Indoor-outdoor relationship of SO2 concentrations in a rural and an urban community of Alberta

Abstract

Passive monitoring techniques were used to measure 7-day average concentrations of SO2 in indoor–outdoor air in two Alberta communities, Boyle (population 860) and Sherwood Park (population 42 000). Sampling occurred during a 5-week period in late fall, a time of year when SO2 is less reactive in the outdoor environment. Outdoor levels of SO2 at 12 homes in Boyle (median 4.3 µg/m3, range 3.7–5.6 µg/m3) were two times lower than those at 13 homes in Sherwood Park (median 9.9 µg/m3, range 8.2–13 µg/m3). Slightly higher indoor SO2 levels were measured in Sherwood Park homes (median 1.4 µg/m3, range 0.9–5.2 µg/m3) than in Boyle homes (median 0.5 µg/m3, range 0.2–2.3 µg/m3). These results are consistent with the characteristics of the two communities involved in this study. Sherwood Park has many more SO2-related emission sources than in Boyle (i.e., increased vehicle traffic and industrial emissions). Indoor and outdoor SO2 levels measured in both communities were [Formula: see text]13 µg/m3. These levels are considered low compared with benchmark levels intended for protection of people: 365 µg/m3 averaged over 24 h (short-term exposure) or 80 µg/m3 averaged over 1 year (long-term exposure). The median indoor–outdoor SO2 concentration ratio was 0.13 for both communities.Key words: air quality, indoor, outdoor, passive monitoring, sulphur dioxide.