Buzzword: Radon

Consumer Reports News: June 30, 2008 10:52 AM

What it means. Radon is a colorless, odorless radioactive gas that results from the natural decay of uranium in soil and rock. The gas moves up from the ground and can diffuse into the air or enter a home, typically through cracks and holes in the foundation or concrete slab. (Radon can also enter the home through well water and by way of some building materials). The presence of radon in the home can pose a danger to your health, according to the Environmental Protection Agency. In fact, radon is the second leading cause of lung cancer in this country.

Why the buzz? Radon has been in the news recently with reports that some granite countertops can release dangerous levels of radon. This isn't a new claim—it surfaced in the 1990s—and it's fairly controversial. In April 2008, BuildClean, a nonprofit that aims to educate consumers about safe and healthy building materials, made news when it announced that its pilot project would provide free in-home radon testing of 300 homes in Houston to determine whether granite countertops emit harmful levels of radon. It's worth noting that two big makers of quartz countertops, Cambria and Cosentino (which also sells granite counters), are the sole funders of BuildClean. "By its nature, granite emits radon—the second leading cause of lung cancer in the U.S.," said Sara Speer Selber, BuildClean's president, in a press release at the time.

Next, in early May, W.J. Llope, Ph.D., a senior faculty fellow at the T.W. Bonner Nuclear Laboratory at Rice University in Houston, released a report in which he analyzed 18 articles covering 95 granite samples. In "Radiation and Radon from Natural Stone" (PDF download), Llope reported that 92 of the granite samples emitted no or very little radon, though two were in the 3.1-to-3.4 picocuries per liter (pCi/L) range, and one registered 4.2. (These measurements assume a hypothetical unventilated room, not a standard home, according to Llope's study.) The EPA estimates that the average indoor radon level is 1.3 pCi/L and suggests that you reduce radon when the level in your home is 4 pCi/L or higher.

Shortly after Llope released his report, the Marble Institute of America trade group announced the results of a study of its own. A professor of geology at the University of Akron tested 52 samples (four each of 13 different types) of the most popular granites used for countertops in the U.S., representing the majority of granite countertops sold here, according to the MIA. Ten added "almost immeasurable amounts of radon to the house," reads the study, while two had radon levels of 0.04 pCi/L. The highest level of radon emitted from one stone was 0.27 pCi/L. The study did not account for natural ventilation in a home, which would dilute the concentration of radon.

Looking for some clarity on this issue, I interviewed Michael Kitto, Ph.D., a research scientist for the New York State Department of Health. As part of a study he's planning to submit for peer review, he measured the radon emissions from more than 40 granite and engineered stones in airtight containers, without ventilation. Kitto found that the engineered stones emitted almost no radon and many of the granite stones were very low emitters of radon. A few stones emitted slightly more radon, and only one emitted a substantial amount of radon. (Kitto defines substantial by saying it could produce from a few to several pCi/L in a room; he adds that the exact value depends on many variables, including kitchen volume and countertop size.) BuildClean and Cosentino also fund Kitto's study.

Consumer Reports has done limited radon testing on granite counters. Using a radon meter in a room with the door closed, we tested two granite counters. None added any radon to the air. (Look for our report on short-term radon tests kits in the September 2008 issue of Consumer Reports, on sale and online this August.)

The EPA emphasizes the importance of testing the air in your home for radon, whether or not you have countertops made from granite. But there are too many variables and too little information to generalize about the radon risk granite counters pose to humans, according to Dave Ryan, an EPA press officer. The EPA has not conducted studies on radon in countertops and has no plans to do so at this time. Limestone, soapstone, and marble countertops do not pose a radon concern, according to Kitto.

If you have granite countertops and want to test them for radon, place a short-term home radon test kit near the granite and another kit in the basement or lowest usable level of the home. Follow the manufacturer's directions carefully, as the test results are affected by heat and humidity.

• If the test results state a radon level of that's lower than 2 pCi/L in your basement, you don't need to do anything.

• If the test reveals a radon level of 2 to 4 pCi/L in your basement, follow up with a long-term test kit to more accurately measure the level.

• If the long-term results from your basement are between 2 and 4 pCi/L, consider professional remediation to minimize risk.

• If the short- or long-term results in the basement are 4 pCi/L or above, hire a radon professional for an assessment and, if necessary, remediation.

• If the kit in the basement/lowest level registers a lower level of radon than the one near the granite, you can be fairly sure that the granite is the source of radon and not something beneath your home. If the level near the granite is 2 to 4 pCi/L, our experts say you might consider remediation—removal. If the level is 4 pCi/L, our experts recommend remove the granite countertop.—Kimberly Janeway

Essential information: Read "Dealing With the Dangers of Radon Gas" for information about remediation and finding a qualified pro in your area. Read about lead and radon test kits, then find out about the best countertops in our Ratings-based report in the August 2008 issue of Consumer Reports.

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