RESUMO
OBJECTIVE: To examine the relationship between CO levels and putative factors including smoking status among residents of Karachi, an urban center with very high levels of air pollution. METHODS: Two hundred and eighteen volunteering subjects were asked to maximally exhale into a Smokerlyzer breath CO analyzer. Each of the volunteers was also asked to reply to a questionnaire-based interview seeking demographic information as well as details of exposure to tobacco, traffic fumes and other air pollutants. RESULTS: Out of the 218 participating subjects, 75% were males and 27% were current or ex-smokers. The mean CO level was 2.92 parts per million (ppm). Cigarette smoking was the only factor found to influence CO levels. Number of cigarettes smoked per day was directly related to CO levels, while time since the last smoke was inversely related. There was no difference in CO levels between ex-smokers and never-been-smokers. Years of residence in Karachi, quantitative exposure to traffic and perception of occupational exposure to air pollutants were not associated with CO levels. CONCLUSIONS: Smoking status, number of cigarettes smoked per day and time since last smoke correlated well with exhaled breath CO levels, in spite of high air pollution levels. This tool therefore continues to provide a valid and real-time assessment of a subject's current smoking status.