What are Nitrates/Nitrites and how are they used?

Nitrates and nitrites are nitrogen-oxygen chemical units which combines with various organic and inorganic compounds.  Once taken into the body, nitrates are converted into nitrites.  The greatest use of nitrates in the U.S. is as a fertilizer.

Why are Nitrates/Nitrites in water being regulated?

In 1974, Congress passed the Safe Drinking Water Act.  This law requires EPA to determine safe levels of chemicals in drinking water which do, or may cause health problems.  These non-enforceable levels, based solely on possible health risks and exposure, are called Maximum Contaminant Level Goals.

The MCLG for nitrates has been set at 10 parts per million (ppm), and for nitrites at 1 ppm, because the EPA believes this level of protection would not cause any of the potential health problems described below.

Based on this MCLG, EPA has set an enforceable standard called a Maximum Contaminant Level (MCL).  MCLs are set as close to the MCLGs as possible, considering the ability of public water systems to detect and remove contaminants using suitable treatment technologies.  Private well water is solely the responsibility of the individual water well homeowner.

The MCL for nitrates has been set at 10 ppm, and for nitrites at 1 ppm, because EPA believes, given present technology and resources, this is the lowest level to which water systems can reasonably be required to remove this contaminant should it occur in drinking water.

These drinking water standards and the regulations for ensuring these standards are met, are called National Primary Drinking Water Regulations.  All public water supplies must abide by these regulations.

What are the health effects?

Short-term: Excessive levels of nitrate in drinking water have caused serious illness and sometimes death.  The serious illness in infants is due to the conversion of nitrate to nitrite by the body, which can interfere with the oxygen-carrying capacity of the child's blood.  This can be an acute condition in which health deteriorates rapidly over a period of days.  Symptoms include shortness of breath and blueness of the skin.

Long-term: Nitrates and nitrites have the potential to cause the following effects from a lifetime exposure at levels above the MCL: dieresis, increased starchy deposits and hemorrhaging of the spleen.

How much Nitrates/Nitrites are produced and released to the environment?

Most nitrogenous materials in natural waters tend to be converted to nitrate, so all sources of combined nitrogen, particularly organic nitrogen and ammonia, should be considered as potential nitrate sources.  Primary sources of organic nitrates include human sewage and livestock manure, especially from feedlots.

The primary inorganic nitrates which may contaminate drinking well water are potassium nitrate and ammonium nitrate both of which are widely used as fertilizers.

According to the Toxics Release Inventory, releases to water and land totaled over 112 million pounds from 1991 through 1993.  The largest releases of inorganic nitrates occurred in Georgia and California.

What happens to Nitrates/Nitrites when they are released to the environment?

Since they are very soluble and do not bind to soils, nitrates have a high potential to migrate to ground water, and eventually into well water.  Because they do not evaporate, nitrates/nitrites are likely to remain in water until consumed by plants, other organisms or people.

How will Nitrates/Nitrites be detected in and removed from my well drinking water?

The regulation for nitrates/nitrites became effective in 1992.  Between 1993 and 1995, EPA required water suppliers to collect water samples at least once a year and analyze tem to find out if nitrates/nitrites are present above 50 percent of their MCLs in drinking water.  If it is present above this level, the water system must continue to monitor this contaminant every 3 months.

If water contaminant levels are found to be consistently above their MCLs, water suppliers must take steps to reduce the amount of nitrates/nitrites so that they are consistently below that level.  The following treatment methods have been approved by EPA for removing nitrates/nitrites: Ion exchange, Home Drinking Water Reverse Osmosis Systems, Electrodialysis.

     For removal of nitrates in drinking water the preferred method that is highly effective is reverse osmosis (RO).  Reverse osmosis drinking water systems are very reasonably priced and can be easily maintained by the average homeowner.

How will I know if Nitrates/Nitrites are in my well drinking water?

If the levels of nitrates/nitrites exceed their MCLs, the system must notify the public via newspapers, radio, TV and other means. Additional actions, such as providing alternative drinking water supplies, may be required to prevent serious risks to public health.

Drinking Water Standards (ppm): MCLG MCL

Nitrate: 10 10
Nitrite: 1 1

Nitrate and Nitrite Releases to Water and Land: 1991 to 1993 (in pounds)

  Water Land
TOTALS 59,014,378 53,134,805

Top Fifteen States*  
GA 12,114,253 12,028,585
CA 0 21,840,999
AL 3,463,097 6,014,674
LA 8,778,237 2,250
MO 6,985,890 206,181
MS 6,952,387 0
KS 5,140,000 877,095
VA 5,091,764 0
NV 0 4,977,482
FL 1,056,560 1,835,736
AR 1,206,610 1,058,294
MD 1,802,219 138,819
IA 1,500,340 132,042
OK 1,436,348 14,199
UT 0 1,045,400

Major Industries*  
Nitrogenous fertilizer 41,584,611 8,607,376
Misc. Ind. inorganics 4,113,312 29,676,919
Misc. Metal ores 0 5,764,976
Misc. Ind. organics 5,091,764 0
Fertilizer mixing 480,000 4,554,916
Explosives 850,921 1,297,590
Paper mills 1,727,061 0
Pulp mills 1,321,500 3,350
Canned foods 0 1,056,794
Phosphate fertilizers 1,000,000 0

* State/Industry totals only include facilities with releases greater than 10,000 lbs.

Nitrates in Well and Ground Water

Nitrates in well water and ground water
















     Concentrations of nitrate were greater than the U.S. Environmental Protection Agency Maximum Contaminant Level of 10 milligrams per liter (mg/L) as N in about 4 percent of the wells. Elevated concentrations of nitrate occurred throughout the Unites States, but least commonly in the Southeast. Concentrations greater than 1 mg/L as N, which is usually considered indicative of human activities in many areas (Nolan and Hitt, 2003), were found in about 40 percent of wells located throughout the sampled areas. >, greater than; <, less than or equal to.