Winter measurements of children's personal exposure and ambient fine particle mass, sulphate and light absorbing components in a northern community

摘要

The relationship between ambient fine particle (PM_(2.5)) concentration and children's personal exposure was investigated in Prince George, British Columbia. Repeated personal exposure measures (10 per subject) of 15 children and ambient concentrations at their neighbourhood schools were collected for a 6-week winter period in 2001. PM_(2.5) mass, sulphate (SO_4~(2-)) and light absorbing carbon (ABS) were determined for all samples and the relationship between ambient concentration and personal exposure was investigated. Overall, lower particle exposures and a lower personal-ambient regression slope were found for Prince George children compared to results from other longitudinal studies of children. This suggests that in this setting indoor environments may have less influence from ambient sources and greater influence from non-ambient sources. Comparison of personal exposures and ambient concentrations for each individual indicated higher Spearman correlations for SO_4~(2-) (median = 0.95) and ABS (median = 0.73) compared to total PM_(2.5) mass (median = 0.55). A large degree of individual variability in the personal-ambient correlation was found for PM_(2.5) mass, while SO_4~(2-) showed very consistent results, supporting its use as an indicator of exposure to particulate matter of ambient origin. ABS was slightly more variable than SO_4~(2-) due to the influence of non-ambient or very local sources in a low number of samples. The impact of local meteorology was also investigated and inversion conditions were connected to all high ambient levels (> 30 μg m~(-3)). In addition, associations were found between inversion strength and personal exposure. This finding suggests that reduction of ambient concentrations during stagnant periods would result in lower personal exposure levels. This study highlights the importance of both ambient and non-ambient sources, supports the use of both SO_4~(2-) and ABS as tracers of background ambient particle exposure and demonstrates the significant effect of winter meteorology on both outdoor levels and personal exposure in a valley community.