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Nitrate is a nitrogen-containing compound (NO3) found in soil and water. Nitrogen is a nutrient needed for plant growth. About 78% of the air that we breathe is composed of nitrogen gas. While nitrate is the most common groundwater and drinking water contaminant. Nitrate in the groundwater at levels below 2 parts per million may be considered to be naturally occurring "background concentrations". Nitrate can come from a variety of sources related to human activity, including animal and human waste, feedlots, fertilizers and septic systems.
Nitrate is a form of nitrogen that cannot attach to soil particles and, as a result, is easily moved by water. The downward movement of nitrate in the soil is referred to as leaching.
Nitrate can be leached through soils by heavy rainfall or excessive irrigation. Nitrate is also component of septic effluent. Groundwater can be impacted in areas where there high densities of septic systems, when the septage effluent cannot be adequately diluted in the groundwater.
While most sources of nitrate contamination in groundwater vary with local or regional land use activities, the primarily nitrate sources are related to human activities. Thus, people can also take an active role in reducing the nitrate impacts of groundwater.These include proper fertilizer and irrigation management on agricultural and residential lands.
High nitrate levels, above 10 parts per million (ppm), have been associated with a risk for methemoglobinemia, also known as Blue Baby Syndrome. It is called Blue Baby Syndrome because infants younger than 6 months of age are the most susceptible. Blue Baby Syndrome occurs because nitrate ingestion interferes with the body’s ability to transport oxygen through the bloodstream to vital tissues and organs in the body. This lack of oxygen in the bloodstream causes a bluish colored tinge to the skin. Parents should seek immediate medical attention if they notice these symptoms. Pregnant or nursing women may also be susceptible to similar health problems from drinking water with elevated nitrate levels.
Little is known about the long-term effects of drinking water with elevated nitrate. Some research has suggested that nitrate in drinking water, even below 10 ppm, may play a role in the development of some cancers in adults, and in thyroid disorders, spontaneous miscarriages and birth defects.