Uranium in well water
Uranium comes from granite and the sand and gravel worn off it, and it's most common in wells in the West. The EPA limit is 30 µg/L. Drinking it for years can damage the kidneys. One lab test tells you where you stand. Reverse osmosis at the kitchen sink removes it.
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What you need to know about uranium
| The limit | 30 µg/L (micrograms per liter, the same as parts per billion). The EPA's health goal is 0. |
|---|---|
| Who it hurts | People who drink it for years. The main risk is kidney damage, with a small added cancer risk. |
| Where it comes from | Natural rock, especially granite, and the sand and gravel worn from it. Most high results are in the West. |
| How often to test | At least once. Nebraska's extension service says 1 sample is enough to judge a well. |
| What removes it | Reverse osmosis, distillation or anion exchange at the kitchen tap. Anion exchange can also treat the whole house. |
| What doesn't | Boiling, and pitcher, faucet or under-sink carbon filters. |
These counties see the most uranium in their wells
Ranked by the share of tested wells with a result over the limit. We only list counties with at least 25 tested wells, so a few bad results can't skew the ranking.
| County | Wells tested | Wells over the limit |
|---|---|---|
| Montrose County, CO | 51 | |
| Stevens County, WA | 44 | |
| Carson City, NV | 34 | |
| Doña Ana County, NM | 148 | |
| Arapahoe County, CO | 67 | |
| Fresno County, CA | 147 | |
| Elbert County, CO | 29 | |
| Goshen County, WY | 25 | |
| Orange County, CA | 52 | |
| Adams County, CO | 36 |
* Likely overstated, because of who tested these wells, when or where.
See the full rankings and download the data
Uranium dissolves out of granite and the sand worn from it
Uranium is a trace element in many kinds of rock. The USGS says it's most concentrated in granite and similar rock, and in sand and gravel that came from those rocks. Water with oxygen in it dissolves uranium easily, so levels depend on the water's chemistry as much as the rock.
The West has the most. In a national USGS study, nearly every well over the 30 µg/L limit drew from sand and gravel aquifers in the West or from 1 western crystalline-rock (granite-type) aquifer. Nationally, about 1.6% of wells sampled were over the limit.
Nebraska is one example. University of Nebraska Extension says public wells with high uranium there tend to sit in the floodplains of the Republican, North Platte and Platte rivers.
Years of drinking it can damage your kidneys
The concern is long-term drinking. The USGS says uranium is only weakly linked to cancer, but it's toxic and can damage the kidneys when people drink too much of it over time.
The EPA lists kidney toxicity and a higher cancer risk as the health effects. Nebraska Extension says the EPA estimated the added lifetime risk at the limit at about 1 in 10,000: if 10,000 people drank 2 liters a day of water at 30 µg/L for 70 years, 1 more fatal cancer might occur among them.
Nebraska Extension says uranium has no taste, smell or color.
One lab test is enough to know where you stand
Test at least once. Nebraska Extension says a single sample is enough to judge how serious the level is, and that a uranium test there typically costs $10 to $25.
Ask the lab for uranium "by mass," reported in µg/L, so you can compare it straight to the 30 µg/L limit. Use a lab certified for uranium.
Many states keep lists of certified labs, and some test private wells for free or at low cost.
Reverse osmosis at the kitchen sink is the common fix
Uranium is a concern in water you swallow, so most well owners treat 1 tap. Nebraska Extension lists reverse osmosis, distillation, anion exchange and special adsorbent media as proven to remove uranium. It also notes that no kitchen-tap unit was certified specifically for uranium when it wrote its guide, so test the treated water.
| Option | What it treats | Typical equipment cost | Things to know |
|---|---|---|---|
| Reverse osmosis | 1 tap | $300 to $2,000 | Also removes many other dissolved minerals |
| Distiller | 1 countertop unit | $300 to $2,000 | Slow; makes small amounts |
| Anion exchange | 1 tap or the whole house | $500 to $1,500 for whole house | Spent media holds uranium; ask your state about disposal |
Costs are equipment ranges from Penn State Extension.
The Minnesota Department of Health adds that ion exchange water softeners and reverse osmosis can lower some radioactive elements in well water.
Questions people ask about uranium
If my well has uranium, does it have radon too?
Not necessarily. Radon forms when uranium breaks down, but the USGS says high uranium and high radon in groundwater don't necessarily show up together. Water chemistry controls uranium; radon depends mostly on the rock. Test for each one.
Can I boil or carbon-filter the water?
No. Nebraska Extension says boiling doesn't remove uranium, and neither do pitcher, faucet-mounted or under-sink carbon filters.
Do I need to test more than once?
Nebraska Extension says 1 sample is enough to judge a well. Retest after you install treatment to make sure it's working.
Is the waste from my filter radioactive?
It holds the uranium the filter took out. Nebraska Extension says buildup from kitchen reverse osmosis or distillers is unlikely to be a problem, and Nebraska lets private well owners send waste from treatment filters to a licensed landfill. Rules vary, so check with your state.
Where this comes from
- U.S. EPA, National Primary Drinking Water Regulations
- USGS, Radionuclides in Groundwater
- USGS Circular 1360, Water Quality in Principal Aquifers of the United States, 1991 to 2010
- University of Nebraska-Lincoln Extension, Drinking Water: Uranium (G1569)
- Minnesota Department of Health, Radionuclides in Drinking Water
- Penn State Extension, Tips for Buying Water Treatment Equipment