Impact of Ambient Temperature on Pollutant Infiltration and Exposure Processes: How Current Field Studies Inform Future Climate Change Effects

摘要

Aim. Rising temperatures associated with climate change are expected to influence future air pollution exposures through changes in home air exchange rates, altering contributions of indoor and outdoor particle sources to indoor air quality. Using data from current field studies of homes in two US cities with different climatic conditions, we examine associations between indoor concentrations of particles of outdoor and indoor origin and ambient temperature to inform future air pollution exposure and health. Methods. We assembled a large database of two retrospective cohorts (321 homes) in the Boston Area and a prospective cohort (840 homes) in Atlanta. Given that generally there is no indoor sulfur sources, indoor-outdoor sulfur ratios were used as a surrogate of total particle infiltration for PM2.5. We used linear mixed-effects models to examine the sulfur ratio-temperature relationship on both the whole population and a subset of naturally ventilated homes, using archived samples in Boston. Projected meteorological values, obtained from an ensemble of 15 Coupled Model Inter-comparison Project Phase 5 (CMIP5) models, were incorporated to predict sulfur ratio for 20 years in the future (2046-2065) and the past (1981-2000). Results. The average sulfur ratio in the cohorts in Boston was 0.55 ± 0.19, with a 0.04 lower sulfur ratio in homes (N=43) without air conditioning (AC) compared to those (N=278) with AC. Temperature was the only meteorological factor found to significantly predict sulfur ratio (p < 0.05) in both population scenarios (whole population and naturally ventilated house only). A positive linear relationship was found between temperature and sulfur ratio for the whole population, with every Celsius degree increase in temperature associated with an increase of 0.006 in sulfur ratio. The predicted future summer-winter difference in sulfur ratio was as high as 54% for naturally ventilated homes and 30% for the whole population, using winter as the baseline. In contrast, the long-term difference was small with a maximum of 7% and 2 % increase in sulfur ratio in summer for the populations, respectively. Conclusion. Substantial increment in sulfur ratio was found particularly in summer or the 20 years in the future. Ongoing analyses on the prospective cohort in Atlanta will be compared to the sulfur ratio-temperature relationship obtained from the cohorts in Boston. Together these analyses can help minimize exposure misclassification in future epidemiologic studies of PM2.5, as well as provide a better understanding of the potential influence of climate change on PM2.5 associated health effects.