Water Education - Water and Health

Nitrate (nitrate nitrogen) in drinking water

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Let’s get to know this Nitrate Nitrogen. The concentration of nitrates is commonly expressed as NO3-. The term "nitrate nitrogen" is used to refer to the nitrogen present which is combined in the nitrate ion. This nomenclature is used to differentiate nitrate-nitrogen from nitrogen in the form of ammonia (ammonia nitrogen), from nitrogen in the form of nitrite (nitrate-nitrogen), etc. The concentrations are usually expressed in milligrams per liter of nitrogen.

Many ground waters contain small amounts of nitrate nitrogen. Concentrations range from 0.1 mg/l to 3 or 4 mg/l in most areas. There are areas where amounts of nitrate can go as high as 100 mg/l have been found, however. Nitrates may occur in both shallow and deep well supplies, but they are most common in water from shallow wells. Nitrate nitrogen can result from the seepage of water through soil containing nitrate-bearing minerals. It may also occur as the result of using certain fertilizers in the soil; however, nitrates are one of the products of the decomposition of animal and human wastes. Thus, the presence of nitrates in a water supply indicates possible pollution of the water.


Nitrate nitrogen has been much publicized in recent years in relation to the problem of "blue babies." In concentrations as low as 10 to 20 mg/1 nitrate nitrogen has caused illness and even death among infants under six months of age. If such water is used for supplemental or for complete bottle feeding, it may affect the ability of the blood to carry oxygen. This oxygen starvation is called methemoglobinemia, or more commonly, the "blue baby" condition. This serious illness in infants is caused because nitrate is converted to nitrite in the higher pH conditions existing in the stomachs and intestinal tracts of infants under six months of age. Nitrite interferes with the oxygen-carrying capacity of a child's or baby animal's blood. This is an acute disease in that the symptoms can develop rapidly. In most cases, health deteriorates rapidly over a period of days. Symptoms include shortness of breath and blueness of the skin.

In the process of decomposition, raw sewage undergoes a chemical change. Bacteria in the soil convert various forms of nitrogen to nitrate. This is beneficial because plants absorb nitrogen in nitrate form. However, nitrate is highly soluble and easily moves with water throughout the soil. During excessive rainfall or over-irrigation, nitrate will drain below the plant’s root zone and eventually reach groundwater. When nitrate-nitrogen occurs, it is considered evidence of pollution either from septic tank fields, cesspools, golf courses, parks, gardens, or naturally occurring sources of nitrogen. Where groundwater is known to contain little or no nitrate-nitrogen naturally, the appearance of any significant increase is a probable indication of pollution. Because of these factors, well waters containing nitrate nitrogen should be checked periodically by local or state health authorities.

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