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The Nature of the Nitrate Problem

The Nitrogen Cycle In recent decades, environmental monitoring has revealed widespread and steadily increasing amounts of nitrate in California's vast underground water resource. The trend is associated with a growing population and with more intensive agriculture. Rising nitrate levels in groundwater are known to result from (1) manure generated by concentrated animal production; (2) fertilizer applied to crops and landscapes; (3) septic systems and sewage treatment plants; and (4) fuel combustion and industrial sources. All of these human activities produce nitrate, which is a soluble compound of nitrogen and oxygen. Nitrate also comes from natural sources - sediments and rocks, and biofixation of nitrogen by plants and lightning. Nitrate can move with water down through the soil to enter the groundwater supply. Although nitrate is a natural component of living systems, too much nitrate can cause problems for human health and for the environment. One well-known potential threat is the relationship between high nitrate levels in drinking water and a rare infant disease called methemoglobinemia (blue-baby syndrome). In the stomachs of very young babies that have not yet developed normal acidity, nitrate can change to a related compound (nitrite) that interferes with the blood's oxygen-carrying capacity.

Cancer and birth defects also have been the subject of concern in relation to high nitrate drinking water, but no firm link has been established.

The current public health standard for acceptable drinking water in California is 45 milligrams/liter (45 parts per million) of nitrate. As shown on map 1, hundreds of wells in various areas of the state currently exceed this level.

There also is an economic dimension to the problem. When nitrate in a public water supply reaches or exceeds the 45 mg/l standard, costly measures are required. The well may have to be deepened or closed down, a different water source may have to be acquired for blending, or expensive water treatment may be required. For example, the Orange County Water District has estimated that wellhead nitrate treatment costs about $375 per million gallons. In 1986, public water systems in California applied to the State Department of Health Services for more than $48 million to correct nitrate violations. The total cost undoubtedly was even larger since many water agencies used other sources of funds to address the problem.

Excess nitrogen can also cause other economic and environmental problems such as oxygen-depleting algae growth in rivers and lakes, toxicity to aquatic life, increased calf abortion rates, and even loss of quality in fruit and other crops. These are often the result of inadequate manure, irrigation and fertilizer management.

Additional costs of nitrate in groundwater include land use restrictions, denial of loans for lack of a suitable water supply, and a reduced tax base. So the problem of increased nitrate levels in California's groundwater is both significant and persistent.