16th Biometeorology and Aerobiology
Fifth Conference on Urban Environment


Exposure to fine particulate air pollution in Prince George, British Columbia, Canada

Melanie Noullett, University of Northern British Columbia, Prince George, BC, Canada; and P. L. Jackson

The relationship between ambient fine particulate pollution (PM2.5) and children’s personal exposure was investigated during the winter of 2001 in the city of Prince George, Canada. Harvard Personal Environmental Monitors (HPEMS) were used to collect personal exposure samples from 15 children aged 10 to 12 years and ambient samples at five outdoor monitoring sites located on their elementary school roofs. PM2.5 mass, sulphate (SO42-) and absorption coefficient (ABS) were determined for all samples (ABS as a surrogate for elemental carbon (EC)). SO42- and EC personal/ambient ratios were used as tracers of ambient PM2.5 to estimate personal exposure to ambient and non-ambient sources. Overall, ambient PM2.5 concentrations were very high for the study period with levels at the downtown school exceeding the Canada-Wide Standard for 2001. Inversion conditions were found to be responsible for all high ambient concentrations (>30µg/m3) and personal exposures were also impacted. Although spatial differences were found for all three measures, high correlations were found between the central PM2.5 TEOM monitor and each outdoor study site suggesting the TEOM could be used to represent relative ambient concentrations at all sites. Personal exposure and ambient concentrations showed stronger personal-ambient correlations for SO42- (r=0.96) and ABS/EC (r=0.73) compared to total PM2.5 (r=0.52). A strong association was found between estimates of ambient generated exposure (derived from personal/ambient SO42- and EC ratios) and ambient concentration at both the closest school monitor (r=0.92) and the central site (r=0.88), suggesting that the central site TEOM was also suitable for assessing average ambient generated personal exposure throughout the city during the study period. Individual longitudinal regressions showed that ambient generated personal exposure was 45% of ambient concentration. Overall ambient generated exposures were slightly higher than non-ambient exposures with each contributing almost equal proportions to total personal exposure. This study describes the relationship between ambient concentration and personal exposure to PM2.5 and demonstrates that the sulphate and elemental carbon components are reliable tracers for exposure to particles of ambient origin. The strong association found between ambient generated exposure and ambient concentration suggests that ambient levels are indeed an appropriate surrogate of exposure to ambient PM2.5 sources. The equal contributions made by ambient and non-ambient sources to total PM2.5 personal exposure, even when subjects were indoors 95% of the time, demonstrates the importance of managing ambient air quality. These findings strongly support the use of ambient data for a longitudinal health study in this city. Use of the regression equations provided will enable future estimation of ambient generated exposures for healthy elementary school children during the winter in the city of Prince George.

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Joint Session 4, Human Biometeorology: Air Quality (Joint between the 16th Conference on Biometeorology and Aerobiology and the Fifth Symposium on the Urban Environment)
Wednesday, 25 August 2004, 10:30 AM-11:45 AM

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