Impacts of High Nitrate Levels

What are the impacts of high nitrate levels?

Although nitrate is necessary, high concentrations can be harmful to the health of the environment, as well as the economy.



    Human Health

Health impacts to humans and animal life occur from drinking water, and/or eating foods high in nitrate such as vegetables and meat.  In humans, pregnant women are advised to avoid high nitrate water because of research showing possible connections to birth defects and miscarriages.  

Also, babies under 6 months, may get a disease commonly called, Blue Baby Syndrome, or medically called Methemoglobinemia. Babies have low intestinal acidity (or a higher intestinal pH), which allows a bacteria to convert nitrate to nitrite. Nitrite is absorbed and combines with hemoglobin to form methemoglobin, which depletes the blood of oxygen.  Early human symptoms include a bluish tint to fingers, lips, and other extremities.   Other symptoms include headache, dizziness, lethargy, syncope, dyspnea, coma, arrhythmias, shock, and convulsions. Even with treatment brain damage or death can occur.  


According to Kross, infants are more susceptible to nitrate toxicity for three reasons:
  1. Infants have a higher intestinal pH, which enhances conversion of nitrate to nitrite


  1. Infants contain more fetal hemoglobin, which more readily oxidizes nitrite to methemoglobin


  1. The enzyme responsible for reducing the  methemoglobin back to a normal level  has only about half the activity in infants 55


According to a National Academy of Science study, the incidents of Blue Baby Syndrome usually occur when nitrate-nitrogen concentrations exceed 11 ppm and when coliform bacteria contamination is also present in the water.65   The article, Blue Babies and Nitrate-Contaminated Well Water, investigates two cases of babies diagnosed with Blue Baby Syndrome.   56 .  (abstract only).  (Reproduced with permission from Environmental Health Perspectives.)

However, other scientists believe the following human illness may possibly be linked to high nitrate levels: Non-Hodgkin's Lymphoma, bladder cancer, cancer in the digestive tract, diabetes, and some birth defects and miscarriages. A few recent studies have linked high nitrate to bladder cancer, especially in women.

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Animal Health

Ruminant livestock with multiple stomachs like cows and sheep tend to experience a similar illness to Blue Baby.  Nitrate is converted to nitrite in the rumen or first stomach of livestock, which depletes the blood of oxygen.

"If too much hemoglobin changes to methemoglobin, the animal will begin to show signs of a lack of oxygen: low tolerance to exercise, lack of coordination, labored breathing, blue coloring of mucous membranes, rapid heartbeat, abdominal pain and vomiting, blood discolored chocolate-brown, and abortions" 58.   Thus far, no symptom or chemical diagnosis specifically points to nitrate poisoning. 58


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Aquatic Health

Links have also been made between high nitrate and toxicity in fish eggs, amphibian eggs, and tadpoles. 

Fertilizers often increase the amount of nitrate and phosphate in surface water and groundwater resulting in accelerated algae and weed growth. When the algae and weeds decay, the decomposers remove oxygen from the water, which can kill fish and other aquatic life.  This process is known as eutrophication.  


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Economic Health

Additionally, the economy can be negatively impacted as demonstrated by the following examples.  

  • A new well could be installed or an existing well could be drilled deeper, but both have high costs.  There are no guarantees that these actions will improve water quality.
  • A nitrate removal system could be installed on a private or municipal water supply, which has varying costs. The installation of a nitrate removal system on Plover and Whiting's municipal water supply cost nearly $3 million dollars. Besides installation costs, households pay annual operation and maintenance costs. 
  • Many people purchase bottled water to drink rather than trying to reduce the amount of nitrate in their well water .
  • Many of Portage County's major agricultural crops, such as potatoes, need additional nitrogen or fertilizer. Some farmers believe they cannot afford the extra costs associated with nitrate reducing decisions and practices.  However, others believe those decisions and practices will save them money.

Drilling a new well.

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The DNR website has more information on impacts of nitrate in drinking water.

Nitrate:  sources  |  explanation  |  PC levels  |  testing  |   in drinking water  | actions

goals and strategies  |  nitrate  |  pesticides  |  quantity
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