Description

Nitrates are a normal part of the diet, but can cause problems at excessive levels, particularly for infants.

Nitrates can build up in soil and groundwater, and they are taken up by plants as they grow. The usual sources of nitrate contamination are human sewage, animal manure (especially from feedlots), nitric oxides, and in particular nitrogen-based fertilizers, of which potassium nitrate and ammonium nitrate are the most common. The dangers of nitrate are related to their formation of nitrites in the body.

Both nitrates and nitrites are used as food additives in cured and processed meats and some smoked fish (see How Common Exposures Occur, below). They give cured meats, like bacon and hot dogs, a pink color. They may also protect against botulism. (But there are safer alternatives.)

Infants under four months of age that drink water or eat food contaminated with high levels of nitrates or nitrites are particularly at risk for health effects. For all children, nitrites are generally worrisome because they can interact with other substances in the body to form potential cancer-causing chemical called nitrosamines.

Health Effects

Immediate Health Effects

If SWALLOWED, nitrite, nitrate is Not Available
If ABSORBED THROUGH SKIN, nitrite, nitrate is Not Available
If INHALED (SNIFFED OR BREATHED IN), nitrite, nitrate is Not Available

Longterm or Delayed Health Effects

Nitrates can react with amino acids to form nitrosamines which can contribute to risk for non-Hodgkin’s lymphoma, esophagus, bladder and prostate cancer. There is some evidence that the risk for stomach cancer could be increased too

Other

Rarely, a baby may develop methemoglobinemia, or blue baby syndrome. This can occur if water (particularly well water) containing high levels of nitrates is used to prepare infant formula, and very rarely if infants eat nitrate-rich spinach which has broken down into nitrite during storage. Nitrites can cause blood to lose its ability to transfer oxygen from the lungs to tissues, which rapidly can result in coma and death if not recognized and treated appropriately. The first symptoms are a blue-gray skin color, shortness of breath, rapid pulse, and irritability or lethargy. Infants with infections or with bacterially-contaminated drinking water are most at risk.
There is a theory but no evidence that maternal consumption will cause cancer in the offspring. It is suspected that it can contribute to brain cancer. The safe bet is to avoid it during pregnancy.
Swallowing nitrate-based fertilizers can cause severe abdominal pain, bloody stools and urine, weakness, and collapse. Eight to fifteen grams of sodium or potassium nitrate is fatal for adults.
Maternal exposure can result in anemia, threatened miscarriage, premature labor or preeclampsia.

How Exposures Occur

From Drinking Water

Nitrate levels are regulated in public water supplies. But drinking water coming from private wells, particularly in agricultural areas can be contaminated with higher levels of nitrates, primarily from runoff of fertilizer, animal manure, and human sewage from septic tanks. The EPA sets a limit of 1 ppm for nitrite and 10 mg/L for nitrate.

If you draw your water from a private well, water testing is advised, particularly if you have a baby or are pregnant (see Detection, below).

From Vegetables

For most people, the highest daily nitrate exposure is through its natural occurrence in vegetables, particularly beets, celery, lettuce, parsley, broccoli, carrots, radishes, rhubarb, spinach, melons and turnip greens. However, these foods contain ascorbic acid (vitamin C) and other vitamins that protect against nitrate poisoning and against the formation cancer-causing nitrosamines. Eating a diet rich in vegetables and fruits is the best way to reduce your overall cancer risk.

Significant Statistics

During the second half of the twentieth century, humans dramatically increased nitrogen compound production in the form of fertilizers or fossil fuel combustion. Since the end of the twentieth century, humans have been adding more nitrogen compounds to the nitrogen cycle than all other sources combined.

Ingested Nitrate and Nitrite. International Agency for Research on Cancer. September 13, 2010.

http://monographs.iarc.fr/ENG/Monographs/vol94/mono94-6.pdf.

The Center for Science in the Public Interest lists sodium nitrate and sodium nitrite as additives that should be avoided.

Chemical Cuisine. Center for Science in the Public Interest. 2009.

http://www.cspinet.org/reports/chemcuisine.htm.

Solutions

How to detect nitrite, nitrate

Nitrates and nitrites are regulated under the Safe Drinking Water Act. This law requires that community water systems monitor nitrate and nitrite levels, and make public when levels exceed the set Maximum Contamination Level (MCL). The MCL for nitrates has been set at 10 mg/liter, or 10 parts per million (ppm), and for nitrites at 1 mg/liter, or 1 ppm.

Community water systems are required to produce annual consumer confidence reports and mail them to every water customer.

If your water source is a well, your water is not monitored for contaminants as is required for public water supplies by the Safe Drinking Water Act. Private testing of the water is necessary.

Even if your water comes from a community water system, contaminant levels can vary from house to house. You can have your water tested by sending samples to a certified laboratory.

You can search for water quality reports from your water provider, obtain information on well water testing and find a list of state-certified drinking water laboratories at the U.S. EPA’s Office of Water’s website or call the EPA’s Safe Drinking Water Hotline, 800-426-4791.
Read labels. As a precaution, you can limit or eliminate your family’s consumption of packaged meats, such as hot dogs and bacon that contain sodium nitrite as a preservative.

How to minimize exposure to nitrite, nitrate

If you draw your water from a private well with water that exceeds the permitted level of 10 mg. of nitrates per liter of water (or 1 mg. of nitrites) and if you are pregnant or have an infant, you may want to filter your drinking water, use bottled water for infant formulas, and breastfeed your baby.
Water filtration devices with only carbon or activated charcoal filters will not remove nitrates. A database of water filters certified by NSF International and the contaminants they remove from water is on NSF’s website. They recommend reverse osmosis filters to remove nitrates and nitrites.

Eat a diet high in antioxidants, such as vitamins C (ascorbic acid) and E, which reduce the conversion of nitrates into more toxic nitrites, and stop the breakdown of nitrites into carcinogenic nitrosamines.
Refrigerate your raw greens and vegetables, especially spinach, which is particularly rich in nitrates. Storing vegetables at room temperature causes their naturally-occurring nitrates to break down more quickly into nitrites, which are more toxic.

Alternatives

Breastfeed your infant, particularly if the water you would use to make infant formulas is drawn from a private well that may contain elevated nitrate and nitrite levels. Breastfed infants receive very little nitrate/nitrite exposure.
Eat fresh produce (locally-grown vegetables are freshest), or those that have been frozen, as nitrates will not convert to nitrites when foods are frozen.
Instead of processed meats, serve nitrite-free, certified organic meats or soy or wheat gluten meat-substitute sandwich meats, hot dogs, and bacon. They are available at most natural foods stores and many supermarkets.
Use natural, and therefore slow-release, fertilizers in place of synthetic nitrogen-based fertilizers, such as ammonium nitrate and potassium nitrate, to minimize your contribution of nitrogen to groundwater.