The commuters’ exposure levels to volatile organic compounds were investigated in the following public transport modes: microbus, bus, private car, and metro along three commuting routes in the Metropolitan Area of Mexico City. The target chemicals were benzene, toluene, ethylbenzene, m/p-xylene, and formaldehyde. Integrated samples were taken while traveling during the morning rush hour (weekdays 7:00 a.m. to 9:00 a.m.) for consecutive 6 weeks in June and July in 2002. Scheffe test showed that the average concentrations of all chemicals were statistically higher inside microbuses and cars than inside metro trains (P<0.05). For non-formaldehyde chemicals, the average levels inside automobiles were significantly higher than in metro trains and buses (P<0.05). The exposure level of formaldehyde in the microbus was much higher than those in the bus, car, and metro (P<0.05). On the other hand, there were no difference in the exposure levels among transport routes. These findings suggest that for commuting trips of comparable durations, microbus and auto passengers are exposed to higher levels of volatile organic compounds than bus and metro commuters. The excess potential carcinogenic incidences due to commuting by microbus compared to metro were 37-51 persons per year, those in bus were 8-13 persons per year, and those in car were 30-65 persons per year in Mexico City. If we take into consideration the other chemicals, the risks for a Mexico City´s commuter could be much higher than what our results showed.
Mexico City, VOCs, Commuting, Excess potential carcinogenic incidences