Arsenic is a naturally occurring element found in rock and soil throughout the United States — including parts of North Carolina. For homeowners on private wells in the Raleigh area and surrounding counties, arsenic is worth taking seriously. Unlike many water quality issues that are primarily nuisances, arsenic is a confirmed health concern at elevated concentrations, and many private well users have never tested for it.
Where Does Arsenic Come From?
Arsenic enters groundwater through natural geological processes — it dissolves from rocks and minerals containing the element as water moves through underground formations. Certain geological zones in North Carolina have higher natural arsenic concentrations, particularly in the crystalline rock formations found in the Piedmont region, which includes much of the greater Raleigh area.
Industrial activity, mining, and some legacy agricultural uses can also contribute arsenic to groundwater in certain areas, though natural geological sources are the primary driver in most central NC counties.
What Are the Health Concerns?
The EPA's maximum contaminant level (MCL) for arsenic in public water supplies is 10 parts per billion (ppb). Long-term consumption of arsenic above this threshold has been associated with increased risk of several serious health conditions. Because the effects are cumulative and long-term, most people don't notice any immediate symptoms — which makes testing the only way to know if you're exposed.
Private wells are not subject to the EPA's MCL — there is no regulatory requirement that compels private well owners to test for arsenic. This means many homeowners in affected areas may be unknowingly consuming water with elevated arsenic levels.
Which NC Counties Have Elevated Arsenic Risk?
Research by the NC Division of Public Health and academic institutions has identified areas of elevated arsenic occurrence in NC groundwater, particularly in Piedmont counties. While Wake, Chatham, Lee, and surrounding counties are not uniformly high-risk, localized pockets of elevated arsenic exist and cannot be predicted without testing. Your neighbor's well water could be fine while yours exceeds recommended levels.
Testing for Arsenic in Your Well
A standard basic well water test does not automatically include arsenic analysis. You need to specifically request it, or choose a comprehensive testing package that includes it. A certified laboratory processes the sample and provides results measured in ppb that you can compare directly to the EPA's MCL.
Treating Arsenic in Well Water
If your well water tests above the recommended threshold for arsenic, effective treatment options include:
- Reverse osmosis systems --- highly effective at the point of use for
drinking and cooking water
- Whole-home arsenic-specific filtration using adsorptive media for
comprehensive household treatment
RO is typically the most practical solution for most households and addresses arsenic along with a wide range of other dissolved contaminants simultaneously.