigation were per- and polyfluoroalkyl substances (PFAS), with particular emphasis on perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and other long-chain and short-chain PFAS compounds commonly detected in municipal wastewater, biosolids, soils, groundwater, surface water, crops, and livestock. Unlike many conventional environmental contaminants, PFAS comprise a large class of synthetic fluorinated compounds characterized by exceptionally strong carbon-fluorine bonds that resist chemical, biological, and thermal degradation under normal environmental conditions. Because of this persistence, PFAS are frequently referred to as “forever chemicals,” reflecting their tendency to remain in environmental media for extended periods and migrate through interconnected environmental systems. The reviewed technical materials focused on evaluating how PFAS originating from municipal wastewater treatment facilities may enter agricultural environments through biosolids land application and subsequently migrate into groundwater, crops, livestock, and ultimately the human food supply.
A major component of the investigation involved evaluating municipal wastewater treatment plants (WWTPs) as an important source of PFAS entering biosolids. Conventional wastewater treatment processes are not designed to destroy PFAS and therefore largely transfer these compounds from incoming wastewater into treated biosolids during solids separation and treatment. California’s statewide PFAS investigation required publicly owned treatment works (POTWs) to conduct PFAS sampling of influent, effluent, biosolids, and related environmental media, creating one of the largest publicly available datasets describing PFAS occurrence within municipal wastewater systems. The reviewed technical documentation summarized the statewide monitoring program, the associated GIS datasets, and the processing of more than 100,000 individual analytical records representing over 200 wastewater treatment facilities. These data provide an important scientific foundation for evaluating how PFAS move from municipal wastewater systems into downstream environmental receptors.
The investigation focused extensively on PFOA and PFOS, two of the most widely studied PFAS compounds because of their persistence, mobility, bioaccumulation potential, and extensive toxicological database. Although production of these compounds has declined in recent years, both remain widely detected in environmental media due to decades of historical use in aqueous film-forming foams, stain-resistant coatings, non-stick cookware, textiles, paper products, industrial manufacturing, and numerous consumer products. Their strong resistance to degradation allows them to persist within wastewater treatment systems and biosolids, where they may subsequently be introduced into agricultural soils through beneficial reuse programs. Because PFOA and PFOS are frequently used as indicator compounds during environmental investigations, laboratory analyses included within the reviewed materials specifically evaluated these compounds together with numerous additional PFAS analytes using EPA Method 1633 analytical procedures.
The investigation also evaluated the environmental mobility of PFAS following biosolids land application. Unlike many hydrophobic organic contaminants that remain strongly bound within soils, numerous PFAS compounds exhibit relatively high water solubility and can migrate vertically through the soil profile into groundwater or laterally through surface runoff into adjacent streams, irrigation canals, and surface water bodies. Environmental transport depends upon individual PFAS chemistry, soil characteristics, rainfall, irrigation practices, groundwater depth, and organic carbon content. The reviewed technical materials emphasized that PFAS migration may occur through multiple interconnected environmental pathways, including direct biosolids placement, leaching through unsaturated soils, groundwater transport, surface-water movement, and subsequent redistribution within agricultural landscapes. This complex contaminant fate and transport behavior distinguishes PFAS from many traditional environmental pollutants and requires integrated hydrogeologic and environmental chemistry evaluations.
An important focus of the investigation involved food-chain transfer and agricultural exposure pathways. Scientific literature and legal case summaries reviewed during the investigation documented that PFAS may accumulate within crops, forage, livestock, dairy cattle, and other agricultural products following long-term environmental exposure. Plants may absorb certain PFAS compounds through root uptake from contaminated soils or irrigation water, while livestock may accumulate PFAS through consumption of contaminated feed, water, or soil. The reviewed materials highlighted several legal investigations demonstrating PFAS accumulation within animal tissues and agricultural products, emphasizing that agricultural contamination extends beyond soil quality to include broader concerns regarding food production and potential human dietary exposure. The investigation therefore identified livestock operations located near biosolids application areas to evaluate farms that may warrant additional environmental investigation based upon proximity to potential PFAS sources.
The investigation further evaluated the analytical chemistry used to characterize PFAS occurrence within environmental media. Laboratory reports documented analysis of solid samples using EPA Method 1633, one of the most comprehensive analytical methods currently available for PFAS determination in solids, biosolids, soils, sediments, and other complex environmental matrices. The analytical methodology incorporated isotope dilution, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), extensive quality assurance and quality control procedures, laboratory calibration, surrogate recovery evaluation, and reporting of dry-weight concentrations. These laboratory procedures provide high analytical sensitivity and reproducibility, allowing environmental professionals to quantify dozens of PFAS compounds simultaneously while maintaining rigorous laboratory performance standards. Review of these laboratory reports demonstrated the importance of standardized analytical methods when conducting environmental forensic investigations involving persistent contaminants.
Another important aspect of the investigation involved evaluating PFAS treatment and destruction technologies. Because conventional wastewater treatment processes largely transfer PFAS into biosolids rather than destroying them, the reviewed materials examined emerging technologies intended to reduce PFAS concentrations prior to land application. Particular attention was devoted to thermal treatment approaches, including high-temperature pyrolysis, which has received increasing attention as a potential technology capable of degrading PFAS while simultaneously reducing biosolids volume and producing recoverable energy products. Although these technologies continue to evolve, the reviewed engineering materials recognized that treatment effectiveness, operating conditions, residual byproducts, and implementation costs remain important areas of ongoing scientific investigation.
Finally, the investigation recognized that PFAS contamination represents a multimedia environmental issue requiring evaluation across wastewater treatment systems, biosolids management, soils, groundwater, surface water, agriculture, livestock, and human exposure pathways. Rather than considering individual environmental media independently, the reviewed technical documentation adopted a systems-based perspective recognizing that contaminants may migrate through multiple environmental compartments over extended periods following their initial release. This integrated approach reflects accepted principles of environmental forensics, contaminant fate and transport, hydrogeology, agricultural science, environmental chemistry, and exposure assessment, and provides the scientific foundation for evaluating PFAS contamination associated with beneficial biosolids reuse programs.
Methods
The investigation was conducted using accepted principles of environmental forensics, environmental engineering, environmental chemistry, hydrogeology, soil science, agricultural engineering, Geographic Information System (GIS) analysis, laboratory analytical chemistry, environmental toxicology, contaminant fate and transport, and exposure assessment. Because PFAS associated with biosolids may migrate through multiple environmental media over extended periods, the technical evaluation integrated laboratory analytical reports, statewide wastewater treatment data, biosolids management records, GIS mapping, scientific literature, agricultural land-use information, hydrogeologic evaluations, and engineering analyses into a comprehensive environmental forensic framework. Rather than relying upon a single environmental dataset, the investigation synthesized multiple independent lines of scientific evidence to evaluate PFAS sources, environmental migration, agricultural exposure pathways, and potential risks to groundwater, livestock, crops, and surrounding communities. This multidisciplinary methodology reflects accepted environmental consulting practice for evaluating widespread environmental contamination involving persistent organic pollutants.
A primary component of the investigation involved regulatory and biosolids management review. Statewide biosolids management reports, wastewater treatment facility data, and regulatory guidance were reviewed to characterize the production, treatment, transportation, and beneficial reuse of biosolids throughout California. Particular emphasis was placed on identifying agricultural regions receiving municipal biosolids, understanding long-term trends in biosolids recycling, and evaluating how state policies encouraging beneficial land application may influence the distribution of PFAS within agricultural environments. The reviewed statewide biosolids inventory documented that land application has historically represented the dominant biosolids management practice in California, with a substantial proportion of biosolids transported to agricultural areas within the Central Valley. These data provided important context for evaluating potential environmental exposure associated with large-scale biosolids reuse programs.
The investigation also relied extensively upon laboratory analytical chemistry. Laboratory reports documented PFAS analysis of biosolids and related environmental solids using EPA Method 1633, which incorporates isotope dilution, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), surrogate recovery evaluation, calibration verification, laboratory quality assurance and quality control (QA/QC), method blanks, laboratory control samples, and duplicate analyses. These procedures provide highly sensitive and reproducible measurement of numerous PFAS compounds within complex environmental matrices while minimizing analytical uncertainty. Review of the laboratory documentation confirmed that standardized analytical procedures were applied consistently and provided scientifically reliable concentration data suitable for environmental forensic interpretation.
A major component of the investigation involved wastewater treatment plant (WWTP) source evaluation. Statewide monitoring data describing PFAS concentrations within wastewater treatment systems were reviewed to evaluate how PFAS enter municipal treatment plants through residential, commercial, and industrial wastewater before partitioning into biosolids during treatment. The investigation included processing and interpretation of large statewide monitoring datasets containing analytical results from publicly owned treatment works (POTWs), together with facility information describing biosolids production, treatment processes, and disposal or reuse practices. Evaluation of these data allowed investigators to identify facilities producing PFAS-containing biosolids and to better understand statewide patterns of PFAS occurrence within municipal wastewater systems.
The technical evaluation further incorporated GIS analysis and spatial exposure screening. Geographic Information System datasets were used to identify biosolids land application sites, wastewater treatment facilities, agricultural properties, livestock operations, dairy farms, and surrounding environmental receptors. Spatial analyses focused on identifying farms located either directly on biosolids application sites or within approximately one-half mile of known application areas where contaminant migration through groundwater, surface water, or runoff could potentially occur. GIS mapping also provided a systematic framework for prioritizing locations requiring additional environmental investigation by integrating biosolids management records with agricultural land-use data and proximity analyses. This spatial screening approach allowed investigators to evaluate potential environmental exposure across broad geographic regions while efficiently identifying locations where more detailed site-specific investigations may be warranted.
The investigation also incorporated contaminant fate and transport evaluation. Hydrogeologic and environmental chemistry principles were applied to evaluate the migration of PFAS following biosolids land application through soil, groundwater, surface water, irrigation systems, crops, and livestock. Factors considered included PFAS solubility, soil adsorption characteristics, groundwater recharge, irrigation practices, rainfall, soil permeability, organic carbon content, and agricultural nutrient management. The investigation recognized that PFAS transport occurs through interconnected environmental pathways rather than a single migration mechanism and therefore evaluated multiple exposure routes simultaneously. This multimedia approach is consistent with accepted environmental forensic methodology because it accounts for the complex environmental behavior exhibited by persistent fluorinated compounds.
An important component of the investigation involved agricultural exposure assessment. Technical materials were reviewed to evaluate how PFAS present within biosolids may enter agricultural production systems through contaminated soils, irrigation water, forage crops, livestock feed, and animal drinking water. The investigation examined published reports describing PFAS uptake into plants, accumulation within livestock tissues, contamination of dairy products, and transfer through agricultural food chains. Rather than limiting the evaluation to direct human contact with contaminated soils, the assessment considered indirect exposure pathways associated with consumption of agricultural products produced on or near biosolids application sites. This systems-based evaluation provides a more comprehensive understanding of long-term environmental exposure associated with agricultural PFAS contamination.
The investigation further reviewed emerging PFAS treatment technologies applicable to biosolids management. Engineering evaluations describing thermal destruction methods, including high-temperature pyrolysis and related treatment technologies, were examined to assess potential approaches for reducing PFAS concentrations prior to land application. The review considered treatment mechanisms, destruction efficiency, engineering feasibility, residual byproducts, and implementation considerations while recognizing that many technologies remain under active development. Evaluation of treatment alternatives provided important context for understanding future opportunities to reduce environmental releases of PFAS associated with beneficial biosolids reuse.
Finally, the investigation employed a comprehensive weight-of-evidence methodology integrating laboratory analytical chemistry, statewide wastewater monitoring, biosolids management data, GIS analysis, hydrogeology, agricultural science, contaminant fate and transport, environmental engineering, and exposure assessment into a unified environmental forensic investigation. Each independent scientific discipline contributed complementary information regarding PFAS sources, environmental migration, agricultural exposure, groundwater protection, and food-chain transfer. By evaluating these independent datasets collectively rather than in isolation, the investigation developed a scientifically supported framework for assessing PFAS contamination associated with biosolids land application while identifying agricultural areas where additional environmental investigation may be appropriate.
Results
Review of the available technical documentation demonstrated that comprehensive evaluation of PFAS associated with biosolids requires integration of environmental chemistry, hydrogeology, agricultural science, laboratory analytical chemistry, wastewater engineering, Geographic Information System (GIS) analysis, contaminant fate and transport, and exposure assessment. Although the reviewed materials included statewide biosolids inventories, wastewater treatment plant monitoring data, laboratory analytical reports, GIS evaluations, agricultural screening analyses, and scientific literature, they consistently demonstrated that understanding PFAS contamination requires evaluation of the complete environmental lifecycle of biosolids—from wastewater treatment through land application and subsequent migration into soils, groundwater, surface water, crops, livestock, and potentially the human food supply. Collectively, these independent datasets established a comprehensive scientific framework for evaluating environmental exposure associated with long-term biosolids reuse programs.
One of the principal findings of the investigation was that municipal wastewater treatment plants represent a significant collection point for PFAS originating from numerous residential, commercial, and industrial sources. Because conventional wastewater treatment technologies are generally designed to remove suspended solids, nutrients, and pathogens rather than persistent fluorinated compounds, much of the incoming PFAS load partitions into wastewater solids during treatment. Consequently, biosolids generated at wastewater treatment facilities may contain measurable concentrations of PFAS even when wastewater treatment processes successfully meet existing discharge requirements. The reviewed statewide monitoring program demonstrated that PFAS occurrence within biosolids represents a predictable outcome of conventional wastewater treatment rather than an isolated operational deficiency at individual facilities.
The investigation further demonstrated that agricultural land application creates multiple environmental pathways through which PFAS may migrate following biosolids reuse. The reviewed technical materials identified direct application to agricultural soils, downward leaching to groundwater, surface-water runoff, irrigation return flows, crop uptake, and livestock exposure as interconnected environmental pathways capable of influencing contaminant distribution over extended periods. Rather than remaining confined to the original application site, PFAS mobility depends upon compound-specific chemistry together with hydrogeologic conditions, soil characteristics, irrigation practices, and local climate. These findings illustrate why environmental forensic investigations involving biosolids require multimedia evaluation across soils, groundwater, agriculture, and surface-water systems rather than consideration of a single environmental compartment.
Another significant finding involved the value of GIS analysis as a regional environmental screening tool. Spatial analyses integrating wastewater treatment facilities, biosolids application areas, agricultural land use, livestock operations, and dairy farms provided an efficient scientific framework for identifying locations potentially warranting additional environmental investigation. Rather than assuming all agricultural properties face equivalent exposure potential, GIS-based screening allowed investigators to prioritize farms receiving biosolids directly or located near known application sites where contaminant migration through groundwater or surface water could reasonably occur. This approach illustrates how modern environmental consulting combines geospatial analysis with environmental chemistry and hydrogeology to efficiently identify potentially vulnerable agricultural receptors.
The investigation also demonstrated the importance of high-quality laboratory analytical methods when evaluating PFAS contamination. Laboratory reports prepared using EPA Method 1633 documented isotope dilution, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), calibration verification, surrogate recoveries, laboratory quality assurance procedures, and rigorous analytical quality control. These standardized laboratory methods provide highly reproducible measurements of numerous PFAS compounds within complex environmental matrices while supporting comparison of analytical results across multiple investigations. Review of the laboratory documentation demonstrated that reliable analytical chemistry forms the foundation upon which environmental forensic interpretations, regulatory evaluations, and exposure assessments are built.
The investigation further demonstrated that food-chain transfer represents an important environmental exposure pathway requiring continued scientific evaluation. The reviewed technical materials summarized published investigations and legal cases documenting PFAS accumulation within crops, forage, livestock, and agricultural products following environmental contamination. These findings emphasize that PFAS investigations extend beyond traditional soil and groundwater evaluations because contaminants may enter agricultural production systems through multiple environmental pathways before ultimately contributing to human dietary exposure. Consequently, environmental assessments involving biosolids benefit from integrating agricultural science, veterinary exposure pathways, hydrogeology, and environmental chemistry into a unified exposure assessment framework.
Review of the engineering documentation also demonstrated growing interest in advanced biosolids treatment technologies designed to reduce PFAS prior to land application. The reviewed materials described emerging thermal destruction technologies, including high-temperature pyrolysis, as potential approaches for reducing PFAS concentrations while simultaneously managing biosolids volumes and recovering useful energy products. Although these technologies continue to undergo scientific evaluation, the investigation illustrates the importance of considering both contaminant management and treatment innovation when evaluating future biosolids management strategies.
Finally, the investigation demonstrated the importance of integrating multiple independent scientific disciplines into PFAS investigations. Wastewater treatment engineering, laboratory analytical chemistry, statewide biosolids inventories, GIS analysis, hydrogeology, agricultural science, contaminant fate and transport, and exposure assessment each contributed complementary information regarding PFAS occurrence and environmental migration. No individual dataset independently characterized the complete environmental behavior of PFAS associated with biosolids. However, when evaluated collectively through a weight-of-evidence approach, these independent lines of evidence provided a scientifically supported framework for understanding how PFAS move from municipal wastewater systems into agricultural environments and identifying locations where additional environmental investigation may be appropriate.
Conclusions
The available technical documentation provides a comprehensive scientific foundation for evaluating PFAS associated with biosolids land application using accepted principles of environmental forensics, environmental engineering, environmental chemistry, hydrogeology, agricultural science, laboratory analytical chemistry, contaminant fate and transport, and exposure assessment. The investigation demonstrates that PFAS contamination associated with municipal wastewater treatment is best understood as a multimedia environmental issue involving wastewater treatment systems, biosolids management, soils, groundwater, surface water, agricultural production, livestock, and potential human exposure rather than as an isolated contamination problem affecting a single environmental medium.
The investigation demonstrated that statewide biosolids management records, wastewater treatment monitoring, EPA Method 1633 laboratory analyses, GIS screening, hydrogeologic evaluations, agricultural research, and engineering studies each contribute unique scientific information regarding PFAS occurrence, environmental migration, and potential exposure pathways. When evaluated collectively through a weight-of-evidence framework, these independent lines of evidence provide a more comprehensive and scientifically defensible understanding of environmental conditions than reliance upon any individual monitoring program or analytical dataset.
Review of the available documentation also illustrates the importance of integrating environmental chemistry with hydrogeology and agricultural science when evaluating PFAS contamination associated with beneficial biosolids reuse. Environmental investigations that combine laboratory analytical chemistry, contaminant fate and transport, GIS analysis, groundwater evaluation, agricultural exposure assessment, and wastewater engineering provide a more technically accurate understanding of long-term environmental behavior than evaluations focused exclusively on biosolids chemistry or soil concentrations alone. This multidisciplinary perspective is particularly important for PFAS because their persistence, mobility, and diverse environmental pathways require coordinated evaluation across multiple scientific disciplines.
More broadly, this investigation demonstrates how modern environmental consulting integrates laboratory science, environmental engineering, hydrogeology, GIS analysis, agricultural science, contaminant transport modeling, exposure assessment, and environmental forensics to evaluate emerging contaminants affecting agricultural systems and regional water resources. These multidisciplinary investigations provide scientifically supported evaluations of contaminant sources, environmental migration, agricultural exposure, groundwater protection, and food-chain transfer while remaining grounded in objective technical analysis, peer-reviewed science, and accepted environmental engineering methodologies.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist, environmental forensic expert, and exposure assessment specialist with extensive experience evaluating emerging contaminants, groundwater contamination, agricultural exposure pathways, wastewater treatment systems, and environmental fate and transport. Throughout his career, Dr. Rosenfeld has investigated PFAS, petroleum hydrocarbons, chlorinated solvents, dioxins, metals, pesticides, ethylene oxide, combustion products, and numerous other contaminants affecting industrial facilities, agricultural operations, public water supplies, and surrounding communities. His work routinely integrates environmental chemistry, hydrogeology, GIS analysis, laboratory analytical interpretation, contaminant transport, environmental engineering, and exposure science to evaluate complex environmental systems involving multiple environmental media.
References
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