Is Your Well Water Radioactive? Radium and Gross Alpha
Radioactive substances can occur naturally in well water, especially in
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Radioactive substances can occur naturally in well water, especially in areas where groundwater moves through rocks containing uranium and thorium. Two terms you may encounter when testing your water are radium and gross alpha radiation.
Although they are related, they measure different things. Radium is a naturally occurring radioactive element, while gross alpha testing measures certain types of radioactive activity in a water sample.
Understanding this difference is important when choosing a water test and interpreting your results. Below, we explain how radium enters well water, what the EPA's drinking water limits mean, and when additional testing may be needed.
Radium is a naturally occurring radioactive metal found in certain rocks and soils. It forms as other radioactive elements, including uranium and thorium, break down over time.
Two forms are particularly important in drinking water: radium-226 and radium-228. Both can enter groundwater, but they release different types of radiation.
Gross alpha, on the other hand, is not a substance. It is a laboratory measurement of alpha radiation released by certain radioactive elements in a water sample.
A gross alpha test can help identify potential radioactive contamination, but it cannot tell you which element is responsible. Additional testing may be necessary to identify the source.
For regulatory purposes, the EPA's gross alpha standard excludes uranium and radon but includes radium-226. This is why you must interpret gross alpha results carefully, especially when comparing them with federal drinking water standards.
One important limitation is that radium-228 primarily emits beta radiation. Because of this, gross alpha testing alone cannot reliably detect all forms of radium. You may need a separate radium analysis even when gross alpha results are low.
Radioactive elements occur naturally in certain rocks and soils. As groundwater moves through these materials, small amounts of radium, uranium, and other radioactive substances can dissolve into the water.
This is more likely in areas with geological formations containing uranium or thorium. However, not every well drilled into bedrock contains elevated radioactivity.
The amount present depends on the minerals in the surrounding rock, groundwater chemistry, and local geological conditions.
Unlike some water contaminants, radioactive elements generally do not change the appearance, taste, or smell of drinking water. Laboratory testing is the only reliable way to detect them.
Radium levels can vary significantly between nearby wells because different rock formations contain different amounts of radioactive minerals.
For example, a USGS study in southeastern Pennsylvania found that radium concentrations exceeded 5 pCi/L in 46% of wells in one quartzite formation, compared with 7% of wells in other geological areas studied.
Water chemistry also matters. Radium can dissolve more readily under certain conditions, including acidic groundwater. This means two wells in the same area may produce very different results.
The Environmental Protection Agency (EPA) sets maximum contaminant levels (MCLs) for certain radioactive substances in public drinking water systems. These limits help reduce the health risks associated with long-term exposure.
The limits differ depending on the substance or type of radiation being measured.
| Contaminant | EPA limit | What it measures |
| Combined radium-226 and radium-228 | 5 pCi/L | The combined activity of both radium forms |
| Adjusted gross alpha | 15 pCi/L | Alpha radiation, including radium-226 but excluding uranium and radon |
| Uranium | 30 µg/L | The concentration of uranium in water |
The unit pCi/L (picocuries per liter) measures radioactive activity, while µg/L (micrograms per liter) measures the mass of a substance in water.
These limits apply to public water systems. Private well owners should use them alongside state and local health department recommendations, which may differ.
For example, Vermont recommends a uranium level below 0.020 mg/L (20 µg/L), compared with the federal limit of 30 µg/L.
A confirmed adjusted gross alpha result above 15 pCi/L exceeds the EPA's maximum contaminant level for public drinking water systems. For private wells, it indicates a result that should be reviewed with your state or local health department.
However, an initial gross alpha screening result may need additional calculations or testing before it can be compared with the federal standard. Follow-up testing can help determine which radioactive substances are contributing to the result.
Some states recommend follow-up testing at lower levels. For example, Vermont advises further evaluation when unadjusted gross alpha exceeds 5 pCi/L.
Radium, uranium, and radon are naturally occurring radioactive substances that may be found in groundwater. Although they are related through radioactive decay, they behave differently in water and require different testing methods.
| Substance | What it is | Main concern | Testing |
| Radium | Radioactive metal | Long-term exposure may increase cancer risk | Radium-226 and radium-228 analysis |
| Uranium | Radioactive metal | Long-term exposure can affect kidney health | Uranium concentration testing |
| Radon | Radioactive gas | Can enter indoor air when water is used, increasing lung cancer risk | Radon testing in water and indoor air |
| Gross alpha | Measurement of radioactive activity | May indicate the presence of certain radioactive substances | Gross alpha screening |
Unlike radium and uranium, radon is a gas. It forms during the natural breakdown of radium and can dissolve into groundwater.
When you use radon-containing water for showering, washing dishes, or other household activities, some of the gas can escape into indoor air. Breathing radon increases the risk of lung cancer, so indoor air testing is also important.
A radon test cannot replace uranium or radium testing. Each measures a different substance, so the appropriate test depends on your specific concern.
For more information, see our guides to uranium in well water and testing well water and indoor air for radon.
The right water test depends on the radioactive substances found in your area and any previous test results.
A gross alpha test commonly screens drinking water for certain types of radioactive activity. However, it doesn't identify individual substances, so you may need additional testing.
If you have an elevated gross alpha result, your state health department or a radiochemistry-specializing laboratory can recommend appropriate follow-up testing.
ETR Laboratories currently offers the following individual tests:
For more comprehensive testing, our Premium Well Water Test ($249) and Ultimate Well Water Test ($899) also include uranium and radon among the substances tested.
If you specifically need either analysis, contact ETR Laboratories to confirm current availability. You can also ask your state drinking water program for a list of laboratories certified to perform radiological water testing.
If your water test detects elevated levels of radium, uranium, or gross alpha activity, the next step is to identify the source and determine if treatment is necessary.
Start by reviewing the results with your state or local health department. They can help you understand applicable drinking water guidelines and recommend additional testing if needed.
Yes. Several water treatment methods can reduce certain radioactive substances, but their effectiveness depends on the contaminant and your water chemistry.
Common treatment options include:
Select treatment based on confirmed laboratory results. A system designed to remove radium may not remove uranium, and standard water softeners do not remove radon gas.
Consult a qualified water treatment professional to choose an appropriate system. Test your water again after installation to confirm that the treatment is working.
Long-term exposure to elevated radium levels in drinking water can increase the risk of cancer, particularly bone cancer. The EPA limits combined radium-226 and radium-228 to 5 pCi/L in public water systems. Private well owners should compare their results with state health department guidance and consider additional testing or treatment if levels are elevated.
No. Boiling water does not remove radium or other dissolved radioactive metals. As water evaporates, these substances can become more concentrated in the remaining water. If your well contains elevated radium levels, a qualified water treatment professional can recommend appropriate removal methods.
Gross alpha levels vary depending on local geology, so there is no single normal concentration for every well. The EPA's limit for adjusted gross alpha in public drinking water is 15 pCi/L. However, some states recommend additional evaluation at lower screening levels. For example, Vermont recommends further testing or calculations when unadjusted gross alpha exceeds 5 pCi/L.
No. Uranium and radium are different radioactive elements with different health risks and treatment requirements. Uranium exposure is particularly associated with kidney damage, while long-term radium exposure can increase cancer risk. Each requires specific testing, and finding one in your water does not necessarily mean the other is present.
If you're concerned about radioactive substances in your well water, laboratory testing can help you understand what's present.
ETR Laboratories offers uranium testing and radon in water testing, along with comprehensive well water testing panels.
If you specifically need radium or gross alpha testing, contact us to discuss available options before ordering.
Contact ETR Laboratories or call (800) 344-9977 for assistance.
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