The effect of ethanol-gasoline blends on organic air toxics emissions was investigated in a four-stroke carburetor motorcycle without a catalytic converter. An inhalation toxicity-based emission ranking for the toxics from each test fuel was also conducted. Four blends containing 3%, 10%, 15%, and 20% (vol) ethanol in gasoline were tested. Commercial unleaded gasoline with methyl tert-butyl ether as the oxygenated additive was also tested as a reference case. Experimental data indicated that addition of ethanol may reduce emissions of selected air toxics, except those of acetaldehyde. Fuel with 15% (vol) ethanol content resulted in the greatest reduction in emissions of organic air toxics. However, acetaldehyde emissions significantly increased by almost 10-fold, using ethanol fuels. In addition, results of the emission ranking of air toxics showed that gasoline blend with 15% (vol) ethanol had the lowest total mass-based emissions of air toxics and ranked high in toxicity-weighted emissions because of associations with cancer and acute health effects.
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