One out of 50 people who live next to coal ash ponds in South Carolina and elsewhere could get cancer from drinking water contaminated with arsenic, a coal ash pollutant, according to federal research that two environmental groups said the Bush administration kept under wraps for years.

"We now have the full picture about coal dump sites across America, and it's not pretty," said Eric Schaeffer, director of Environmental Integrity Project, adding that the EPA has "known about these (health) hazards for a long time."

His group and Earthjustice obtained a 2002 report by the Environmental Protection Agency that the Bush administration had refused to release, despite numerous requests under the Freedom of Information Act.

The study examined potential health risks of more than 200 coal ash waste dumps across the country, including a dozen in South Carolina. The groups made the information public Thursday.

Among other things, the data show that coal ash ponds have a statistical chance of polluting waterways with boron at concentrations up to 2,000 times higher than what the EPA says is safe for wildlife.

Much of the data was used to produce a report in 2007 about the health risks of coal ash impoundments, but environmental watchdog groups said the release of the 2002 data shows that EPA officials knew about the dangers of coal waste for years before informing the public.

Ben Moore of the Coastal Conservation League said the findings also add new fuel to the debate over Santee Cooper's plan to build a new coal-fired power plant near Florence, which could have two ash dumps.

A Post and Courier Watchdog report last fall documented how ash ponds and landfills in South Carolina have contaminated groundwater with arsenic, selenium and other toxic chemicals. Utilities and industries that operate these dumps say they've taken pains to monitor the contamination and improve the structural integrity of these impoundments.

Last December, the ash issue made national headlines when an impoundment next to a coal plant in Tennessee failed, spilling a billion gallons of ash-tainted muck. Schaeffer said the spill was an "Exxon Valdez moment" for the coal industry that has led to new calls to regulate coal ash. Right now, the EPA considers coal ash a non-hazardous waste. In March, the EPA said it would take a new look at the safety of ash ponds and landfills and develop new regulations by year's end.