Radiological Contaminants
Radiological contaminants are radioactive particles that occur naturally in areas of uranium and radium deposits and in waste from man-made nuclear reactive processes. Radiological contaminants, even in very small concentrations, pose a cancer risk. The implementation of the Radionuclide Rule will result in the reduced exposure to uranium for 620,000 persons, resulting in protection from toxic kidney effects of uranium and a reduced risk of cancer.
Does the radiological contaminant regulation apply to my water system?
If your system is a community public water system your system must test for these contaminants. Radiological contaminants have been regulated since 1976 with Maximum Contaminant Levels currently set for five types.
Frequency of Sampling
Samples must be taken at each entry point to the distribution system after treatment.
Initial monitoring
Four consecutive quarters of monitoring for:
Gross Alpha, Combined Radium-226/228, and Uranium.
No monitoring required for most community water systems for:
Beta Particle and Photon Radioactivity
Vulnerable community water systems must sample quarterly for Gross beta and annually for Tritium and Strontium-90.
Reduced Monitoring
Gross Alpha, Combined Radium-226/228, and Uranium
- If the average of the initial monitoring results for each contaminant is below the detection limit: One sample every nine years.
- If the average of the initial monitoring results for each contaminant is greater than or equal to the detection limit, but less than or equal to one-half the Maximum Contaminant Level: one sample every six years.
- If the average of the initial monitoring results for each contaminant is greater than one-half the Maximum Contaminant Level but less than or equal to the Maximum Contaminant Level: one sample every three years.
Beta Particle and Photon Radioactivity
- If the running annual average of the gross beta particle activity minus the naturally occurring potassium-40 activity is less than or equal to 50 pCi/L: one sample every 3 years.
Increased Monitoring
Gross Alpha, Combined Radium-226/228, and Uranium
- A system with an entry point result above the Maximum Contaminant Level must return to quarterly sampling until four consecutive quarterly samples are below the Maximum Contaminant Level.
Beta Particle and Photon Radioactivity
- If the gross beta particle activity minus the naturally occurring potassium-40 activity exceeds 50 pCi/l, the system must sample at the initial monitoring frequency
If your tests indicate levels of radiological contaminants higher than the Maximum Contaminant Level, your water must:
- Resample to confirm the test results. The State may also require your system to continue quarterly sampling until the Maximum Contaminant Level is met.
- Follow the Drinking Water Program’s instructions regarding when and what type of public notice they need to give.
- Enter into an agreement with the Drinking Water Program to allow the water system to continue to use the water supply while solutions to the Maximum Contaminant Level violation are being explored and any needed financing is being planned.
- Start working with the Drinking Water Program to consider options to eliminate the radiological contaminants from your system. In nearly all very small community water systems, finding a different source of water supply is the most economical solution to a radionuclide problem. Radon can be removed with aeration. Any treatment may produce radioactive wastes that will be difficult to dispose of.
- Agencies listed at the end of this section may be able to help your water system to arrange for financing to solve the violation problem.
- Remember that exposure to radiological contaminants at levels found in water is a risk over long term exposure. It is not an acute risk for short periods of time. Proceed to work out a reasonable and affordable solution for your drinking water supply.
Radiological Contaminants
Contaminant |
MCL* |
Potential Health Effects |
Sources In Drinking Water |
Gross Alpha Particles |
15 picocuries per Liter (pCi/L) |
Increased risk of cancer |
Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation |
beta particles and photon emitters* |
4 millirems per year |
Increased risk of cancer |
Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation |
Radium 226 and Radium 228 (combined) |
5 pCi/L |
Increased risk of cancer |
Erosion of natural deposits |
*Maximum Contaminant Levels
These are the current Maximum Contaminant Levels for radiological contaminants and the levels that are proposed. The units of measure are peculiar to radioactivity and represent very small quantities. A total of 168 individual beta particle and photon emitters may be used to calculated compliance with the Maximum Contaminant Level
