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What is Sulfate?

Sulfates usually occur naturally in the groundwater in New Mexico because the water dissolves it out of rocks, such as gypsum. Natural levels can be increased by contamination from mines, mills, landfills, sewage, and other manmade sources.

Drinking water with sulfate concentrations above the EPA secondary standard of 250 milligrams per liter (mg/L) may have undesirable taste and odor.

Sulfate in Private Wells, New Mexico

Levels of various naturally-occurring and man-made constituents in New Mexico groundwater including sulfate, might be elevated above the Environmental Protection Agency (EPA) Safe Drinking Water secondary standards (related to odor and taste). Ongoing drought conditions and aquifer mining have raised further concern that increases in constituents may occur in the absence of significant ground water recharge events.

Sulfate levels in water samples from private wells vary between New Mexico counties and even within the same county. The groundwater system in New Mexico is very complex. This complexity can lead to sulfate concentration variability even amongst neighboring wells. Therefore, to know the sulfate concentration in your water from your own well, you need to test. Some of the water samples from wells in all counties appear to exceed this Environmental Protection Agency (EPA) Safe Drinking Water secondary standard. However, counties with at least 45 percent of samples that exceed this standard are in southeastern NM.

The information available on this page, including the maps, demonstrates sulfate found in tested private wells in New Mexico based on the data available from various sources.

Interpolated groundwater sulfate concentrations (mg/L) from private wells data Aug. 1903 - Oct. 2018
Average sulfate distribution in groundwater by county (mg/L) from private wells data Aug. 1903 - Oct. 2018
Percentage of samples exceeding the secondary EPA MCL of 250 mg/L for sulfate: private wells data Aug. 1903 - Oct. 2018.

Sulfate in Water and Health

The secondary safe drinking water concentration for sulfate, related to aesthetics (odor and taste), is 250 milligrams per liter (mg/L). To avoid loose stool and diarrhea in persons not used to high levels of sulfate, the EPA advises public water systems and private wells not have sulfate above 500 mg/L. Drinking water with sulfate levels above 600 mg/L can cause strong laxative effects. Diarrhea and resulting dehydration may be more pronounced (and serious) for certain groups of people such as babies and people not used to higher sulfate water (visitors).

Bacteria and Sulfate in Water

Hydrogen Sulfide and Sulfur bacteria can be present in low oxygen water (such as deep wells). These bacteria use sulfur as a source of energy and produce hydrogen sulfide gas which has a "rotten egg" smell. There is no established EPA safe drinking water level for hydrogen sulfide. The concentrations in private drinking water supplies are usually below any levels that would cause health concerns. The odor can be detected at concentrations as low as 0.03 parts per million (ppm).

Treatment for sulfur bacteria (which can produce hydrogen sulfide) may include shock chlorination. See link in the Downloads and Resources section below for the Center for Disease Prevention and Control (CDC) well disinfection guidelines.

How can sulfate be removed from the drinking water?

Sulfate can be removed by treating the water with reverse osmosis or distillation. These treatment methods require careful maintenance. Carbon or other mechanical filters, standard water softeners or boiling do NOT remove sulfate. To find a treatment system certified to remove sulfate consult with the Water Quality Association or at 630-505-0160 or NSF international (formerly the National Sanitation Foundation) or at 1-800-NSF-MARK (1-800-673-6275).

Sulfate in Drinking Water: Other Uses

  • Showering and bathing: There is not a significant health risk from bathing or showering in water with high levels of sulfate. Avoid getting the water in your mouth. If you use treatments in your hair, consult with your hair stylist.
  • Sulfate and animals: Animals are sensitive to high levels of sulfate, so you might consider providing bottled water to your pets and livestock until you have consulted with a veterinarian.
  • Sulfate and plants: It is okay to water your household plants with the tap water. If you are concerned about your garden or agricultural crop you should contact your local Extension Office for guidance.

Public Water Systems and Sulfate

If you get your water from a public drinking water system, contact:
  • Your community water system by telephone
  • Look up your community water system online through the New Mexico Environment Department (NMED) Drinking Water Watch
  • Call the NMED Drinking Water Bureau, TOLL FREE 1-877-654-8720