In 2007, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified working as a firefighter as possibly carcinogenic (Group 2B). However, recent meta-analyses show no increase in overall cancer risk except for a few cancer sites. The specific exposure of firefighters to hazardous materials during actual fire operations remains unclear. Hazardous substances can be absorbed through the respiratory tract, the digestive tract, and the skin.
Fire smoke is a mixture of many hundreds of chemical compounds, the composition of which varies greatly depending on the fire. Nevertheless, a major fraction of fire smoke is composed of polycyclic aromatic hydrocarbons (PAH), many of which are known carcinogens. In Germany, there is currently no knowledge as to whether and, if so, how much carcinogenic PAHs are absorbed by firefighters during firefighting operations on duty. For this reason, the DGUV sponsored this research project.
The study was carried out at the fire departments in the City of Hamburg and the Berlin, and included 217 firefighters from the professional and volunteer fire departments, as well as employees from the respiratory protection and hose repair units/facilities. First, personal baseline exposure to 1-hydroxypyrene (1-OHP), a metabolic product of the PAH pyrene, was measured in urine during the initial examination. There are already numerous studies available that have previously investigated exposure to 1-OHP in the non-occupationally exposed general population, as well as from occupationally exposed workers to PAHs.
After the fire event, participating responders were asked to provide a urine sample at three different time points. In addition, each participating responder was asked to complete a questionnaire at the end of the assignment, which required relevant details about the fire and the operation itself, such as the amount of smoke and the selected personal protective equipment. The average exposure, the variability of 1-OHP exposure, and the maximum exposure in predefined scenarios were evaluated. Further parameters, such as the activity, smoke exposure, duration and function during the fire mission, and the personal protective equipment used were also considered for the assessment. Two references were used to evaluate the measured 1-OHP biomonitoring values: the "Biological Exposure Index” (BEI®) of the US-American society ACGIH and the “Biological Work Substance Reference Value" (BAR) of the Senate Commission for the Examination of Harmful Work Substances (MAK Commission) of the German Research Foundation. No BAR currently exists for smokers; therefore, the 95th percentile of the general population was appropriately set as the assessment level for non-occupational exposure to PAHs for the smoking study participants from the 1998 Environmental Survey.
A total of 70 fire incidents were documented by responders during the study. Of these, 49 were with full time firefighters and 21 with volunteer firefighters. Seven workdays were monitored in the respiratory protection and hose repair facilities, with the results showing that 1-OHP concentrations were below the level of detection in employees of these areas. However, valid conclusions are not possible for this group due to the small number of participants. The 70 fire operations showed an increase in the mean 1-OHP concentration independent of creatinine adjustment compared with the initial examination. The number of values below the limit of quantitation decreased significantly in the post-fire samples. Concentrations that were significantly above the BEI®, the BAR, or the reference value for smokers also occurred sporadically. However, the majority of samples remained below these assessment values. Overall, the results suggest an intake of pyrene by fire use which is then metabolized to 1-OHP. These results are comparable to the three other biomonitoring studies in real fire operations conducted in Canada and US. Compared to industrial PAH-exposed workplaces, the concentration of 1-OHP in responders is generally much lower as a result of fire operations. In contrast to (professional) firefighters, the industrial workers are exposed to PAHs for more than eight hours each workday, and consequently are exposed to much higher concentrations during the course of their years employed than firefighters.
The concentrations determined in biomonitoring show that properly-fitted, functional protective clothing and the wearing of self-contained breathing apparatus as required prevents the absorption of PAHs or, in most cases, at least reduces absorption to such an extent that the assessment standards are met. However, there are individual situations in which the concentrations rise above the assessment standards. In these cases, the skin is shown to be the primary route of uptake, in particular for this study. Here, suitable preventive measures must be used to reduce exposure. A possible approach for such reduction is provided by the results of a co-project "Development of exposure prevention strategies in firefighting operations", which was published in 2020 in the form of DGUV Information 205-035 Hygiene and contamination prevention in the fire department and an accompanying explanatory film. Among the many topics addressed, both the publication and film contain concrete examples by which fire departments can introduce steps to avoid exposure.
In order to assess dermal exposure, a subgroup of 14 firefighters operating in two different fire scenarios (residential building fire and vehicle or other outdoor fire) and three employees in a hose and respiratory protection workshop wore a set of cotton undergarments consisting of a shirt, trousers, bonnet, gloves and socks under their operational clothing. Pieces of fabric were punched out of the worn undergarments, which served as carrier material, and analysed for PAHs. The idea was that detectable levels of PAHs would provide evidence of dermal exposure to PAHs due to a lack of adequate protection by the worn protective clothing.
The analytical measurements of the cotton undergarment however led to inconclusive results. For example, the low volatile, higher molecular weight PAHs (e.g., benzo[a]pyrene), which are considered to be carcinogenic were measured in only 12 of 270 analysable punched-out pieces of fabric and were present in low concentrations. In some cases, higher concentrations of PAHs were quantified, but mainly in conspicuously soiled areas of the cotton undergarment. However, here too, all concentrations were below the assessment benchmarks used as reference.
In this study, only one biomonitoring parameter, 1-OHP representing the medium volatile PAHs was investigated. Further investigations for other carcinogenic substances can be carried out using the urine samples stored in the IPA Biobank in order to obtain a comprehensive and more complete picture of the exposure situation of volunteer and full-time fire department members, since the substance matrix produced during a fire incident is very complex and individual. In particular, this includes metabolites of benzo[a]pyrene, benzene, naphthalene, chlorophenols and heavy metals. In addition, blood samples are still available to determine the dioxin contamination of the firefighters. In addition to the scenarios considered here, there is need for further research to determine the exposure situation in vegetation firefighting activities, the operation of wood-fired fire training facilities, as well as to fully evaluate the effectiveness and safe treatment of contaminated PPE and firefighting equipment.
-cross sectoral-Type of hazard:
work-related health hazards, dangerous substancesCatchwords:
working environment (load, hazards, exposure, risks), carcinogenic substances, exposureDescription, key words:
cancer risk, firefighter, fire event, fire smoke