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Miami University
Oxford, Ohio 45056
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Results of Lake Tahoe study support impending engine ban


OXFORD, Ohio -- Controversy over the decision to ban outboard engines and personal watercraft from Lake Tahoe's waters will continue, according to the results of a scientific report released this week.

Studies conducted last summer by Dr. James T. Oris, Miami University professor of zoology, showed that emissions from motorized watercraft, including outboard engine-powered boats and personal watercraft such as jet-skis and wet bikes, killed zooplankton and stunted the growth of fish larvae in the lake.

Results from the study will be presented at the European Society of Environmental Toxicology and Chemistry meeting April 14-18, in Bordeaux, France.

The problem, Oris says, is that these emissions work together with the ultraviolet rays of the sun for a combination lethal to aquatic plants and animals. Oris has studied the phototoxicity of fossil fuel products for the past 15 years, but this is the first study demonstrating a link between natural levels of marine engine emissions and harm to aquatic life.

"On many bodies of water, phototoxicity would be limited to surface waters," Oris says. "But because Lake Tahoe is so clear, the potential problem could run as deep as 65 feet into the lake."

Much of the concern over phototoxicity of engine emissions involves carbureted, two-stroke engines.

"Because of the way carbureted two-stroke engines work, up to 20 percent of the fuel passes through unburned," he said. "For every five gallons of gas pumped into these engines, up to one gallon is released into the water."

In an agreement between the U.S. Environmental Protection Agency and the National Marine Manufacturer's Association, cleaner burning, fuel-injected two-stroke engines will be phased-in over the next five to ten years. These engines became available on a limited basis in the past year.

"Until the phase-in of cleaner burning marine engines is complete," he says, "the potential for bans on personal watercraft and other boating activities around the country is high."

Oris is available at 513-529-3194 or He will be at the European Society of Environmental Toxicology and Chemistry meeting in Bordeaux, France from April 14-18.


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