Nitrate in North Carolina well water
In North Carolina, <1% of 46,033 private wells tested between 1998 and 2019 had nitrate above the EPA limit (10 mg/L), according to the NC State Laboratory of Public Health (NCWELL).
Nitrate reaches wells from fertilizer, septic systems and manure. Above the limit it can cause methemoglobinemia (blue baby syndrome) in infants under six months, and long-term exposure is associated with some cancers. Shallow and dug wells near farmland or dense septic systems are most at risk.
Check your nitrate number
Type the value from your lab report. It is compared to the EPA limit and the EPA limit, the same way the full interpretation does it.
Getting it fixed
Book a free in-home water test with a licensed local company, or see the treatment guide for what removes nitrate.
By county, from homeowner tests
Share of private wells above the state guidance level (10 mg/L) in tests homeowners sent to the state lab, 1998 to 2019.
| County | Wells tested | Above state level | Highest | |
|---|---|---|---|---|
| Richmond | 323 | 9% | 29 mg/L | |
| Sampson | 602 | 7% | 36 mg/L | |
| Northampton | 113 | 5% | 15 mg/L | |
| Robeson | 61 | 5% | 11 mg/L | |
| Edgecombe | 97 | 4% | 13.7 mg/L | |
| Hertford | 60 | 3% | 11 mg/L | |
| Greene | 30 | 3% | 12 mg/L | |
| Wayne | 271 | 3% | 44 mg/L | |
| Anson | 37 | 3% | 31 mg/L | |
| Harnett | 115 | 3% | 14 mg/L | |
| Lenoir | 79 | 3% | 15 mg/L | |
| Alleghany | 81 | 2% | 13 mg/L | |
| Chatham | 1,761 | 2% | 120 mg/L | |
| Johnston | 558 | 2% | 16 mg/L | |
| Scotland | 130 | 2% | 12 mg/L |
Sources
- NCWELL private well summaries: County summaries of private well tests run by the NC State Laboratory of Public Health, 1998 to 2019, compiled by the UNC Superfund Research Program (NCWELL database). Counts are tests, not distinct wells; since 2008 every new well is tested once, so most tests are unique wells. Shares are against the NC 2L groundwater standard where one exists (manganese 50 ug/L, lead 15, iron 300) and otherwise the EPA limit. Medians are not used because more than half of results sit at the reporting limit for most analytes. Retrieved September 9, 2026.
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. nitrate counts and shares are listed on each county and town page with their sources.