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Silent, Invisible, and Deadly, Radon Gas Accumulates in Many Houses

Silent, Invisible, and Deadly, Radon Gas Accumulates in Many Houses

By Michael Smith, MedPage Today Staff Writer
Reviewed by Robert Jasmer, MD; Assistant Professor of Medicine, University of California, San Francisco
August 22, 2005

MedPage Today Action Points

Advise patients that household radon is regarded as the second leading cause of lung cancer.

Note that reducing household radon is relatively inexpensive.

Suggest regular household testing for the presence of radon.


WASHINGTON-An invisible silent killer stalks the nation, causing a plague of lung cancer, but most people are only dimly aware of the deadly hazard. People can take precautions without much effort although relatively few do.

That, according to many authorities, is the status in America of radon, a colorless, odorless, radioactive gas that seeps into people's houses from the soil beneath and causes occupants to die of lung cancer many years later. The annual toll may top out at 21,000 deaths a year, according to the Environmental Protection Agency.

Of course, that pales next to the 150,000 lung cancer deaths caused by smoking. Yet it's enough to make radon the second leading cause of lung cancer deaths in the country, says Phil Jalbert, acting director of the EPA's center for radon and air toxics.

Radon is a major risk, he said, even compared with other common causes of death, such as drunk driving (about 18,000 deaths a year), accidental falls in the home (8,000), and fires in the home (3,000).

The scientific consensus is that radon "represents a major environmental health hazard," says Bill Field, Ph.D., of the University of Iowa's College of Public Health. That consensus has been strengthened by several recent developments, Dr. Field says:

A pooled analysis of seven different North American residential radon studies, published in the journal Epidemiology in January, showed an 11% to 21% increase in lung cancer risk for those exposed to the gas. The risk grew with increasing radon exposure.

A similar study in Europe, published in the British Medical Journal in January, concluded that radon in European homes accounts for about 9% of deaths from lung cancer.

The World Health Organization launched a radon program, after concluding that the gas causes between 6% and 15% of all cases of lung cancer in the world. "Radon poses an easily reducible health risk to populations all over the world, but has not up to now received widespread attention," says Mike Repacholi, coordinator of WHO's Radiation and Environmental Health Unit.

U.S. Surgeon General Richard H. Carmona issued a national health advisory in January, urging citizens to take action against radon.

Radon comes from the radioactive decay of uranium in the soil. It has no immediate health effects, but it in turn gives rise to so-called "daughter products." Among them are two radioactive isotopes of polonium that can lodge in the lungs and cause cancer.

In the outside air, the concentration of radon is low - about 0.4 picoCuries per liter on average - but when it seeps into houses from soil, it can build up to higher levels.

The EPA argues that householders should have their houses tested for radon and take steps to reduce it if the average concentration is greater than the co-called "action level" of 4 picoCuries per liter of air.

Because uranium is not uniformly distributed, some places have less radon than others. In the U.S., for instance, Iowa has the highest radon concentrations, while states like Florida are relatively low.

But, Jalbert said, even in areas where radon is generally low, it can still build up to the action level in any given house, depending on how it is built and ventilated. "It's impossible to predict," he said.

Radon has not always been the bad guy. After its discovery in 1900, it was regarded as having curative powers and was added to everything from toothpaste to hair cream.

The link between lung cancer and radon was first shown in uranium miners, exposed to high levels of the gas during their work. Based on theoretical models, the EPA and many researchers argue that there's no safe threshold. What kills miners at high levels will also kill average citizens at lower levels.

And indeed, many studies seem to show just that. The European pooled analysis in January, for instance, concluded that the dose-response curve was linear, with no evidence of a threshold of safety.

The contrary view is championed by Bernard Cohen, Ph.D., a physicist at the University of Pittsburgh, who has argued for years that such studies are based on a flawed model -- the so-called linear, no-threshold model -- and buttressed by weak statistics.

The model essentially says that there's no safe threshold below which exposure to radon is safe. "We do not know at what level there might not be a cancer effect," said the EPA's Jalbert.

With colleagues, Dr. Cohen looked at average radon levels in 1,600 counties in the U.S., containing more than 90% of the nation's population, and plotted them against lung cancer deaths.

If the model were correct, he argues, counties with the highest average radon levels should have the highest rates of lung cancer -- but they don't. "It's just the other way around," he said.

To Dr. Cohen, the EPA's action level is a waste of time. "To worry about 4 picoCuries is really not justified," he says.

But if you are worried, says Dr. Field, the hazard can be banished without much effort.

In fact, the EPA's action level was set not because the agency thinks it's a safe level but because if the radon is at 4 picoCuries, it is relatively easy and inexpensive to reduce it sharply, says Jalbert.

The standard way of reducing radon levels is called sub-slab depressurization. Dr. Field says.

It works like this. A homeowner hires someone to drill through the basement floor (the "slab"), dig out some of the soil to create a hole, and insert a piece of plastic pipe. Attach a fan to the pipe and run the other end through the wall of the house into the open.

The idea is that the fan will create an area of low pressure in the small hole under the slab; soil gas, including any radon, will seep into that area, rather than the house itself, and be vented harmlessly into the atmosphere.

"It costs anywhere from $700 on up," Dr. Field says. Testing radon levels costs between $5 and $15 and should be done every few years, even if a radon mitigation system is installed in the house, he said.

The EPA says millions of American homes have been tested and about 575,000 have had mitigation systems installed.

People aren't worried about radon because there are "no sensory reminders," Dr. Field says - the gas is colorless, tasteless and odorless. "Because people don't see it, they don't think about it," he says.

"If radon were purple, people would be testing like crazy."

Primary source: British Medical Journal
Source reference:
Darby S et al. Radon in Homes and Risk of Lung Cancer: Collaborative Analysis of Individual Data from 13 European Case-control Studies. BMJ 2005 January 29, 330 (7485): 223.

Additional source: Epidemiology
Source reference:
Krewski D et al. Residential radon and risk of lung cancer: a combined analysis of 7 North American case-control studies. Epidemiology. 2005 Mar;16(2):137-45.

Additional source: Health Physics
Source reference:
Cohen BL. Lung cancer rate vs. mean radon level in U.S. counties of various characteristics. Health Phys. 1997 Jan;72(1):114-9.

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