Ethanol has been blended with gasoline since the 1990's to reduce harmful carbon monoxide emissions. Blending ethanol into gasoline also reduces toxic pollutants found in gasoline

Using ethanol means that less oil (a nonrenewable fuel) is used to make gasoline.  Unlike gasoline, ethanol is nontoxic and biodegradable, quickly breaking down into harmless substances if spilled.

When small amounts of ethanol are added to gasoline, usually less than 10 percent, there are many advantages. Ethanol reduces carbon monoxide and other toxic pollution from the tailpipes of vehicles, making the air cleaner. It keeps engines running smoothly without the need for lead or other chemical additives.

Source: US Department of Energy