The influence of Canadian forest fires on pollutant concentrations in the United States

High carbon monoxide (CO) concentrations from uncertain origins occurred ep isodically in the southeastern United States during the summer of 1995. We show that these episodes were caused by Large forest fires in Canada. Over a period of 2 weeks, these natural emissions increased CO concentrations in the southeastern United States as well as along the eastern seaboard, a re gion with one of the world's highest rates of anthropogenic emissions. With in the forest fire plumes, there were abo high concentrations of ozone, vol atile organic compounds, and aerosols. These results suggest that the impac t of boreal forest fire emissions on air quality in the mid-latitudes of th e Northern Hemisphere, where anthropogenic pollutant sources have been cons idered predominant, needs to be reevaluated.