A survey of street sellers' exposure to carbon monoxide in Mexico City.

The aim of this study was to explore the CO exposure experienced by street sellers working on busy roads in Mexico City. In January 1991, CO measurements were taken at street level of selected avenues in the city centre. A survey of the numbers of street sellers working on the monitored streets, and their working schedules, was also undertaken. Pavement CO levels were compared with the concurrent concentrations measured at the nearest fixed-site monitoring station. Short term pavement CO concentrations ranged from 2.0 to 70.0 ppm with a mean concentration of 26 ppm. There was a significant positive correlation between pavement and fixed-site CO concentrations. CO concentrations at the pavements were consistently higher than the concurrent fixed-site monitor levels; the average ratio of street/fixed-site concentrations was 2.2. There were more than 1000 street sellers working in the surveyed avenues. More than 80% of the sellers reported that they work at least 6 days a week, with an average working shift of 10 hours per day. The findings of this study suggest that street sellers in Mexico City are exposed to CO concentrations well above national and international air quality criteria. Further research is needed to evaluate the health effects caused by CO exposures among such occupationally exposed groups.