Evaluation of 7 urinary metabolites of polycyclic aromatic hydrocarbons during a wildfire response as part of the Wildland Firefighter Exposure and Health Effects Study

The occupation of firefighting, including wildland firefighting, has been classified as a known human carcinogen by the International Agency for Research on Cancer. Wildland firefighters (WFFs) can be exposed to polycyclic aromatic hydrocarbons (PAHs) present in wildfire smoke, some of which are known or probable carcinogens. Currently, there is no approved respiratory protection for WFFs against wildfire smoke, making inhalation exposure to PAHs a health concern. Recent studies have also highlighted the risk of dermal exposure to PAHs for WFFs due to factors like elevated skin temperature, sweat, and the inability to shower or routinely conduct good skin hygiene practices during wildfire incidents. This pilot study aimed to assess PAH exposure among 19 WFFs in different job positions during a wildfire incident by determining urine concentrations of 7 PAH metabolites in samples collected before and after shifts across 3 days. Overall, we observed increases from pre- to post-shift for all 7 PAH metabolites when we combined all WFF samples across the 3 days. When we stratified by job position and by day, concentrations of the PAH metabolites significantly increased from pre- to post-shift for 88% (37/42) of the comparisons (P-values <0.05). Additionally, median post-shift creatinine-corrected concentrations of 2-hydroxynaphthalene exceeded the 95th percentile of the nonsmoking US general population in 67% (4/6) of comparisons. Post-shift concentrations of hydroxynaphthalenes also exceeded concentrations measured in structural firefighters responding to training fires. Overall, 2-hydroxynaphthalene was highest on Day 2 (median creatinine-corrected concentrations of 2-hydroxynaphthalene from pre- to post-shift increased 425% for crew member/overhead; 146% for saw team). Despite this finding, we did not observe significant differences by job position. However, future studies could evaluate how job position affects WFF exposures while also exploring how dermal and inhalation contribute to WFFs' PAH exposure burden.