Occupational exposure assessment of highway toll station workers to vehicle engine exhaust

Toll station workers are occupationally exposed to vehicle engine exhaust, a complex mixture of different chemical substances, including carcinogenic compounds. Therefore, a study was carried out on attendants of two highway toll stations to describe their occupational exposure to vehicle engine exhaust, based on a worst-case scenario approach. Personal sampling was conducted during the day shift for all attendants, testing for three groups of chemical substances: polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs) and aldehydes (formaldehyde and acrolein). Concentrations of total PAH, BTEX (benzene, toluene, ethylbenzene, and xylenes) and formaldehyde content varied between 97.60-336.08 ng/m3, 5.01-40.52 μg/m3, and 0.06-19.13 μg/m3, respectively. No clear relationships could be established between exposure levels and the number of vehicles. Furthermore, no differences were found between truck versus car lanes, or inside versus outside the tollbooth. Not all the detected VOCs were related to vehicle exhaust; some were consistent with the use of cleaning products. The measured concentrations were far below the established occupational exposure limits, but tended to be higher than values reported for outdoor urban environments. There are very few international studies assessing occupational exposures among toll station workers, and this is the first such study to be conducted in Spain. The results suggest that further, more detailed studies are necessary to characterize exposure properly, and ones which include other airborne pollutants, such as ultrafine particles. The comparison of the results to other similar studies was difficult, since no data related to some important exposure determinants have been provided. Therefore, it is recommended that these determinants be considered in future studies.