Associations between personal exposures and fixed-site ambient measurements of fine particulate matter, nitrogen dioxide, and carbon monoxide in Toronto, Canada

A longitudinal study investigating personal exposures to PM2.5, nitrogen dioxide (NO2), and carbon monoxide (CO) for cardiac compromised individuals was conducted in Toronto, Canada. The aim of the study was (1) to examine the distribution of exposures to PM2.5, NO2, and CO; and (2) to investigate the relationship between personal exposures and fixed-site ambient measurements of PM2.5, NO2, and CO. In total, 28 subjects with coronary artery disease wore the Rupprecht & Patashnick ChemPass Personal Sampling System one day a week for a maximum of 10 weeks. The mean (SD) personal exposures were 22 μg m−3 (42), 14 p.p.b. (6), and 1.4 p.p.m (0.5) for PM2.5, NO2, and CO, respectively. PM2.5 and CO personal exposures were greater than central fixed-site ambient measurements, while the reverse pattern was observed for NO2. Ambient PM2.5 and NO2 were correlated with personal exposures to PM2.5 and NO2 with median Spearman's correlation coefficients of 0.69 and 0.57, respectively. The correlations between personal exposures and ambient measurements made closest to the subjects' homes or the average of all stations within the study were not stronger than the correlation between personal exposures and central fixed-site measurements. Personal exposures to PM2.5 were correlated with personal exposures to NO2 (median Spearman's correlation coefficient of 0.43). This study suggests that central fixed-site measurements of PM2.5 and NO2 may be treated as surrogates for personal exposures to PM2.5 and NO2 in epidemiological studies, and that NO2 is a potential confounder of PM2.5.