Frequent Questions: Drinking Water Testing
View frequently asked questions about the RadNet drinking water testing.
On this page:
- What federal standards exist that address radiation in drinking water?
- Where can I find the analytical results from drinking water samples?
- How does the EPA sample drinking water for radionuclides?
- Why does the EPA test drinking water for radionuclides?
- Where can I find more information about radionuclides in drinking water?
What federal standards exist that address radiation in drinking water?
Under the Safe Drinking Water Act (SDWA), the EPA sets legal limits on the levels of certain radionuclides in drinking water. These limits are applicable to all federal, state and local jurisdictions, including local city public works facilities. Under SDWA, the Agency established a dose-based Maximum Contaminant Level (MCL) for beta particle and photon (gamma) radioactivity of 4 mrem/yr. The MCL is based on lifetime exposure criteria, which assume 70 years of continued exposure to contaminants in drinking water.
For more information, visit Laws and Regulations.
Where can I find the analytical results from drinking water samples?
All RadNet drinking water sampling results are available on the RadNet Envirofacts website.
How does the EPA sample drinking water for radionuclides?
More than 60 drinking water sampling locations reported results in the United States in 2018 as part of the RadNet monitoring network. Drinking water samples are typically collected four times a year from taps and are sent to the EPA’s National Analytical Radiation Environmental Laboratory (NAREL) for analysis. Each of these samples is analyzed for tritium (H-3) One sample per year from each location is analyzed for iodine-131 (I-131).
An annual composite sample from each sampling location is analyzed for gross alpha and beta radiation. Any sample with elevated gross alpha radiation (greater than 2 pCi/L) will be analyzed for radium-226 (Ra-226), plutonium (Pu-238, Pu-239 Pu-240), and uranium (U-234, U-235, and U-238). If the radium-226 result is between 3 and 5 pCi/L, then the sample is analyzed for radium-228 (Ra-228). All of the annual composite samples are also analyzed for gamma-emitting radionuclides. Twenty-five percent (25%) of the annual composite samples are analyzed for strontium-90 (Sr-90), rotating locations so Sr-90 is analyzed for each location every four years.
For more information about precipitation and drinking water sampling analysis, visit Envirofacts.
Why does the EPA test drinking water for radionuclides?
Having a monitoring system in place to screen drinking water for radionuclides ensures that in the event of an emergency the RadNet monitoring system is able to measure radionuclide levels in local water supplies. This is valuable inform which can help to inform decision makers whether protective actions or additional sampling are needed. Routine monitoring helps establish expected (background) activity ranges for any radionuclides that are normally present at detectable levels, and confirms the absence of those that are not.
Where can I find more information about radionuclides in drinking water?
Under the Safe Drinking Water Act (SDWA), the EPA sets legal limits on the levels of certain radionuclides in drinking water. Under SDWA, the Agency established a dose-based Maximum Contaminant Level (MCL) for beta particle and photon (gamma) radioactivity of 4 mrem/yr. The MCL is based on lifetime exposure criteria, which assume 70 years of continued exposure to contaminants in drinking water.
Additionally, the EPA has developed a non-regulatory drinking water protective action guide (PAG) that can protect the public in the event of a radiological incident that affects drinking water supplies. The purpose of the protective action guidance for drinking water is to restrict the use of contaminated water for drinking and to provide recommendations for local communities on providing alternative sources of drinking water. The drinking water PAGs apply during the intermediate phase of an incident, which may last for weeks to months but not longer than one year. This guidance does not in any way affect public water systems' compliance obligations under applicable National Primary Drinking Water Regulations promulgated under the Safe Drinking Water Act (SDWA).
For more information, visit Safe Drinking Water Act or Protective Action Guides (PAGs).