States are taking the lead with studying levels of radon in drinking water and air even as federal regulators lag, as a coincidence of geology and population density leaves some more at risk than others of suffering from the naturally occurring radioactive toxin.
Nine states have guidelines for radon in drinking water, with New Jersey considering the most stringent levels, fourfold tighter than a limit proposed but never mandated by U.S. EPA in 1999.
Pennsylvania, New Hampshire, Maine, Rhode Island, Connecticut, Vermont, Massachusetts and Wisconsin are the other states that have some guidance levels for the chemical, said Ted Campbell, a hydrogeologist with the North Carolina Department of Environment and Natural Resources, and chairman of a committee tasked with recommending its own levels.
But most of the recommendations are at levels scientists say are insufficient to protect human health.
Radon is a known carcinogen that is allowed in drinking water at relatively high levels of risk in certain places. If a toxic dump in water were to confer the same levels of cancer as does radon, EPA would have taken a tougher stance on limiting public exposure, said Campbell.
"If you just look at radon in water contribution and compare that to compounds that EPA regulates like [trichloroethylene] and benzene and some of the pesticides, it turns out that radon in water carries with it higher risk that many or most of EPA-regulated compounds at their standards," Campbell said.
The President's Cancer Panel this year examined the link between chemicals in the environment and cancer and stressed the importance of reducing radon exposure. As a rash of houses got built amid the real estate boom in the early 2000s, few states mandated developers to account for the gas.
It is difficult to quantify exactly how many people are exposed. A person would have to live for more than 20 years within a house built on soil containing radon, or use water with dissolved gas, before there is a significant health threat. A disease itself would not show up until age 40, said William Field, a radon researcher at the College of Public Health at University of Iowa who testified on the gas to the President's Cancer Panel.
Lung cancer statistics reveal a grim picture, however, with radon exposure causing nearly 14,000 Americans to die each year. It is the primary cause of lung cancer in non-smokers, an effect that is not surprising given that it is radioactive. The 2010 President's Cancer Panel report stressed exposure to the gas as among the most ignored phenomena in the United States.
Unlike other toxins that carry cancer risk, radon-222 is a naturally occurring gas that results from the breakdown of uranium found in all rocks and soils of the Earth. Its presence in water is measured in picocuries, a measure of radiation given off per gram of the material.
Not all states are at equal risk; some such as Iowa and Pennsylvania have higher levels of the gas, while others such as Texas or Florida have low levels.
The scenario is further complicated by the fact that radon is a bigger problem in air than it is in drinking water.
"Some folks say that it's an even greater threat in air, and an argument that's often made is that, 'Why should we even bother to deal with drinking water?'" said David Pringle, campaign director at New Jersey Environmental Federation, who participated in New Jersey's study on radon-222.
But more people die from drunken driving accidents than they do from jaywalking, but that does not mean we do not need crosswalks, he said.
For air, EPA recommends a limit of 4 picocuries per liter (piC/L). Field said two-thirds of all lung cancer cases happen below that limit, and half occur below 2 piC/L. He recommended levels below 0.4 piC/L in air.
EPA limits in limbo
EPA has not published a final maximum limit for radon in water. In 1999, the agency proposed that states adopt different radon mitigation programs that reduce exposure from air and water. In places where they are implemented, the levels of radon in drinking water could be set at 4,000 piC/L. Otherwise, the agency advised water companies to use a limit of 300.
But the agency never finalized the limits because utilities protested against the costs of controlling for the gas, a cost they said would have ultimately trickled down to ratepayers, according to Bill Wolfe, director of New Jersey's Public Employees for Environmental Responsibility.
EPA said in a statement that it continues to evaluate and consider "stakeholder concerns with the proposed rule while we work to address other Safe Drinking Water Act priorities." It suggests all homeowners test for the gas.
States that have higher levels of the gas are taking their own steps to study the threat in water. Some are looking at advisory guidelines, above which homeowners are advised to do voluntary sampling of their homes to determine risk.
A panel appointed by New Jersey's Department of Environmental Protection called the Drinking Water Quality Institute came up with its recommended level in February 2009. It chose 800 piC/L, a level five times lower than EPA's, at which it calculated the costs of water treatment would be compensated for by the number of lives saved. Since then, the limit has not been used in any constructive rulemaking.
John Plonski, assistant commissioner for water resources management at the state DEP, said scientists at the department have been evaluating the recommendation of the panel.
"New Jersey DEP, like many other environmental agencies, is struggling with resources," Plonski said. "If New Jersey DEP would adopt it, that would be the first standard adopted in the U.S."
North Carolina authorities have appointed their own panel to come up with advisory guidelines and that process should be done in early 2011, said Campbell, who is on the panel.
Estimates vary, but about half of North Carolina's population -- under half of the about 9 million residents -- have low levels of radon in their water, he said. Risk could be higher for owners of private drinking water wells, he said.
"Radon could potentially contribute more risk to a well owner than if they were sitting beside a Superfund site," Campbell said. "All that said, the soil gas portion tends to be a lot more important."