health effects of nitrate in drinking water

Health Effects of Nitrate in Drinking Water

Sarah Yang, Ph.D.

Groundwater Toxicologist

February 26, 2020

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High levels of nitrate can affect everyone’s health.

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Nitrate is one of the most common contaminants in Wisconsin's groundwater.

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Our major source of nitrate depends on age.

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When we eat or drink nitrate, it goes through our body to our small intestine.

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Most nitrate is absorbed in our blood.

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While most nitrate in our blood leaves our body when we urinate, about 25% goes into our saliva.

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Intestines Blood

Stomach

In saliva, most nitrate goes back through the intestines, but some is turned into nitrite and moves to the stomach.

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Blood Beneficial substances

Harmful substances

In the stomach, nitrite can move into the blood or be turned into other substances.

Nitrite in the blood can affect the body’s ability to transport oxygen.

Nitrite

Hemoglobin

Fe2+

Methemoglobin

Fe3+

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High levels of methemoglobincan cause health problems.

3 Skin discoloration10 Weakness, excess heart rate

20 Headache, dizziness, fatigue, nausea

70 Death (very rare)

1 Normal

% methemoglobin in the blood

Adapted from Shihana, F. et al (2010)

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High levels of nitrate can cause blue baby syndrome (methemoglobenemia) in infants.

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Infants are at a greater risk for blue baby syndrome because of their size and how their bodies work.

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The drinking water standard for nitrate is 10 mg/L.

0

5

36

81

92

51–100

≤ 10 0

11–20

21–50

> 100

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Level of nitrate-nitrogen in formula (mg/L)

Cases of blue baby syndrome

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Nitrate-Nitrogen Nitrate

United States 10 mg/L

Europe 50 mg/L

The United States uses a different measure of nitrate than other countries.

45 mg/L

11 mg/L

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High levels of nitrate can also affect women who are or may become pregnant.

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High levels of nitrate in drinking water may increase the incidence of neural tube defects.

Neural tube defects can occur in the first 3 weeks of pregnancy.

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High levels of nitrate in drinking water can cause long-term health effects in everyone.

Strongest Evidence

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Recent studies among people have evaluated the health effects of high nitrate in drinking water.

Thyroid disease Colon cancer

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High levels of nitrate may affect the thyroid by blocking iodine uptake.

Iodine(from diet)

Hypothyroidism

Thyroid

T3

(hormone)

T4

(hormone)

Nitrate

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Harmful substances

Nitrite can form N-nitrosocompounds in the stomach –some of which have been shown to cause cancer in research animals.

(N-nitroso compounds)

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Take action to protect yourself and your family

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Test your well for nitrate at least once a year.

When nitrate levels are high:

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Do not give water to babies less than 6 months old or used to make infant formula.

Women who are or may become pregnant should immediately stop using the water for drinking and preparing foods that use a lot of water.

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Everyone should avoid long-term use of the water for drinking and preparing foods that use a lot of water.

Thanks!

Sarah Yang, Ph.D.

Groundwater ToxicologistBureau of Environmental and Occupational Health

Division of Public HealthWisconsin Department of Health Services

sarahp.yang@wi.gov608-266-9337

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