Environmental Forensic Investigation of Firefighter PFAS Exposure from AFFF and Cancer Risk Assessment
Project Overview
Per- and polyfluoroalkyl substances (PFAS) have emerged as one of the most significant environmental and public health issues of the past several decades because of their widespread use, environmental persistence, bioaccumulation, and growing association with numerous adverse health effects. Among the many historical applications of PFAS, aqueous film-forming foam (AFFF) has represented one of the largest and most concentrated occupational sources of exposure. For decades, firefighters have routinely handled AFFF during emergency response, vehicle fires, petrochemical incidents, airport operations, military training exercises, and live-fire training. While numerous epidemiological investigations have demonstrated elevated PFAS concentrations in firefighter blood serum, comparatively little research has quantified the cumulative cancer risks associated with the multiple exposure pathways encountered during firefighting activities. This project addressed that important scientific gap by integrating environmental chemistry, industrial hygiene, toxicology, exposure science, environmental forensics, and quantitative risk assessment into a comprehensive evaluation of firefighter PFAS exposure.
RoseyFields conducted one of the most comprehensive investigations to evaluate cumulative firefighter exposure to PFAS associated with AFFF use. Rather than focusing on a single pathway such as contaminated drinking water, the investigation evaluated multiple occupational exposure routes that firefighters routinely encounter throughout their careers. These included inhalation of airborne AFFF aerosols, incidental ingestion of foam droplets, hand-to-mouth transfer of PFAS residues from turnout gear, ingestion of PFAS-contaminated firehouse dust, dermal absorption during foam application, dermal contact with contaminated protective equipment, and exposure resulting from contaminated drinking water at firefighter training facilities. The investigation recognized that firefighter exposure is cumulative and that multiple relatively small exposure events may collectively contribute to significant lifetime PFAS body burdens.
A central objective of the project was to develop a scientifically rigorous methodology capable of translating environmental PFAS concentrations into quantitative estimates of cumulative cancer risk. Recent advances in toxicology, epidemiology, and regulatory science have resulted in the publication of cancer slope factors for key PFAS compounds, providing an opportunity to evaluate firefighter exposures using modern risk assessment methodologies. The investigation incorporated these recently developed toxicity values together with established U.S. Environmental Protection Agency exposure equations to quantify cancer risks associated with occupational PFAS exposure through multiple pathways. This integrated methodology represents an important advancement beyond earlier studies that documented elevated PFAS concentrations without translating those measurements into estimates of lifetime cancer risk.
An important component of this project involved conducting controlled experimental studies designed to characterize airborne exposure during realistic firefighting operations. Experimental evaluations were performed during simulated vehicle fire suppression using AFFF under carefully controlled conditions. Airborne sampling devices were positioned throughout the firefighter breathing zone to quantify the mass of foam particles potentially available for inhalation and incidental ingestion at varying distances from active foam application. These measurements provided one of the first experimentally derived datasets evaluating near-field airborne PFAS exposure generated during AFFF deployment and supplied quantitative information necessary for evaluating inhalation exposure that had previously been recognized but rarely measured directly.
Unlike many previous investigations that emphasized only environmental contamination of groundwater surrounding military bases or airports, this project recognized that firefighters experience repeated occupational exposures occurring directly at the point of foam application. During firefighting and training exercises, personnel frequently work within a few feet of concentrated foam streams while generating substantial quantities of airborne droplets capable of entering the respiratory tract or depositing on exposed skin, protective clothing, helmets, gloves, and equipment. The investigation therefore emphasized that occupational exposure during active firefighting may represent an important contributor to cumulative PFAS dose in addition to environmental exposure from contaminated drinking water.
The evaluation further incorporated a comprehensive review of firefighter work practices and occupational behaviors that influence exposure potential. Firefighters often perform physically demanding activities while repeatedly entering and exiting contaminated environments, handling equipment coated with foam residues, removing respiratory protection during overhaul operations, consuming food while wearing contaminated turnout gear, and returning contaminated protective equipment to fire stations where PFAS-containing residues may accumulate within settled dust. Evaluating these behaviors required integration of industrial hygiene principles with environmental exposure science to understand how repeated occupational activities contribute to cumulative PFAS exposure over an entire career.
From an environmental chemistry perspective, PFAS compounds present unique scientific challenges because they differ fundamentally from many conventional contaminants. Rather than degrading rapidly following environmental release, PFAS are characterized by exceptional chemical stability resulting from strong carbon-fluorine bonds that resist biological degradation, hydrolysis, photolysis, and most naturally occurring environmental transformation processes. Consequently, PFAS released during firefighting activities may persist within environmental media for decades while simultaneously accumulating within human tissues through repeated exposure. Understanding these persistence mechanisms is essential when evaluating firefighter exposure because cumulative dose depends not only upon individual firefighting events but also upon long-term occupational contact occurring over many years.
The project also integrated epidemiological evidence demonstrating elevated PFAS concentrations in firefighter blood serum compared with the general population. Numerous peer-reviewed investigations have consistently reported higher serum concentrations of PFOA, PFOS, and other PFAS compounds among firefighters, supporting the conclusion that occupational activities represent important exposure sources. The investigation synthesized these biomonitoring studies with experimental exposure measurements and quantitative risk assessment methods to better understand the relationship between occupational exposure, internal dose, and potential long-term health outcomes. Rather than relying exclusively upon biomonitoring, however, the project sought to identify and quantify the individual exposure pathways responsible for producing elevated PFAS body burdens.
Another distinguishing feature of this investigation was its multidisciplinary integration of environmental chemistry, industrial hygiene, occupational health, toxicology, exposure reconstruction, environmental forensics, aerosol science, and quantitative risk assessment. Environmental measurements alone cannot fully explain firefighter cancer risks without understanding how contaminants are released, transported through the environment, contact workers, enter the human body, and accumulate over time. Likewise, epidemiological observations require supporting exposure assessments capable of identifying the relative importance of inhalation, ingestion, dermal absorption, and secondary contamination pathways. By integrating these scientific disciplines, the investigation developed a comprehensive framework for evaluating firefighter PFAS exposure that extends well beyond traditional environmental site investigations or occupational monitoring programs.
Finally, this project illustrates the expanding role of environmental consulting in addressing emerging contaminants that affect both occupational and environmental health. PFAS investigations increasingly require expertise extending beyond groundwater contamination to include exposure science, industrial hygiene, toxicology, environmental fate and transport, regulatory science, environmental forensics, and quantitative human health risk assessment. By combining experimental exposure measurements with peer-reviewed toxicological data, regulatory guidance, environmental chemistry, and advanced exposure modeling, RoseyFields developed a scientifically robust methodology for evaluating cumulative firefighter PFAS exposure and associated cancer risks. The investigation demonstrates how multidisciplinary environmental science can be applied to complex occupational exposure scenarios involving persistent contaminants and multiple concurrent exposure pathways, providing technically defensible evaluations that support environmental investigations, occupational health assessments, litigation, and regulatory decision-making.
Chemicals of Concern
The primary chemicals evaluated during this investigation were per- and polyfluoroalkyl substances (PFAS), a large class of synthetic fluorinated compounds widely recognized for their exceptional chemical stability, resistance to environmental degradation, and tendency to bioaccumulate in humans and wildlife. Because of the extraordinary strength of the carbon-fluorine bond, PFAS are often referred to as “forever chemicals,” reflecting their persistence in environmental media and their ability to remain in the human body for years following exposure. These unique physicochemical properties have made PFAS valuable in numerous industrial and commercial applications, including aqueous film-forming foams (AFFF), while simultaneously creating significant long-term environmental and public health concerns.
Among the thousands of known PFAS compounds, this investigation focused primarily on perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) because these compounds have historically been major constituents of many AFFF formulations, have been extensively studied in occupational and environmental settings, and are supported by recently developed cancer slope factors that permit quantitative human health risk assessment. These compounds have received considerable scientific attention because of their persistence, widespread occurrence in environmental media, accumulation within blood serum, and associations with multiple adverse health outcomes identified through epidemiological and toxicological investigations.
Unlike many conventional environmental contaminants that degrade through biological activity, hydrolysis, photolysis, or natural weathering processes, PFAS remain chemically stable under most environmental conditions. Once released during firefighting operations or training exercises, these compounds may partition among air, surface water, groundwater, soil, sediments, dust, protective equipment, and building surfaces while remaining available for repeated human exposure. Their persistence substantially increases the importance of understanding cumulative occupational exposure because firefighters may encounter PFAS repeatedly over careers spanning several decades. Consequently, even relatively small individual exposures may contribute to measurable body burdens through repeated accumulation over time.
An important characteristic of PFAS is their ability to contaminate multiple environmental media simultaneously. During AFFF deployment, PFAS may become incorporated into airborne aerosols available for inhalation, deposit onto turnout gear and exposed skin, contaminate surrounding soils and paved surfaces, infiltrate surface water and groundwater, accumulate within firehouse dust, and remain on firefighting equipment following routine operations. The investigation therefore recognized that firefighter exposure cannot be adequately characterized by evaluating a single environmental medium. Instead, multiple interconnected exposure pathways were evaluated to determine the cumulative contribution of inhalation, incidental ingestion, dermal absorption, contaminated drinking water, contaminated dust, and contaminated protective equipment.
One of the distinguishing environmental chemistry characteristics of PFOA and PFOS is their tendency to bioaccumulate within blood serum. Unlike lipophilic contaminants that accumulate primarily within fatty tissues, many PFAS compounds bind to blood proteins, resulting in prolonged residence within the circulatory system. Numerous biomonitoring studies have consistently demonstrated elevated serum concentrations among firefighters relative to background populations, providing strong evidence that occupational activities represent important exposure sources. These biomonitoring observations formed an important scientific foundation for evaluating cumulative exposure while recognizing that blood concentrations alone do not identify the relative contribution of individual exposure pathways.
The toxicological significance of PFAS has increased substantially during the past decade as epidemiological and laboratory investigations have identified associations with numerous adverse health outcomes. Scientific literature has linked occupational and environmental exposure to selected PFAS compounds with kidney cancer, liver tumors, immune system effects, elevated cholesterol, thyroid dysfunction, developmental effects, reduced vaccine response, reproductive toxicity, and several additional chronic health conditions. Of particular importance to this investigation, recent epidemiological research has strengthened the evidence supporting an association between PFOA exposure and renal cell carcinoma, providing the scientific basis for development of quantitative cancer slope factors used throughout this project.
The investigation also evaluated the unique exposure characteristics associated with aqueous film-forming foam itself. AFFF is designed to rapidly suppress flammable liquid fires by producing a stable aqueous foam blanket that spreads across burning fuel surfaces. During foam application, however, substantial quantities of airborne droplets may be generated within the firefighter breathing zone. These aerosols provide opportunities for simultaneous inhalation and incidental ingestion while also depositing PFAS onto exposed skin, protective clothing, helmets, gloves, breathing apparatus, firefighting equipment, and surrounding surfaces. Consequently, firefighters may experience multiple concurrent exposure pathways during a single suppression event, followed by secondary exposures occurring during equipment handling, cleanup, and routine station activities.
Beyond PFOA and PFOS, the investigation recognized that firefighters may also encounter additional PFAS compounds commonly detected in occupational biomonitoring studies, including PFHxS, PFNA, PFDA, PFDoA, PFHpS, and related fluorinated substances. Although quantitative cancer risk calculations emphasized PFOA and PFOS because sufficient toxicological information is presently available, these additional compounds contribute to cumulative occupational PFAS exposure and further demonstrate the complex chemical mixtures encountered during firefighting operations. Their presence reinforces the importance of evaluating firefighter exposure from a cumulative rather than chemical-by-chemical perspective.
The project further considered contaminants that may occur concurrently with PFAS during firefighting operations. Firefighters responding to structural, vehicle, industrial, or fuel fires are simultaneously exposed to combustion by-products including particulate matter, volatile organic compounds, polycyclic aromatic hydrocarbons (PAHs), brominated and chlorinated dioxins and furans, brominated flame retardants, polychlorinated biphenyls (PCBs), and numerous additional hazardous substances generated during combustion. Previous biomonitoring investigations have documented elevated concentrations of several persistent organic pollutants in firefighter serum, illustrating that firefighter occupational exposure frequently involves complex chemical mixtures rather than isolated contaminants. Although the primary emphasis of this project remained PFAS associated with AFFF, these concurrent exposures provide important context for evaluating the cumulative occupational environment experienced by firefighters.
Overall, this investigation recognized PFAS as a uniquely challenging class of environmental contaminants whose persistence, mobility, bioaccumulation, and toxicological significance require a multidisciplinary scientific approach. By integrating environmental chemistry, industrial hygiene, toxicology, exposure assessment, biomonitoring, environmental fate and transport, occupational health, and quantitative risk assessment, the project developed a comprehensive framework for evaluating firefighter exposure to PFAS across multiple environmental media and exposure pathways. This approach reflects the current scientific understanding that cumulative occupational exposure—not a single isolated event—provides the most meaningful basis for evaluating long-term health risks associated with PFAS-containing firefighting foams.
Methods
This investigation employed a multidisciplinary methodology integrating environmental chemistry, industrial hygiene, toxicology, occupational exposure assessment, environmental forensics, experimental exposure characterization, aerosol science, biomonitoring, regulatory science, and quantitative cancer risk assessment to evaluate cumulative firefighter exposure to PFAS associated with the use of aqueous film-forming foam (AFFF). Rather than evaluating a single environmental medium or exposure pathway, the investigation reconstructed the complete occupational exposure scenario encountered during firefighting and training activities by integrating experimental measurements, published toxicological data, peer-reviewed epidemiological studies, environmental chemistry, and established human health risk assessment methodologies.
A primary component of the investigation involved identifying and evaluating the multiple exposure pathways through which firefighters encounter PFAS during routine emergency response and fire training operations. The assessment considered inhalation of airborne AFFF aerosols, incidental ingestion of foam droplets, ingestion of contaminated drinking water, hand-to-mouth transfer of PFAS residues from turnout gear and firefighting equipment, incidental ingestion of contaminated firehouse dust, dermal absorption during foam application, and dermal exposure resulting from repeated contact with contaminated protective clothing. Rather than evaluating these pathways independently, cumulative lifetime exposure was assessed by integrating all pathways into a unified risk assessment framework.
One of the distinguishing features of this investigation was the incorporation of controlled experimental exposure measurements designed to characterize airborne PFAS exposure under realistic firefighting conditions. Experimental evaluations were performed during simulated vehicle fire suppression exercises using AFFF. Firefighters applied foam under controlled operating conditions while passive airborne sampling devices were positioned throughout the breathing zone at multiple distances from the foam application point. These samplers quantified the mass of airborne material potentially available for inhalation and incidental ingestion during active foam deployment. The experimental design provided one of the first quantitative datasets directly evaluating firefighter exposure to airborne AFFF aerosols during suppression activities.
Environmental chemistry principles were applied throughout the investigation to evaluate the behavior of PFAS following release from AFFF. Unlike many conventional environmental contaminants, PFAS remain chemically stable during firefighting operations and after environmental release. The investigation therefore evaluated the movement of PFAS among airborne aerosols, deposited surface residues, contaminated turnout gear, firehouse dust, drinking water, and other environmental media that collectively contribute to cumulative occupational exposure. Consideration was also given to the persistence of PFAS residues on protective equipment and work surfaces, recognizing that repeated handling of contaminated materials may continue long after active firefighting operations have concluded.
The investigation also incorporated industrial hygiene principles to characterize firefighter work practices influencing exposure. Occupational activities including foam application, equipment handling, removal of respiratory protection, overhaul operations, decontamination practices, handling of turnout gear, equipment storage, and routine firehouse activities were evaluated to determine how contaminants generated during firefighting could subsequently be inhaled, ingested, or absorbed through the skin. Particular attention was devoted to secondary exposure pathways that may continue after emergency response activities have ended, including repeated contact with contaminated protective equipment and settled dust within fire stations.
Quantitative exposure calculations were performed using established U.S. Environmental Protection Agency human health risk assessment methodologies. Exposure equations incorporated contaminant concentrations, inhalation rates, ingestion rates, exposure duration, exposure frequency, body weight, dermal absorption parameters, and other standard exposure variables used throughout environmental risk assessment. These calculations were combined with recently published cancer slope factors for PFOA and PFOS to estimate cumulative excess lifetime cancer risk associated with firefighter exposure. By applying standardized regulatory equations to experimentally measured and literature-derived exposure concentrations, the investigation developed a transparent and reproducible methodology for estimating occupational cancer risk.
The investigation further incorporated an extensive review of peer-reviewed epidemiological literature evaluating PFAS concentrations in firefighter blood serum. Biomonitoring studies comparing firefighters with background populations were reviewed to determine whether occupational exposure resulted in elevated internal PFAS concentrations. These published serum data provided an independent line of evidence supporting the exposure assessment while also allowing comparison between predicted exposure pathways and observed biological accumulation. Rather than relying exclusively upon blood serum measurements, however, the investigation integrated biomonitoring with experimental exposure characterization to better understand the environmental sources contributing to elevated firefighter PFAS concentrations.
Another important component of the methodology involved evaluating toxicological and regulatory guidance published by the U.S. Environmental Protection Agency (EPA), California Office of Environmental Health Hazard Assessment (CalEPA), National Institutes of Health (NIH), National Cancer Institute (NCI), and numerous peer-reviewed scientific publications. These resources provided the toxicological basis for selecting cancer endpoints, identifying appropriate toxicity values, interpreting epidemiological findings, and developing scientifically defensible quantitative risk estimates. Particular emphasis was placed on recently published cancer slope factors and epidemiological evidence supporting associations between PFOA exposure and renal cell carcinoma as well as PFOS exposure and liver-related tumors.
The investigation also evaluated occupational behaviors influencing respiratory protection effectiveness. Published studies examining firefighter respirator use, self-contained breathing apparatus (SCBA) removal practices, fireground monitoring, and overhaul operations were reviewed to better understand realistic occupational exposure conditions. These evaluations recognized that firefighters do not continuously wear respiratory protection throughout all phases of emergency response and that removal of respiratory protection during certain activities may increase opportunities for inhalation exposure to airborne contaminants generated during firefighting operations.
Finally, the project employed a comprehensive weight-of-evidence methodology integrating experimental exposure measurements, environmental chemistry, industrial hygiene, biomonitoring, toxicology, epidemiology, quantitative risk assessment, regulatory guidance, and environmental forensics. Rather than relying upon any single study or dataset, multiple independent scientific disciplines were synthesized to reconstruct firefighter exposure, identify dominant exposure pathways, quantify cumulative cancer risk, and evaluate the contribution of repeated occupational exposures over an entire firefighting career. This multidisciplinary approach provides a technically rigorous framework for evaluating PFAS exposure that is applicable to occupational investigations, environmental litigation, firefighter health assessments, regulatory evaluations, and future scientific research involving emerging contaminants.
Results
The investigation demonstrated that firefighters are exposed to PFAS through multiple simultaneous occupational pathways rather than a single dominant source, and that cumulative lifetime exposure is best understood by evaluating all relevant routes together. By integrating experimental measurements, environmental chemistry, biomonitoring data, toxicology, and quantitative cancer risk assessment, the study demonstrated that inhalation, incidental ingestion, dermal contact, contaminated drinking water, contaminated turnout gear, and firehouse dust each contribute to cumulative PFAS body burden. The findings indicate that firefighter exposure should be viewed as a continuous occupational process occurring throughout training, emergency response, equipment handling, and routine station activities rather than being limited solely to active fire suppression.
One of the most significant findings of the investigation was the successful experimental characterization of airborne PFAS exposure during realistic AFFF application. Controlled field testing demonstrated that airborne foam droplets capable of being inhaled or incidentally ingested were present throughout the firefighter breathing zone during foam deployment. Passive sampling conducted at multiple distances from the point of application documented measurable exposure potential extending beyond the immediate nozzle position, confirming that firefighters operating near active foam streams may inhale PFAS-containing aerosols during suppression activities. These findings provide experimental support for inhalation as an important occupational exposure pathway that has historically received substantially less attention than contaminated drinking water or biomonitoring studies.
The investigation further demonstrated that measurable cancer risks were associated with repeated occupational exposure even during relatively short-duration firefighting activities. Quantitative risk calculations indicated that individual exposure events may appear modest when evaluated independently; however, repeated exposures accumulated over years or decades of firefighting may collectively contribute to substantially greater lifetime cancer risks. The study therefore emphasized that cumulative occupational dose, rather than any single firefighting event, provides the most scientifically meaningful basis for evaluating firefighter health risks associated with PFAS-containing foams.
Another important finding involved the relative importance of multiple exposure pathways. While contaminated drinking water has received considerable public attention, the investigation demonstrated that firefighters may receive significant occupational exposure directly during AFFF deployment through inhalation, incidental ingestion, and repeated contact with contaminated turnout gear and equipment. Hand-to-mouth transfer of PFAS residues deposited on gloves, protective clothing, and firefighting equipment also represented an important contributor to cumulative exposure. These findings illustrate that occupational activities occurring during and immediately following emergency response may substantially influence total PFAS body burden independent of environmental contamination of drinking water.
Review of published biomonitoring studies also demonstrated that firefighters consistently exhibit elevated PFAS concentrations in blood serum compared with background populations. These independent epidemiological observations support the conclusion that occupational activities represent an important source of PFAS exposure. By integrating biomonitoring data with experimental exposure measurements, the investigation established a coherent scientific framework linking environmental release, occupational exposure pathways, internal dose, and long-term health risk. Rather than relying exclusively upon serum concentrations, the study identified the environmental mechanisms responsible for producing elevated firefighter PFAS body burdens.
The investigation also demonstrated that occupational behaviors significantly influence exposure potential. Published studies reviewed during the investigation documented that firefighters do not consistently wear respiratory protection throughout all phases of emergency response and that respiratory protection is frequently removed during overhaul operations or after active fire suppression. These observations indicate that inhalation exposure may continue after visible flames have been extinguished and reinforce the importance of considering realistic occupational practices when evaluating cumulative firefighter exposure. Similarly, repeated handling of contaminated turnout gear, helmets, gloves, hoses, and other equipment may extend exposure well beyond active firefighting operations.
From an environmental chemistry perspective, the investigation confirmed that PFAS persistence substantially increases cumulative occupational exposure potential. Because PFAS resist degradation and remain chemically stable in environmental media, contaminants deposited onto protective equipment, station surfaces, firehouse dust, and surrounding environmental media may remain available for repeated human contact long after foam application has ceased. This persistence distinguishes PFAS from many conventional contaminants and emphasizes the importance of evaluating chronic occupational exposure resulting from repeated handling of contaminated materials rather than focusing exclusively on acute exposure during individual firefighting events.
The investigation further demonstrated the importance of applying modern toxicological methods to occupational exposure assessment. By incorporating recently developed cancer slope factors together with established regulatory risk assessment equations, the study translated environmental exposure measurements into quantitative estimates of lifetime cancer risk. This represents a significant advancement over earlier investigations that documented elevated PFAS concentrations without providing estimates of associated health risks. Integrating contemporary toxicological information with experimentally measured exposure data provides a scientifically robust framework for evaluating firefighter cancer risk associated with PFAS-containing firefighting foams.
Finally, the investigation demonstrated the value of a multidisciplinary weight-of-evidence approach. Experimental exposure measurements, environmental chemistry, industrial hygiene, occupational epidemiology, biomonitoring, toxicology, quantitative risk assessment, and environmental forensics all independently supported the conclusion that firefighter PFAS exposure results from multiple concurrent occupational pathways. Collectively, these independent lines of evidence provide a technically defensible scientific foundation for evaluating firefighter exposure, assessing cumulative cancer risk, improving occupational health practices, and supporting environmental investigations involving AFFF and other PFAS-containing materials. This comprehensive methodology illustrates how modern environmental consulting can integrate laboratory science, field investigations, exposure reconstruction, and human health risk assessment to address complex occupational exposure questions involving persistent emerging contaminants.
Conclusions
This investigation demonstrates that evaluating firefighter exposure to per- and polyfluoroalkyl substances (PFAS) requires a comprehensive scientific approach that extends beyond traditional environmental investigations of contaminated drinking water or soil. Firefighters are routinely exposed to PFAS through multiple occupational activities, including foam application, equipment handling, contaminated turnout gear, firehouse dust, and repeated contact with PFAS-containing materials throughout emergency response and training operations. By integrating environmental chemistry, industrial hygiene, toxicology, exposure science, occupational health, and quantitative cancer risk assessment, this project developed a scientifically rigorous framework for evaluating cumulative occupational exposure resulting from multiple concurrent pathways.
One of the most important conclusions of this investigation is that occupational PFAS exposure is cumulative rather than episodic. While individual firefighting events may represent relatively short periods of exposure, firefighters often respond to hundreds or thousands of incidents during their careers. Repeated inhalation of airborne foam aerosols, incidental ingestion of PFAS-contaminated materials, dermal absorption, contact with contaminated turnout gear, and continued interaction with contaminated equipment collectively contribute to increasing body burdens over decades of service. Evaluating these pathways together provides a more realistic representation of firefighter exposure than examining any single pathway in isolation.
The investigation also demonstrates that experimental exposure measurements provide critical information that complements epidemiological and biomonitoring studies. Numerous investigations have documented elevated PFAS concentrations in firefighter blood serum, confirming that occupational exposure occurs. However, blood measurements alone do not identify the specific environmental pathways responsible for those elevated concentrations. By conducting controlled field experiments during realistic AFFF application scenarios, this project directly quantified airborne exposure potential within the firefighter breathing zone and established an important link between environmental release, occupational exposure, and cumulative human health risk.
Another significant conclusion is that inhalation exposure has likely been underestimated in previous firefighter risk assessments. Historically, considerable attention has focused on contaminated drinking water because of its importance as a community exposure pathway. This investigation demonstrates that firefighters may also experience direct occupational exposure while operating in close proximity to AFFF application, where airborne droplets capable of inhalation and incidental ingestion are generated during suppression activities. These findings support expanding future firefighter exposure assessments to include airborne PFAS generated during active firefighting, overhaul operations, and live-fire training exercises.
The project further illustrates the importance of integrating multiple scientific disciplines when evaluating emerging contaminants. Environmental chemistry explains the persistence and transport of PFAS following release. Industrial hygiene characterizes occupational activities that influence exposure. Aerosol science describes airborne transport within the firefighter breathing zone. Toxicology establishes dose-response relationships. Epidemiology documents elevated serum concentrations and disease associations. Quantitative risk assessment integrates these disciplines to estimate lifetime cancer risk. Environmental forensics reconstructs historical occupational exposures and identifies the dominant mechanisms contributing to cumulative dose. Together, these complementary disciplines provide a technically defensible scientific framework for evaluating firefighter exposure to persistent contaminants.
An additional conclusion of the investigation is that occupational work practices substantially influence long-term exposure potential. Firefighters frequently handle contaminated turnout gear, protective equipment, hoses, helmets, gloves, and other materials long after active suppression activities have concluded. PFAS persistence on protective equipment and within firehouse environments creates opportunities for repeated secondary exposure through dermal contact, incidental ingestion, and contaminated dust. Consequently, improving decontamination procedures, equipment handling protocols, respiratory protection practices, and station hygiene may substantially reduce cumulative occupational PFAS exposure throughout a firefighter’s career.
The investigation also highlights the importance of applying modern toxicological methodologies to environmental and occupational investigations. Recent development of cancer slope factors for PFOA and PFOS now permits quantitative estimation of lifetime cancer risks associated with occupational PFAS exposure. Integrating these toxicity values with experimentally derived exposure measurements represents an important advancement over earlier investigations that documented environmental contamination without estimating associated human health risks. This methodology provides environmental consultants, industrial hygienists, occupational health professionals, and regulatory agencies with a transparent and reproducible framework for evaluating firefighter cancer risk associated with PFAS-containing firefighting foams.
Beyond firefighter health, this project demonstrates RoseyFields’ broader expertise in addressing complex emerging contaminants through multidisciplinary environmental consulting. The same scientific framework developed for this investigation can be applied to occupational exposure assessments, environmental contamination investigations, regulatory evaluations, toxic tort litigation, military installations, airport firefighting operations, industrial facilities, and other settings where PFAS have been released into the environment. Combining experimental field measurements, environmental chemistry, industrial hygiene, exposure reconstruction, toxicology, environmental fate and transport, and quantitative risk assessment allows RoseyFields to provide scientifically rigorous evaluations of complex environmental and occupational exposure scenarios involving persistent contaminants.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental chemist, exposure scientist, industrial hygienist, and environmental forensic expert with more than twenty-five years of experience evaluating complex environmental contaminants and human exposure pathways. Dr. Rosenfeld has directed numerous investigations involving PFAS, drinking water contamination, occupational exposure, industrial emissions, environmental chemistry, contaminant fate and transport, quantitative risk assessment, and emerging contaminants. His work integrates environmental science, industrial hygiene, toxicology, exposure assessment, atmospheric transport, environmental forensics, and regulatory science to develop technically defensible evaluations that support environmental investigations, litigation, regulatory decision-making, and protection of human health.
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