Uranium in Water

The short answer

Uranium in water usually comes from the ground. EPA lists erosion of natural deposits as the source of uranium in drinking water, and ATSDR, the federal agency for toxic substances, describes uranium as a mildly radioactive element that is naturally present in nearly all rocks and soils. The Connecticut Department of Public Health (CT DPH) adds that uranium has no smell or taste, so you can't tell it is there by looking at or tasting your water.

Two numbers frame every uranium result:

• The legal limit for public water is 30 µg/L^[1]. That is EPA's maximum contaminant level (MCL), in force since December 8, 2003^[1].
• The health goal is zero. EPA's maximum contaminant level goal (MCLG) for uranium is 0 µg/L^[1]. It is a health target, not a legal limit.

Your utility must meet the MCL. A private well has no such duty: EPA says private wells are not regulated by the federal government under the Safe Drinking Water Act, nor by most state governments. Around 15 percent^[3] of the U.S. population relies on a private well, and nobody tests that well unless the owner does.

The only way to know your level is a test by a state-certified lab. Our uranium water test guide explains who should test, which lab method to ask for and how to take the sample. If the lab doesn't detect uranium, no treatment is needed based on that result.

Uranium levels and what to do

The table below lines up the federal uranium benchmarks with what each kind of result means for your household. The values come from our versioned benchmark data, which records EPA's figures and the date we last checked them.

How the uranium limit works

EPA defines the MCL as the highest level of a contaminant allowed in drinking water, set as close to the health goal as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards for public water systems. EPA defines the MCLG as the level below which there is no known or expected risk to health, and calls MCLGs non-enforceable public health goals.

For uranium the health goal is zero, and the MCL sits above it. So read your result in two steps. First, compare it with the MCL of 30 µg/L^[1]. A result at or above it is above the legal limit for public water. Second, remember that a result below the MCL is under the legal limit, not a sign that the water has no uranium at all. Some households with a detected result below the MCL choose to retest and track it over time.

Check the units on your report

Uranium numbers appear in more than one unit. The limit above is shown in micrograms per liter, while ATSDR writes the same EPA limit in milligrams per liter. A microgram is one thousandth of a milligram. Before you compare your number with the limit, check which unit your report uses. If you're not sure, ask the lab to give you the result in the same unit as the limit. Our guide on how to read your lab report explains the units, detection limits and lab flags you will see on it.

Health effects of uranium in drinking water

Uranium in drinking water is a long-term concern. EPA's drinking water regulations list the possible effects of long-term exposure above the MCL as an increased risk of cancer and kidney toxicity.

Chemistry more than radiation. Uranium is radioactive, but in drinking water its chemistry is the bigger concern. ATSDR says the health effects of natural uranium are due to chemical effects and not to radiation, and EPA says swallowing uranium is a hazard because of its chemical properties. CT DPH puts it the same way: the chemical properties of uranium in drinking water are of greater concern than its radioactivity.

The kidneys. ATSDR says kidney damage has been seen in humans and animals after inhaling or ingesting uranium compounds, and that exposure to high levels of natural uranium can cause kidney disease. It adds that swallowing water-soluble uranium compounds affects the kidneys at lower doses than insoluble compounds do. CT DPH says studies show that drinking water with elevated levels of uranium can affect the kidneys over time.

What happens to uranium you swallow. CT DPH says most ingested uranium is eliminated from the body, but a small amount is absorbed and carried through the bloodstream. ATSDR says the absorbed uranium is deposited throughout the body, with the highest levels in the bones, liver and kidneys.

Children. ATSDR says the health effects seen in children from toxic levels of uranium are expected to be similar to those seen in adults.

Showering and bathing. Drinking is the main concern. CT DPH says bathing and showering with water that contains uranium is usually not a health concern, and that uranium gets into the body mainly by swallowing it, not through the skin or by breathing. EPA adds that the skin blocks the alpha particles uranium gives off.

A water test measures uranium in your water, not in anyone's body, and it can't diagnose anything. If you have been drinking water with uranium above the MCL, or you are worried about your health, talk to a health professional and bring your lab report.

Uranium in well water: where it comes from

Most uranium in well water comes from the rock around the well. EPA says uranium is present naturally in virtually all soil, rock and water. CT DPH explains how it reaches a well: when a well is drilled into bedrock that contains uranium, the uranium can get into the well water, and the amount in bedrock and well water varies greatly from place to place.

Which rocks. The U.S. Geological Survey says uranium is a common trace element in many rock types but is particularly enriched in certain rocks, such as granites. Like arsenic, its presence in groundwater depends on the chemistry of the aquifer. USGS names dissolved oxygen and carbonate alkalinity as the conditions that favor uranium dissolving into the water.

Where it shows up in wells. USGS studied about 2,100^[6] domestic wells sampled in 1991–2004^[6]. Uranium was above the EPA MCL in 1.7 percent^[6] of them. The highest concentrations occurred most often in basin-fill aquifers in the West and in crystalline-rock aquifers in the Rocky Mountains and the Northeast. USGS names the Central Valley of California, the Newark Basin sediments of northern New Jersey and the crystalline-rock aquifers of New England among the places with relatively high uranium in groundwater. ATSDR says that in most areas of the United States, low levels of uranium are found in drinking water, and that higher levels may be found where rocks and soil hold more natural uranium.

Your well, not your neighbor's. Because the amount varies so much, CT DPH says testing your well water is the only way to find out whether your well has high uranium. A neighbor's result is a reason to test your own well, not a substitute for it.

Human sources. EPA and ATSDR both say people who live near facilities that mine or process uranium may have higher exposure. EPA notes that waste from uranium mining can contaminate water, soil and air if it is not disposed of properly.

Radium and radon. CT DPH says radium and radon may be found with uranium in bedrock. EPA explains why: uranium decays to radium, and radium decays to release radon, a radioactive gas.

Food counts too. ATSDR says food and drinking water are the main sources of uranium intake for the general public, and that root crops such as potatoes, parsnips, turnips and sweet potatoes contribute the most uranium to the diet.

If you are on a well, uranium is one test among several. Our well water testing guide covers the yearly well check, and our page on arsenic in water covers another natural contaminant that USGS ties to the same aquifer conditions. You can also build a test plan that fits your water source and household.

When to retest for uranium

CT DPH advises testing a private well for uranium at least once, and names two moments: when you buy a house with a well, and when a new well is drilled. Connecticut has required a uranium test for newly drilled wells since October 1, 2022^[5]. After that first test, plan to retest in these situations:

• To confirm a result before acting. If uranium was detected at or above the MCL, retest with a state-certified lab before you decide anything.
• If your well has a detectable level. CT DPH says uranium levels in well water can fluctuate, and suggests testing again every 5 years^[5] if your water has a detectable level.
• After you install treatment. CT DPH says to test the treated water every year to be sure the system is working properly.
• After work on the well. CDC lists replacing or repairing any part of your well system among the times to have your well water tested again.
• When your household changes. CDC also names the times when you or someone you live with becomes pregnant, or a child starts living with you.

If uranium was not detected and nothing about the well has changed, keep the report as a baseline. CDC suggests asking your local health department which tests to add based on where you live.

How to lower uranium in your water

Start with a confirmed result from a state-certified lab. What you do next depends on what it shows, and "no treatment needed" is a real outcome.

If uranium was not detected, no treatment is needed based on that result. Keep the report.

If uranium was detected below the MCL, no treatment is needed based on the federal limit. The health goal is zero, so keep the report and retest on the schedule above to see whether the level changes.

If a confirmed result is at or above the MCL, CT DPH says you will need to treat your water to remove the uranium. While you follow up, ATSDR suggests considering bottled water if elevated levels are found, and CDC suggests contacting your local health or environmental department, which can help you understand the result and what to do next.

Treatment options. CT DPH says reverse osmosis systems are the most common type of treatment used for uranium removal and are very effective. Because uranium gets into the body mainly by drinking it, CT DPH says it is usually not necessary to treat all the water in your home, only the water you drink, with a point-of-use unit at one faucet. It adds that a refrigerator water or ice dispenser should also be considered as a place for point-of-use treatment.

A few rules apply whatever you choose:

1. Get help with the choice. CT DPH says the right system depends on other things in your water, your water use, and installation and maintenance costs, and suggests consulting a water treatment expert. It notes that NSF International certifies many water treatment devices.
2. Think about radium. CT DPH suggests checking whether a uranium system also removes radium. If it doesn't, CT DPH recommends testing your water for radium too.
3. Retest the treated water with a certified lab after installation, and every year after that, as CT DPH advises.

Weigh the options against your confirmed result, not a single unconfirmed reading.