Case Study 149: PFAS: Firefighter Cancer Risk Resulting From Exposure to PFOA

Firefighter Cancer Risk Resulting From Exposure to PFOA and PFOS in Aqueous Film-forming Foam During Simulated Car Fires

Paul E Rosenfeld, PhD¹, Aidan J Ryan, BS¹, Alexander E Martin, BS¹, Carolina Gomez Navarro, BS¹

¹RoseyFields LLC, 1317 12th Street, Suite 7, Santa Monica, CA 90401

Corresponding author

Paul E. Rosenfeld, PhD

Email: prosenfeld@swape.com

Phone: (310) 795-2335

Email addresses and ORCiDs:

PER: prosenfeld@swape.com, ORCiD 0000-0002-2483-3862

AJR: aidan@swape.com, ORCiD 0009-0009-6337-4468

AEM: alex@swape.com, ORCiD 0009-0005-4426-3026

CGN: carolina@swape.com, ORCiD 0009-0005-9668-9520

Abstract

This study quantified per-minute cancer risks from inhalation and incidental ingestion of PFOA and PFOS during firefighting activities involving aqueous film-forming foam (AFFF). On April 29–30, 2025, SWAPE conducted 11 controlled AFFF application trials at the Birmingham Fire Training Facility in Alabama. Firefighters applied AFFF to a totaled vehicle from approximately 5 feet using a 3% solution at 95 gallons per minute. To simulate breathing zone exposure, 219 passive cellulose adsorbers were deployed at a height of 62 inches at distances of 4, 5, 7.5, 10, 15, 20, and 25 feet from the application point. These samplers captured mass potentially available for inhalation and incidental ingestion during each minute of foam application. Cancer risk was calculated per minute of exposure using EPA equations, published concentrations of PFOA and PFOS in AFFF, and established cancer slope factors. Results indicated that each minute of exposure posed a measurable cancer risk at all distances. For PFOA, the per-minute excess lifetime cancer risk per million was: 58.1 (4 ft), 31.6 (5 ft), 12.2 (7.5 ft), 2.6 (10 ft), 0.65 (15 ft), 0.72 (20 ft), and 0.063 (25 ft). For PFOS, the corresponding risks were: 4.0, 2.2, 0.84, 0.18, 0.045, 0.049, and 0.004 per million, respectively. These findings demonstrate that even brief, repeated exposures to AFFF can cumulatively pose significant cancer risks, and that no distance within 25 feet fully eliminates per-minute risk without respiratory protection. Enhanced protective protocols are recommended during AFFF use in fire training and response.

Key Words

Firefighter, risk assessment, cancer risk, AFFF, PFAS

List of Abbreviations

ADDAverage Daily Potential Dose (ng/kg-day)

AFFFAqueous Film Forming Foam

ATAveraging time (period over which exposure is averaged – days)

BWBody Weight (kg)

C_mediumChemical Concentration in Medium

CSFCancer Slope Factor

ED Exposure Duration (years)

EFExposure Frequency (days/year)

IRIngestion Rate (liters-day)

NHANESNational Health and Nutrition Examination Survey

PFASPer- and Polyfluoroalkyl Substances

PFDAPerfluorodecanoic Acid

PFDoA Perfluorododecanoic Acid

PFHpSPerfluoroheptanesulfonic Acid

PFHxS Perfluorobutanesulfonic Acid

PFNAPerfluorononanoic Acid

PFOA Perfluorooctanoic Acid

PFOSPerfluorooctane Sulfonic Acid

PHGPublic Health Goal

RCCRenal Cell Carcinoma

USEPAUnited States Environmental Protection Agency

1 Introduction

Firefighters represent a unique occupational cohort frequently exposed to aqueous film-forming foam (AFFF) during training exercises and emergency response activities. Many have been handling AFFF for decades. Numerous studies have shown that firefighters exhibit elevated levels of per- and polyfluoroalkyl substances (PFAS) in their blood serum when compared to the general population (Rotander et al., 2015; Aylward et al., 2020; Dobraca et al., 2015; Khail et al., 2020; Graber et al., 2021; Shaw et al., 2013; Jin et al., 2011; Leary et al., 2020; Burgess et al. 2022).

Table 1: PFOA and PFOS in the Blood of Firefighters vs Control

*130 of these individuals later participated in the Aylward 2020 study.

** Shaw uses the 2003-2004 NHANES Data Set, and Graber (2021) uses both the 2015-2016 and the 2017-2018 NHANES Data Set.

In April 2024, the United States Environmental Protection Agency (USEPA) published cancer slope factors (CSFs) for two congeners of PFAS. The perfluorooctanoic acid (PFOA) CSF was set at 0.0293 per ng/kg-day. The endpoint of this slope factor is for renal cell carcinoma (RCC), a common type of kidney cancer that is approximately 90% of all kidney cancers (California Environmental Protection Agency (CalEPA) 2023). The perfluorooctane sulfonic acid (PFOS) CSF was set at 3.95 x 10-5 per ng/kg-day for combined hepatocellular adenomas and carcinomas. While many PFAS are believed to have carcinogenic properties, this study focuses on the increased cancer risks associated with PFOA and PFOS due to the recent development of their CSFs. To our knowledge, this is the first study to present a quantitative cancer risk assessment of AFFF-related exposure via inhalation and ingestion pathways using CSFs developed by USEPA.

This study assessed firefighter exposure to PFAS through inhalation and incidental ingestion and dermal adsorption of diluted AFFF during firefighting and training activities. However, several additional exposure pathways were not evaluated. These include ingestion of hand-to-mouth exposure from handling AFFF or PFAS-contaminated turnout gear; incidental ingestion of PFAS-contaminated dust within firehouses; and dermal absorption of PFAS from gear worn during and after firefighting activities, and ingestion contaminated drinking water at fire training facilities and fire stations

Manufacturers of AFFF have failed to provide adequate warnings on their MSDS documents for decades. Table 2 summarizes the evolution of respiratory protection guidance in MSDSs for AFFF products from 1999 to 2009. Early documents, such as those from 3M (1999) and Viking (2001), mentioned respirators but lacked clear criteria for when they were needed. Angus Fire (2002) stated that no protection was necessary during “normal” use, without defining what “normal” entailed and using irritation as a reason to initiate respirator use . Chemguard (2006) used similarly vague language, recommending an organic vapor respirator “if needed” but provided no thresholds or triggers. Ansul (2006) was similarly unclear. These approaches relied on subjective judgment, providing little practical value for workers needing to make real-time PPE decisions. By 2009, 3M issued an MSDS explicitly warning to avoid breathing vapors, mists, or sprays and recommending a full-face supplied-air respirator or air-purifying respirator with organic vapor cartridges and N95 filters (3M , 2009). This reflects a systemic failure in hazard communication, where manufacturers withheld known toxicity data from MSDSs, critically endangering firefighters who were misled by these omissions and routinely exposed to AFFF aerosols and vapors.

Table 2: Chronology of AFFF Material Data Safety Sheets and Adequacy of Respiratory Protection Warning

While SCBA is critical for protecting firefighters from inhalation hazards, multiple studies have shown that the physiological burden it imposes can make continuous use unsustainable during prolonged operations. The added weight, restricted airflow, and heat retention associated with SCBA contribute significantly to heat stress, dehydration, and fatigue, particularly in high-temperature environments (Smith et al., 2015; Horn et al., 2018). SCBA has also been shown to impair balance, increase the risk of falls, and exacerbate cardiovascular strain (Horn et al., 2015). In some situations, temporarily removing SCBA may be a necessary mitigation strategy to prevent heat-related illness or sudden cardiac events—the leading cause of firefighter line-of-duty deaths (Smith et al., 2015). Thus, even when SCBA use is recommended, there are operational scenarios where continued use may present greater immediate health risks than removal.

2.1 Blood Data

Several biomonitoring studies have shown that firefighters, particularly those who use aqueous film-forming foam (AFFF), consistently exhibit elevated concentrations of per- and polyfluoroalkyl substances (PFAS) in their blood compared to the general population. A Rotander et al. (2015) study analyzed serum samples from 149 Australian firefighters who trained with AFFF and found that PFOS and PFHxS levels were approximately 6–10 times and 10–15 times higher, respectively, than levels observed in the general populations of Australia and Canada. A subsequent, larger investigation by Aylward et al. (2020) examined 799 current and former Australian Airservices personnel, confirming widespread PFAS exposure. More than 90% of participants had detectable levels of PFOS, PFHxS, PFHpS, and other PFAS, and concentrations of PFOS, PFHxS, and PFHpS were above the 95th percentile of the general Australian population. PFAS concentrations were positively correlated with years of AFFF use, and individuals who began working prior to the 2005 phase-out of Lightwater AFFF had significantly higher PFAS levels than those hired after that year. Although overall PFAS concentrations declined between 2013 and 2019, the reduction was more pronounced among Airservices personnel than in the general population.

In the United States, at least five studies have compared PFAS blood levels in firefighters to those in the general population using data from the National Health and Nutrition Examination Survey (NHANES) as a reference. Dobraca et al. (2015) reported that Southern California firefighters had perfluorodecanoic acid (PFDeA) concentrations approximately three times higher than NHANES levels. Khail et al. (2020) found elevated PFHxS levels in Arizona firefighters, while Graber et al. (2021) reported that New Jersey volunteer firefighters exhibited higher concentrations of PFNA and PFDA, and that perfluorododecanoic acid (PFDoA) was present in nearly 50% of firefighter samples, compared to only 3% of NHANES participants. Shaw et al. (2013) identified twofold increases in PFOA and PFNA in San Francisco firefighters within 24 hours of responding to a fire.

Additional research in Ohio further supports these findings. Jin et al. (2011) observed significantly higher PFHxS levels, along with modest increases in PFOS and PFNA, in a cohort of 36 firefighters compared to industrial workers and unemployed controls. Leary et al. (2020) examined 47 airport and suburban firefighters and found that serum PFAS concentrations were 18% to 74% higher than NHANES values. Notably, airport firefighters—who were more likely to handle AFFF—had PFOS levels that were 62% higher than those of suburban firefighters and 29% higher than those of the general population.

Collectively, these studies demonstrate a consistent pattern of elevated PFAS exposure among firefighters, with serum concentrations of PFOS and PFOA ranging from 10% to 374% higher than those in control populations. These findings highlight the occupational risks associated with AFFF use and underscore the need for continued monitoring and protective measures for firefighter health.

The Table 1 summarizes blood serum concentrations of PFOA and PFOS in firefighters and control populations from relevant studies. As displayed below, firefighters experience blood serum concentrations of PFOA and PFOS 10% to 374% higher than control populations.

T

2.2 PFAS Concentrations in AFFF Foam

Three studies were identified that characterized the PFAS composition of various AFFF formulations (Weiner et al., 2013; Hoisaeter et al., 2019; Annunziato et al., 2020). Data from these studies are summarized in Table 3, which reports both the maximum and average concentrations of specific PFAS in diluted AFFF—typically consisting of 1–6% concentrate mixed with 94–99% water.

The maximum measured concentrations of PFOA and PFOS in diluted AFFF were 7.35 mg/L and 282.3 mg/L, respectively. The upper confidence limit concentrations were 2.68 mg/L for PFOA and 104.3 mg/L for PFOS. Average concentrations were 1.09 mg/L for PFOA and 57.4 mg/L for PFOS. Additional research on PFAS concentrations in AFFF formulations would be valuable to support future exposure and risk assessments.

Table 3: PFAS in AFFF and Concentration of PFAS in AFFF Diluted Foam Spray

*Assumed 1% dilution in cases where the percentage of dilution of AFFF was unclear

**All nondetects were assigned a value of 0

2.3 USEPA Slope Factor Development

This study employs the U.S. Environmental Protection Agency’s (USEPA) 2024 Human Health Toxicity Assessments (HHTAs) to estimate lifetime cancer risks associated with exposure to PFOA and PFOS via inhalation and ingestion pathways (USEPA, 2024a; USEPA, 2024b). Slope factors developed by the USEPA are critical for quantifying cancer risk in this study. They establish the relationship between internal PFAS exposure and the probability of developing cancer in specific target organs—primarily the kidney for PFOA and the liver for PFOS.

2.3.1 USEPA Method for Developing PFOA Dose Slope Factors

The USEPA utilized a study by Shearer et al. (2021) as the key reference for dose-response modeling and developing the 2024 intake CSF for RCC. The USEPA followed methodology described in the CalEPA 2021 and in the Public Health Goals for Arsenic in Drinking Water from OEHHA 2004. The USEPA used a blood serum CSF, which calculates the excess cancer risk from a ng/mL increase in serum PFOA, to calculate the external dose CSF for RCC (intake CSF). The intake CSF gives the increase in cancer risk per 1 ng/(kg-day) increase in dose. The resulting CSF is 0.0293 (ng/kg/day)⁻¹ (or 29,300 (mg/kg/day)⁻¹) and is used throughout this paper.

2.3.2 USEPA Method for Developing PFOS Dose Slope Factors

In April 2024, the USEPA also finalized the Human Health Toxicity Assessment for Perfluorooctane Sulfonic Acid (PFOS) and Related Salts in April 2024 (USEPA 2024b). In this assessment, the USEPA followed agency guidelines for risk assessment to develop a CSF. The agency evaluated epidemiological and animal studies of medium and high confidence, conducted benchmark dose modeling, and used pharmacokinetic modeling to develop candidate CSFs.

The USEPA did not select epidemiological studies for a variety of reasons, including lack of supporting studies, mixed evidence for the occurrence of the type of cancer, potential for selection bias, and a lack of analyses to develop a CSF. Therefore, the animal toxicological study, which was first published as an industry-sponsored report (Thomford 2002) and later in a journal as a peer-reviewed article (Butenhoff et al., 2012), was selected. The USEPA created four candidate CSFs based on this study and selected the CSF for hepatocellular adenomas and carcinomas in female rats. Liver cancers, including hepatocellular carcinoma, have also been connected to PFOS in epidemiological studies (Cao et al., 2022; Goodrich et al., 2022). The developed CSF (oral slope factor) was 39.5 (mg/kg/day)^-1 (or 3.95 x 10^-5 (ng/kg/day)^-1) for combined hepatocellular adenomas and carcinomas based upon Butenhoff et al. (2012) and Thomford (2002b).

3 Materials and Methodology

To estimate firefighter exposure to aqueous film-forming foam (AFFF) during simulated car fire suppression, 11 trials were conducted on April 29–30, 2025, at the Birmingham Fire Training Facility in Alabama. Each trial involved Birmingham Fire Department personnel spraying a totaled 2006 Volvo S40 sedan from a distance of 5 feet using a 3% foam solution applied with an Akron Brass Style 1763 Turbojet® nozzle (1.5″ NH), operating at 95 gallons per minute. Each application lasted approximately 3 to 5 minutes (range: 2:46–5:14).

3.1 Materials

Firefighter exposure was characterized using passive cellulose samplers (2-inch diameter, 0.5-inch thick discs; Celox Medical, NY) positioned at a height of 62 inches to represent the human breathing zone. Twenty-two tripods held samplers at distances of 4, 5, 7.5, 10, 15, 20, and 25 feet from the foam application point. Samplers were weighed before and after each trial using two calibrated Bonvoisin precision balances (500g x 0.001g), and average mass was used for analysis.

In order to understand the moisture content of the passive cellulose media, 21 additional samplers were given ID numbers and weighed using the same precision balances. They were then desiccated and weighed again. The change in mass was recorded and divided by the initial mass in order to determine the moisture content that was removed. On average, the desiccated cellulose media lost 33.41% of its mass after drying (SD: 2.064%; range: 28.99%-37.70%). Due to cellulosic media containing an estimated 33.41% moisture content, field blanks were used to account for potential evaporation of moisture, humidity changes, and other variables.

Passive sampling was chosen over active air sampling due to foam interference, which obstructed pumps and compromised measurement accuracy. Passive media—used in NIOSH and EPA-validated methods for contaminants such as formaldehyde and benzene—was determined to be the most practical and scientifically valid approach under dynamic field conditions (NIOSH 2003; OSHA 2005; USEPA, 2015). Passive samplers function without power, simplify sample collection, and are well suited for time-weighted average exposure estimation, particularly in emergency response settings where logistical constraints prevent the use of powered equipment.

To minimize firefighter exposure during testing, we used Baum’s Novacool Fire Extinguishing Foam (Lot #17-655, manufactured December 27, 2017) as a surrogate AFFF formulation, rather than legacy foams known to contain elevated levels of PFOA and PFOS. Cancer risks were estimated using PFOA and PFOS concentrations reported in the peer-reviewed literature for legacy AFFF formulations (see Table 1). This allowed for realistic historical risk modeling without exposing participants to hazardous PFAS compounds during the trials.

While passive samplers cannot differentiate between inhalation and incidental ingestion, their breathing-zone placement reflects actual exposure conditions in the absence of respiratory protection. For consistency with U.S. EPA methodology, exposure was modeled using ingestion equations; however, since PFOA and PFOS exert systemic effects regardless of exposure route, estimated cancer risks are considered equivalent across pathways.

Passive sampling has been extensively validated as a reliable method for occupational and environmental exposure assessment. Literature from Seethapathy et al. (2008), Górecki and Namieśnik (2002), and Fan et al. (2011) confirms its suitability in scenarios requiring time-weighted average exposure estimates, especially in field conditions lacking electricity or subject to physical obstructions like foam. The U.S. EPA (2022) also recognizes passive samplers as providing comparable accuracy to traditional active sampling methods.

3.2 Field Methodology

For each experiment, the time, weather, and wind direction were recorded, and 24 passive cellulose samplers were weighed using two precision balances. Balances were placed in a temporary indoor laboratory area, protected from wind and foam spraying. Following data collection of initial mass, 22 cellulose samplers were placed at varying sample locations and at a height of 62 inches. The grid displayed in Figure 2 below displays the location of the car and samplers. This grid contains 64 unique sampling locations, with 10 sampling locations at each distance from the vehicle, separated by 10° between each sampler.

Figure 2 -Sampler Placement

Figure 3 – Firefighter Spraying during an Experiment

In addition to the 22 cellulose samplers for each experiment, two field blank samplers were placed outside in a protected area with similar weather conditions to the testing area. For each experimental event, the firefighter placed the nozzle five feet from the vehicle and sprayed for three to five minutes, as seen in figure 3. Following each spray, the experimental samples and field blanks were immediately collected and weighed in the laboratory area.

3.2 Data Processing Methodology

Following data collection, the mean initial mass and mean final mass were calculated for each sample using the two independent balances. The change in mass (Δm) was determined by subtracting the average initial mass from the average final mass. To account for environmental influences such as evaporation and humidity, the mean Δm of the two corresponding field blanks for each trial was subtracted from each sample’s Δm, yielding a corrected mass change. Corrected Δm values were then normalized by the duration of each trial to calculate an absorption rate (g·min⁻¹) for each sample. Statistical analysis of absorption rates by distance from the centerpoint (the sprayed vehicle) is presented in Section 4.

3.3 Risk Analysis Methodology

For the purposes of this assessment, we assume that the cancer risk associated with exposure to PFOA and PFOS is determined by the absorbed dose, irrespective of whether the compounds are inhaled or ingested. Both chemicals are systemically acting toxicants that are efficiently absorbed through the gastrointestinal tract, and existing toxicokinetic data indicate that inhalation absorption is also high, particularly for vapor-phase or respirable aerosol exposures (Gustafsson et al., 2022). Consistent with EPA’s Regional Screening Level (RSL) guidance, which assumes 100% relative absorption for ingestion, we applied the oral cancer slope factors, typically associated with the ingestion of chemicals, for both compounds to estimate risk (USEPA, 2024d). At the time of this assessment, an inhalation cancer slope factor for PFOA or PFOS has not been developed by the USEPA. This approach is scientifically appropriate when evaluating systemically acting contaminants with high absorption across multiple exposure pathways.

Cancer risk estimations for inhalation and accidental ingestion of AFFF spray during firefighting activities were calculated using the USEPA CSFs and multiplying them by the Average Daily Potential Dose (ADD) (USEPA 1989). The ADD equation is presented below with default body weight and lifetimes from the USEPA Regional Screening Level User’s Guide (USEPA, 1989; USEPA, 2024d):

where:

4 RESULTS

The results of the analysis are presented in Table 4 and Figure 3 below. Passive sampling results demonstrate a strong inverse relationship between distance from the spray source and AFFF mass collected on the surrogate mouth samplers. The highest average exposure was observed at a distance of 4 feet (1.982 g/min), where the sampler was positioned directly in front of the firefighter and within the spray trajectory. In contrast, all other samplers were positioned behind the firefighter, outside the direct path of the nozzle. At 5 feet—the approximate position of the firefighter operating the nozzle—the average exposure was 1.077 g/min, reflecting significant potential for self-exposure during active application of foam.

Exposure levels declined sharply with increasing distance. At 7.5 and 10 feet, average values dropped to 0.436 g/min and 0.092 g/min, respectively. Beyond 10 feet, exposures were minimal: averages at 15, 20, and 25 feet were 0.024, 0.009, and 0.027 g/min, respectively. Upper 95% confidence limits at these distances remained below 0.04 g/min, indicating consistent low-level exposure outside the immediate spray zone.

Figure 3: Ingestion/Inhalation Rate (grams/minute) over Distance (feet) From Exposure to AFFF Application During a Simulated Car Fire by Distance

Table 4: Summary of AFFF Inhaled/Ingested Per Minute During Car Fire Simulation

The preliminary step in the risk assessment is presented in Table 5 showing that the cancer risk from the PFOA in AFFF ingestion is 15.6, 29.5 and 105.5 using the average, upper confidence level, and maximum PFOA concentration in AFFF. Furthermore, the cancer risk from PFOS ingestion is 1.11, 2.02 and 5.5 excess cancers using the average, upper confidence level, and maximum PFOS concentration in AFFF.

Table 5: Cancer Risk from Ingestion of AFFF Using EPA Slope Factors And PFOA and PFOS Concentrations Presented in Table 1

Table 6 presents the PFOA and PFOS cancer risk calculations for AFFF ingestion at various distances. At a spraying distance of 5 feet from the simulated car fire using the average, UCL, and maximum concentrations of PFOA (see Table 1), the risks were calculated to be 17, 32, and 113 in a million, respectively. For PFOS, the corresponding excess cancer risks were calculated to be 1.2, 2.2, and 5.9 in a million. These results apply only to the individuals spraying at 5 feet, although concentrations and risks were measured at distances of 4, 5, 7.5, 10, 15, 20, and 25 feet.

While the cancer risk dropped at a distance of 25 feet, it was not calculated to be zero, so this study has not calculated a safe distance away from the AFFF spray to show no exposure.

Table 6: Excess Cancers In A Million From Inhalation/Ingestion of PFOA and PFOS in AFFF During Simulated Car Fires by Distance

5 Discussion and Conclusions

This study’s findings must be viewed in light of the historical failure of manufacturers to provide adequate warnings about the inhalation hazards of AFFF exposure. MSDSs downplayed or omitted respiratory guidance, while firefighters were uninformed on the cancer risks associated with PFAS inhalation. In many cases, the physiological burden of wearing SCBA—particularly heat stress—made continuous use impossible, leaving firefighters vulnerable during training and response scenarios.

This study demonstrates that firefighters operating within 25 feet of AFFF spray zones may experience significantly elevated cancer risks from short-duration exposures to PFOA and PFOS. Passive cellulose samplers, positioned at mouth height to represent the human breathing zone, served as area source samplers to capture airborne foam droplets and vapors under realistic fire suppression conditions. This approach aligns with established passive sampling methodologies used by NIOSH and the U.S. EPA and offers a reliable proxy for assessing breathing zone exposures when active air sampling is not feasible.

Although the exposure model conservatively assumes complete ingestion or inhalation of foam contacting the mouth, this bounding assumption is consistent with EPA risk assessment practices and provides an upper-limit estimate of risk. Because PFOA and PFOS are systemically acting toxicants with high absorption via both inhalation and ingestion, the cancer risk is driven by total absorbed dose, regardless of exposure route. Accordingly, the modeled risks reflect realistic exposure scenarios for unprotected firefighters in training environments.

By incorporating both average and 95% upper confidence limit (UCL) concentrations of PFOA and PFOS in legacy AFFF formulations, the study offers a range of plausible cancer risk outcomes. The data reveal that while cancer risk decreases with distance from the foam source, it remains nonzero even at 25 feet. These findings provide a valuable screening-level assessment of firefighter exposure risk and underscore the need for enhanced respiratory protection, improved exposure tracking, and revised safety protocols during fire training and emergency response involving AFFF.

Statements and Declarations

Funding Sources

This research was supported by a grant from the Plaintiff’s Common Benefit Fund established in the Aqueous Film-Forming Foam (AFFF) Multidistrict Litigation (MDL No. 2873, U.S. District Court for the District of South Carolina). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Acknowledgements

The authors would like to thank the Birmingham Fire Department for providing access to their facilities.

Declaration of Competing Interests:

RoseyFields LLC, paid for the analysis and came up with the study design. Dr. Rosenfeld is a testifying expert in AFFF litigation.

Data Availability

The data that support the findings of this study are provided as supplementary information with further data available on request from the corresponding author, PER.

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