Characteristics of heavy metals in the hair of firefighters: concentration dynamics and elemental interactions

Heavy metal pollution poses a major threat to human health. Firefighters, a high-risk occupational group, are regularly exposed to airborne heavy metals and fly ash. Consequently, detailed investigations into their heavy metal exposure levels are essential. This study evaluated the heavy metal exposure of 14 firefighters across five stages before and after firefighting, with a focus on concentration trends and element interactions. The concentration order was Zn > Cu > Fe > Pb > Mn > Cr > As > Ni > Cd > Co. Comparisons with health reference values and other regions indicated that while most metals were within reference ranges, Zn concentrations were elevated. The elevated Zn concentrations may result from its attachment to hair through chemisorption and absorption from airborne particles and fly ash during combustion. Heavy metal concentrations in the hair of firefighters increased after firefighting, and continued firefighting missions may further accumulate heavy metals in the body. However, concentrations decreased after a period of firefighting. Correlation analysis revealed that, except for Zn, metals exhibited synergistic interactions, with correlations strengthening significantly after firefighting. Variation in heavy metals reflects long-term pollutant exposure, and Zn in hair may serve as a biomarker of fire-related exposure.