Spatial assessment of forest fire smoke exposure and its health impacts in Southeastern British Columbia during the summer of 2003

Forest fires are a significant source of episodic air pollution resulting in elevated ambient concentrations of inhalable particulate matter (PM). Although PM from fossil fuel combustion has been conclusively associated with respiratory and cardiovascular morbidity and mortality, the health effects of fire-related PM are not clearly understood. Air quality monitoring is sparse in many fire-affected areas, so it is challenging to apply epidemiologic methods that require individual-level exposure assessment. Data from dispersion models and remote sensors are spatially extensive and may provide viable exposure estimation alternatives. Firestorms across southeastern British Columbia during the summer of 2003 produced a unique opportunity to compare rigorous epidemiologic results based on new exposure assessment methods to those based on air quality monitoring data. A population-based cohort of ~280 000 subjects was identified from administrative health data and three daily smoke exposure estimates were assigned for each individual according to residential location: TEOM averaged PM concentrations measured by the nearest of six air quality monitors; SMOKE indicated the presence of a plume over the area in satellite imagery; and CALPUFF averaged PM concentrations estimated by a dispersion model. The latter was initialized and run for this project using remote sensing data to simplify the model as much as possible. For example, emissions were calculated with the radiative power of satellite-detected fires and were comparable to those estimated by much more complex methods. Overall performance of the model was moderate when evaluated using PM measurements, satellite imagery and atmospheric aerosol measurements. Longitudinal logistic regression was used to examine the independent effects of each exposure over the 92-day study period. Respiratory outcomes were associated with smoke-related PM, but no cardiovascular effects were detected. While odds ratios for the TEOM metric were consistent with other reports, those for the CALPUFF metric were biased towards the null. Results for SMOKE tracked with those for TEOM, but with much wider confidence intervals. This study (1) highlights the potential of new smoke exposure assessment methods, (2) demonstrates that plume dispersion models can be simplified with remote sensing data, and (3) confirms the respiratory health effects of forest fire smoke.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat