NITRATE IN ONSITE WATER SUPPLY SYSTEMS
Large amounts of nitrate in drinking water can cause serious illness in infants less than six months of age. The U.S. Environmental Protection Agency has established a maximum contaminant level (MCL) for nitrate (as nitrogen) at 10 milligrams per liter (mg/L) and nitrite at 1 mg/L.
Nitrate (NO3) is a form of nitrogen combined with oxygen. It can be converted in the body to nitrite (NO2). The major adult intake of nitrate is from food, but sometimes, excessive amounts of nitrate get into drinking water.
Nitrate can get into a water supply if a water well is improperly constructed or located where it is subject to contamination sources. Typical sources of nitrate include:
- Wastes from livestock operations
- Onsite sewage disposal system effluent
- Crop and lawn fertilizers
- Municipal wastewater sludge application
- Natural geologic nitrogen
Kalamazoo County aquifers are made up of glacial drift and therefore are highly susecptible to nitrate contamination. Shallow water wells in sandy unconfined aquifers are more vulnerable to nitrate contamination than deeper wells protected by overlying clay strata. Private water supply owners with excessive nitrate or nitrite should contact Environmental Health or your family physician for more information.
Elevated nitrate in drinking water can cause a disease called methemoglobinemia, a blood disorder primarily affecting infants under six months of age. Methemoglobinemia reduces the ability of the red blood cells to carry oxygen. The acutely poisoned person will have a blue discoloration of the skin (blue baby syndrome) due to the reduction of oxygen in the blood. The condition can be fatal if not attended by a physician immediately.
Nitrate and infants
There are four reasons infants are more suseptable to nitrate contamination:
- Infants have a lower stomach acidity, which allows growth of bacteria capable of converting nitrate to nitrite. Nitrite can change hemoglobin to methemoglobin, which cannot carry oxygen.
- Young infants still have considerable amounts of fetal hemoglobin, which is more easily converted to methemoglobin than the adult hemoglobin.
- Infants are deficient in certain enzymes that are able to convert methemoglobin back to normal hemoglobin.
- In relation to body weight, an infant consumes a much larger volume of water than an adult.
Nitrate can be removed from drinking water using reverse osmosis, ion exchange, and/or distillation. Equipment for this removal requires frequent, careful maintenance, and water sampling to achieve and confirm effective operation. Improperly installed, operated, or maintained equipment can result in nitrate passing through the treatment process. In some cases, the nitrate will be concentrated above the incoming levels. Bacteriological problems can also develop in improperly installed and poorly maintained treatment systems. Environmental Health recommends that an alternate source of drinking water be used (i.e., deepened well or municipal connection), where possible, and bottled water be used for preparing infant formula. If a nitrate removal system is to be used, one with NSF or equivalent certification should be selected. Boiling water will not remove nitrate and can concentrate it.
Households are not required by law to sample for nitrate on a routine basis. If your area is known to have nitrate contamination or a sample result indicates nitrate or nitrite levels approaching the drinking water standards (10.0 mg/L), a minimum of annual sampling is recommended. Nitrate concentration will vary thoughout the seasons. If sample results indicate a nitrate concentration close to the drinking water standard, sample seasonally to more closely monitor nitrates in your water supply.