Population health effects of air quality changes due to forest fires in British Columbia in 2003 - Estimates from physician-visit billing data

Background: Major forest fires near populated areas during 2003 exacted a huge economic toll on communities in British Columbia. We designed a study to examine associations between PM2.5 and PM10 levels and physician visits in two affected communities. Methods: Measurements of 24-hour averages of particulate matter (PM10 and PM2.5) obtained from the monitoring network of the BC Ministry of Water, Land and Air Protection were used to define weeks where forest fires resulted in increases in ambient PM. Weekly rates of physician visits for respiratory (ICD-9 codes 460-519), cardiovascular (390-459) and mental illnesses (290-319) obtained through the Medical Services Plan of BC, were compared for 2003 and aggregates of the 10 previous years. Results: Both the Kelowna and Kamloops regions experienced five weeks of elevated 24-hour average PM levels, although maximum levels in Kelowna were greater. In the Kelowna region, increases in physician visits for respiratory diseases of between 46 and 78% above 10-year mean rates were observed for three weeks during the forest fire period. Similar effects were not observed in Kamloops. Effects on visits for cardiovascular diseases or mental disorders were not seen in either community. Interpretation: Forest fire smoke was associated with an excess of respiratory complaints in Kelowna area residents. The lack of a similar effect in Kamloops is likely due to the population being exposed to lower levels of PM. The absence of apparent cardiovascular health effects may be due to selective effects of forest fire smoke on respiratory tract disease.