Utility of outdoor central site monitoring in assessing exposure of school children to ultrafine particles

The Representativeness of Outdoor Particulate Matter Concentrations for Estimating Personal Dose and Health Risk Assessment of School Children in Lisbon

This study investigated the suitability of outdoor particulate matter data obtained from a fixed monitoring station in estimating the personal deposited dose. Outdoor data were retrieved from a station located within the urban area of Lisbon and simulations were performed involving school children. Two scenarios were applied: one where only outdoor data were used assuming an outdoor exposure scenario, and a second one where an actual exposure scenario was adopted using the actual microenvironment during typical school days. Personal PM₁₀ and PM_2.5 dose (actual exposure scenario) was 23.4% and 20.2% higher than the ambient (outdoor exposure scenario) PM₁₀ and PM_2.5 doses, respectively. The incorporation of the hygroscopic growth in the calculations increased the ambient dose of PM₁₀ and PM_2.5 by 8.8% and 21.7%, respectively. Regression analysis between the ambient and personal dose showed no linearity with R² at 0.07 for PM₁₀ and 0.22 for PM_2.5. On the other hand, linear regression between the ambient and school indoor dose showed no linearity (R² = 0.01) for PM₁₀ but moderate (R² = 0.48) for PM_2.5. These results demonstrate that ambient data must be used with caution for the representativeness of a realistic personal dose of PM_2.5 while for PM₁₀ the ambient data cannot be used as a surrogate of a realistic personal dose of school children.