Radon guidelines miss the mark
More than 21,000 people die each year in the U.S. and tens of thousands perish worldwide from radon-induced lung cancer, according to the U.S. EPA.
Silent, odorless, and colorless, radon gas in homes waits decades to kill its victims, making it an overlooked public-health risk. Now that improved detection tools and research breakthroughs have proven that low doses of radon cause lung cancer, radon-prevention techniques for homeowners have advanced to the cutting edge. In response, Health Canada and the World Health Organization (WHO) are poised to release new voluntary guidelines to tame the problem, but experts say that mandatory changes in building codes are needed.
Canada will soon announce a new voluntary radon action guideline of 200 becquerels per cubic meter (Bq/m3), down from 800 Bq/m3 set in 1988, says Bliss Tracy, a nuclear physicist at Health Canada. A becquerel measures the rate of radioactive decay in a substance. WHO's International Radon Project is planning to release final guidelines for testing, action, and mitigation by June 2007.
Canada's draft guideline is in keeping with other developed countries, including the U.S., where homeowners are encouraged to reduce radon when it reaches concentrations above 150 Bq/m3. The U.S. Clean Air Act doesn't provide the U.S. EPA with the authority to regulate indoor air, including radon in homes. Instead, Congress directed EPA to conduct outreach and education efforts that would eventually lead to the attainment of outdoor levels of radon inside all homes.
Radon is produced by the decay of natural uranium in rocks and soil and, depending on the underlying geology, can build up to high levels indoors when it slips through cracks and openings in foundations.
About 10% of lung-cancer deaths in Canada are due to radon, which kills more Canadians than homicide, drowning, or fires, Tracy says. More than 21,000 people die each year in the U.S. and tens of thousands perish worldwide from radon-induced lung cancer, according to EPA.
Scientists have known since the 1950s that radon, at high doses such as those found in uranium mines, causes lung cancer. But individual studies of the relatively low doses in homes have had ambiguous results, Tracy says. In 2005 and 2006, two projects in North America and Europe pooled the results of more than 20 studies and, for the first time, provided direct evidence that radon in homes causes lung cancer, says Dan Krewski, an epidemiologist at the University of Ottawa and a coauthor of one of the studies.
The studies found that long-term exposure to radon concentrations of 200 Bq/m3 doubles the risk of lung cancer for nonsmokers compared with the risk at average background levels of 10 Bq/m3, Tracy says. If levels in all homes in Canada were below 200 Bq/m3, deaths from radon would fall from 1589 to 1242 per year. Health Canada set the new guideline at 200 Bq/m3 because it fell where lung-cancer risk becomes significant and where mitigating homes to the standard is affordable, he adds. It can cost $1000–3000 to clear radon from an existing home.
However, roughly 90% of radon-caused lung cancer cases occur from exposures to less than 200 Bq/m3, according to Sarah Darby, a medical statistician at Oxford University (U.K.). If radon were regulated like other pollutants, where an acceptable cancer risk might be 1/100,000, the guideline would be less than 40 Bq/m3, says Bill Field, an epidemiologist at the University of Iowa. Instead, the current guidelines reflect what is economically and technically feasible to achieve, he says.
"In Britain and most other countries, the concept of an action level has been overemphasized. It would be more appropriate to ask, 'What is the cost-effectiveness of reducing radon?'" Darby says. Building radon-prevention measures into a new home can cost as little as $350 and bring radon levels down as low as 50 Bq/m3, she says.
The most successful approach to the radon challenge would be to first set a strong net-risk reduction goal on the basis of the number of homes with radon concentrations above the action level, says Bill Angell, a building scientist at the University of Minnesota. Currently, more than 10 million homes in the U.S. exceed the action level. But EPA has not set a goal for the number of houses above the action level, only for the number of homes tested, mitigated, and built radon-resistant. "There are more homes [in the U.S.] above the action level for radon than at any time in history," Angell says. In addition to a net-risk-reduction goal, countries should adopt compulsory limits for new construction, as required in Sweden and Norway, he says.
