Issued The General Accounting Office weighed into the debate on acid rain yesterday with a lengthy report that concluded there are too many scientific uncertainties to make any recommendations on the subject.

"At the present time, scientific information alone does not lead unequivocally to a conclusion on whether it is appropriate to begin control actions now or to await better understanding," the GAO said in a report that is not likely to provide much ammunition for either side of the acid-rain debate.

Acid rain is caused by air pollutants that change chemically in the atmosphere and return to earth as dry particles or acidic rain and snow. The phenomenon has been blamed for killing aquatic life in hundreds of lakes and streams in Canada and the northeastern United States, and recent studies suggest that it may be damaging forests as well.

But the GAO said that scientists disagree sharply on whether the damage is likely to get worse or stay the same, suggesting that the question of what to do about controlling acid rain is essentially a crap shoot.

Federal regulators and Congress "must weigh the risks of further, potentially avoidable environmental damage against the risks of economic impacts from acid rain control actions which may ultimately prove to be unwarranted," it said.