Several independent study groups have reached the same general conclusions about tha acid rain problem. It was concluded that in the northeastern United States, acid rain (both dry and wet deposition) derives chiefly from man-made pollutants. The acid is doing significant damage to the environment, among other things, killing off species of freshwater fish. The scientists who did the studies have recommended strong measures to control the problem, because some of the effects of acid rain may be severe, possibly irreversible. Although the new reports have made the case for regulation stronger, the debate still continues over whether additional controls should be imposed.