Environmental Forensic Investigation of PFAS Air Emissions, Drinking Water Contamination, Source Attribution, and Human Exposure Assessment
Project Overview
Per- and polyfluoroalkyl substances (PFAS) have emerged as one of the most challenging classes of environmental contaminants due to their extraordinary persistence, environmental mobility, and widespread occurrence in air, soil, groundwater, surface water, and drinking water. Often referred to as “forever chemicals,” many PFAS resist natural degradation and can remain in the environment for decades while migrating considerable distances through atmospheric and hydrologic pathways. As scientific understanding of PFAS has evolved, environmental forensic investigations have increasingly focused on reconstructing historical releases, identifying contaminant sources, evaluating environmental transport mechanisms, and assessing potential human exposure through multiple pathways. These investigations require an integrated approach combining environmental chemistry, air quality modeling, hydrogeology, contaminant fate and transport, exposure assessment, and human health risk assessment.
This environmental forensic investigation evaluated historical PFAS releases associated with a large fluorochemical manufacturing facility that operated for several decades producing fluorinated polymers and related industrial products. Rather than evaluating only a single environmental pathway, the investigation examined how historical air emissions, environmental deposition, groundwater migration, surface water transport, and drinking water contamination collectively influenced long-term human exposure. Historical manufacturing records, engineering documentation, regulatory information, environmental monitoring data, hydrogeologic studies, atmospheric dispersion modeling, and published scientific literature were integrated to reconstruct historical PFAS releases and evaluate contaminant migration from industrial operations into surrounding environmental media.
A principal objective of the investigation was to determine whether historical industrial emissions could explain observed PFAS concentrations in environmental media and public drinking water supplies. To accomplish this, investigators reconstructed historical emission source terms, evaluated contaminant transport through both atmospheric and hydrologic pathways, and compared modeled environmental concentrations with available monitoring data. Atmospheric transport was evaluated using EPA-approved air dispersion modeling techniques, while groundwater and surface water evaluations incorporated hydrogeologic information, watershed characteristics, historical contaminant loading, and drinking water monitoring results. This integrated environmental forensic approach allowed investigators to evaluate multiple exposure pathways simultaneously while strengthening scientific source attribution through independent lines of evidence.
The investigation also evaluated the environmental behavior of both legacy PFAS compounds and newer fluorinated replacement chemicals. Scientific literature demonstrates that different PFAS exhibit markedly different environmental transport characteristics depending upon molecular structure, chain length, functional groups, and interactions with soils, minerals, groundwater, and organic matter. Consequently, the investigation incorporated current research regarding PFAS adsorption, groundwater mobility, atmospheric deposition, environmental persistence, and bioaccumulation to develop conceptual site models describing contaminant migration following decades of industrial operations. These environmental chemistry evaluations provided the scientific basis for interpreting both modeled contaminant transport and measured environmental concentrations.
Finally, the investigation integrated environmental chemistry, engineering analyses, hydrogeology, air quality modeling, exposure science, and toxicology into a comprehensive human health risk assessment. Rather than evaluating air emissions or drinking water independently, investigators assessed cumulative exposure through multiple environmental pathways using accepted U.S. Environmental Protection Agency methodologies and published toxicological literature. This multidisciplinary environmental forensic investigation demonstrates how modern environmental consulting combines historical site reconstruction, contaminant fate and transport, environmental data analysis, source attribution, air dispersion modeling, groundwater evaluation, drinking water assessment, and human health risk assessment to objectively evaluate complex PFAS contamination associated with historical industrial operations.
Chemicals of Concern
The environmental forensic investigation focused on a group of per- and polyfluoroalkyl substances (PFAS) that have historically been associated with fluorochemical manufacturing and environmental contamination. PFAS comprise a large class of synthetic fluorinated compounds valued for their exceptional resistance to heat, water, oil, and chemical degradation. These same properties, however, contribute to their remarkable environmental persistence, allowing many PFAS to remain in soil, groundwater, surface water, sediments, and biological tissues for decades. Their resistance to natural degradation has resulted in widespread environmental distribution and increasing concern regarding long-term human and ecological exposure. Consequently, understanding the environmental chemistry, transport mechanisms, and toxicological properties of PFAS represented a central component of this environmental forensic investigation.
The principal legacy compound evaluated during the investigation was perfluorooctanoic acid (PFOA), which has historically been used in the manufacture of fluoropolymers and other fluorinated products. PFOA is highly persistent, readily transported in groundwater and surface water, and has been detected globally in environmental media, wildlife, and human blood serum. Numerous toxicological and epidemiological studies have associated long-term PFOA exposure with adverse health outcomes, including kidney cancer, testicular cancer, elevated cholesterol, immune system effects, thyroid dysfunction, developmental toxicity, and reduced vaccine response. Because of its historical use, persistence, and extensive environmental occurrence, PFOA served as one of the primary indicators for evaluating historical contaminant releases and long-term environmental exposure.
The investigation also evaluated ammonium perfluorooctanoate (APFO), a fluorinated processing aid historically used during fluoropolymer production. Although APFO readily dissociates to form PFOA in environmental systems, understanding its historical use was important for reconstructing manufacturing operations and estimating historical emission source terms. Engineering evaluations incorporated production history, process chemistry, historical manufacturing practices, and available regulatory documentation to estimate potential emissions over multiple decades of facility operation. These reconstructed source terms subsequently served as inputs for atmospheric dispersion modeling and environmental fate analyses.
Another major focus of the investigation involved hexafluoropropylene oxide dimer acid (HFPO-DA), commonly referred to as GenX, together with other fluorinated ether compounds developed as replacements for legacy PFAS. Although these replacement compounds generally exhibit shorter biological half-lives than PFOA, scientific research indicates that many remain highly mobile within groundwater and surface water because they adsorb less strongly to soils and organic matter. Laboratory studies evaluating PFAS-soil interactions demonstrated that these compounds exhibit relatively limited retention by mineral surfaces, increasing the potential for migration through aquifers and drinking water sources. Consequently, investigators evaluated both historical and current PFAS releases while recognizing that environmental transport characteristics differ substantially among individual PFAS compounds.
The investigation further considered fluoropolymer manufacturing byproducts, including fluorinated ether acids and proprietary processing intermediates that may serve as environmental indicators of historical manufacturing activities. Unlike naturally occurring contaminants, these compounds can provide valuable forensic evidence linking environmental contamination to specific industrial processes. Their presence within groundwater, surface water, or environmental samples may therefore strengthen source attribution when interpreted alongside historical manufacturing information, atmospheric transport modeling, and hydrogeologic evaluations. Integrating multiple PFAS compounds into the investigation also allowed evaluation of changing manufacturing practices over time as industries transitioned away from certain legacy compounds toward newer fluorinated alternatives.
Because PFAS contamination rarely involves a single chemical or environmental pathway, investigators integrated atmospheric transport, soil chemistry, groundwater migration, surface water transport, drinking water exposure, environmental persistence, and human toxicology into a comprehensive environmental chemistry evaluation. This multidisciplinary approach provided a scientifically robust framework for reconstructing historical contaminant releases, evaluating source attribution, estimating long-term human exposure, and supporting environmental consulting, regulatory investigations, remediation planning, and environmental litigation involving fluorochemical manufacturing facilities.
Methods
The environmental forensic investigation employed a multidisciplinary methodology integrating historical document review, environmental chemistry, air dispersion modeling, hydrogeologic evaluation, source-term reconstruction, drinking water exposure assessment, contaminant fate and transport analysis, geographic information systems (GIS), regulatory record review, and human health risk assessment. Because historical PFAS releases occurred over several decades and involved multiple environmental pathways, investigators synthesized engineering documentation, manufacturing history, environmental monitoring data, hydrogeologic information, scientific literature, and regulatory records to reconstruct historical emissions and evaluate long-term contaminant migration. This weight-of-evidence approach allowed investigators to objectively evaluate multiple independent datasets while minimizing uncertainty associated with any single analytical method.
The investigation began with a comprehensive review of historical manufacturing records, engineering documentation, environmental permits, publicly available regulatory reports, scientific publications, and historical production information to reconstruct facility operations over time. Particular emphasis was placed on identifying changes in manufacturing processes, emission control technologies, fluoropolymer production, waste management practices, and environmental regulations that could influence historical PFAS emissions. This historical reconstruction established the foundation for estimating emission source terms and evaluating contaminant releases during multiple operational periods rather than relying upon a single representative year.
Historical atmospheric releases were evaluated using the U.S. Environmental Protection Agency’s AERMOD air dispersion modeling system. Investigators reconstructed historical source terms using manufacturing information, engineering calculations, published process chemistry, production estimates, and available environmental records. Model inputs included stack parameters, emission estimates, meteorological data, terrain characteristics, receptor grids, and particle properties to estimate historical airborne PFAS concentrations and atmospheric deposition over multiple decades of facility operation. Sensitivity analyses were also performed to evaluate the influence of alternative emission assumptions and particle characteristics on modeled environmental concentrations, providing a technically robust framework for evaluating historical atmospheric transport.
Hydrogeologic evaluation represented another major component of the investigation. Investigators reviewed groundwater flow characteristics, aquifer properties, watershed features, river transport, drinking water system information, and available environmental monitoring data to evaluate the migration of PFAS following historical releases. Surface water and groundwater pathways were incorporated into conceptual site models describing contaminant transport from industrial operations to downstream water supplies. Historical drinking water concentrations were reconstructed using environmental monitoring records, mass-balance calculations, and published hydrogeologic information to estimate long-term exposure where direct historical measurements were unavailable. Integrating hydrogeology with atmospheric transport provided a comprehensive evaluation of both air and water exposure pathways.
Environmental chemistry analyses incorporated published research describing PFAS adsorption, groundwater mobility, soil interactions, particle-size distributions, atmospheric deposition, and environmental persistence. Investigators evaluated how differences in molecular structure among legacy PFAS compounds and newer fluorinated replacement chemicals influenced contaminant transport through soils, groundwater, and surface water. Published laboratory studies describing PFAS adsorption to mineral surfaces, together with particle-size distributions used in air dispersion modeling, were incorporated into environmental fate and transport evaluations to improve estimates of long-term environmental migration and exposure.
Finally, modeled air concentrations, reconstructed drinking water concentrations, environmental chemistry, hydrogeologic analyses, and published toxicological information were integrated into a comprehensive human health risk assessment using accepted U.S. Environmental Protection Agency methodologies. Investigators evaluated inhalation and drinking water exposure pathways, reconstructed historical contaminant concentrations, and compared estimated exposures with current toxicological guidance and peer-reviewed scientific literature. By integrating atmospheric modeling, hydrogeology, environmental chemistry, source attribution, exposure science, and risk assessment, the investigation developed a scientifically rigorous environmental forensic framework suitable for environmental consulting, regulatory investigations, remediation planning, and expert witness evaluations involving historical PFAS contamination.
Results
The environmental forensic investigation demonstrated that historical fluorochemical manufacturing operations represented a long-term source of PFAS releases capable of affecting multiple environmental media through interconnected atmospheric and hydrologic pathways. Historical manufacturing information, engineering records, source-term reconstruction, environmental monitoring data, air dispersion modeling, and hydrogeologic analyses collectively indicated that PFAS released during industrial operations migrated through both the atmosphere and regional water resources over extended periods. Rather than identifying a single dominant exposure pathway, the investigation found that airborne emissions, atmospheric deposition, groundwater migration, surface water transport, and drinking water contamination each contributed to the overall environmental distribution of PFAS. Integrating these pathways into a unified conceptual site model substantially strengthened source attribution by demonstrating consistency among multiple independent scientific datasets.
Atmospheric dispersion modeling demonstrated that historical PFAS emissions were capable of transporting contaminants beyond facility boundaries under representative meteorological conditions. Using reconstructed emission source terms and EPA-approved AERMOD modeling techniques, investigators estimated historical airborne concentrations and atmospheric deposition across surrounding areas. Sensitivity analyses further demonstrated that modeled concentrations remained consistent under a range of reasonable source-term assumptions, increasing confidence in the overall exposure reconstruction. The modeling also highlighted the importance of particle size, atmospheric stability, and meteorological variability in determining both airborne concentrations and long-term deposition patterns. These engineering evaluations provided an independent line of evidence supporting historical airborne transport of PFAS.
Hydrogeologic evaluation demonstrated that PFAS released during historical operations could migrate considerable distances through interconnected groundwater and surface water systems before reaching downstream drinking water supplies. Review of regional hydrogeology, watershed characteristics, historical monitoring data, and reconstructed contaminant loading supported the conclusion that both groundwater flow and river transport contributed to long-term PFAS migration. Reconstruction of historical drinking water concentrations using mass-balance calculations and available monitoring information provided a scientifically defensible estimate of exposure during periods when direct analytical data were limited or unavailable. Combining hydrogeologic analyses with historical monitoring records strengthened the evaluation of long-term drinking water exposure while providing an independent line of evidence separate from atmospheric modeling.
Environmental chemistry evaluations further demonstrated that differences among PFAS compounds significantly influenced contaminant transport and environmental persistence. Legacy compounds such as PFOA exhibited long-term persistence and bioaccumulation potential, while certain fluorinated replacement compounds displayed greater mobility through soils and groundwater because of weaker adsorption to mineral surfaces and organic matter. Published laboratory studies reviewed during the investigation supported these observations and helped explain why different PFAS compounds exhibited distinct spatial distributions within groundwater, surface water, and drinking water systems. Incorporating compound-specific environmental behavior into conceptual site models improved interpretation of monitoring data and strengthened contaminant source attribution.
The investigation also demonstrated the value of integrating multiple exposure pathways into a single human health risk assessment. Rather than evaluating inhalation or drinking water exposure independently, investigators reconstructed cumulative exposure by combining modeled air concentrations, reconstructed drinking water concentrations, environmental monitoring data, and published toxicological information using accepted U.S. Environmental Protection Agency methodologies. This integrated assessment provided a more comprehensive evaluation of potential long-term exposure than would have been achieved through analysis of either pathway alone. The approach also allowed investigators to compare modeled environmental concentrations with peer-reviewed toxicological literature and contemporary health-based guidance, providing an objective scientific framework for interpreting potential human health implications.
Collectively, historical reconstruction, environmental chemistry, atmospheric dispersion modeling, hydrogeologic evaluation, source-term development, environmental monitoring, and exposure assessment demonstrated the value of integrating multiple scientific disciplines into a unified environmental forensic investigation. Rather than relying on a single dataset or analytical method, investigators synthesized engineering analyses, environmental data, contaminant fate and transport, and toxicological science to objectively evaluate historical PFAS releases and long-term environmental exposure. This multidisciplinary methodology provides a technically rigorous framework for environmental consulting, regulatory investigations, remediation planning, environmental litigation, and expert witness evaluations involving historical PFAS contamination from industrial manufacturing operations.
Conclusions
This environmental forensic investigation demonstrates that evaluating historical PFAS contamination requires a comprehensive scientific framework that integrates environmental chemistry, engineering analysis, atmospheric science, hydrogeology, exposure assessment, and human health risk evaluation. Because PFAS are highly persistent, environmentally mobile, and capable of migrating through multiple environmental media, a scientifically defensible investigation cannot rely upon environmental sampling or historical records alone. Instead, reconstructing historical contaminant releases requires combining source-term development, air dispersion modeling, groundwater evaluation, drinking water assessment, contaminant fate and transport analysis, and multiple independent lines of scientific evidence to objectively characterize long-term environmental conditions.
The investigation further demonstrates the importance of evaluating multiple environmental exposure pathways rather than considering air emissions or drinking water contamination independently. Atmospheric transport, atmospheric deposition, groundwater migration, surface water movement, and drinking water exposure each contributed unique information regarding contaminant distribution and historical human exposure. Integrating these pathways into a unified conceptual site model provided a more complete understanding of contaminant behavior while strengthening source attribution through agreement among engineering analyses, environmental monitoring data, hydrogeologic evaluations, and environmental chemistry. This multidisciplinary approach substantially reduced uncertainty compared with relying upon any individual environmental dataset.
Another important finding was the value of incorporating compound-specific environmental chemistry into the forensic evaluation. Scientific literature demonstrates that legacy PFAS compounds and newer fluorinated alternatives exhibit substantially different adsorption characteristics, groundwater mobility, and environmental persistence. Accounting for these differences improved interpretation of environmental monitoring results, strengthened contaminant fate and transport analyses, and enhanced reconstruction of historical exposure conditions. Integrating laboratory research describing PFAS-soil interactions with engineering modeling and hydrogeologic analyses provided a scientifically robust basis for evaluating contaminant migration over extended periods of industrial operation.
The investigation also highlights the importance of combining historical reconstruction with quantitative environmental modeling. Source-term reconstruction, EPA-approved air dispersion modeling, hydrogeologic evaluation, mass-balance calculations, and environmental monitoring collectively provided complementary lines of scientific evidence supporting evaluation of historical PFAS releases. This integrated methodology allowed investigators to estimate historical environmental concentrations during periods where direct measurements were unavailable while maintaining consistency with established environmental engineering and risk assessment practices. Such approaches are increasingly important for evaluating contaminants characterized by long environmental persistence and extended operational histories.
More broadly, this investigation illustrates how modern environmental forensic investigations integrate environmental consulting, environmental chemistry, atmospheric dispersion modeling, hydrogeology, contaminant fate and transport, exposure science, human health risk assessment, and engineering analysis to objectively evaluate complex PFAS contamination. By combining historical operational information with scientific literature, environmental monitoring, engineering calculations, and quantitative risk assessment, investigators developed a technically rigorous framework suitable for environmental due diligence, regulatory investigations, remediation planning, environmental litigation, and expert witness testimony. As understanding of PFAS chemistry and environmental behavior continues to evolve, multidisciplinary environmental forensic investigations will remain essential for accurately reconstructing historical releases, evaluating long-term environmental exposure, and supporting science-based environmental decision-making.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in environmental exposure assessment, toxicology, air quality, environmental fate and transport, risk assessment, and environmental forensics. Through RoseyFields LLC, Dr. Rosenfeld provides scientific consulting, environmental forensic analysis, regulatory support, and expert witness services involving environmental contamination, human exposure, and public health. His technical oversight helped ensure that the methodologies, scientific interpretations, and conclusions presented in this case study are consistent with accepted scientific principles and current best practices.