Occupational exposure to BTEX compounds among enclosed multi-storey car park workers in central Bangkok area

Multi-storey parking structures have potentially high concentrations of benzene (B), toluene (T), ethylbenzene (E) and xylene (X) – known as BTEX which could cause adverse health effects to humans. This study sought to estimate BTEX exposure concentrations among car park workers and to evaluate the extent to which, if at all, changes in urine metabolites are associated with BTEX exposure. Personal BTEX samples were collected from workers. Pre-shift and post-shift urinary metabolites, trans,trans-muconic acid (t,t-MA), hippuric acid (HA) and methyl hippuric acid were assessed using standard procedures. Linear regression models were used to examine associations between BTEX exposure concentrations and changes in urinary metabolites. BTEX concentrations in the car park on Sunday were lower than other days of the week, for instance median concentrations of toluene were 23.3 µg/m³ on Sunday and 48.3 µg/m³ during average weekdays (Tuesday–Friday). Benzene and toluene concentrations adjusted for day of week differences were associated with changes from pre-shift to post-shift in urine t,t-MA and HA, respectively. Car park workers were more likely to be exposed to lower concentrations of BTEX during weekdays compared to weekends. Provision of personal chemical safety protection and rigorous evaluation of its effectiveness in reducing BTEX exposure should be provided to protect workers of car parks.