Dona Ana County, New Mexico: drinking water report. Dona Ana County in southern New Mexico has a population of about 220,000, centered on Las Cruces.
Dona Ana County in southern New Mexico has a population of about 220,000, centered on Las Cruces. The county draws water from the Mesilla Bolson and Jornada del Muerto aquifers, supplemented by Rio Grande surface water. White Sands Missile Range, the largest military installation in the United States by area, occupies the county's eastern boundary. The Chihuahuan Desert climate means water is scarce, and every drop drawn from the aquifer is slow to recharge.
Arsenic is the primary water quality concern in Dona Ana County. The volcanic geology of the region produces naturally elevated arsenic in groundwater, and according to the New Mexico Environment Department's 2024 compliance data, four public water systems in the county have operated under arsenic compliance schedules with levels between 10 and 30 ppb – above the MCL of 10 ppb. Some small community water systems have been unable to afford the treatment infrastructure needed to achieve compliance.
White Sands Missile Range has a complex environmental history involving rocket propellant testing, munitions disposal, and nuclear weapons detonation (the Trinity test site is within its boundaries). According to the Army's 2024 environmental report, perchlorate and other propellant residues have been detected in groundwater monitoring wells on the range, though migration toward population centers has not been confirmed.
Arsenic in Dona Ana County is a natural feature of the geology, not a failure of the water system. But it still requires treatment to be safe for daily consumption, and smaller systems may not always achieve full compliance.
Check your water for the latest data on your system. For arsenic, only reverse osmosis and specific adsorptive media filters work – standard carbon filters are ineffective. Our water filter guide identifies certified systems. Pull your detailed report for historical data, and visit our New Mexico page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Dona Ana County, NM.
The EPA places Dona Ana County, NM in Zone 2 - a moderate-risk category, with a predicted average indoor radon level between 2 and 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
34% of homes in Dona Ana County, NM were built before 1980, and 5% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Dona Ana County, NM averages 5.8 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide