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The newspaper of The Johns Hopkins University December 20, 2004 | Vol. 34 No. 16
Impact of Canadian Forest Fires Felt 700 Miles Away in Baltimore

By Kenna Lowe
School of Public Health

Researchers from the Johns Hopkins Bloomberg School of Public Health analyzed how airborne particulate matter from forest fires in the Canadian province of Quebec traveled more than 700 miles to homes in Baltimore. The study authors found a dramatic increase in outdoor and indoor fine particulate matter — an atmospheric pollutant that is harmful to people with respiratory diseases — in Baltimore during the first weekend of July 2002, which coincided with several forest fires in Quebec.

The same fine particulate matter that the authors found to be transported across large distances readily penetrated people's homes, where they spend most of their time. The researchers believe this should be a public health concern because fine particulate matter can penetrate deep into the lungs. The study is published in the current online issue of Environmental Science & Technology.

"This study provides a dramatic example of the significance that global air pollution has, not only on the outdoor air quality in our communities but on air quality indoors, where even the most susceptible among us look for protection," said Timothy J. Buckley, associate professor in the Bloomberg School's Department of Environmental Health Sciences and the study's senior author.

The researchers used satellite images, trajectory models, light detection and ranging measurements to track emissions from the Canadian forest fires to levels of particulate matter in Baltimore. During the peak of the episodes, ambient PM 2.5 levels increased eightfold from 25 mg/m3 to 199 mg/m3 on July 7, 2002. The EPA's National Ambient Air Quality Standard was exceeded on this particular day. Indoor levels closely tracked the outdoor concentrations, indicating that being at home offered little protection from the pollution episode. At the peak of the episode, PM2.5 levels as high as 366 ug/m3 were recorded inside.

The researchers said that their study is a stark example of how air pollution can impact vulnerable individuals in communities hundreds of miles away. In light of the reported findings, the study authors suggest that health advisories that encourage people to stay indoors during high particulate matter events should be reviewed.

"Although the source discussed in this study is natural, similar analogies can be drawn about the long-range transport of pollutants from man-made sources," said Amir Sapkota, lead author of the study and a postdoctoral fellow in the Bloomberg School's Department of Environmental Health Sciences. "This underscores the point we have long realized — air pollution is both a local and global issue. In addition to working locally, we need to bring other countries together to tackle the issue of transcontinental transport of air pollution."


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