Study assesses pollution impact on aquatic life

Much research on atmospheric contaminants in the Great Lakes has focused on “persistent” compounds, such as PCBs and mercury that break down slowly in the environment and accumulate in the tissues of plants and animals.

However, aquatic organisms are also exposed to thousands of shorter-lived compounds that are deposited from the atmosphere, and very little is known about their toxicity.

With support from UW Sea Grant, James Schauer is changing that. Schauer, a civil and environmental engineering professor, is employing a new, holistic approach to assessing the impact of thousands of airborne, nonpersistent contaminants on water fleas and green algae, two organisms that serve as biological benchmarks in wastewater and surface water toxicity tests.

Instead of analyzing individual compounds, Schauer and graduate student Rebecca Sheesley are looking at the overall effects of nonpersistent compounds deposited along the southern shores of Lake Michigan in Milwaukee, Chicago and northern Indiana.

Schauer and Sheesley are also discovering where the particles come from. Using techniques Schauer developed, they are identifying the unique chemical signatures of several sources of airborne contamination, including gasoline and diesel engine exhaust, coal combustion exhaust, wood smoke, road dust, brake-wear debris and tire-wear debris. They are also analyzing the pollution that comes from cooking meat.

“We’ve conducted experiments where we’ve had industrial, institutional kitchens cook 200 hamburgers for us. During the cooking operations, we collected the smoke for chemical analysis,” Schauer says. “We can actually measure the cholesterol level of the atmosphere that comes from meat cooking.”

This “source approach” helps Schauer cope with the complexity of the chemical cocktail swirling in the atmosphere. Studying the individual effects of the thousands of particulate compounds is highly impractical, let alone investigating all their possible interactions. By analyzing these source categories, however, Schauer will be able to determine their relative contribution to the overall toxicity of atmospheric pollution.

A preliminary finding of this continuing study is that, in general, the ambient mix of aerosols is toxic to aquatic organisms at high doses. In short-term exposures, the mortality rate of the test organisms reaches 50 percent — a standard toxicological reference point — at about 10-20 milligrams per liter of water.

Establishing the acute effects of atmospheric pollution in a laboratory is a first step to understanding their long-term effects at much lower environmental exposures, Schauer says.

Understanding the relative contributions of road dust, coal combustion and other contaminant sources to atmospheric pollution will help regulatory agencies develop practical controls that efficiently protect humans and aquatic organisms from adverse effects of that pollution, Schauer says.