According to the Environmental Protection Agency (EPA), a nationwide survey of radon levels in schools estimates
that nearly one in five has at least one classroom with radon exposure above the 4.0 picocuries per liter of air (pCi/L) --the EPA action level in the United States. The Southwestern Pennsylvania Environmental Health Project indicates that 69% of the schools have not been tested and 28% of those tested report radon levels above 4.0 pCi/L. 更多
