WHO cuts radon limits due to lung cancer risks

updated 11:44 a.m. ET Sept. 22, 2009

GENEVA - The World Health Organization on Tuesday drastically reduced the amount of radon from natural sources that countries should allow to accumulate in buildings, given the fatal lung cancer it can cause.

Radon is a naturally occurring gas found in mines, caves and water treatment plants. But radon contained in rocks and soil also can enter homes and other buildings through cracks in concrete, floor gaps, small holes in walls and drains.

In 2003, the U.S. Environmental Protection Agency said that radon accumulating in buildings is responsible for an estimated 21,000 deaths from lung cancer in the United States each year.

Two years later, the U.S. surgeon general issued a national health advisory warning about the dangers of indoor radon, an invisible, odorless and tasteless gas. Inexpensive test kits to determine radon levels in homes are commercially available, and U.S. authorities suggest people test their houses for radon levels every two years.

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WHO, the U.N. health agency, said Tuesday that studies conducted in Europe, North America and China in 2005 and 2006 showed that the presence of the radioactive gas in homes is more dangerous than previously thought. The agency said radon is a significant cause of 3 percent to 14 percent of worldwide lung cancer cases.

"Radon is the second most important cause of lung cancer after smoking in many countries," said Dr. Maria Neira, a WHO specialist on health and environment. "Most radon-induced lung cancers occur from low and medium dose exposures in people's homes."

Referring to a common measure of radiation, WHO's new handbook recommends countries to set radon limits in homes of 100 becquerel per cubic meter. The agency's previous limit was set in 1996 and allowed for 10 times greater radon exposure.

WHO said there is now far more scientific evidence about the effects of the gas. But WHO expert Ferid Shannoun acknowledged that it had taken experts from around the world quite a long time to recommend the change in WHO radon limits.

The agency's new recommendation is close to the limit for safe homes set by the U.S. Environmental Protection Agency. However, many other countries allow radon levels two to four times higher, according to WHO.

It said easy building improvements can reduce radon levels significantly and protect inhabitants from the gas.

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