Nitrate—the oxidized form of dissolved nitrogen— is the main source of nitrogen for plants. It occurs naturally in soil and dissipates when the soil is extensively farmed. Thus, nirtrogen fertilizers are applied to replenish the soil. However, these nitrates can be toxic, especially when they enter the food chain via groundwater and surface water.

In California, the State Water Resources Control Board lists nitrate as one of California’s most challenging and growing water problems.

Nitrate Contamination Overview

Nitrate contamination occurs in surface water and groundwater, leaching into the soil and from there into the water supply from various sources. Irrigation water containing fertilizers is a common culprit as are septic systems, wastewater treatment plants, dairies and natural conditions.

Although a necessary nutrient for plants, high nitrate levels in people can harm the respiratory and reproductive system, kidney, spleen and thyroid in children and adults.  It is particularly harmful to infants.

In California, nitrate is one of the most common groundwater contaminants. While 98 percent of the state’s community water systems meet all primary drinking water standards, between 10 to 15  percent of the public wells exceed the state’s standards for nitrate. They in turn have to be treated or blended with high-quality water.

A recent report found 680 community water systems serving 21 million people in California had contaminated groundwater including nitrate. Most are in the eastern San Joaquin Valley, and in Kern, Madera, and Tulare counties, particularly in rural, economically disadvantaged communities.

Responding to Nitrate Contamination

Tackling nitrate contamination directly is difficult and expensive.

Nitrate is expensive to remove from drinking water supplies, especially in public and private systems that rely on untreated groundwater and do not have the necessary water treatment infrastructure. For example, a 2011 report by the Pacific Institute estimated the cost of cleanup in California to be $150 million.

There are some regulatory controls in place that address salinity, including nitrates, but it is generally agreed that a much more comprehensive approach is needed.

Meanwhile, there are also local efforts to handle nitrate. The Central Valley Water Board, for example, addresses nitrate in groundwater through four programs:

• irrigated lands, minimizing discharge from irrigated agricultural lands
• CV Salts, aiming to develop and implement a salinity and nitrate management program
• groundwater quality protection strategy, providing a roadmap for future regulatory and control activities
• dairy programs, focusing on control and abatement of nitrates to groundwater