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Biomarker concentrations depended on the type of exercise, fuel package, and number of exercises per day.
The highest polycyclic aromatic hydrocarbon (PAH) exposures came from exercises involving oriented strand board as fuel.
Instructors’ PAH exposures may be higher from repeated training fires than responding to a single residential fire.
Skin contamination likely contributed to the biomarkers and should be minimized.
Training exercises should be selected that provide realistic training while limiting unnecessary exposures.
Training fires may constitute a major portion of some firefighters’ occupational exposures to smoke. However, the magnitude and composition of those exposures are not well understood and may vary by the type of training scenario and fuels.
To understand how structure fire training contributes to firefighters’ and instructors’ select chemical exposures, we conducted biological monitoring during exercises involving combustion of pallet and straw and oriented strand board (OSB) or the use of simulated smoke.
Urine was analyzed for metabolites of polycyclic aromatic hydrocarbons (PAHs) and breath was analyzed for volatile organic compounds (VOCs) including benzene.
Median concentrations of nearly all PAH metabolites in urine increased from pre-to 3-hr post-training for each scenario and were highest for OSB, followed by pallet and straw, and then simulated smoke. For instructors who supervised three trainings per day, median concentrations increased at each collection. A single day of OSB exercises led to a 30-fold increase in 1-hydroxypyrene for instructors, culminating in a median end-of-shift concentration 3.5-fold greater than median levels measured from firefighters in a previous controlled-residential fire study. Breath concentrations of benzene increased 2 to 7-fold immediately after the training exercises (with the exception of simulated smoke training). Exposures were highest for the OSB scenario and instructors accumulated PAHs with repeated daily exercises.
Dermal absorption likely contributed to the biological levels as the respiratory route was well protected. Training academies should consider exposure risks as well as instructional objectives when selecting training exercises.
Studies suggest that firefighters have increased risk for numerous types of cancer (Daniels et al., 2014, 2015; Glass et al., 2014; Pukkala et al., 2009; Tsai et al., 2015) and the International Agency for Research on Cancer (IARC) classified occupational exposure as a firefighter to be possibly carcinogenic to humans (Group 2B) (IARC, 2010). Firefighters’ exposure to chemical carcinogens during emergency fire responses may contribute to this increased risk (Daniels et al., 2015). Firefighters could also be exposed to chemical carcinogens during training fires. A recent study found a dose-response relationship between estimated exposures from training fires and cancer incidence at a fire training college in Australia (Glass et al., 2016). The high exposure group at the fire training college had increased risk of all cancers, testicular cancer, and melanoma compared to the general population.
Training fires may constitute a major portion of some firefighters’ occupational exposures to smoke. Many fire departments require routine live-fire training for their firefighters to maintain and build proficiencies and certifications. Training institutes often utilize firefighters and officers from surrounding communities, or employ dedicated personnel, to serve as instructors. Instructors often oversee 3–5 live instructional fires per day over a combined period of several weeks or even months. This could add up to as many or more live-fire exposures (albeit in a controlled setting) than what firefighters in busy fire departments experience.
Fuels used for fire training vary, but typically follow recommendations from the National Fire Protection Association (NFPA) standard NFPA 1403 Standard on Live Fire Training Evolutions in an attempt to control the risk involved with this type of training (NFPA, 2018). Such training scenarios will often include Class A materials such as pallet and straw, which tend to produce light grey smoke for obscuring visibility, as well as elevated temperatures. In recent years, many training institutes have also begun to use engineered wood products, such as oriented strand board (OSB) in addition to the pallet and straw to generate products of combustion that more closely replicate those encountered in residential structure fires (e.g., flames “rolling” across the ceiling, darker smoke and higher temperatures) (Horn et al., 2011). Some fire training institutes have begun using simulation technologies to produce training environments with no live fire. These systems typically use theatrical smoke or pepper fog for visual obscuration; they may also incorporate propane burners or an electronic display of fire glow. While simulated smoke exercises are assumed to be less hazardous than live-fire training, chemical hazards like insoluble aerosols and formaldehyde have been measured at concentrations above or just below occupational exposure limits during these exercises (NIOSH, 2013). The relative risk of these varying approaches has not been studied in an integrated manner to allow direct comparison between fire training environments.
A relatively small number of studies have investigated firefighters’ exposures during various types of live-fire training exercises, including those that used firewood, particle chipboard, plywood, OSB, diesel fuel, and heating oil as fuel sources (Feunekes et al., 1997; Kirk and Logan, 2015; Laitinen et al., 2010; Moen and Ovrebo, 1997; Stec et al., 2018). These studies generally show that firefighters can be exposed to single-ring and polycyclic aromatic hydrocarbons (PAHs) during training fires, leading to contamination of protective clothing and skin, as well as potential for biological uptake of benzene and pyrene. However, the accumulation of toxicants from repeated training exercises, especially among instructors, has not been fully characterized.
In a recent companion paper (Fent et al., In Press-a), we reported airborne contamination levels measured during firefighting exercises that used pallet and straw alone or in concert with OSB as fuel for the fires or used simulated smoke. Generally, the magnitude of contaminants measured in air were highest for the OSB exercises, followed by pallet and straw and then simulated smoke exercises. Although the participants wore self-contained breathing apparatus (SCBA) prior to entering the structure, as is typically the case for firefighters, some biological absorption could still take place via inhalation before donning respirators while outside of the structure. Dermal absorption may also be responsible for the biological absorption of toxicants. A number of firefighter exposure studies have documented absorption of toxicants despite the consistent use of SCBA, suggesting that the dermal route contributes substantially to the dose (Fent et al., 2014; Fent et al., In Press-b; Keir et al., 2017).