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 pageNitrate in Maryland well water, by county
Nitrate is widespread, over the limit in 15% or more of tested wells, in 4 of the 19 Maryland counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. 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 nitrate over the EPA limit of 10 mg/L (71 of 734). Across all tested wells in the US it's about 1 in 12. Maryland is about average, so the county you live in tells you more than the state does.
Why it matters: It's dangerous for babies under 6 months, because it keeps their blood from carrying enough oxygen.
Nitrate soaks down into groundwater from fertilizer, manure and septic systems.
Nitrate in tested wells, county by county
Share of each county's tested wells with at least one result over the EPA limit of 10 mg/L. 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 |
|---|---|---|---|
| Kent County | 47 | Widespread | |
| Queen Anne's County | 45 | Widespread | |
| Carroll County | 10 | Widespread | |
| Talbot County | 12 | Widespread | |
| Wicomico County | 19 | Widespread | |
| Washington County | 16 | Worth checking | |
| Caroline County | 26 | Worth checking | |
| Dorchester County | 41 | Worth checking | |
| Worcester County | 41 | Worth checking | |
| Baltimore County | 166 | Rare | |
| Montgomery County | 30 | Rare | |
| Anne Arundel County | 68 | Rare | |
| Garrett County | 51 | Rare | |
| Harford County | 49 | Rare | |
| St. Mary's County | 23 | Rare | |
| Frederick County | 20 | Rare | |
| Charles County | 18 | Rare | |
| Cecil County | 12 | Rare | |
| Calvert County | 10 | Rare |
* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:
- Kent County: All of these tests come from the US Geological Survey, mostly before 2013 in one small part of the county, so this likely overstates it.
4 more Maryland counties have 1 to 9 tested wells for nitrate, too few to rate.
Download this table (CSV) ยท Free to reuse under CC BY 4.0
Where to get your well tested for nitrate in Maryland
A lab Maryland certifies
Ask for nitrate 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 nitrate.
Compare kitsKeep reading about wells in Maryland
- Well water testing in Maryland: how to get tested and what turns up statewide
- Nitrate in well water: where it comes from, what it does and how to remove it
- Arsenic in Maryland wells, by county
- Uranium in Maryland wells, by county
- Manganese in Maryland wells, by county
- Lead in Maryland wells, by county
- Radon in Maryland wells, by county
Questions people ask about nitrate in Maryland
Is there nitrate in Maryland well water?
Nitrate is widespread, over the limit in 15% or more of tested wells, in 4 of the 19 Maryland counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. Across Maryland, about 1 in 10 tested wells had nitrate over the EPA limit of 10 mg/L (71 of 734). Across all tested wells in the US it's about 1 in 12. Maryland is about average, so the county you live in tells you more than the state does.
Where can I get my well tested for nitrate in Maryland?
Use a lab certified by Maryland for drinking water, or a mail-in kit that includes nitrate 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 the EPA limit of 10 mg/L. 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.