Environmental regulations in North America have succeeded in cutting acid rain, but many North American lakes and streams damaged by the phenomenon still have not recovered, according to new research published today in the journal Nature. In contrast, the study, which was conducted by 23 prominent scientists, found that lakes and streams in Europe have declined in acidity, probably because Europe imposed sulfur-dioxide regulations sooner than the U.S. Sulfur-dioxide emissions from coal-burning power plants are considered to be largely responsible for acid rain. Environmental Defense Fund scientist Michael Oppenheimer said the study shows that stricter laws are needed in the U.S. The EPA is expected to propose regulations by the end of the year to reduce pollution from old, dirty, coal-fired power plants.