For years, nitrates have been effective in lawn and garden fertilizers by providing grass and shrubs with life-giving nutrients. However, the accumulation of these fertilizers can eventually leach through the soil to invade wells.
While this is not surprising with shallow wells, deep wells are frequently affected, particularly if they were dug subsequent to a first well. An Iowa State University Special Report(1) found that old or depleted wells, often just abandoned and not filled with concrete as most water specialists recommend, become readily available reservoirs for runoff and excessive groundwater. As they refill with surface water, they may become concentrated with potentially toxic lawn care and agricultural chemicals, contaminating the new well.
In January 1992, the U.S. Environmental Protection Agency (EPA) released the results of a sophisticated national survey(2) of nitrates and pesticides in drinking water wells. The National Pesticide Survey (NPS) tested water from 1,349 community and domestic rural wells. Samples were taken in every state. Nitrate detection was projected in 57 percent of the rural domestic wells (RDWs), and 52.1 percent of the community water system (CWS) wells in the United States. Approximately 22,500 infants younger than one year old consuming water from RDWs were projected to be exposed to nitrate-nitrogen exceeding the 10 milligram per liter safe drinking water limit. The CWS population is projected to be 43,500 infants.
Nitrates which are ingested by infants or young farm animals changed into dangerous nitrates, which can seriously affect the blood's ability to release oxygen. Once these nitrites enter the circulatory system, they combine with the blood's hemoglobin and prevent life-sustaining oxygen from being carried to body tissues.
Nitrates and Hemoglobin
Hemoglobin is the part of the red blood cell which distributes oxygen to the body's cells. Under normal conditions, the hemoglobin is an efficient transporting mechanism, easily releasing oxygen to the cells. However, infants less than three months of age have nitrate reducing bacteria in their digestive systems. These bacteria convert nitrates to nitrites, which bind strongly with blood hemoglobin and prevent sufficient oxygen transport in the baby. Shortness of breath, susceptibility to illness, heart attack, or even death by asphyxiation can result. By age six months, hydrochloric acid concentrations in the stomach rise, killing the the nitrate reducing bacteria. Nitrates are therefore not a concern in older children and adults.
When In Doubt, Test It Out!
The presence of nitrates and nitrites can be confirmed through testing by the County Health Department or by a state- or EPA-certified laboratory. Once detected, point-of-use (POU) water treatment equipment is generally required to lower these levels acceptably.
For acceptable levels of nitrite in drinking and cooking water, the reverse osmosis and distillation processes are widely used.
Those users on the more than 15 million private wells in the country are solely responsible for their water's safety, and widely use POU treatment to solve problems. Where there is a municipal system, some communities have tried to control high nitrate levels in their central water system by using a "split stream" arrangement. In this system, a portion of the water is drawn off and treated using an anionic nitrate removal process. The treated water is then blended with the untreated water to dilute the nitrate concentrations. While this method is effective in lowering nitrate levels, a point-of-use system should still be preferred by consumers who want to control harmful nitrate levels in their home water system.
If you suspect a problem, have your water tested at once. It's a simple step towards protecting your family's health.
References:
- "The Nitrate Problem. Special Report No. 34." Iowa State University of Science and Technology, Cooperative Extension Service in Agriculture and Home Economics; Ames, Iowa, August 1963.
- "National Pesticide Survey - Phase II" Office of Pesticides and Toxic Substances, USEPA, Washington , D.C., 1992.