EPA Report on Radon in Water
Radionuclides in Drinking Water:
1991 Proposed Rule
In July 1991, the U.S. Environmental Protection Agency (EPA) proposed a National Primary Drinking Water Regulation (NPDWR) for radon-222, three other radionuclides (radium-226, radium-228, and uranium), and two categories of radionuclides (adjusted gross alpha emitters; beta and photon emitters) (56 FR 33050). The Maximum Contaminant Level (MCL) for radon was proposed at 300 pCi/l and (at the time of proposal) was estimated to have the following impacts:
- Estimated lifetime cancer risk of about 2 x 10-4 (2 of every 10,000 individuals exposed)
- About 26,000 Public Water Systems Affected
- Total Annual Cost of about $180 Million
- Avoidance of about 80 cancer cases per year
Those commenting on the 1991 proposal for radon raised several concerns, including cost of implementation, especially for small systems, and the larger risk to public health from radon in indoor air from soil under buildings. Per the 1996 amendments to the Safe Drinking Water Act (SDWA), EPA plans to withdraw the 1991 radon proposal in summer, 1997, and will be developing a new proposal based on a risk assessment to be conducted by the National Academy of Science and any new information that may be available.
1994 Report to Congress:
Multimedia Risk
and Cost Assessment of Radon
In 1992, Congress directed EPA to report on the risks from exposure to radon, the costs to control this exposure and the risks from treating to remove radon. The report estimates the risk, fatal cancer cases, cancer cases avoided and costs for mitigating radon in water and in indoor air. It found that cancer risks from radon in both air and water are high. While radon risk in air typically far exceeds that in water, the cancer risk from radon in water is higher than the cancer risk estimated to result from any other drinking water contaminant. EPA conducted a quantitative uncertainty analysis of the risks associated with exposure to radon in drinking water. This analysis, reviewed by the Science Advisory Board (SAB), is discussed in the Report to Congress.
Findings in brief:
- People are exposed to waterborne radon in three ways: from ingesting radon dissolved in water; from inhaling radon gas released from water during household use; and from inhaling radon progeny derived from radon released from water.
- The estimated total U.S. cancer fatalities per year due to waterborne radon from all three routes of exposure is 192, with a range from about 51 to 620. The report notes that the regulated industry has estimated much higher costs than EPA for a 300 pCi/L MCL.
- For example, the American Water Works Association (AWWA) estimated national costs at $2.5 billion/year (October, 1991, AWWA).
- The final part of the report includes the SAB comments and an EPA discussion of the issues raised by the SAB.
|
Radon Risks
(source: 3/94 Report to Congress on Radon in Drinking Water) |
|
Drinking Water |
Indoor Air |
| # of Fatal Cancer Cases per Year (above &
below target or action level; for drinking
water, includes community ground water
systems only) |
192 |
13,600
|
| Proposed Level or Target Level |
300 pCi/L (water) [1991] |
4 pCi/L (air) |
| Individual Lifetime Risk of Fatal Cancer at
Target Level |
2 in 10,000 |
1 in 100 |
| Total Number of People Above Target Level |
19 million |
15 million |
| Number of Fatal Cancer Cases Avoided
Annually by Meeting the Target Level |
84 |
200 (annually, expected to
increase)[updated 5/97]
2,200 (annually, if 100% voluntary
monitoring
& mitigation) |
| Total Annual Cost for Mitigating Radon |
$272 million
|
$1,504 million
(to avoid 2,200 fatal lung cancers) |
1996 Amendments to Safe Drinking Water Act
Add New Radon Requirements [§1412 (b) (13)]
The following is a summary of pertinent portions of the 1996 SDWA Amendments for radon:
Withdraw 1991 proposed national primary drinking water regulation for radon
Withdraw the 1991 proposed MCLG, MCL, monitoring, reporting, and public notification requirements for radon (56 FR 33050, July 18, 1991).
National Academy of Sciences
Arrange for the National Academy of Sciences (NAS) to conduct an independent risk assessment for radon in drinking water and an assessment of the health risk reduction benefits associated with various mitigation methods of reducing radon in indoor air.
Health Risk Reduction and Cost Analysis
Publish a radon health risk reduction and cost analysis for possible radon MCLs for public comment, by February 1999; the analysis must consider the following [§ 1412 (b)(3)(C)]:
- Health risk reduction benefits (directly from controlling radon).
- Health risk reduction benefits likely to occur from reductions in co-occurring contaminants.
- Costs.
- The incremental costs and benefits associated with each MCL considered.
- The effects on the general population and on groups within the general population likely to be at greater risk.
- Any increased health risk that may occur as the result of compliance.
- Other relevant factors.
(Note: EPA is developing a new framework for cost-benefit analysis of drinking water regulations, in accordance with SDWA)
Propose Radon Regulation by 1999
Propose an MCLG and National Primary Drinking Water Regulation (NPDWR) for radon by August, 1999.
Promulgate Radon Regulation by 2000
Publish an MCLG and Final NPDWR for radon by August 2000.
Multimedia Radon Mitigation Programs
If EPA promulgates an MCL "more stringent than necessary to reduce the contribution to radon in indoor air from drinking water to a concentration that is equivalent to the national average concentration of radon in outdoor air," the Agency must establish an "alternative MCL."
