General Populations

Most dietary intake of nitrate comes from the consumption of certain vegetables; those particularly high in nitrate include celery, lettuce, and spinach. Selected meats and meat products contain sodium nitrate and/or sodium nitrite as preservatives and can be a source of overexposure to sodium nitrate and/or sodium nitrite. Drinking water from water supplies contaminated by nitrate from fertilizer runoff, animal waste, and/or nitrate-containing substances at waste disposal sites may result in overexposure to nitrate. Release of nitrate and/or nitrite to soil from fertilizer runoff, animal waste, and/or waste disposal sites could result in increased uptake by plants used for human consumption. Occupational Populations Workers who are employed in occupations where fertilizer use is common (e.g., farming, greenhouse operations) may be exposed to nitrate and nitrite through dermal routes and inhalation of dust particles. Toxicokinetics There is no information regarding the toxicokinetics of nitrate or nitrite following inhalation or dermal exposure. Gastrointestinal absorption of nitrate and nitrite occurs after drinking water or eating food that contain these compounds. Some of the nitrate in your body moves from blood to the salivary glands where some of it is changed to nitrite. Both nitrate and nitrite can be produced inside the body. Nitrate and nitrite are widely distributed in the body. Most of the nitrate that you take into your body each day leaves in the urine the same day it enters your body. Some nitrite in the stomach forms other substances called nitrosamines, some of which may be harmful. Normal Human Levels National surveys of the U.S. general population conducted in 2005-2008 showed that the geometric mean level of nitrate in urine of nearly 18,000 participants was 42.7 or 46.3 mg/L. Biomarkers There are no biomarkers specific to nitrate or nitrite exposure because these substances are also produced in the body. Methemoglobinemia has been used as a biomarker of nitrate and nitrite toxicity; however this effect is not specific to nitrate and nitrite