In its first regulations on the burial of carbon dioxide underground, the EPA on Tuesday announced measures to protect drinking water from the gas behind the bubbles in carbonated beverages. The fledgling technology, known as carbon sequestration, is critical to reducing carbon dioxide released into the air from coal-fired power plants, one of the country's largest sources of the greenhouse gas.

"This rule paves the way for technologies that will protect public health and reduce the effects of climate change," said Benjamin Grumbles, an assistant administrator in the agency's water office.

The proposal upgrades the 1974 Safe Drinking Water Act to include a new category of injection wells solely for carbon dioxide storage, and creates extensive siting, testing and monitoring requirements to prevent leaks. The EPA already regulates injection wells used to boost oil production and dispose of hazardous and other waste.

Though carbon dioxide in water isn't necessarily a problem -- think Perrier or Diet Coke -- too much of it can turn water acidic and leach toxic heavy metals and other contaminants out of the surrounding rock and into water supplies, according to scientists. Injecting carbon dioxide underground can also push other pollutants, such as saltwater, into underground aquifers.

"The risks are small, but if sequestration was to be used very widely, a small risk becomes large," said Susan Hovorka, a scientist with the Bureau of Economic Geology at the University of Texas in Austin who has done research on long-term storage of carbon dioxide.

Besides water concerns, one of the major environmental issues facing carbon sequestration is the potential for the buried gas to slowly escape into the atmosphere, where it can contribute to global warming.

The United States has the capacity to store 3,900 gigatons of carbon dioxide at 230 different underground storage sites, according to Energy Department estimates. The U.S. emits about 7 gigatons of carbon dioxide every year.