Gross alpha radiation is a type of energy released when certain radioactive elements decay or break down. For example, uranium and thorium are two radioactive elements found naturally in the Earth’s crust. Over billions of years, these elements slowly change form and produce “decay products” such as radium and polonium. During this change process, energy is released. Gross alpha radiation is one form of the energy released. As a result, gross alpha radiation can be found in your drinking water.
The amount of gross alpha radiation in water varies because the Earth’s bedrock contains varying amounts of radioactive elements. As radioactive elements decay, gross alpha radiation continues to be released into groundwater as positive ions called cations (e.g. radium 226 and 228), negative ions called anions (e.g. uranium), or as radiation with no charge.
Gross alpha radiation may cause health effects over time. Because gross alpha radiation loses energy rapidly and within a short distance, it does not pass through skin. It's not a hazard outside of the body. However, the radiation can be harmful if you eat, drink or breathe in something containing gross alpha radiation.
Over a long period of time and at elevated levels, radium increases the risk of bone cancer and uranium increases the risk of kidney damage. There are no immediate health risks or symptoms from drinking water that contains gross alpha radiation.
You cannot see, smell or taste gross alpha radiation or radioactive elements. Testing is the only way to know if they're in your water. The Health Department recommends testing your private water source for gross alpha radiation and uranium every five years.
Levels of uranium and radium in drinking water are regulated by the Environmental Protection Agency (EPA) and the State of Vermont. However, there may be more radioactive elements in your water. To account for this remaining radioactivity, the gross alpha level is also regulated. Public water systems in Vermont must keep the gross alpha radiation at or below the following maximum contaminant levels (MCLs) at each entry point of their distribution system:
- Adjusted Gross Alpha = 15 pCi/L (picoCuries per liter)
- Combined radium 226/228 = 5 pCi/L
- Uranium = 0.020 mg/L (milligrams per liter)
Adjusted Gross Alpha (AGA) is a calculated value based on the gross alpha radiation and uranium result. If the AGA is above the MCL, the water system is notified, and a plan is made to find the source of the radiation and lower its level in the water. You can estimate the AGA, if you have the results for gross alpha and uranium, by using the AGA Calculator.
- If the AGA result is less than 5 pCi/L and the uranium result is less than 0.02 mg/L, no more testing or treatment is necessary. Retest again in five years.
- If the uranium result is above 0.02 mg/L, but the AGA result is less than 5 pCi/L, consider treating for uranium. Retest again in five years.
- If the AGA result is above 5 pCi/L, but the uranium result is less than 0.02 mg/L, consider treating for radium or verify result by testing for radium-226/228. Retest again in five years.
- If the AGA result is above 5 pCi/L, and the uranium result is above 0.02 mg/L, consider treating for uranium and radium or verify the radium result by testing for radium-226/228. Retest again in five years.
Because gross alpha radiation causes cancer, any exposure to it will increase your risk of getting cancer. If you would like to lower or eliminate your exposure, consider treating your water for gross alpha radiation, even if it is under the MCL.
The radium-226/228 test is not offered at the Health Department
Radioactive elements can be removed from drinking water. There are different treatments for different elements.
Reverse osmosis treatment addresses all gross alpha radiation contaminants. It uses a synthetic membrane that allows water to go through but leaves radium, uranium and other gross alpha radiation contaminants behind. The membrane is continually rinsed. It is usually installed under the kitchen sink (point-of-use or POU), but can also be installed as a whole house system (point-of-entry or POE).
Cation Exchange Treatment
A conventional water softener (also called a cation exchange softener) can be used to reduce the level of radioactive ions with a positive charge, like radium. This treatment exchanges radium for sodium or potassium, which remains in the water. The radium is flushed away with the wastewater when the softener is cleaned. This type of treatment is typically installed as a POE system.
Anion Exchange Treatment
Anion exchange is a treatment like water softening, but uses a different media that exchanges the negatively charged radioactive ions, like uranium for chloride. This is also typically a POE system.
Your water may need to be treated for other water quality issues—such as hardness, iron, manganese and pH level—before it’s treated for radium or uranium. A water treatment professional will be able to determine which water treatment system is best for your water.
Re-test for gross alpha radiation after any treatment system is installed to make sure levels are below the MCL.