Nitrate and Your Health
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 litre 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 nitrites, which can seriously
affect the blood's ability to release oxygen. Once these nitrites
enter the circulatory system, they combine with the blood's haemoglobin
and prevent life-sustaining oxygen from being carried to body
tissues.
Nitrates and Haemoglobin
Haemoglobin is the part of the red blood cell which distributes oxygen to the
body's cells. Under normal conditions, the haemoglobin 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
haemoglobin 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 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 USA 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.
