Automotive gasoline-induced epigenetic modifications and genotoxic effects in occupationally exposed workers

Occupational exposure to automotive gasoline, a complex mixture containing carcinogenic compounds such as benzene, toluene, and xylene (BTX), has been associated with both genotoxic and epigenetic effects. However, the specific molecular mechanisms underlying these alterations remain unclear. This study aimed to investigate global and gene-specific DNA methylation alterations in gas station workers occupationally exposed to automotive gasoline. A cross-sectional study was conducted with 217 participants from Rio de Janeiro, Brazil, divided into three groups: unexposed individuals, workers exposed via inhalation only, and workers exposed through both inhalation and dermal routes. Urinary trans,trans-muconic acid (t,t-MA), hippuric acid (HA) and methylhippuric acid (MHA) were quantified as biomarkers of benzene, toluene and xylene exposure, respectively. Global DNA methylation (LINE1 and ALU elements) and promoter methylation of DNA repair genes (MGMT, MSH3, and PARP1) were analyzed by pyrosequencing. Exposed groups showed significantly higher urinary MHA levels compared to unexposed individuals, though no significant correlation was found between exposure biomarkers and genotoxic damage. Workers exposed via inhalation only exhibited increased DNA damage. MGMT methylation levels were decreased in workers exposed through both inhalation and dermal routes, PARP1 exhibited increased methylation levels in workers exposed exclusively via inhalation, whereas MSH3 showed higher methylation in both exposed groups compared to the unexposed group. Additionally, PARP1 promoter methylation levels were directly correlated with urinary HA and MHA concentrations. Lower methylation of ALU elements was also observed upon exposure. Finally, mediation analysis showed that MGMT methylation significantly partially mediated exposure effects on DNA damage. These findings suggest the concurrent contribution of direct genotoxic mechanisms, related to the induction of DNA damage by BTX and epigenetic mechanisms, by which changes in DNA methylation may lead to the silencing of repair genes, thereby indirectly contributing to BTX-induced genomic instability. In this context, the observed methylation patterns show potential as effect biomarkers, providing relevant tools for the early detection of biological alterations, as well as for risk monitoring and prevention in occupationally exposed workers.