Urban air pollutionThe transport sector is responsible for the vast majority of air pollutants in our urban areas, including carbon monoxide and nitrogen oxides, which form ground-level ozone. Tens of millions of Americans live in areas that do not meet at least one federal air quality standard. In 1990, Congress passed amendments to the Clean Air Act to combat high levels of emissions of carbon monoxide, nitrogen oxides, and the creation of ground-level ozone from petroleum-based transportation fuels. . This law specifically called for the production and distribution of cleaner-burning gasoline, containing oxygenated substances such as ethanol, in America's most polluted cities. Tighter emissions standards are also causing diesel users to find fuel options for cleaner air. Both ethanol and biodiesel have been shown to reduce emissions that contribute to urban air pollution. When ethanol is added to gasoline, it replaces the components of the gasoline, generally reducing all pollutants. And because ethanol causes fuels to burn more completely, it further reduces emissions of carbon monoxide, volatile organic compounds and toxic air emissions. Biodiesel in a 20% blend with petroleum diesel reduces visible smoke and odor, particulate matter, carbon monoxide, total hydrocarbons and sulfur dioxide. and lead. And when the mixture is used with an oxidation catalyst, particulate matter is reduced even further. Water Pollution Water pollution associated with gasoline includes marine oil spills, groundwater contamination from underground gasoline storage tanks, and motor oil and vehicle fuel runoff. Marine oil spills like the Exxon V spill... middle of the paper... all in unpopulated regions. When this happens, our agricultural crops, forests and lakes suffer enormous damage. Acidcraine damages $2 to $3 billion worth of agricultural crops in the United States each year. Natural forests are dying due to acid rain, along with their biological diversity of species. Metal deposits in the soil resulting from acid rain are subsequently released into lakes and streams and are toxic to fish. Thousands of lakes in the United States and Canada have suffered severe losses of aquatic life due to acidity. Replacing petroleum fuels with biofuels can dramatically reduce the amount of sulfur dioxide emissions from the transportation sector. Using any amount of ethanol or biodiesel in blends displaces the corresponding amount of sulfur in the oil, thereby decreasing sulfur emissions. .