North Carolina Private Well Water Risk: Arsenic & Nitrate

These figures are USGS statistical estimates for private (domestic) wells in North Carolina. They describe the area's modeled risk — not any single well.

This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.

Nitrate

0%

of the private-well population is modeled above the 10 mg/L nitrate limit

~370

people on wells estimated above the limit

~2,160,000

total residents on private wells statewide

Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.

Arsenic

Across North Carolina, an estimated ~119,631 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Mecklenburg County (~19,183 people).

Counties with the highest modeled arsenic exposure

CountyEst. well residents over arsenic limit90% range
Mecklenburg County~19,18311,31031,626
Wake County~11,4488,25115,632
Guilford County~8,1875,06113,358
Rowan County~7,7644,63312,434
Durham County~4,6082,6218,112
Cabarrus County~4,1242,4536,742
Gaston County~3,7252,2375,945
Orange County~2,7531,4365,295
Alamance County~2,6881,4345,101
Iredell County~2,4931,6293,755
Forsyth County~2,4361,6213,644
Franklin County~2,3571,6583,325
Randolph County~2,1201,0304,441
Lincoln County~1,8571,2702,676
Nash County~1,7421,2042,500
Johnston County~1,5961,1792,158
Granville County~1,5929372,757
Person County~1,5038792,631
New Hanover County~1,4921,0062,224
Pitt County~1,4309202,193
Buncombe County~1,3511,0051,796
Union County~1,2577202,341
Vance County~1,2098341,732
Cumberland County~1,2059321,561
Surry County~1,0968271,457
Chatham County~1,0595722,007
Wayne County~1,0277131,482
Davie County~9775711,573
Wilson County~9085891,369
Cleveland County~8456141,168
Davidson County~8435051,390
Catawba County~8125831,119
Sampson County~7786011,011
Beaufort County~7685061,150
Brunswick County~7595141,123
Yadkin County~7444891,132
Caswell County~7364911,102
Moore County~6974251,226
Columbus County~642481857
Pender County~632457871
Edgecombe County~595382924
Robeson County~586451764
Carteret County~583378852
Caldwell County~580419805
Rockingham County~568426767
Macon County~543347831
Stanly County~5182731,011
Harnett County~517398672
Craven County~506347735
Halifax County~470305721
Henderson County~456337606
Rutherford County~445323616
Alexander County~442298658
McDowell County~441344569
Wilkes County~436314609
Martin County~411264636
Haywood County~407300545
Bladen County~385293511
Hertford County~381243586
Burke County~377291488
Duplin County~359271480
Onslow County~348240512
Stokes County~336241478
Hoke County~334265428
Bertie County~329209510
Jackson County~308209450
Ashe County~292217390
Lee County~264187377
Northampton County~264172399
Camden County~259181366
Madison County~253180357
Cherokee County~234162338
Scotland County~229178294
Watauga County~216162285
Currituck County~194125263
Montgomery County~18890402
Warren County~175124249
Transylvania County~170116247
Richmond County~164124218
Anson County~156107228
Lenoir County~152117198
Washington County~14396207
Swain County~13292194
Mitchell County~12888183
Clay County~11374176
Yancey County~10777145

14 additional North Carolina counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit).

Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).

Treating arsenic in North Carolina

Arsenic is not removed by carbon pitchers or faucet filters. Reverse osmosis is the treatment that brings it below the federal limit at your tap.

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