Ambient air 1,3-butadiene concentrations in Canada (1995–2003): seasonal, day of week variations, trends, and source influences

Since 1987, the Environmental Protection Service of Environment Canada has operated a field program for measuring 1,3-butadiene and other volatile organic compounds (VOCs) in ambient air. With the co-operation of provincial and municipal environmental agencies, samples have been collected at urban and rural monitoring sites across the country. Samples were collected in evacuated canisters and analyzed by gas chromatography with a mass-selective detector. Using data from all sites, the composite average 1,3-butadiene concentration at urban sites in Canada for the years 1995–2003 was found to be 0.22 μg m−3 and the composite median was 0.17 μg m−3. In general, 1,3-butadiene concentrations were higher at commercial and industrial sites than at residential sites, particularly at sites close to street level in the urban core. The highest 24-h 1,3-butadiene concentration of 2.58 μg m−3 was measured at the Sarnia, Ontario, site in 2001; this site was significantly influenced by industrial point sources. Mean 24-h 1,3-butadiene concentrations at rural sites were typically an order of magnitude lower than at urban sites. 1,3-Butadiene concentrations varied by season, particularly in western Canada, and by day of week. Concentrations of 1,3-butadiene decreased from 1995 to 2003 in response to reduced rates of emissions from mobile and point sources. At most urban monitoring sites, the concentrations of 1,3-butadiene and acetylene were highly correlated; this supports the hypothesis that 1,3-butadiene is emitted primarily by mobile sources.