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Drinking Water: Nitrate

What is nitrate?

Nitrate is a molecule that is needed by plants and animals to live and grow.

Child's hand holding a glass of water

Low levels of nitrate can be found in fruits and vegetables, fish, dairy, beers, cereals, and cured meats. Nitrate is also naturally found in air, soil, and water at low levels.

Higher levels of nitrate are sometimes found in surface water (lakes, rivers, and streams) and groundwater from human and animal waste and fertilizer use.

How can I be exposed to nitrate?

The most common way people are exposed to nitrate is through drinking water.

Nitrate is one of the most common groundwater contaminants in Wisconsin. Studies estimate that at least 10% of private wells in Wisconsin have high levels of nitrate.

How can nitrate affect health?

Exposure to high levels of nitrate can affect everyone.

In babies, nitrate can cause blue baby syndrome. This is a condition that affects how the blood carries oxygen leading to weakness, excess heart rate, fatigue, and dizziness.

Nitrate can increase the risk of neural tube defects – a type of birth defect that affects how the brain and spinal cord form. These defects occur very early in pregnancy often before a person even knows that they are pregnant.

In all people, nitrate may increase the risk of thyroid disease and may increase the risk of colon cancer.

How can I protect myself and my family from nitrate?

Public water systems are required by the Wisconsin Department of Natural Resources (DNR) to test for nitrate regularly.

If the level of nitrate is above Wisconsin's drinking water standard (10 milligrams nitrate-nitrogen per liter), the system will issue a do not drink advisory for sensitive populations. If this happens,

  • People who are or may become pregnant should use immediately use a different source of water for drinking and making foods that take up a lot of water (like rice, oatmeal, and gelatin).
    • Options include bottled water, water from a public system without violations, and water from a private well without issues.
  • Use different water for babies to drink and to make baby formula.
  • It is ok to use the water for bathing, brushing teething, and washing dishes.

The DNR will work with your water system find a long-term solution.

Private well users should test for nitrate regularly using a Wisconsin certified lab.

  • Test at least once a year.
  • Also test before the water is used someone who is or may become pregnant or it is given to a baby.
  • Test right away if you notice a change in the color, taste, or smell of your water.
  • Households with pregnant people and young children may be eligible for free testing through their local health department.

Take action if the nitrate level is equal to or greater than 10 milligrams nitrate-nitrogen per liter (mg/L):

  • People who are or may become pregnant should immediately use a different source of water for drinking and making foods that take up lot of water (like rice, oatmeal and gelatin).
    • Options include include bottled water, water from a well without issues, and water from a public system.
  • Use different water for babies to drink and to make baby formula.
  • It is ok to use the water for bathing, brushing teething, and washing dishes.
  • Retest your well to verify to results.

If the nitrate level is still high:

Our Nitrate in Private Wells fact sheet, P-02128 has these steps in printable format.

Who regulates nitrate in Wisconsin?

Nitrate is naturally occurring in the environment. The DNR regulates direct releases of nitrate into groundwater.

The DNR also regulates how much nitrate can be in water served by public water systems and establishes environmental requirements to limit runoff from fields, pastures and livestock facilities.

Related topics

Our groundwater standards page has information on how Wisconsin's groundwater standards are set, the Department of Health Service's role in the process, and a summary of the current and recommended standards including nitrate.

The DNR's information for private well owner's page has information on testing, finding well records, well abandonment, and more.

The Wisconsin Groundwater Coordinating Council's Annual Report to the Legislature summarizes the operations and activities occurring within the state to address groundwater issues including nitrate.

The University of Wisconsin - Steven Point Well Water Quality Interactive Viewer shows water quality data from a variety of contaminants (including nitrate) at a county, township, and section levels.

The Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs page has more information on nitrate exposure routes and health effects.

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Last revised October 16, 2023