Alternatives to CFCs May Harm Wetlands : Environment: The chemicals could lead to acidity buildup, researchers say. But EPA officials doubt that study will slow effort to protect the ozone layer.

Raising new ecological fears, researchers will report today that chemicals soon to be widely used in place of ozone-depleting compounds could damage sensitive wetlands, especially in arid urban regions such as Southern California.

Under an international treaty, production of CFCs, or chlorofluorocarbons, which thin the Earth’s protective ozone layer, has gradually been banned. Compounds that are far less damaging to the ozone layer are taking their place.

But in today’s edition of the journal Nature, Massachusetts researchers report that the CFC substitutes react in the atmosphere with oxygen to form acidic rain that could be toxic to vegetation in some wetlands.

The acid would not accumulate in most wetlands, including coastal marshes, lakes and streams, but seasonal wetlands in highly populated urban areas “could attain appreciable concentrations . . . within a few decades,” according to the study by Atmospheric and Environmental Research Inc.

Wetlands, which provide foraging grounds for migratory birds and nurseries for fish, are one of the nation’s most depleted natural resources. Over 90% have been paved or drained.

The potentially harmful side effect is unlikely to affect the international phaseout of CFCs, which began in 1989. But it could prompt questions about the U.S. Environmental Protection Agency’s endorsement of the CFC alternatives, which are replacing Freon in automobile air conditioners and household refrigerators.

EPA officials said Wednesday that the results come from a single preliminary study and that they have no plan to retreat from the alternatives, called hydrofluorocarbons, or HFCs, and hydrochlorofluorocarbons, or HCFCs.

“This is an interesting study and warrants further research, but it will probably not change EPA’s perspective on HFCs and HCFCs,” said Drusilla Hufford, who heads an EPA program exploring the safety of the substitutes. “CFCs do definite damage that translates into effects on human health, so I think moving ahead [with the alternatives} is definitely justified.”

In the United States, manufacture of all CFCs is prohibited after the end of this year. Although old CFCs and stockpiles can be legally used, use of the alternatives is surging.

The study focused on three alternative chemicals that produce the acid, including HFC-134a, a refrigerant for automobile air conditioners that is expected to approach 300,000 tons produced per year by 2025.

Steven Schwarzbach, U.S. Fish and Wildlife Service contaminants specialist in Sacramento, called the impact on wetlands a “potential new risk” that warrants exploration because the CFC alternatives will be used worldwide.

“Clearly a transition away from CFCs must be made. As sometimes happens, however, the solution to one problem is not without unintended risks,” Schwarzbach wrote in an accompanying article in Nature.

Despite some environmental drawbacks, scientists generally believe that the substitutes pose far less of a global threat than CFCs. EPA officials and chemical manufacturers worry that critics of the ban will use the findings to try to keep the ozone-depleting chemicals in production.

“The only alternatives people can move to rapidly are things like [HFC] 132a, and we would be concerned if people used this as an excuse not to phase out CFCs,” said Tony Vogelsberg, an environmental manager for DuPont.

The chemical companies emphasized that the results were based on a worst-case scenario.

“The risk is very low,” Vogelsberg said.

Since 1989, chemists have known that the CFC replacements could form trifluoroacetic acid in the air. But this study is the first projecting that the acidity could reach high levels in some wetlands.

Using mathematical models, the researchers calculated that the acid “will be exceedingly low in the oceans” and most freshwater lakes and streams because waters flush in and out.

“However, there are numerous water bodies characterized by little to no outflow and high evaporation rates. This type of water body may have the potential to accumulate air and rain-borne acids,” the report says.

The researchers concluded that high acidity could accumulate within 30 years in these types of wetlands, often found in arid climates.

Rare vernal pools, found in the Central Valley and Southern California, may be the most susceptible, Schwarzbach said. Rainfall is the only source of water in vernal pools, which are shallow depressions in grasslands, so the acid would concentrate in soil and plants as the water evaporates in dry seasons.

Vernal pools at the Santa Rosa Plateau near Murrieta in Riverside County and in southwestern San Diego County may be among the highest at risk because of their proximity to major urban centers.

Air in heavily populated regions can contain CFC emissions 10 to 20 times greater than the global average, the researchers reported. In the Los Angeles Basin, CFC emissions measure several thousand tons annually, and volumes of the alternatives could be comparable.

“You have a large population down there that will use the CFC replacement compounds in cars and everywhere else,” said Tom Maurer, a U.S. Fish and Wildlife Service environmental contaminants specialist. “The potential rainfall concentrations [of acid] in that part of the state are likely to be high.”

Once common in California, vernal pools are now scarce and contain a variety of rare species. As the rainwater evaporates each spring, the pools are filled with circular bands of colorful wildflowers. During the wet season, they are used by wintering ducks and other waterfowl.

“They are a very special kind of wetland,” Maurer said.

Since the study found acidity buildup would take several decades, Hufford and industry officials said they have plenty of time to conduct more research while allowing use of the alternative compounds.

Chemical manufacturers have spent years and millions of dollars studying the acidity issue and other environmental impacts of replacements for CFCs, which are used not only as refrigerants but as industrial cleaning solvents.