Personal exposure to carcinogenic and toxic air pollutants in Stockholm, Sweden: A comparison over time

Benzene, 1,3-butadiene, benz(a)pyrene, NOx and NO2 were measured by personal sampling, stationary indoor sampling, and at two reference sites (urban background/traffic site) in Stockholm, Sweden during September–December 2009. The aim was to investigate whether the air pollution levels had decreased since a previous study conducted six year earlier, and to compare personal exposure levels (one-week average) and indoor levels with levels at outdoor reference sites. Participants were 20–50 years of age, randomly selected among residents in the Stockholm municipality. The personal exposure levels to benzene and 1,3-butadiene were higher than the levels at the reference sites. Personal exposure to NOx and NO2 were higher than urban background levels, but the NO2 exposure level was lower than traffic site levels. Benz(a)pyrene showed lower concentrations indoors compared to outdoor levels, although a significant correlation was found between indoor and outdoor levels. All of the air pollutant levels had decreased since the previous study, both for personal exposure and reference site levels. The results from the present study indicate that urban background measurements for these compounds are suitable for monitoring decreasing or increasing trends in air pollution levels but since the personal exposure levels did not correlate well with weekly ambient levels, personal sampling seems essential for assessing population exposure.