Fact Sheet 9 Two Strokes and You're Out! Pleasure boats are the largest source of toxic contamination in American waterways. Over 9 million American pleasure boats, including "jet-skis," are powered by two-stroke engines. 30% of the fuel and oil that powers a two-stroke engine is emitted unburned in the engine's exhaust. Every year two-stroke engines put 1,000,000,000 -- one billion -- pounds of hydrocarbons into the environment. EPA acknowledges that every year, pleasure boats spill as much oil, by volume, as 15 Exxon Valdez disasters. Many hydrocarbons are toxic, and some, including polycyclic aromatic hydrocarbons (PAH), are carcinogenic and mutagenic. PAHs are found in two-stroke exhaust. When PAHs are exposed to sunlight, they become thousands of times more toxic. An average outboard motor pollutes 250 times more than an average car, horsepower for horsepower. An average afternoon of boating can dump 2-4 gallons of unburned fuel into the water. Hydrocarbon contamination collects at the uppermost millimeter of the water's surface, both from the water column and from atmospheric deposition. This region, called the microlayer, is critical for the reproduction and development of many fish species, and is a feeding zone for birds, marine mammals, and fish. Sources: EPA, Bluewater Network, Polluting For Pleasure, John Hardy, PhD., John Geisy, PhD., U. Of Wisconsin.

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Updated 6/23/97