NITRATE IN DRINKING WATER

Nitrate and Your Diet

Nitrate (NO₃) is a compound of nitrogen and oxygen and is found in many food items in your every-day diet. Generally, the concentration in groundwater is low. The major source of nitrates for adults is food rather than water. Vegetables such as spinach, lettuce, beets, and carrots have significant nitrate concentrations. Drinking water normally contributes only a very small percentage of the total nitrate intake.

Nitrate Levels in Drinking Water

Although low levels of nitrate occur naturally in water, sometimes higher levels which are potentially dangerous to some infants are discovered. New Mexico has adopted a drinking water standard of 10 milligrams per liter (mg/l) for nitrate (as nitrogen). This standard is mandatory for public water supplies and is used as a guide for private water supplies. The U.S. Environmental Protection Agency also uses the 10 ml/l as a mandatory national standard for public supplies under the Safe Drinking Water Act passed by Congress.

Sources of High Nitrates

It is often difficult to pinpoint sources of nitrate because there are so many possibilities.
Sources of nitrogen and nitrate may include the following:

   cesspools
   septic tanks and leachfields
   refuse dumps
   animal feed lots
   runoff or seepage from fertilized agricultural lands
   municipal and industrial wastewater
   urban drainage
   decaying plant debris

The geological formations, depth to groundwater, and directions of groundwater flow influence the possibilities of nitrate contamination from a particular source.

Health Concerns

Since 1945, health officials have known that high nitrate levels in drinking water disrupt the normal body processes of some infants. Their concern is that high nitrate concentrations may cause methemoglobinemia. This condition has been rare in New Mexico.

Questions have been raised as to whether nitrate can lead to other health problems such as cancer in healthy adults and birth defects, but definitive studies are lacking.

The toxicity of nitrate to infants occurs when nitrate is converted to nitrite (NO₂), a process that can occur in the stomach as well as in the saliva. Nitrite acts in the blood to change the hemoglobin to methemoglobin, which reduces the ability of the red blood cells to carry oxygen to the tissues.

Infants under six months of age are most susceptible; however, because of individual differences in infants, some may not be affected. If an infant is affected, the skin takes on a bluish cast similar to the color of the blood vessels located close to the skin. If this condition is observed, seek medical help immediately. The infant is suffocating because oxygen cannot be transported by the changed blood cells. Prompt medical attention normally results in quick recovery of the infant. Lack of medical attention can be fatal.

Why Are Infants More Susceptible?

Adults can consume large quantities of nitrate in drinking water or food without experiencing the same health effects as infants. The adult stomachs, which contain strong acids, do not promote the growth of bacteria which convert nitrate to the more toxic nitrite. Infants, however, are more susceptible because their stomach juices are less acidic, and therefore more favorable for the growth of these bacteria.

Remember, not all infants are affected by high nitrate.

Recommended Precautions and Procedures

When water with nitrate exceeding the drinking water standard has been discovered, a number of important points should be remembered:

 1. Do not give the water to infants under six months of age either direct or in formula. Use only safe water from a known low-nitrate source.

 2. Do not boil high-nitrate water. Boiling actually increases the nitrate due to evaporation of the water.

 3. Seek medical help if the skin of an infant takes on a bluish tone or tint.

Testing for Nitrate

Federal law requires the testing of public water systems, but high nitrate can occur in any well. If infants will be consuming water from a private well, an inexpensive water test for nitrate should be requested, in addition to a normal bacteriological test. Water samples can be tested at private laboratories. Look for listings in the Yellow Pages under "laboratories-testing."

Ask your local NMED office if there is a day of free well-water testing scheduled for your community.

NMED Offices

   Alamogordo 437-7115
   Albuquerque 841-9450
   Carlsbad 885-9023
   Clovis 762-3728
   Deming 546-7559
   Española 753-7256
   Farmington 327-9851
   Gallup 722-4160
   Grants 287-8845
   Hobbs 393-4302
   Las Cruces 524-6300
   Las Vegas 425-3621
   Los Lunas 865-9797
   Rio Rancho 892-4483
   Roswell 624-6046
   Ruidoso 258-3272
   Santa Fe 476-8537
   Silver City 388-1934
   Socorro 835-1287
   Taos 758-8808
   Tucumcari 461-1671

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