Polycyclic Aromatic Hydrocarbon Contamination of Personal Protective Equipment of Brazilian Firefighters During Training Exercise

Abstract

This study presents the first quantification of polycyclic aromatic hydrocarbons (PAHs) deposited on the personal protective equipment (PPE) of Brazilian firefighters during a controlled training exercise. Twelve participants took part in the simulation, and samples were collected before and after exposure using wipes from gloves, chest, sleeves, and shoulders. Eight PAHs were detected and quantified by gas chromatography-mass spectrometry analysis (GC-MS), including naphthalene and phenanthrene, which showed the highest prevalence. Contamination increased significantly after training, even for exposures shorter as 3 min, with concentrations ranging from 0.007 to 1.066 µg mL^-1. A positive correlation between exposure time and PAH concentration was observed, with the highest levels found in the instructor exposed for 25 min. These findings corroborate international reports indicating that firefighting activities result in occupational exposure to PAHs and highlight the potential for contamination even under controlled conditions. Additionally, they underscore the relevance of monitoring and decontaminating PPE to prevent long-term exposure and cross-contamination.

Keywords:
firefighter exposure; occupational health; polycyclic aromatic hydrocarbons; surface contamination; workplace clothing hazard

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that are commonly detected in air, soil and water.¹ These compounds are generally formed by two or more aromatic rings, are characterized by various structures and varied toxicity.¹-³ Some PAHs have carcinogenic, mutagenic and teratogenic properties and have been related to the development of cancer.⁴,⁵ Given this, the US Environmental Protection Agency (US EPA) has classified 16 PAHs as priority pollutants of environmental concern. PAHs are characterized by hydrophobicity, moderate to low volatility, high adsorption tendency and moderate to low biodegradability, due to the molecular size of the compounds.⁵,⁶

PAHs enter the environment through different pathways, both by human activities and by natural processes. The incomplete combustion of synthetic compounds used in urban environments (such as various plastics) and fossil fuels is the most prominent source of PAHs in the environment. As a combustion reaction happens, the organic compounds present in the fuel are fragmented into free radicals that react through various pathways, producing the first aromatic ring. This ring can react with small molecules, such as acetylene, leading to the formation of other aromatic rings. A further reaction leads to the formation of more stable and higher molecular size PAHs.¹-³

Residential heating, coal gasification and liquefying plants, carbon black, coal-tar pitch, asphalt production, coke and aluminum production, catalytic cracking towers and related activities in petroleum refineries are the most common anthropogenic sources of PAHs. On the other hand, open burning, natural losses or seepage of petroleum or coal deposits and volcanic activities are the major natural sources of PAHs.¹

Firefighters are constantly called to combat fires, recently more often due to an increase in the number of fires resulting from extreme weather events. As an example, we can mention the strong and abundant fires that occurred in Brazil, Portugal and Canada in 2024, in addition to the more recent megafires in California.⁷-¹⁰ The firefighters at these events are frequently in contact with toxic and carcinogenic compounds, like PAHs, as fires are characterized by incomplete combustion reactions due to the lack of O₂ and the presence of lower temperatures than necessary to generate a complete combustion.¹¹-¹⁴ The International Agency for Research on Cancer (IARC) has classified this exposure to fire as “carcinogenic to humans” (Group 1) based on the collection of sufficient evidence for cancer in humans involved in firefighting.⁵,¹⁵

There are some studies that have dealt with the presence of PAHs in fabrics.¹⁶-²³ Stec et al.¹⁶ conducted the first study on the remnants of PAHs in personal protective equipment (PPE) of firefighters in the United Kingdom. To some extent, the work our group developed here is similar to that presented by Stec et al.¹⁶ In addition to methodological differences, however, our work is distinguished by being the first investigation conducted with Brazilian firefighters, addressing a context that had not been previously explored. This distinction is significant, considering the unique firefighting practices, climatic conditions, and potential PAH exposure scenarios in Brazil. Fent et al.¹⁷ evaluated the contamination of firefighters’ turnout gear after controlled residential firefighting, collecting swabs samples preand post-fire. They found that PAH contamination on PPE had increased with each use in a fire. Furthermore, Fent et al.¹⁸ investigated dermal absorption of PAHs and demonstrated that controlled firefighting conditions could result in significant PAH exposure, even under non-extreme situations, underscoring the importance of monitoring contamination levels under a variety of operational scenarios. Kirk and Logan¹⁹ studied the accumulation of PAHs on the PPE of firefighting instructors and highlighted that their exposure to PAHs during a live-fire training exercise was comparable to industrial occupational exposure over an entire shift. This comparison reinforces the relevance of evaluating PPE contamination in different contexts and geographic locations, such as the one investigated in this study.

Given this, the aim of this research was to evaluate the presence of PAHs on PPE of Brazilian firefighters following training exercise of fire combat.

Experimental

Chemicals and reagents

Polynuclear aromatic hydrocarbons analytical standard solution in acetonitrile were purchased from Sigma-Aldrich (Darmstadt, Germany). The solution contained: acenaphthene, acenaphthylene, anthracene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[ghi]perylene, benzo[a]pyrene, chrysene, dibenzo[a,h]anthracene, fluoranthene, fluorene, indeno[1,2,3-cd]pyrene, naphthalene, phenanthrene and pyrene. Acetonitrile, suitable for high-performance liquid chromatography (HPLC) with a purity of greater than 99.9%, was purchased from the companies Exodo (Sumaré, Brazil) and JT Baker (Phillipsburg, USA).

All glassware was washed with a neutral soap solution and rinsed with deionized water. Subsequently, rinses were carried out with the ethanol (Synth, Diadema, Brazil), ethyl acetate (Synth, Diadema, Brazil) and dichloromethane (Merk, Darmstadt, Germany) solvents, all of them HPLC grade.

Simulated fire scenario - sample generation

In this work, it was used a firefighting exercise of a Fire Brigade. For the training exercise, a simulated fire scenario was set up in a 40-foot shipping container (12 m × 2.35 m × 2.40 m), as shown in Figure S1 of the Supplementary Information (SI) section. The structure was divided into two parts: an observation chamber and a combustion chamber. Seven pieces of 10 mm plywood (2.20 × 1.10 m²) and two pine pallets (1.2 × 0.8 m²) were placed in the combustion chamber for fire ignition (Figure S1).

For the exercise, 10 firefighters and 2 instructors took part in the simulated fire. They were positioned in pairs in the observation chamber, side by side, in rows to carry out the fire attack (as can be seen in Figure S1). The main objective of the exercise was to train two-line branch techniques focused on cooling the smoke layer and suppressing hot spots of fire on command of the instructor. During the exercise, the positions were switched so that all firefighters could attack the fire as well as practice the branch techniques. As the objective was to train branch techniques, the instructors managed the scenario using the container openings (doors and chimney) to simulate similar conditions of smoke, heat and fire for all firefighters. The training exercise took place for 25 min.

All firefighters were required to wear their own personal protective equipment (without prior decontamination) according to Brazilian’s firefighting instruction manual,²⁴ as described in Figure S2 (SI section). All participants had given consent for their voluntary participation in this research before any procedures were undergone.

Sample collection of material accumulated on the PPE of firefighters

Samples of personal protective equipment from 12 firefighters were collected, using wet wipes, at 4 different points: shoulder (P1), chest (P2), sleeve (P3) and gloves (P4), as shown in Figure S2 (SI section) and performed following Wilkinson et al.²⁵

The samples were collected using isopropyl alcohol 70% volume wipes (3.5 × 3.0 cm²) at two different times: before-training exercise (pre-fire) and after-training exercise (post-fire). The before training exercise samples were collected in the left side of the PPE and the after-training exercise samples were collect in the right side.

Wipe sampling was done so that the integrity of the equipment was preserved, without the need to cut the material to extract the contaminants. After the collection, the swabs were placed in amber flasks and stored in a freezer (about -10 °C) until extraction procedure (done on the same day).

Extraction procedure

Each swab was placed into a test tube with 5 mL of acetonitrile sonicated in an ultrasonic bath for 20 min at room temperature. The extract was stored, and another 5 mL of acetonitrile was added and sonicated for more 20 min, in order to complete extraction of contaminants. After extraction, the extracts were placed in amber flasks and stored in a freezer. In addition, raw wipes and pure solvent were used to accesses blank curves. It is important to point out that no contaminant was observed neither in wipes nor in solvents.

Gas chromatography-mass spectrometry analysis (GC-MS)

The presence, and the respective concentration, of the 16 PAHs was determined by gas chromatograph (Agilent model 6890N, USA) coupled with mass spectrometer (Agilent model 5973 inert, USA). EPA method 8270E²⁶ was used, with a Rxi®-1ms stationary phase capillary column, with 100% methylpolysiloxane with dimensions of 25 m × 0.20 mm × 0.33 µm (RESTEK, France).

The injector temperature was maintained at 280 °C, in splitless mode, with 1.3 µL injection. The column was maintained with a constant flow (0.5 mL min^-1) of helium. The chromatographic oven programming began at an initial temperature of 40 °C, held for 4 min, then the heating rate was raised by 10 °C min^-1 up to 320 °C, remaining at this temperature for 2 min. The total time of analysis was 34 min. A solvent delay was used of 4.00 min and a gain factor of 20.

The GC-MS interface was maintained at 280 °C and the mass spectrometer was operated in scan mode in the range from 35 to 500 m/z, with HiSense.u. Mass spectra were analyzed using the Chemstation Data Analysis program and the NIST Search program (version 2.3). All the equipment used were under ISO 17025:2017,²⁷ which ensures reliability during working.

Quantification was conducted with external analytical curves, prepared using the analytical standard of 16 polynuclear aromatic hydrocarbons solution in acetonitrile (Sigma-Aldrich, Darmstadt, Germany). The analytical standard solution used was 10 μg for each PAH mL^-1. The 16 PAH in this standard were acenaphthene, acenaphthylene, anthracene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[ghi]perylene, benzo[a]pyrene, chrysene, dibenzo[a,h]anthracene, fluoranthene, fluorene, indeno[1,2,3-cd]pyrene, naphthalene, phenanthrene and pyrene.

Also, an analysis of variance (ANOVA) was performed, and all data are available in the SI section (Figures S4 to S11 and Tables S1 to S16). The F-test was performed, outliers were evaluated and the limit of detection (LOD) and limit of quantification (LOQ) for each of the 16 PAHs were obtained from the analytical curve.

Results and Discussion

The focus of this research was to evaluate the presence of PAHs on PPE of Brazilian firefighters used during a training activity. Evaluation of the exposure of Brazilian firefighters to the 16 PAH priority pollutants during training is important to assess the level of exposure of firefighters to PAHs and consequently the risk to their health. This is the first study on potential carcinogenic hazards in equipment used by a group of firefighters in Brazil, relating their occupational environment and the direct effect on their health. This discussion is even more necessary given the occasions of large and intense fires experienced by Brazil in recent years,⁷ which have required frequent action by firefighters and exposed them to more unhealthy routines.

Figure 1a shows the PAHs found in firefighters PPE preand post-fire clothing. In both situations (preand post fire), PAHs were found in different concentrations (Figure 1b). The following compounds were detected: naphthalene, phenanthrene, fluoranthene, pyrene, acenaphthene, acenaphthylene, anthracene and fluorene, (the former 4 compounds found in both preand post-fire conditions). These compounds are low molecular mass PAHs. Rapid burning, in addition to a relatively low temperature, favored their formation. Higher temperature and longer periods are expected to provide higher molecular mass compounds.²³

Figure 1
(a) Number of samples that presented PAHs preand post-fire and (b) concentration of each PAH per volume of acetonitrile (solvent) used in the extraction, summed across all sampling points (P1 + P2 + P3 + P4), under preand post-fire conditions.

Before the training exercise (pre-fire), the most common PAH was naphthalene, which was found in in 33% of the samples, in a concentration of 0.223 μg mL^-1 across all sampling points (P1 + P2 + P3 + P4) (Figure 1), that is, in 16 of a set of 48 collected samples (12 volunteers and 4 sampling areas per volunteer). The second one was phenanthrene, found in 12.5% of the samples, 0.261 μg mL^-1, followed by fluoranthene and pyrene (concentration of 0.003 and 0.097 μg mL^-1, respectively). The presence of PAHs in the pre-fire condition shows the persistence of these compounds on the suits and suggests that they have suffered long-term exposure and the possibility of cross-contamination via storage, transport and handling of PPE.

The post-fire samples presented all 8 PAHs, with a prevalence of the same 4 PAHs found pre-fire. However, the incidence of the compounds is much higher, with a higher concentration. Naphthalene, for example, was found in around 77% (1.202 μg mL^-1) of samples and phenanthrene in 52% (1.236 μg mL^-1).

Figure 2 shows PAHs found in different sampling areas. We can observe small differences between sampling areas and, as expected, notable differences between preand post-fire. In pre-fire samples, a small variety of PAHs (typically naphthalene and phenanthrene) were found in a small number of samples. In post-fire samples, as expected, this pattern changed and an increase the variety and amount of PAH was found.

Figure 2
Number of samples that presented each PAHs collected in points (a) P1 (shoulder), (b) P2 (chest), (c) P3 (sleeve) and (d) P4 (glove) preand post-fire.

Post-fire samples from the shoulder show a lower concentration of PAHs. In these samples there is a prevalence of naphthalene (in about 65% of samples), phenanthrene (in 45% of samples) and fluoranthene (in about 34% of samples). In samples collected from the chest, sleeves and gloves, all 8 PAHs can be seen (except acenaphthene in the sleeves). The most frequent PAH in the chest was phenanthrene, found in 50% of the samples, while naphthalene was the most common in gloves and sleeves (present in 63% of the samples).

An analysis of the firefighter’s clothing one by one (Figure 3), showed that the samples collected from firefighter No. 1 (FF1) are different from the others by both greater variety and quantity of deposited PAHs. FF1 was the instructor and remained inside the container throughout most of the training period. Thus, his equipment presented greater contamination when compared to that of the other volunteers. Prior to the exercise, only naphthalene was found in FF1 samples but after the firefighting exercise, all 8 PAHs were found in high concentration. Kirk and Logan¹⁹ studied the exposure of firefighting instructors to PAH and stated that cumulative exposures of firefighting instructors to toxic contaminants generated from live-fire training potentially far exceeded firefighter exposure arising from operational fires. Therefore, the health of instructors deserves special attention and close monitoring.

Figure 3
Concentration of PAH per volume of acetonitrile (solvent) used in the extraction (μg mL^-1) for each firefighter participant (PFF 1-PFF12) collected at points (a) P1 (shoulder), (b) P2 (chest), (c) P3 (sleeve) and (d) P4 (glove), preand post-fire.

Figure 4
PAHs concentration (ng cm^-2) found in P1, P2, P3, P4 and average of all 4 points, preand post-fire.

Two things merit our attention: the first one is that even firefighters (FF2 to FF3 and FF5 to FF12) who spent a very short time (about 2.5 min) inside the burning container showed an increase in PAHs deposited on their PPE when compared to pre-fire conditions. The second point is that the instructor (FF1) who spent about 25 min inside the container showed a very high incidence of PAHs. This scenario is closer to fighting a real fire and demonstrates that a high concentration of PAHs is generated and deposited on firefighters during their professional activity.

It is noteworthy that the FF4 gloves showed such a high concentration of all 8 PAHs. FF4 was the second instructor in the group, and he spent most of his time near the container door (further away from the fire) handling the water hose (touching a very contaminated surface). This specific activity explains why we did not find many PAHs on his suit, but a very high concentration on his gloves. This result corroborates the fact that PAHs deposited on PPE constitute a source of prolonged exposure and a source of cross-contamination. Further, these findings suggest that if PPE is not properly cleaned and decontaminated periodically, the contaminants that remain on the clothing may create a health issue for firefighters.

The results obtained in this study and in the literature are summarized in Table 1, revealing that the concentration of PAHs varied primarily due to differences in experimental methodologies. Although methodological variations are present, a general trend of PAH contamination across different contexts can be observed, with naphthalene and phenanthrene being the dominant compounds in both the previous study by Kirk and Logan¹⁹ and this study. This consistency highlights a common pattern in PAH formation and accumulation during firefighting activities, potentially linked to the combustion characteristics and materials involved in fire scenarios.

Table 1
Concentration limits for 16 PAHs determined by three works from the literature compared with this work

Compound	Concentration limit / (ng cm-2)
	Stec et al.16 a	Fent et al.18 b	Kirk and Logan19c	This researchd
Acenaphthene		0.46		3.03
Acenaphthylene			20	8.00
Anthracene		0.38	16.15	8.20
Benzo[a]anthracene	101.56	0.90	14.1
Benzo[a]pyrene	114.15	1.08	11.175
Benzo[b]fluoranthene	209.20	0.75	15
Benzo[ghi]perylene		0.82	10
Benzo[k]fluoranthene	177.08	0.39
Chrysene	69.88	0.70	10.33
Dibenzo[a,h]anthracene		1.91
Fluoranthene		8.71	37	3.11
Fluorene		0.26	14	4.90
Indeno[1,2,3-cd]pyrene	74.65	1.17	11
Naphthalene		0.78		7.92
Phenanthrene		2.58	45	12.73
Pyrene		2.18	40	7.39

• ^a
  Mean of PAHs concentration foin in PPE wipe samples, post-exposure, of four firefighters attending the training, collected from the gloves.
• ^b
  Mean of specific PAHs collected with wipes measured on hands of firefighters, post-fire.
• ^c
  Concentration (ng cm^-2) of polycyclic aromatic hydrocarbons on structural fire fighting ensembles of instructors during live fire training. Extraction of pieces of Nomex fabric attached to the ensemble.
• ^d
  Figure 4.

In this work, PAH had varied in the range of 3.03 12.73 ng cm^-2 (average of acenaphthene and phenanthrene, respectively, shown in Figure 4). These values were typically lower than those reported by Kirk and Logan¹⁹ and higher than those found by Fent et al.¹⁸ The lower concentrations observed by Fent et al.¹⁸ could be attributed to controlled experimental conditions, while the higher levels found by Kirk and Logan¹⁹ may reflect more intense or prolonged exposure during live fire training. The similarities in dominant compounds across studies, despite quantitative differences, suggest a consistent PAH formation mechanism. However, the greater number of PAHs identified by Fent et al.,¹⁸ albeit in lower concentrations, indicates that certain controlled conditions may promote broader but less intense PAH generation.

These findings emphasize that, despite methodological discrepancies, there is a recurring pattern of PAH contamination in firefighter PPE, with implications for risk assessment and protective equipment maintenance. The higher levels found in this study compared to Fent et al.¹⁸ highlight the need for region-specific monitoring strategies, particularly in Brazil, where this is the first investigation of its kind. Therefore, this work provides a valuable contribution to understanding PAH exposure in firefighters and reinforces the need for tailored protective measures under varying operational contexts.

Conclusions

The presence of the 16 main PAHs monitored by the US EPA was evaluated on Brazilian firefighters PPE, before and after training exercise, in a 12-participant study. Samples were collected from the turnout gear (chest, shoulder, sleeve) and gloves, preand post-training, by using wet wipes.

Ninety-six samples were analyzed by GC-MS to determine the presence of PAH, of which 64 were positive (67%). Of the 16 compounds monitored, 8 were found, mainly in post-fire samples, but also in pre-fire. These compounds are low molecular mass PAH, like naphthalene and pyrene, and their prevalence is due to the mild conditions of the fire (more drastic conditions of time and temperature and the burning of different materials would favor the generation of PAHs with higher molar mass). Naphthalene and phenanthrene were the most frequently found, presenting a concentration that ranged from 0.007 to 1.066 μg mL^-1.

An important issue revealed by the study is that even for very short time exposures (less than 3 min), there is a significant increase in the concentration of PAHs found. If the exposure time is longer, as observed for the clothing of the instructor in this study, this concentration increases significantly. Exposure for a period of approximately 25 min was sufficient to find all 8 PAHs generated in these fires in significant quantities. This study highlights the risk to which firefighters are exposed, even under relatively mild and controlled conditions, such as training. It also shows that PPE, if not properly cleaned and decontaminated, can be a source of prolonged exposure and cross-contamination long after the actual fire. Today, the Military Fire Department of the Federal District (CBMDF) still does not promote the habit of decontaminating firefighting suits immediately after use, and these suits are still stored in personal lockers (along with other objects) and washed mostly at home. Efforts must be made to reduce this risk of potential contamination in order to preserve the health of firefighters and also to reduce cross-contamination. These efforts become even more important when we consider the scenario of extreme weather events, which has led to a notable increase in the number of forest fires in a number of countries.

Supplementary Information

Supplementary data (details for firefighting experiments, analytical curve constructed using linear fit and residues and GC-MS ANOVA data for each analyte) are available free of charge at http://jbcs.sbq.org.br as a PDF file.

Acknowledgments

The authors would like to thank the Brazilian funding agencies (CAPES, CNPq and FAPDF) and the military fire brigade. A very special thanks for Dr Caroline Ribeiro. The English text of this paper has been revised by Sidney Pratt, Canadian, MAT (The Johns Hopkins University), RSAdip - TESL (Cambridge University).

Data Availability Statement

All data are available in the text.

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  » Link

Edited by

• Editor handled this article:
  César Ricardo Teixeira Tarley (Associate)

Publication Dates

• Publication in this collection
  04 July 2025
• Date of issue
  2025

History

• Received
  18 Feb 2025
• Published
  26 May 2025