Abstract:
Air pollutant monitoring is utilized for determining compliance with National Ambient Air Quality Standards (NAAQS), detecting sources of pollutants, and investigating the health effects of air pollution through epidemiological studies. The effectiveness of monitoring depends on how representative monitoring sites are of overall ambient air concentrations to which a population is most exposed. Recent promulgation of NAAQS for PM2.5 has prompted the question of where to site PM2.5 monitors in Seattle. This research investigates how PM2.5 and NO2, a co-pollutant, vary spatially; and how these spatial characteristics can be used to identify potential monitoring sites that are the most representative of the overall ambient exposures of the Seattle population using Geographic Information Systems (GIS). Data were collected at outdoor sites from the homes of participants of a larger study. Forty outdoor sites throughout the Seattle metropolitan area were monitored for 10 consecutive days, producing 24-hour average PM2.5 concentrations and 10-day average NO2 concentrations. The PM2.5 data were analyzed using a fixed-effects ANOVA model to determine locations that best represent the average concentrations in Seattle with the least amount of variability. This was quantified in the variance of the residuals of the model, which was then compared to different spatial characteristics. The results showed that the most representative PM2.5 sites were located at elevations of 80-120 meters above sea level, and at distances of 100-300 meters from the nearest arterial road. The most representative NO2 sites were also at distances of 100-300 meters from the nearest arterial road⦠Additionally, representative sites should be in areas of high population density of elderly persons (a population highly susceptible to the health effects of PM2.5).
The representative spatial characteristics obtained from the data were used as criteria in a GIS analysis to determine where the most representative sites are located. The GIS analysis produced a map with all the areas that meet these criteria. The neighborhoods with the most areas suitable for monitor sighting were Crown Hill, Capitol Hill, Maple Leaf and West Seattle.