Impact of Fire Emissions and Tobacco Consumption on the Salivary Content of Metal(loid)s and PAHs: Exposure Levels and Assessment of Oral and Intestinal In Vitro Toxicity.

Human exposome via ingestion, by assimilation of health-relevant pollutants in the oral cavity and/or intestinal tract, has been poorly explored, principally in heavily exposed professionals. This work assessed the salivary content of 18 polycyclic aromatic hydrocarbons (PAH) and 16 metal(loid)s in smoker/non-smoker firefighters enrolled in (forest/structural) firefighting activities and explores the associated in vitro toxicities on buccal (TR146; HSC-3) and intestinal (Caco-2; HT29 MTX) cell lines. Total PAH levels (1.95-3.61 µg/L) were predominantly increased after firefighting compared to control groups, with naphthalene (up to 1.9 times in forest fires), phenanthrene (up to 4.5 times in the industrial fire), and anthracene (up to 3.1 times in forest fires) presenting the highest increments. Total salivary content of metal(loid)s (23.6-90.9 µg/L) was increased in exposed firefighters, being the highest increments found in the samples collected after an industrial fire (Pb: up to 45 times; Ba: up to 4-6 times; Sr: up to 2.8-5.6 times; Hg: up to 1.7 times). The impact of tobacco consumption was globally less pronounced than firefighting work. The salivary concentrations of PAHs and metal(loid)s were positive and globally moderate to strongly correlated. A principal component analysis was constructed to evaluate source apportionment and allowed the differentiation of firefighting activities at forest, controlled structure, and industrial fires; the impact of tobacco consumption was not evidenced. An in vitro health risk assessment was performed, and no significant toxicity was found in buccal/intestinal cell lines. Additional studies are needed to corroborate these preliminary studies and more peely explore the human exposome via ingestion.