Canada forest fires, transboundary air pollution and hospitalizations among the elderly in the Northeastern USA in July 2002

In the first week of July 2002, dry lightning strikes ignited more than 250 fires that destroyed more than 1 million ha of Canadian forest. The smoke plume generated from the forest fires in Quebec, Canada in July 2002 had major impacts on air quality across the east coast of the US. To evaluate the public health impact of the smoke on the elderly population, hospital admission rates for cardiovascular and pulmonary causes were estimated in 79 counties located in the northeastern and mid-Atlantic region of the US, before and during the period of plume presence. Using the Medicare National Claims History File and EPA's National Monitoring Network, we estimated significant associations between short-term increases in ambient PM2.5 concentrations and hospitalizations for cardiovascular and respiratory diseases in 11 Eastern U.S states affected by the smoke plume. We found that a 10 µg/m3 increase in PM2.5 was associated with an 8.33% (95% CI: 5.32, 11.43) increase in cardiovascular hospitalization rates in the Northeast U.S., a day later. Similar estimates were reported from state-specific models, at various lags, and for respiratory hospitalizations. We found significant differences in the association between hospitalization rates and PM2.5 comparing a control period with the pollution episode. This research adds to the growing body of literature demonstrating the significant impact of transboundary air pollution on human health. Our study suggests that the effect of abrupt increases in PM2.5 concentrations from wildfire smoke on hospitalizations among the elderly is not negligible.