Radioactive granite countertops?
Last month, Suzanne Zick, who lives in Magnolia, Tex., a small town northwest of Houston, called the E.P.A. and her state’s health department to find out what she should do about the salmon-colored granite she had installed in her foyer a year and a half ago. A geology instructor at a community college, she realized belatedly that it could contain radioactive material and had it tested. The technician sent her a report indicating that the granite was emitting low to moderately high levels of both radon and radiation, depending on where along the stone the measurement was taken.
“I don’t really know what the numbers are telling me about my risk,” Ms. Zick said. “I don’t want to tear it out, but I don’t want cancer either.”
The E.P.A. recommends taking action if radon gas levels in the home exceeds 4 picocuries per liter of air (a measure of radioactive emission); about the same risk for cancer as smoking a half a pack of cigarettes per day. In Dr. Sugarman’s kitchen, the readings were 100 picocuries per liter. In her basement, where radon readings are expected to be higher because the gas usually seeps into homes from decaying uranium underground, the readings were 6 picocuries per liter.
The average person is subjected to radiation from natural and manmade sources at an annual level of 360 millirem (a measure of energy absorbed by the body), according to government agencies like the E.P.A. and the Nuclear Regulatory Commission. The limit of additional exposure set by the commission for people living near nuclear reactors is 100 millirem per year. To put this in perspective, passengers get 3 millirem of cosmic radiation on a flight from New York to Los Angeles.