Clean air legislation intended to help people breathe easier may have an unintended benefit: It may help fish in the Chesapeake Bay, and other East Coast estuaries, breathe easier as well.

That's a message that a group of state and federal air pollution officials and water quality managers plan to drive home to the public and public officials in the coming months and years.

The decision was made at the second "Shared Resource" conference, one of an ongoing series of meetings in which officials dealing with East Coast bays and estuaries discuss issues of mutual concern. The two-day October conference, which focused on the impact of airborne nitrogen deposition on coastal waters, drew representatives from state and federal air pollution programs as well.

Linking air emissions to water quality would be a fundamental shift in 25 years of pollution control policy during which air and water issues have been strictly segregated. Air and water officials within state and federal agencies often do not even know each other.

Yet recent research, coupled with computer models, has pointed to air pollution as a major source of nitrogen, one of the two nutrients of concern in the Bay system.

"We need to get started thinking about the breadth of things," Bruce Hicks, of the National Oceanic and Atmospheric Administration's Air Research Laboratory, implored participants as the conference opened.

Generated by fossil fuel combustion, the nitrogen oxides emitted from tailpipes and smokestacks account for anywhere between 20 percent and 35 percent of all the nitrogen entering the Bay. Some of those emissions originate in places as far flung as Detroit, Toronto, Cincinnati and Knoxville, Tenn.

Their impact on the Bay is great enough that full implementation of the Clean Air Act amendments of 1990, something that may be unlikely, would significantly expand the amount of "breathing room" for fish beyond what would result from the Bay Program's 40 percent nutrient reduction goal, according to calculations by Lewis Linker, modeling coordinator with the EPA's Chesapeake Bay Program Office.

Most aquatic species require oxygen to survive, only less of it than land dwellers. Much of the Bay's water quality woes in recent decades are linked to nutrient pollution that has reduced oxygen levels in the water.

Excessive amounts of the nutrients phosphorus and nitrogen spur large algae blooms in the Bay. When the algae dies, it sinks to the bottom and is decomposed by bacteria in a process that depletes the water of oxygen. When water becomes anoxic, depleted of oxygen, many species must abandon those areas. Species that can't move may die or suffer other ill-effects, such as poor reproduction or stunted growth.

The Bay states have commited to reducing nutrients 40 percent by the turn of the century through controls on sewage treatment plants and on nutrient-laden runoff from farms and urban areas. That would reduce the amount of anoxia in the Bay by about 20 percent in a typical year, according to Bay Program calculations.

But if reductions of airborne nitrogen oxides that could result from Clean Air Act implementation were factored in, anoxia in the Bay could be reduced by 25 percent, according to Linker.

More stringent air controls could result in even greater reductions. For example, stronger pollution controls being contemplated by the Ozone Transport Commission to control chronic smog problems in the Northeast would result in further reductions in deposition, and improvements in water quality. The commission, a panel created by the 1990 air act which includes the top environmental officials of a 12-state area stretching from Virginia to Maine, is charged with finding ways to reduce ozone in the region.

Nitrogen oxides are a major contributor to the ozone problem, so efforts to reduce ozone also have the potential to benefit the Bay and other coastal waters. As a result, conference participants targeted the commission's February meeting to begin making their case that air pollution controls will help water ways, too.

But reductions that the commission could make are just the beginning. Estimates made by the EPA's Regional Atmospheric Deposition Model indicate that 75 percent of all the airborne nitrogen falling on the Bay's 64,000-square mile watershed comes from outside the watershed: mostly from an "airshed" that is 5.5 times larger.

If pollution controls being contemplated for the Northeast were extended throughout the airshed, according to estimates from the model, nitrogen deposition on the Bay watershed would be cut three times more than what would be achieved just through Clean Air Act controls.

"These [reductions] help all coastal estuaries, not just the Chesapeake Bay, but from the Chesapeake Bay on north," said Robin Dennis, a scientist with NOAA's Atmospheric Modeling Division.

Much of those emissions are coming from the west areas that are not part of the 12-state region overseen by the Ozone Transport Commission.

Still, those western areas may not be out of reach. Tom Maslany, director of the Air, Radiation and Toxics Division of EPA Region III, which includes almost all of the Bay watershed, noted that state and federal officials had recently formed a new Ozone Transport Assessment Group. The group covers the entire eastern two-thirds of the nation and is charged with developing even broader control strategies to control ozone, a recognition that nitrogen oxides and other airborne pollutants contributing to the ozone problem can travel huge distances.

But conference participants also recognized that significant hurdles are ahead. First, it is unclear that the 1990 Clean Air Act amendments will be fully implemented. Many states have refused, or delayed, implementation of an advanced vehicle inspection and maintenance program to control automobile exhaust, opting for less-thorough programs which do not control emissions of nitrogen oxides. Regulations that would require burners on power plants to control nitrogen oxide emissions have also been delayed. In addition, more than 30 measures have been introduced in Congress to repeal parts, and in some cases all, of the 1990 amendments to the act.

And then there is the problem with the laws themselves. The Clean Air Act is designed to protect air quality, not water quality. The Clean Water Act is aimed at controlling discharges into waterways, not into the air.

"The two statutes were not designed to work together and on their face they do not work together," said Mary Nichols, EPA assistant administrator for air and radiation. But, she added, "I don't believe that the difficulties necessarily require a major rewrite of either the Clean Air Act or the Clean Water Act to solve the problem."

Robert Perciasepe, EPA assistant administrator for water, said it would be difficult under the present laws to regulate air pollution specifically to benefit water quality. But he said it was legitimate to make the case that certain air control actions would offer "more bang for the buck" by also helping water quality. "Clearly, providing more benefits for air pollution reductions is a good thing," he said.

Both Perciasepe and Nichols encouraged the group in their effort to present the issue to decision makers and the public. Nichols suggested that people interested in water quality should begin commenting on proposed air regulations, including a current EPA proposal to require additional controls on emissions from heavy diesel engines.

Conference participants also acknowledged that they will have to bolster their arguments with scientifically defensible data. While a series of studies have pointed to air as a major contributor of nitrogen to the Bay and other coastal areas, serious questions remain.

The largest question is how much of the nitrogen oxides dropping out of the sky makes it into the Bay. About 10 percent of the deposition is falling directly on the Bay and its tributaries. The rest falls on land throughout the watershed, and much of that nitrogen is retained by trees and other plants. As a result, estimates of the total airborne contribution of nitrogen reaching the Bay ranges from a low of 20 percent of the total to more than 30 percent.

"We're talking about a level of impact that, even if it is off by a significant factor, is still worth pursuing," said Bill Matuszeski, director of EPA's Chesapeake Bay Program Office. "Over time, we will get better numbers. But meanwhile, we know enough to move forward."

And other participants agreed that the time had come to begin making the case for taking a "multimedia" approach, a comprehensive air and water pollution control strategy, toward coastal environmental issues.

"Multimedia management, I think, is now possible for the first time, in a defensible way," Robert Thomann, a professor of environmental engineering at New York's Manhattan College, told conference participants.

Thomann is one of the leading water quality modelers in the world, and has worked as a consultant to the Bay Program in the development of models that helped the Bay Program establish its 40 percent nutrient reduction goal.

"Everything that we have done in the last 6-7 years or longer has been translated into policy, and I think that was a good idea, within the basin, Thomann said. "Extending it beyond the basin into the airshed, I think, is in the right direction from a policy point of view."

For more information about the impact of air pollution on the Bay, see "Detroit and Toronto meet the Bay," in the March 1995 Bay Journal, and "Air Act would boost Bay cleanup," in the October 1995 Bay Journal.