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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