Per- and Polyfluoroalkyl substances, or PFAS, are chemicals that contain one or more perfluoroalkyl moieties.[24][25] While they do not occur naturally, there are more than 3000 available on the global market.[26][27][28] The first PFAS, Teflon™, was synthesized by Plunket in 1938.[29] These materials are highly stable, have extremely low surface tensions, bioaccumulate in the environment, and are environmentally persistent.[30]
PFAS can be separated into polymers and non-polymers.[31] In a firefighting context, both the polymers and the non-polymers are of interest. Non-polymer PFAS, such as PFOA and PFOS, are of high interest as they are found in firefighting foams (fluorinated surfactants) and other environmental sources. PFAS polymers, like PTFE, are also of interest as moisture barriers within turnout gear certified against NPFA 1971 contain them. PFAS are also present in treated carpers, clothing, cosmetics, food preservatives, as well as in oil and water repellant products.
In recent years, firefighter, community, and regulatory concerns regarding the potential for long term health impacts arising from the use of AFFF has increased. Releases of fluorinated chemicals, including foams, into the environment have generated increased concern about the environmental fate and persistence of PFAS. During the recent past, a number of regulatory programs started to restrict the manufacturing approaches and use of PFAS.[32][33][34] Unfortunately, despite the research efforts, there remain many uncertainties about their chemistry and distribution in the environment.
REFERENCES
[24] Australia Department of Environment and Heritage Protection. 2016. Environmental management of firefighting foam policy: Explanatory notes.
[25] Organization for Economic Cooperation and Development. 2013. Synthesis paper on per and poly fluorinated chemicals. Environment, Health and Safety, Environment Directorate, OECD.
[26] Wang Z, DeWitt J, Higgins C, Cousins I. 2017. A never ending story of per and poly fluoroalkyl substances (PFASs). Environ. Sci. Technol. 51, 2508.
[27] Wang Z, Cousins I, Scheringer M, Buck R, Hungerbuhler K. 2014. Global emissions inventories for C4-C14 perfluoroalkylcarboxylic acid (PCFA) homologues from 1951 to 2030, part 1: production and emissions from quantifiable sources. Environ. Int. 70, 62.
[28] Wang Z, Cousins I, Scheringer M, Buck R, Hungerbuhler K. 2014. Global emissions inventories for C4-C14 perfluoroalkylcarboxylic acid (PCFA) homologues from 1951 to 2030, part 2: the remaining pieces of the puzzle and emissions from quantifiable sources. Environ.Int. 69, 166.
[29] Plunkett R. 1941. Tetrafluoroethylene polymers. United States Patent 2230654A.
[30] Franko, J. et al. 2012. Dermal Penetration Potential of Perfluorooctanoic Acid (PFOA) in Human and Mouse Skin, Journal of Toxicology and Environmental Health, Part A, 75(1): 50-62.
[31] Buck, et al. 2011. Perfluoroalkyl and Polyfluoroalkyl Substances in the Environment: Terminology, Classification, and Origins. Integrated Environmental Assessment and Management, Volume 7 (4): 513-541.
[32] United States Environmental Protection Agency. Risk Management for Per- and Polyfluoroalkyl Substances {PFASs) under TSCA. https://www.epa.gov/assessing-and-managing-chemicalsunder-tsca/risk-management-and-polyfluoroalkyl-substances-pfass. Accessed September 25, 2017.
[33] United States Environmental Protection Agency. 2014. Emerging contaminants perfluoroctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA).
[34] Stockholm concentration on persistent organic pollutants. PFOA, its salts and PFOA related compounds draft risk profile. http://chm.pops.int/TheConvention/P0PsReviewCommittee/Meetings/P0PRC11/POPRC11Fo11 owup/tabid/4723/Default.aspx Accessed December 4, 2019.
Studies have reported associations between PFAS concentrations and adverse health effects such as fetal development, alterations to lipid metabolism, and thyroid disease.[35][36][37] Barry reported a link to kidney and testicular cancer, and more recently the IARC classified PFOA as a Class 2B carcinogen, i.e. possibly carcinogenic to humans.[38][39] Further information about the toxic effects of perfluorochemicals has been published by de Witt and more recently by the Expert Health Panel for Per and Poly fluoroalkyl Substances.[24][40]
REFERENCES
[24] Australia Department of Environment and Heritage Protection. 2016. Environmental management of firefighting foam policy: Explanatory notes.
[35] ATSDR. 2015. Toxicological profile for Perfluoroalkyls. United States.
[36] Dewitt J. 2015. Toxicological Effects of Perfluoroalkyl and Polyfluoroalkyl Substances. Springer Press.
[37] Lau C. 2012. Perfluorinated compounds. Molecular, Clinical and Environmental Toxicology. 3, 47.
[38] Barry V, Winquist A, Steenland K. 2013. Perfluorooctanoic acid (PFOA) exposures and incident cancers among adults living near a chemical plant. Environ. Health Perspect. 121, 1313.
[39] IARC. 2014. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. The International Agency for Research on Cancer (IARC) reported PFOA is a possibly carcinogenic to humans (Class 2B). 117.
[40] Dewitt J. 2015. Toxicological Effects of Perfluoroalkyl and Polyfluoroalkyl Substances. Springer Press.
NIOSH demonstrated that PFOA would permeate the skin at a rate of 4.4 x 10-5 cm/hr under maximum potential exposure conditions including elevated temperatures and a liquid challenge level of 3000 µg/mL. [1]PFOA was measured in its fully ionized state to demonstrate its effect on the outermost layer of skin. [1] If you look closely at p. 59 you will see the following statement:
These experiments were performed at 37°C (98.6°F). [1] Horn’s team evaluated the thermal response to firefighting activities in residential structures and found that the highest mean skin temperatures observed during interior firefighting were 37.67 ± 0.76°C (measured at the neck, n=16) and during overhaul were 38.06 ± 0.46°C (measured at the neck, n=15). [2] Therefore, the Franko experiments and the inferences drawn therein are applicable in the context of firefighting.
Finally, the levels of chemical applied to the skin during the NIOSH study were higher than would be seen in the real world, providing yet another measure of safety. The NIOSH study used a continuous exposure at high concentrations for many hours which is not in line with the way in which protective clothing is worn. [1] Work performed at North Carolina State University demonstrated a maximum amount of polyfluorinated chemicals in turnout gear to be 0.017 µg/mL which is considerably lower than the lowest dose tested by the NIOSH team. [3] This again assumes that the entire amount able to be extracted from the gear is available for exposure, which is not likely and therefore errs on the side of safety. In addition, the Bundesinstitut für Risikobewertung (Germany’s Federal Institute for Risk Analysis) found that toxicological data indicate that the fluorinated polymers are of little dermatological relevance because of the rigid binding of the fibers and because of the high molecular weight. [4] Therefore, in addition to the toxicological data being relevant to firefighting, it is also likely overestimated for dermal exposure considerations, erring on the side of safety.
Evidence from the US and Germany demonstrated that PFAS materials are of limited concern via dermal exposure. [1] [4] Much work has been performed providing an overview of the many ways in which people are exposed to PFAS chemicals. [21] [22]The work by NIOSH clearly demonstrated that the risk of exposure to PFAS chemicals via the skin was very low, even at levels that far exceed that found operationally and at temperature profiles closely matching that of firefighters’ skin during suppression and overhaul activities. [1] [2] Food ingestion was demonstrated to be the major contributor to total daily PFOA and PFOS intakes on individuals accounting for 99% of the total intake. [22] PFOA and PFOS intakes corresponded to less than 1% of the tolerable daily intake in another study. [23] If ingestion accounts for 99% of the intake and other forms of intake including inhalation are more likely than dermal exposure, then a reasonable assumption would be that less than 1%, if any, of the total exposure could be due to dermal exposure.
REFERENCES
[1] J. Franko, B. J. Meade, H. F. Frasch, A. M. Barbero and S. E. Anderson, "Dermal penetration potential of perfluorooctanoic acid (PFOA) in human and mouse skin," J. Tox. Environ. Health, Part A, vol. 75, p. 50, 2012.
[2] G. P. Horn, R. M. Kesler, S. Kerber, K. W. Fent, T. J. Schroeder, P. C. Fehling, B. Fernhall and D. L. Smith, "Thermal response to firefighting activities in residential structure fires: impact of job assignment and suppression tactic," Ergonomics, vol. 61, no. 3, pp. 404-419, 2018.
[3] C. P. Zane, "Hazard Assessment of Fluorochemicals Present on Firefighter Gear," 2020.
[4] BfR (Federal Institute of Risk Assessment), "Introduction to the problems surrounding garment textiles," BfR, 2012.
[22] D.H. Kim, J.H. Lee and J.E. Oh, "Assessment of individual-based perfluoroalkyl substances exposure by multiple human exposure sources," Journal of Hazardous Materials, vol. 365, pp. 26-33, 2019.
[23] S. Poothong, J. A. Padilla-Sanchez, E. Papdopoulou, G. Giovanoulis, C. Thomsen and L. S. Haug, "Hand Wipes: A Useful Tool for Assessing Human Exposure to Poly- and Perfluoroalkyl Substances (PFASs) through Hand-to-Mouth and Dermal Contacts," Environmental Science & Technology, vol. 53, no. 4, pp. 1985-1993, 2019.
PFAS exposure can occur via dermal exposure (liquids and solids), ingestion (hand-to-mouth transfer, indoor dusts, foods), and inhalation. These routes of exposure have been widely reported. There is a general agreement amongst the studies that dietary intake is the largest source of PFAS exposure rather than inhalation or dermal contact. [5] From a dermal perspective, we know that polyaromatic hydrocarbons (PAHs), phthalate diesters, and other semi-volatile materials penetrate the skin at varying rates. PAHs have half-lives on the skin of between 5 and 8.8 hours and must be removed as soon as feasible to minimize the amount that are able to make it through the skin. [6] For example, the IARC Group 1 human carcinogen benzo[a]pyrene is a combustion byproduct with a dermal half-life of 6.7 hours. [6] [7] This is one of the driving forces between the “shower within the hour” concept in firefighting today. [8] Combustion byproducts like benzo[a]pyrene and chrysene have skin permeability coefficients of 2 – 3 x 10-4 cm/h that will permeate through the skin far faster than PFOA which is estimated to have a skin permeability coefficient of 4.4 x 10-5 cm/h. [1] [9]
The firefighting environment produces a mix of particulate and gaseous combustion byproducts (e.g., carbon monoxide, nitrogen dioxide, sulfur dioxide, hydrogen cyanide, acid gases, volatile organic compounds, aldehydes, PAHs, phthalate diesters, etc.) that range widely in their water and oil solubility. In addition to the requirement for firefighters to shower as soon as feasible, the current durable water resistant (DWR) treatments on turnout gear fabrics provides oil repellency properties which minimize the movement of semivolatile compounds from the firefighting environment on and through the turnout gear, on and through the clothing underneath, and then on and through the skin. Field decontamination of turnout jackets resulted in an 85% reduction of PAH contamination while cleansing wipes on the neck were able to reduce PAH contamination on the skin by 54%. [10] Garment designs, materials, and finishes all provide a role in minimizing the total amount of these contaminants that a firefighter has available for a potential dermal exposure.
We need to ensure that there are no “unintended consequences” when introducing new durable water repellents that have the added benefit of providing excellent protection against the permeation of semi-volatile fireground threats. It is imperative that we evaluate the potential product solutions and ensure that the firefighter is receiving the best available protection utilizing the gear that is currently available and under development – this protection must balance thermal protection, with contamination resistance, comfort, ergonomics, and more [11].
Initial studies in Sweden [41] evaluated fluorinated, silicon-based, and hydrocarbon-based DWR finishes and found the following:
REFERENCES
[1] J. Franko, B. J. Meade, H. F. Frasch, A. M. Barbero and S. E. Anderson, "Dermal penetration potential of perfluorooctanoic acid (PFOA) in human and mouse skin," J. Tox. Environ. Health, Part A, vol. 75, p. 50, 2012.
[5] E. M. Sunderland, X. C. Hu, C. Dassuncao, A. K. Tokranov, C. C. Wagner and J. G. Allen, "A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects," Journal of Exposure Science & Environmental Epidemiology, vol. 29, pp. 131-147, 2019.
[6] D. A. Dankovic, C. W. Wright, R. C. Zangar and D. L. Springer, "Complex mixture effects on the dermal absorption of benzo[a]pyrene and other polycyclic aromatic hydrocarbons from mouse skin," Journal of Applied Toxicology, vol. 9, no. 4, pp. 239-244, 1989.
[7] IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, "IARC Mongraphs on the Evaluation of Carcinogenic Risks to Humans, No. 100F (Benzo[a]pyrene)," International Agency for Research on Cancer, Lyon, FR, 2012.
[8] C. M. Baxter, "Firefighter Exposure: Assessing and Minimizing Dermal Risk," Fire Engineering, vol. PPE Supplement, pp. 28-30, 2019.
[9] N. B. Hopf, P. Spring, N. Hirt-Burri, S. Jimenez, B. Sutter, D. Vernez and A. Berthet, "Polycylic aromatic hydrocarbons (PAHs) skin permeation rates change with simultaneous exposures to solar ultraviolet radiation (UV-S)," Toxicology Letters, vol. 287, pp. 122-130, 2018.
[41] S. Schellenberger, P. Gillgard, A. Stare, A. Hanning, O. Levenstam, and S. Roos. "Facing the rain after the phase out: Performance evaluation of alternative fluorinated and non-fluorinated durable water repellents for outdoor fabrics," Chemosphere, vol. 193, pp. 675-684, 2018.
While inhalation is not considered to be the most prolific route of exposure, many studies have demonstrated high levels of PFAS in dust in a variety of settings, including fire stations. [12] [13] [14] [15] [16] [17] [18]The recently released paper by Young and team provides a review of the PFAS in fire station dust. [17] The team concluded that “the study identified turnout gear as a potential source of PFAS inside fire stations, either due to the addition of PFAS in the gear itself or contamination of the gear from firefighting activities involving AFFF or consumer products in fires”. [17] The highest concentrations of PFAS in dust were found in the apparatus bay area and the gear locker area. [17] The apparatus bay floor and the gear locker area are also the areas where the highest level of exposure from firefighting boots and gloves would be, both PPE items that are known to be heavily contaminated on fire scenes. In addition, many other PFAS containing consumer products and fluorine containing cleaners are often in use in those areas. The PFAS levels in the living quarters of the fire stations tested were lower than those found in an evaluation of 48 fire stations in North America. [17] [19] It would be interesting to know if the samples were collected over the last year as the reduction in levels would be expected due to increased cleaning of surfaces during the pandemic as it might provide further insight into the need for more frequent cleaning of fire stations. Insufficient data yet exists to determine if the dust on turnout gear is due to fireground operations, the user of consumer products, clothing worn under turnout gear, or the degradation of the durable water resistance (DWR) treatment applied to the turnout gear, or any of the other many potential sources. [18] The specific PFAS moieties found need to be characterized to assist in identifying potential exposure routes and sources; preferably, this data will also be correlated with blood serum work like that underway through the Fire Fighter Cancer Cohort Study led by Dr. Jeff Burgess. [20] The recommendations put forth in this most recent paper are consistent with those recommendations that are in use today for exposure to combustion byproducts. [8] [18] [20]
REFERENCES
[8] C. M. Baxter, "Firefighter Exposure: Assessing and Minimizing Dermal Risk," Fire Engineering, vol. PPE Supplement, pp. 28-30, 2019.
[12] L. S. Haug, S. Huber, G. Becher and C. Thomsen, "Characterization of human exposure pathways to perfluorinated compounds - comparing exposure estimates with biomarkers of exposure," Environment International, vol. 37, pp. 687-693, 2011.
[13] R. Vestergren, I. T. Cousins, D. Trudel, M. Wormouth and M. Scheringer, "Estimating the contribution of precursor compounds in consumer exposure to PFOS and PFOA," Chemosphere, vol. 73, pp. 1617-1624, 2008.
[14] D. Trudel, L. Horowitz, M. Wormuth and M. Scheringer, "Estimating consumer exposure to PFOS and PFOA," Risk Analysis, vol. 28, pp. 251-269, 2008.
[15] R. Verstergren and I. T. Cousins, "Tracking the pathways of human exposure to perfluorocarboxylates," Environmental Science and Technology, vol. 43, pp. 5565-5575, 2009.
[16] Z. Tian, S.-K. Kim, M. Shoeib, J.-E. Oh and J.-E. Park, "Human exposure to per- and polyfluoroalkyl substances (PFASs) via house dust in Korea: implication to exposure pathway," Science of the Total Environment, vol. 553, pp. 266-275, 2016.
[17] A. S. Young, E. H. Sparer-Fine, H. M. Pickard, E. M. Sunderland, G. F. Peaslee and J. G. Allen, "Per- and polyfluoroalkyl substances (PFAS) and total fluorine in fire station dust," Journal of Exposure Science & Environmental Epidemiology, 2021.
[18] G. F. Peaslee, J. T. Wilkinson, S. R. McGuiness, T. Meghanne, N. Caterisano, S. Lee, A. Gonzalez, M. Roddy, S. Mills and K. Mitchell, "Another Pathway for Firefighter Exposure to Per- and Polyfluoroalkyl Substances: Firefighter Textiles," Environmental Science & Technology Letters, vol. 7, no. 8, pp. 594-599, 2020.
[19] S. M. Hall, S. Patton, M. Petreas, S. Zhang, A. L. Phillips, K. Hoffman and H. M. Stapleton, "Per- and polyfluoroalkyl substances in dust collected from residential homes and fire stations in North America," Environmental Science & Technology, vol. 54, pp. 14558-14567, 2020.
[20] University of Arizona, "Public Health Researchers Study Health Risks of Chemicals in Firefighter Foam," University of Arizona, 2021. [Online]. Available: https://www.publichealth.arizona.edu/news/2020/public-health-researchers-study-health-risk-chemicals-firefighter-foam. [Accessed 12 February 2021].
The community needs to continue to identify suitable materials, finishes, and the application methods to minimize the total amount of contaminants available for potential exposures to firefighters. In doing so, they must ensure that the products do not have unexpected properties that might impact performance, user health, and the environment. We need to continue to identify exposure sources, confirm exposure pathways, and develop measures to reduce the opportunities for exposure.
In the interim, to reduce exposure:
1. Wear your SCBA to minimize potential for inhalation exposure.
2. Wash skin immediately following any firefighting activities to minimize length of exposure. Remember, it takes up to 5 hours for any material to penetrate the dermal barrier.
3. Avoid foods known to contain large amounts of PFAS.
4. Do not bring contaminated gear into the fire station living quarters.
5. Avoid food packaging materials containing anti-stain or anti-grease repellant materials.
6. Avoid drinking water in areas that may have received high contamination due to AFFF run-off.
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