Your county health department
Maryland doesn't run a statewide free testing program that we know of. Some county health departments test wells or sell kits, so call yours first.
Maryland's private well pageRadon in Maryland well water, by county
Radon is widespread, over the limit in 15% or more of tested wells, in 2 of the 11 Maryland counties with 10 or more tested wells. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.
How Maryland compares with the rest of the country
Across Maryland, about 1 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (29 of 293). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Maryland wells about twice as often as in the country as a whole, and a test is worth adding even if your county isn't on the list below.
Why it matters: It escapes into the air when you shower or run the tap, and breathing it raises the risk of lung cancer.
Radon is a gas given off by uranium in granite and similar rock.
Radon in tested wells, county by county
Share of each county's tested wells with at least one result over 4,000 pCi/L, a level the EPA proposed. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.
| County | Wells tested | Wells over the limit | Level |
|---|---|---|---|
| Baltimore County | 59 | Widespread | |
| Howard County | 10 | Widespread | |
| Garrett County | 43 | Rare | |
| Anne Arundel County | 20 | Rare | |
| Caroline County | 20 | Rare | |
| Dorchester County | 16 | Rare | |
| Queen Anne's County | 14 | Rare | |
| Charles County | 13 | Rare | |
| Calvert County | 10 | Rare | |
| Frederick County | 10 | Rare | |
| Talbot County | 10 | Rare |
12 more Maryland counties have 1 to 9 tested wells for radon in water, too few to rate.
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Where to get your well tested for radon in water in Maryland
A lab Maryland certifies
Ask for radon in water by name. Results from a certified lab count for a home sale or a loan.
Labs certified by Maryland (PDF)A mail-in kit
Fill the bottles at your kitchen tap and mail them back. We mark the kits that include radon in water.
Compare kitsKeep reading about wells in Maryland
- Well water testing in Maryland: how to get tested and what turns up statewide
- Radon in well water: where it comes from, what it does and how to remove it
- Nitrate in Maryland wells, by county
- Arsenic in Maryland wells, by county
- Uranium in Maryland wells, by county
- Manganese in Maryland wells, by county
- Lead in Maryland wells, by county
Questions people ask about radon in water in Maryland
Is there radon in water in Maryland well water?
Radon is widespread, over the limit in 15% or more of tested wells, in 2 of the 11 Maryland counties with 10 or more tested wells. Across Maryland, about 1 in 10 tested wells had radon in water over 4,000 pCi/L, a level the EPA proposed (29 of 293). Across all tested wells in the US it's about 1 in 24. So radon in water turns up in Maryland wells about twice as often as in the country as a whole, and a test is worth adding even if your county isn't on the list below.
Where can I get my well tested for radon in water in Maryland?
Use a lab certified by Maryland for drinking water, or a mail-in kit that includes radon in water from a certified lab. Some county health departments test wells too, so call yours first.
See Maryland's list of certified labs (a PDF list), or compare mail-in kits.
Where these numbers come from
- Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over 4,000 pCi/L, a level the EPA proposed. Wells tested for studies and monitoring, not a random sample of homes.
- Likely overstated: our own check of who tested the wells, when and where. How we check.
- State programs and links: Maryland Department of the Environment.