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Researchers explore wood smoke's threat to Great Lakes environment

CHICAGO, August 28 — The Great Lakes region has long been valued for its recreational opportunities, but there may be a price to be paid for these pleasures: A new study has found that wood smoke, most likely from campfires and residential fireplaces, is toxic to certain aquatic organisms in the lakes and is a source of air pollution in the region. The study was described today at the 222nd national meeting of the American Chemical Society, the world’s largest scientific society.

Previous studies of the impact of pollution on the area have focused on polychlorinated biphenyls (PCBs), mercury and other toxins regulated by the federal government. This is believed to be the first study to explore the potential toxicity of the area’s recreational smoke.

Rebecca J. Sheesley, a graduate student at the University of Wisconsin-Madison and a contributing researcher in the study, cautions that the study so far is limited to toxicity tests exposing aquatic animals to smoke residues. Although the study does not address the impact of wood burning emissions on human health, it raises concern over the impact of these emissions on the health of the Great Lakes, she says.

To determine the impact of atmospheric pollutants on aquatic life in the Great Lakes, the researchers collected particulate matter samples from different areas along the shores of southern Lake Michigan. Those sampling areas included sites in Milwaukee and Waukesha, Wis.; Indiana Dunes National Lakeshore in Portage, Ind.; and Warren Dunes State Park in Sawyer, Mich.

From Aug. 2000 to March 2001, the researchers collected air samples from each of these sites using special air filters. Each sampling event consisted of three consecutive 24-hour sampling periods. They then extracted particles from the filters and exposed each sample extract to a population of a hundred water fleas, which are used as a standard model for testing wastewater toxicity.

For each site sampled, extract concentrations as low as 10-15 milligrams of particulate matter per liter killed 50 percent of the fleas in a 24 hour exposure, indicating that air samples from these areas were toxic to the test animals at this concentration, according to the researchers.

Although the concentration of wood smoke in the Great Lakes waters is expected to be significantly lower than the laboratory exposure concentrations, these tests are used as a screening tool to identify pollutants that can adversely impact populations of aquatic organisms at longer low-level exposures, they say.

Detailed chemical analysis involving several hundred compounds found in the extracts showed the presence of levoglucosan, a chemical marker that characterizes wood smoke, indicating that there was some amount of particulate matter from smoke present in the air at the sample sites, Sheesley and her colleagues say.

The study is similar to a previous study by Sheesley’s graduate advisor and the study’s lead researcher, James J. Schauer, Ph.D., which reported that smoke from wood burning was a significant contributor to atmospheric particulate matter pollution in both the Los Angeles basin and California’s San Joaquin Valley in winter months. The charbroiling of meats by households and fast-food restaurants was also found to be a major source of pollutants in the Los Angeles area, according to Schauer.

Sheesley and Schauer assert that charbroiling of meats is also likely to be a major source of air pollutants in the Great Lakes region. Other possible sources include vehicle exhaust, coal-powered plants and other smaller sources, they add.

In the future, the researchers hope to determine the rate and concentration at which pollution from wood smoke is actually deposited into the lakes.

The Great Lakes, which form a natural border between the United States and Canada, constitute the largest freshwater surface in the world. Camping is one of the major recreational activities in the area, which has become the focus of extensive environmental interest in recent years due to persistent pollution problems.

This study was funded by Sea Grant, a federal program that supports university research related to the Great Lakes and marine science.

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The paper on this research, ENVR 72, will be presented at 9:15 a.m., Tuesday, August 28, at McCormick Place South, Room S502A, Level 5, during the symposium, "Emerging Issues in the Great Lakes."

Rebecca J. Sheesley is a graduate student in the environmental chemistry and technology program at the University of Wisconsin, in Madison, Wis.

James J. Schauer, Ph.D., is a professor in the environmental chemistry and technology program at the university.

— by Mark Sampson