When a leak in a storage tank or Pipeline occurs, Petroleum products can also get into the ground, and the ground must be cleaned up. To prevent leaks from underground storage tanks, all buried tanks are supposed to be replaced by tanks with a double-lining. This hasn't happened everywhere yet. In some places where Gasoline has leaked from storage tanks, one of the gasoline ingredients called methyl tertiary butyl ether (MTBE) has made its way into local water supplies. Since MTBE makes water taste bad and many people are worried about drinking it, a number of states are banning the use of MTBE in gasoline, and the refining industry is voluntarily moving away from using it when blending reformulated gasoline.

Gasoline is used in cars, diesel fuel is used in trucks, and heating Oil is used to heat our homes. When petroleum products are burned as fuel, they give off Carbon dioxide, a greenhouse gas that is linked with global warming. The use of petroleum products also gives off pollutants - carbon monoxide, nitrogen oxides, particulate matter, and unburned Hydrocarbons - that help form air pollution. Since a lot of air pollution comes from cars and trucks, many environmental laws have been aimed at changing the make-up of gasoline and diesel fuel so that they produce fewer emissions. These "reformulated fuels" are much cleaner-burning than gasoline and diesel fuel were in 1990. In the next few years, the amount of sulfur contained in gasoline and diesel fuel will be reduced dramatically so that they can be used with new, less-polluting engine technology.

Sources: Energy Information Administration, Petroleum Supply Annual 2004, June 2005., U.S. Department of Energy, Environmental Benefits of Advanced Oil and Gas Exploration and Production Technology, October 1999.
National Academies Press, Oil in the Sea III, Chapter 3, 2003.