By now it is difficult to escape the scientific conclusion that firefighting is associated with an increased risk for several types of cancer, but the specifics of how and why are still being researched. Several studies have documented known and suspected fireground carcinogens like polycyclic aromatic hydrocarbons (PAH), benzene, asbestos and styrene, which is not surprising, but attention is now being paid not only to what is present but how it is getting into firefighters’ bodies.
There is often a perception that, because firefighters wear bunker gear and SCBAs, the PPE provides 100% protection. Unfortunately, studies of firefighters post-incident have found evidence of carcinogens not only on the firefighters’ gear, but under it as well.
In a study by Hakan Wingfors and colleagues, it was found that naphthalene, the most volatile PAH, aggressively penetrated the protective layers of gear compared to PAHs known to be less volatile.
The next step of research focused on questions like which tasks and tactics put firefighters most at risk.
Studying exposure by fireground task
In the June Issue of the Journal of Exposure Science and Environmental Epidemiology, Dr. Kenneth Fent (NIOSH) and colleagues published an article that looked not only at the presence of PAHs and volatile organic compounds (VOCs) on the fireground, but also how exposures varied based on what the firefighter was doing and how the fire was being fought.
Their team recruited 41 firefighters to participate in a series of 12 live burns. They measured exhaled breath pre-fire, immediately after the fire was out, and 1 hour after the fire, given that peak levels of exhaled VOCs are typically back to normal after an hour post-exposure. Urine was collected before and 3 hours after the fires were put out (the peak PAH excretion time). Half of the interior attack scenarios also collected urine 6, 12 and 23 hours after the event to measure longer extraction values.
Firefighters were rotated through jobs: inside operations (fire attack and search/rescue), outside operations (command, pump operator, outside ventilation), and overhaul (this team also set up a RIT team or pulled backup lines during the fire). The fires took place over a series of days, with lags between to ensure findings were relevant to the role taken on that particular fire.
Every firefighter was outfitted with NFPA-compliant gear, including a double layer Nomex hood and SCBA. With the exception of instructing firefighters that they needed to be on air for interior attack, firefighters were asked to perform as they typically would on the fireground with regard to SCBA use and PPE.
Fire scenarios involved bedroom fires within a 111-m2 wood-frame residential structure furnished with modern furniture. Each fire was allowed to grow for about 4-5 minutes until the rooms reached flashover before the crews were deployed.
Not surprisingly, higher PAH biomarkers and benzene concentrations were present for firefighters who conducted fire attack and search operations compared to other job tasks, even with the use of PPE and SCBAs through the time when they reached the breath data collection area. It’s possible the firefighters inhaled smoke before donning their SCBA or after they removed their gear, but the findings also highlight the suggestion that chemical absorption occurs through the skin.
The second highest concentrations were those assigned to outside ventilation and overhaul tasks. Those who were in the command/pump positions did not show an increase in PAHs 3 hours post-fire but did show a 30% increase 6 hours after the fire.
Exhaled breath concentrations also found higher rates of benzene for command/pump operators than for those conducting overhaul. It was noted in the data collection that incident commanders and pump operators did not, as a rule, go on air during the fires. While not entering the structure seems like relatively safe/low-risk task, the study findings suggest that exposure occurs even for those not inside the fire. For some departments this is leading to practice changes where even pump operators stay on air during the event.
Studying attack type: transitional vs. interior
The scientists also compared exposures by type of attack (transitional versus interior). While previous research by the team suggested there might not be a difference in exposures, urine analysis from the current study indicated 20% lower levels of hydroxyflourenes, 36% lower levels of hydroxyphenanthrenes and 50% lower levels of 1-hydroxypyrene for transitional attacks compared to more typical interior attacks.
These results are particularly important because hydroxyphenanthrenes were the chemicals most increased for search and attack positions, and 1-hydroyxpyrene, in particular, represents the PAH thought to be one of the most toxic firefighters are exposed to on the fireground.
While the exact mechanisms are unknown, Fent and colleagues suggest these differences might be due to the environmental changes (e.g., more moisture but lower temperatures) that occur during a transitional attack which, in turn, may change the state of the byproducts making them harder to absorb. The authors suggest that, when possible given the fireground needs, transitional attacks may reduce PAH exposure for firefighters.