Early refineries in the U.S. processed crude oil to recover the kerosene. Other products (like gasoline) were considered wastes and were often dumped directly into the nearest river. The invention of the automobile shifted the demand to gasoline and diesel, which remain the primary refined products today. Refineries pre-dating the US Environmental Protection Agency (EPA) were not subject to any environmental protection regulations. Today, national and state legislation requires refineries to meet stringent air and water cleanliness standards. In fact, oil companies in the U.S. perceive obtaining a permit to build a modern refinery to be so difficult and costly that no new refineries have been built (though many have been expanded) in the U.S. since 1976. Some attribute increasing dependence in the U.S. on imports of finished gasoline, to lack of new refineries. On the other hand, studies have revealed that accelerating mergers among the refineries have further reduced capacity, resulting in tighter markets particularly in the U.S.
