The EPA's recommended action level for indoor radon is what value?

The Environmental Protection Agency (EPA) has established a recommended action level for indoor radon at 4 picocuries per liter (pCi/L). This value is significant because it represents the point at which remediation efforts should begin to reduce radon levels in residential spaces. The rationale behind this action level is grounded in health considerations, as radon is a known carcinogen. Long-term exposure to radon levels above this threshold can increase the risk of lung cancer, particularly for individuals who smoke. By setting the action level at 4 pCi/L, the EPA aims to protect public health by encouraging homeowners to take preventative or corrective measures when radon levels are found to be high. This guideline helps to inform homeowners, real estate transactions, and public health policies related to radon exposure.