点击显示 收起
June 1, 2000 -- The longer you live in a house, the less concerned you tend to be about radon gas. But new research involving more than 1,000 Iowa women indicates that it may be time to think about it, and get your home tested.
Women who had lived in the same house for 20 years or more -- and whose homes had radon levels that met, but did not exceed, the level at which the Environmental Protection Agency suggests taking action -- had a 50% increased risk of developing lung cancer, says the study published in the American Journal of Epidemiology.
"As the radon exposure increased, the lung cancer rates also increased," says study author R. William Field, PhD.
Radon is a colorless, odorless, tasteless radioactive gas that is produced by the breakdown of natural radium in earth, rock, and water. The gas typically enters a house -- or school, office, or other building -- through the basement.
"Radon decays into solid radioactive particles," Field explains. When sensitive lung tissue is exposed to these particles, the DNA of the cells is damaged, and lung cancer may result. Unfortunately, there are no symptoms to warn you that you're inhaling the radioactive particles.
Earlier studies have shown that radon exposure causes lung cancer, but the Iowa Radon Lung Cancer Study, which was funded by the National Institute of Environmental Health Sciences, is the first to rigorously measure radon exposure in the home.
The researchers said they limited the study to women because they tend to spend more time at home than men and have less occupational exposure to substances that may cause lung cancer. They looked at a group of women ages 40-84 who were recently diagnosed with lung cancer and had lived in their present home for 20 years or more. The women completed detailed questionnaires, were interviewed, and had radon measurements taken in their homes over a period of a year.
By analyzing where the women spent time in their houses, and including estimates of their radon exposure outside the home, the researchers were able to determine each woman's exposure level. These women were then compared with another group of women who were similar in every way except that they had no history of lung cancer when the study began.
"Iowa has the highest radon concentration in the nation," says Field, a research scientist in epidemiology at the University of Iowa. He and his colleagues report that approximately 60% of the radon concentrations found in the basements of the study participants' homes, and 30% of the first-floor radon concentrations, exceeded the EPA's so-called "action level" of 4 pCi/liter (picocuries per liter).
The "action level" is not a health-based standard, Field explains, as even lower radon levels pose some risk. The EPA recommends correcting radon levels in houses that exceed this level.
The study definitely adds to the body of knowledge about radon, says EPA spokeswoman Kristy Miller. "It was well designed and well executed," she says. In contrast to earlier research, Miller says, the IRLCS looked at long-term exposure in homes that had high radon levels.
The National Academy of Sciences published its report on radon last year. "That report looked at all the research in the world and included some of the preliminary data from the Iowa study. [The report] said that radon causes 15,000 to 22,000 cases of lung cancer a year in this country," Miller says.
The EPA recommends that everyone living below the third floor test their homes for radon. Check the yellow pages for services that do radon testing, or you can buy a simple home test kit for under $50, Miller says. The EPA suggests using the 90-day test, but people who prefer the two- to-seven day test should do the test twice and average the results, Miller says.
If the radon level is 4 pCi/liter or higher, steps should be taken to correct it. For example, Field says, radon leaking from a drain in the basement floor can be remedied by sealing the drain. A depressurization system can also be installed, though that may cost several thousand dollars in an old home. Putting the system in a new home is far less expensive.
For information about radon and home testing, call the National Safety Council at (800) SOS-RADON.
Vital Information:
作者： 2006-6-27