Uranium in Well Water: What the ATSDR Report Says About Your Test Result
If uranium showed up on your well-water report, ATSDR’s public health statement on uranium makes a point worth knowing first: the health effects of natural and depleted uranium are due to chemical effects and not to radiation. This explainer covers where uranium in well water comes from, which organ it affects, what the cancer evidence shows and what it doesn’t, and the steps ATSDR and EPA suggest for households on private wells.
A metal from the bedrock
Uranium is a naturally occurring chemical substance that is mildly radioactive, and everyone is exposed to low amounts through food, air, and water. It is naturally present in nearly all rocks and soils. It gets into water by dissolving soil, eroding soil and rocks, or in releases from processing plants.
Most of the difference between one well and another comes down to geology. In most areas of the United States, low levels of uranium are found in drinking water, with higher levels where rocks and soil are naturally high in uranium. For well owners, higher levels tend to come from wells drilled in uranium-rich rock formations. Industry also matters near some sites. Mining, milling, and processing of uranium can release it into the environment, and inactive uranium industries may continue to do so.
Uranium also brings related elements with it. EPA notes that uranium decays to form radium, which breaks down into the radioactive gas radon, and all three can dissolve in water and build up in wells.
Is your well your biggest source?
Not always. For most people, food and drinking water are the main sources of uranium exposure. ATSDR estimates that people take in 0.9 to 1.5 micrograms of uranium per day.
Food is a bigger part of that than many people expect. Root crops such as potatoes, parsnips, turnips, and sweet potatoes contribute the highest amounts of uranium to the diet, and the amount is directly related to the uranium in the soil they grow in. Some of it is on the surface of the vegetable: uranium can stick to plant roots, and unwashed potatoes, radishes, and other root vegetables are a primary source in the diet.
Each metal tends to reach people mainly through one route, and that route is often not the one people worry about most, as covered in this site’s guide to where heavy metals come from.
Why the kidneys are the concern
Uranium’s main target is the kidneys, and kidney damage has been seen in humans and animals after inhaling or ingesting uranium compounds. ATSDR’s short summary says it directly: exposure to high levels of uranium can cause kidney disease.
It helps to know what the body does with uranium in the first place. Most of the uranium you breathe or ingest is not absorbed and leaves the body in the feces. Absorbed uranium is deposited throughout the body, with the highest levels found in the bones, liver, and kidneys, and 66% of the uranium in the body found in your bones. It can remain in the bones for a long time, with a half-life of 70-200 days, while most of the uranium that is not in bones leaves the body in the urine in 1-2 weeks.
The chemical form matters. ATSDR reports that swallowing water-soluble uranium compounds causes kidney effects at lower doses than insoluble compounds.
The evidence has limits. Kidney damage has not been consistently found in soldiers who carried uranium metal fragments in their bodies for several years. Metal fragments in the body are a very different exposure from drinking water, though, so this finding doesn’t settle questions about wells.
What does the cancer evidence show?
ATSDR says uranium is not known to cause cancer, but can decay into other radioactive materials that may. Humans and animals exposed to high levels of uranium did not have higher cancer rates. The Committee on the Biological Effects of Ionizing Radiation (BEIR IV) reported that eating food or drinking water with normal amounts of uranium will most likely not cause cancer.
It helps to know where the official classifications stand. Neither the National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC) nor the EPA have classified natural uranium or depleted uranium with respect to carcinogenicity.
Uranium miners are the obvious counterexample. Studies have reported lung and other cancers in uranium miners, but the miners also smoked and were exposed to other cancer-causing substances such as radon and silica dust. Because the miners had all these other exposures, it is hard to blame their cancers on uranium itself.
For children, ATSDR says very large exposures might cause kidney damage like that seen in adults, but it is not known whether children are more or less sensitive than adults.
On medical tests, ATSDR notes that natural uranium is in your normal diet, so there will always be some level of uranium in all parts of your body. Uranium can be measured in blood, urine, hair, and body tissues, and normally, urinary sampling is the preferred method for assessing uranium exposure.
What to do with your result
About 15% of Americans use private wells as their main source of drinking water, and unlike public water systems, wells usually aren’t regulated or routinely inspected for radionuclides. That leaves testing up to you.
| When | Step | Source |
|---|---|---|
| Every year | Test for bacteria, nitrates, viruses | EPA |
| Every three years | Test for radionuclides | EPA |
| You suspect high uranium | Have your water tested | ATSDR |
| High levels are found | Consider using bottled water | ATSDR |
| You garden in high-uranium soil | Wash produce, discard outer layer | ATSDR |
Different tests measure different things, so EPA suggests you ask your local drinking water office or radiation control program which tests are most useful for your area. The same habits for reading a lab report are covered in this site’s guide to arsenic in private well water, which shows how to compare a result against a national standard and when to confirm it with a second test.
ATSDR’s advice on food is simple. Avoid eating root vegetables grown in soils with high levels of uranium, consider washing fruits and vegetables grown in that soil, and discard the outside portion of root vegetables. These steps cost little, and they address the part of your exposure your water test doesn’t measure.
Reading the result
The number to compare your result against is EPA’s: the EPA established a maximum drinking water contaminant level of 0.03 mg/L for uranium. Check the units on your report before you compare. If your result is above that, ATSDR’s advice is the one in the table: if elevated levels are found, consider using bottled water.
The same evidence also supports some calm. Everyone takes in some uranium every day, exposure in most places is low, and ATSDR says the health effects come from uranium’s chemistry, not its radiation.
Sources
- atsdr.cdc.gov – “Health Consultation: Durango Discovery Museum” (2010)
- wwwn.cdc.gov – “Uranium | Public Health Statement | ATSDR”
- epa.gov – “Natural Radionuclides in Private Wells | US EPA” (2018)
- wwwn.cdc.gov – “Uranium | ToxFAQs™ | ATSDR”
- wwwn.cdc.gov – “Uranium | Toxicological Profile | ATSDR”