A decade after federal regulations were enacted to reduce the effects of acid rain, the results, according to a new study in the journal BioScience, suggest some progress has been made but also show a clear need for tougher standards. The study gives Congress powerful evidence that, despite wavering by the Bush administration, the recently reintroduced Clean Power Act provides the appropriate reductions of sulfur dioxide and nitrogen oxides emissions required to let the Northeast environment recover to a healthy condition.

The study looks at new data from the Hubbard Brook Experimental Forest in New Hampshire, the site used for data for the 1990 Clean Air Act amendments on acid rain. The new study shows, among other things, that acid rain has led to the depletion of calcium, an important plant nutrient, and has mobilized a form of aluminum harmful to forests and aquatic organisms.

These changes have caused trees such as red spruce and sugar maple to become more susceptible to stress and dieback from, for instance, cold weather, while lakes and streams in the region have not measurably improved despite reductions in sulfur dioxide emissions. Fish that are acid-sensitive appear to be declining as a result. More broadly, these pollutants are associated with other environmental problems, including mercury deposition, smog and climate change.

Maine should be particularly interested in these results because it has hundreds of lakes and streams considered sensitive to acidification, and while sulfate levels in surface waters have declined in Maine the level of acidity in the water has not. This suggests that broad improvements in emissions standards are needed to make a difference to Maine’s aquatic life.

To see real improvements in the water, reductions of sulfur emissions of at least 50 percent will be needed, according to the study. Significant reductions in nitrogen oxides from power plants are necessary, too, but also need to be extended to cuts from transportation sources. The sooner the reductions can be put into place the sooner improvements in the region should be seen, but even under the best circumstances full recovery will take decades.

The study arrives at an excellent time, as President Bush, by removing his support for reductions in carbon dioxide, unintentionally focused attention on the Clean Power Act. In addition to carbon dioxide, the act calls for 75 percent reductions of sulfur dioxide, nitrogen oxide and 90 percent reductions in mercury emissions, all by 2007. Close enough to meet the conclusions in the study.

Both Sens. Olympia Snowe and Susan Collins are sponsors of the bill. Rep. Tom Allen will introduce a companion bill in the House, which Rep. John Baldacci will also sponsor. Both bills are likely to attract bipartisan support in the Northeast and bipartisan opposition in the Midwest, where coal- and oil-fired electric generators are the source of a substantial part of the problem.

Christopher Cronan, of the University of Maine and an author of the acid rain study, points out that a tougher nitrogen-oxides level helps out in numerous ways in addition to acid rain reductions. NOx reductions also cut ground-level ozone, the amount of greenhouse gas and the depletion of stratospheric ozone. The benefit in terms of human and environmental health are enormous compared with the cost of cleaning up this pollutant.

President Bush’s recent decisions on the environment have been anything but encouraging, and there is a chance congressional Republicans will try to spare him further political damage by keeping the Clean Power Act off his desk. That would be a mistake. The long-term problems of global warming and acid rain require a strong response at the federal level. Mr. Bush seemed to know that during the campaign and needs Congress now to remind him that the problems have not gone away.