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The- "EPA believes that any radon exposure carries some
risk - no level of radon is safe. "-Citizens Guide.
Realizing that there will always be some exposure to radon the EPA will be setting a Maximum Contaminant Level
(MCL) that will apply to public water supplies.
What is the Maximum Contaminant Level (MCL) for water
radon?
To date there has not been an MCL set for water radon. There
have been, however, a number of levels proposed both by the EPA and individual states. Once set, this MCL will
become the recommended standard used for private water supplies as have all the other MCL's.
What is the EPA doing about setting an MCL for water
radon?
- 1991 EPA proposed an MCL of 300 pCi/L
- 1991-1996 Debate raged on about the cost of doing this for
public water supplies and the need to better address air radon problems
- 1996 Congress made an amendment to the Safe Drinking Water
Act (SDWA) and added new radon provisions some of which are as follows:
- Withdraw the 300 pCi/L proposal
- Have the National Academy of Sciences (NAS) conduct a risk
assessment study
- Propose MCL in 1999
- Publish Final MCL in 2000
- If the MCL is "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 EPA must establish an "alternative MCL (AMCL)".
The level of the AMCL must be linked to average outdoor radon levels.
What could the AMCL be and what does it mean?
It is assumed that for every 10,000 pCi/L of radon in
water an increase in the indoor air radon as a result of using this water will be 1 pCi/L. If one assumes
the outdoor radon level is .4 pCi/L, then, the concentration of water radon that would cause this is 4000
pCi/L. The AMCL would then be 4000 pCi/L.
If the EPA decides to set the MCL for water radon below 4000 pCi/L,
it must allow a state to use 4000 pCi/L as their limit if the state creates an alternative indoor air radon
program. This program must create more of a health benefit then reducing water radon to the MCL set by the EPA.
What do I use for a limit now?
Presently, the state of Maine is recommending 4,000 pCi/L
for a limit for water radon. The State of New Hampshire is presently recommending 2,000 pCi/L.
click
here to see the latest explanation from the State of Maine on the new recommendation of 4,000 pCi/L
click
here to see EPA's latest information on the radon water rule
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