Do Legal Limits Exist?

Radon in Water: As of the time of this writing there is no official U.S. limit on radon in water. By the authority granted to the EPA under the Safe Drinking Water Act (SDWA), the EPA has proposed a Maximum Containment Level (MCL) of 300 picocuries of radon per liter of water.

Under the SDWA, each state would be required to monitor and enforce this regulation among public water supplies in their state. The SDWA does not require compliance among private wells or community water supplies (those serving less than 25 households annually).

This proposed MCL has been promulgated and published in the Federal Register (July 1991) to become effective in April 1993. That limit may not, however, become effective, as proposed limits are subject to debate and legislative processes.

Radon in Air: There is no federal limit on the amount of indoor airborne radon, as the EPA does not have the authority to regulate indoor residential air. The EPA has however established advisories and recommended action levels. Please refer to the section in this guide titled: "When Should I be Most Concerned About Radon".