The United States Environmental Protection Agency (EPA) recommends homes be fixed if an occupant's long-term exposure will average 4 picocuries per liter (pCi/L) that is 148 Bq/m3.[101] EPA estimates that one in 15 homes in the United States has radon levels above the recommended guideline of 4 pCi/L.[2] EPA radon risk level tables including comparisons to other risks encountered in life are available in their citizen's guide.[102] The EPA estimates that nationally, 8% to 12% of all dwellings are above their maximum "safe levels" (four picocuries per liter—the equivalent to roughly 200 chest x-rays). The United States Surgeon General and the EPA both recommend that all homes be tested for radon.