Nitrate is Essential for Crop Health and Food Security
But Compromises Environmental and Human Health in Excess
But Compromises Environmental and Human Health in Excess
Nitrogen is Essential for Life
All living systems require nitrogen to exist, it is an essential component in building proteins, DNA, RNA, vitamins, hormones and enzymes. Animals (including humans), cannot use simple forms of nitrogen such as nitrate and ammonium, but rather must use complex forms of nitrogen such as amino acids and nucleic acids. Plants provide the provide the bulk of nitrogen for all living systems. Most microbes, like bacteria, can make their own complex nitrogen compounds.
Plants Use Nitrate as a Crop Nutrient
In order for plants to make complex nitrogen compounds, they need a supply of simple nitrogen compounds, and nitrate is ideal. Nitrogen based fertilizers have been applied in very large amounts to field crops since the 1950's to stimulate plant growth and ultimately ensure food security. When a field is routinely planted, the nutrients are taken up by the crop and must be replenished for soil health. General practice, until recently, has been to apply a generous amount of fertilizer to make up for the loss of nutrients from the previous planting.
Over Fertilization Results in Nutrient Rich Runoff
Since plants often cannot utilize all of the nitrogen applied to the soil, the excess accumulates in ground water. Not all of the applied nitrogen reaches deeper soil, some of which is washed off the fields in the form of runoff, flowing into surface waters such as streams and rivers. Recently, studies have shown that phosphate is also a nutrient of concern when applied in excess. An overload of these nutrients in streams and rivers promotes algal blooms, oftentimes creating harmful levels of microcystin, a toxin created by cyanobacteria. Microcystin poses a major threat to drinking and irrigation waters, in addition to environmental health. These algae blooms create dead zones, hypoxic conditions, starving the water of oxygen required to support most marine life, as seen during certain times in the Gulf of Mexico, Lake Erie, and beyond.
What is Nitrate?
Nitrate is a negatively charged ion comprised of one nitrogen molecule and three oxygen molecules. Nitrate represents the most oxidized chemical form of nitrogen found in natural systems. Since nitrate is a negatively charged ion (anion), it must be paired with a positively charged ion (cation) such as potassium nitrate, which is a common form of fertilizer. Nitrate is one of the most water soluble anions known, and is tasteless, odorless, and colorless in water.
The Nitrate Problem
- Non-point source runoff from the over-application of nitrogen fertilizers
- Point-sources such as Concentrated Animal Feeding Operations
- Point-sources from poorly or untreated human sewage
Nitrate is a widespread contaminant of ground and surface waters worldwide (1, 2). The accumulation of nitrate in the environment results mainly from:
Effects of large amounts of nitrogen include poor environmental health and a potential for human health complications. In addition, nitrate-containing wastes are produced by many industrial processes including paper and munitions manufacturing. Burning of fossil fuels in power plants and cars, SUVs and all internal combustion engines results in the production of nitric acid and ammonia as air pollution.
Acid-Rain and Atmospheric Dry Deposition of Nitrogen
While most of the sources of nitrogen pollution result in contamination of surface and ground waters, air-borne nitrogen pollution leads to acid rain in the Midwest and East Coast regions of the United States where rain falls on a regular basis. However, in the far-West, California, Colorado and other Southwestern states, where rain events are more scattered, ammonium nitrate (combination of ammonia and nitric acid) is deposited in dry form (called dry deposition) on the plants and land. When rainfall occurs in these dry regions, the nitrogen along with other nutrients is flushed from the soils into streams, rivers and lakes, and eventually into the estuaries of the Pacific Ocean. Furthermore, dry deposition may result in alteration of the natural flora and fauna of a region like coastal chaparral forests in California or high altitude lakes in Rocky Mountain National Park, Estes, Colorado. For info on the extent of atmospheric deposition of nitrate and ammonium, see the National Atmospheric Deposition Program website: http://nadp.sws.uiuc.edu/
Risk to Human Health
Nitrate is a potential human health threat especially to infants, causing the condition known as methemoglobinemia, also called "blue baby syndrome". When nitrate is taken in by eating food and drinking water, nitrate is converted to nitrite in the digestive tract, which then combines with hemoglobin to form methemoglobin, decreasing the ability of the blood to carry oxygen. Infants are more susceptible to nitrate toxicity than older children or adults. Fatalities are rare, but sub-acute methemoglobinemia can be asymptotic while affecting development, making the condition particularly insidious. Chronic consumption of high levels of nitrate may also cause other health problems, for example some cancers and teratogenic effects; data are inconclusive, but cause for concern (3, 4).
Nitrate in Drinking Water
As stated in the EPA publication "Is Your Drinking Water Safe?" (5): "Only two substances for which standards have been set pose an immediate threat to health whenever they are exceeded: bacteria and nitrate." Nitrate levels are monitored in municipal water supplies world-wide and in food to prevent exposure to harmful or toxic levels. Monitoring private wells and other sources of drinking water, however, is the responsibility of the land owner. The U.S. EPA maximum contaminant limit for human consumption is set at 10.0 ppm Nitrate-N, and rural areas where land is primarily used for agriculture are most at risk for nitrate contamination. Elevated nitrate levels in well water are also a good indicator that there might be other contaminants present.
Nitrate Contamination of Ruminant Forage, Feed, and Water
High levels of nitrate in livestock feed and drinking water can result in reduced vitality and increased stillbirth, low birth weight, and slow weight gain and even death of the animals affected (6). Chronic nitrate poisoning is correlated with abortions, still births and stunted calves. Abortion is attributed to maternal and fetal methemoglobinemia resulting in fetal anoxia (particularly in the last tri¬mester of pregnancy). Unpublished data indicates serum progesterone is reduced in chronic nitrate toxicosis in cattle and, possibly, horses. Chronic nitrate toxicosis causes loss of condition, loss of weight, reduced milk production and weakness. Deficiencies of vitamin A & E and hypothyroidism are reported in cattle and swine.
Nitrate Contamination Risk Factors
Because agriculture is implicated in the nitrate pollution problem, farmers and rural communities are most at risk for nitrate contamination. In the United States, the problem is concentrated in the Mid-West and the Far-West, with large areas of Iowa, Illinois, Kansas, Michigan, Wisconsin, Washington and California being heavily affected (1). The USGS (US Geological Survey) released a report in 1995 which revealed that nitrate concentration in the nation’s groundwater supply was increasing steadily: 9% of wells tested had nitrate concentrations exceeding the EPA maximum contaminant level (MCL) for nitrate of 10.0 ppm Nitrate-N, up from 2.4% in prior studies. Estimated nitrate concentration in groundwater used for drinking can be found at the U.S. EPA's website.
Preventing Excess Nutrient Runoff
There are many practices used in agriculture to help combat nutrient runoff. When nutrients from fertilizer or manure leave a field, they aren't being uptaken by the crops, which wastes valuable resources for farmers in addition to putting the environment and human health at risk. Environmental stewardship practices for agriculture include implementation of buffer strips, riparian zones, cover crops, and other methods in effort to have the excess nitrate and other nutrients to be taken up by the roots and stored in plant tissue rather than running off into the watershed where it may contribute to algal growth. Another important preventative measure to combat nutrient runoff is soil and plant tissue nutrient testing. By analyzing the current levels of nutrients such as nitrate in the soil and plants, farmers can make more informed decisions about supplemental nutrient application - to be able to apply the right amount at the right time. Soil and plant analysis of nitrate results in fertilizer cost savings, a healthier environment, and cleaner water.
Reducing Nitrate Health Risks
Consumer concern and awareness regarding the quality and safety of water, food and the environment is well established. Strong evidence of this trend was the public outcry in 1995 when the Clean Water Act was endangered in Congress. Recent news about water quality in Des Moines, Iowa has brought nitrate contamination to the spotlight during fall of 2015 when their water treatment facilities continuously operated their costly nitrate removal reverse osmosis systems. Algae blooms are becoming more and more prevalent in our nation's rivers, streams, oceans and lakes - and are harming ecological systems, recreational opportunities, human health, and ultimately local economic impact because of the aforementioned effects. Because nitrate is such a potentially harmful substance and nitrate contamination is such a widespread problem, NECi believes that a safe, reliable, and easy-to-use nitrate test kit should be available for consumers to make sure that their water is safe to drink.
Testing Your Water for Nitrate Levels
With NECi's on-site nitrate test kits, you can measure the amount of nitrate in your water within 30 minutes of collecting your sample. Designed with ease-of-use in mind, these test kits can be used by anyone - and are based on validated laboratory methods - so you can have the confidence that your results are accurate and reliable. Our standard range water nitrate test kit measures nitrate levels in water up to the maximum contaminant limit, 10.0 ppm Nitrate-N. These kits can be used for any type of water, including drinking water, environmental samples, and more. Low range kits measure up to 2.0 ppm Nitrate-N and will produce more precise data when testing environmental samples that should be low in nitrate levels. Used in conjunction with NECi's handheld photometer, digital results can be stored and tracked on any Android mobile device.
What's Different About NECi's Nitrate Test Kits
Nitrate analysis of water is one of the most common tests done by individuals, commercial laboratories and government regulatory laboratories. This is because nitrate pollution of water presents a significant health risk for humans and animals. Many commercial nitrate test kits and most US EPA-certified nitrate analysis methods use the heavy metal cadmium to reduce nitrate in the process of nitrate testing. Cadmium is a toxic chemical that is regulated by the US EPA under the Clean Water Act. Nitrate analysis using cadmium poses a human health risk. The waste generated during nitrate analysis using cadmium also puts the environment at risk of pollution. NECi has developed an alternative method for nitrate analysis using the enzyme nitrate reductase (11). Nitrate reductase is a naturally occurring enzyme found in plants and is completely non-toxic. This enzymatic nitrate analysis method is a "green chemistry" analytical method, which is sustainable and environmentally benign. The nitrate reductase method does not generate toxic waste, and doesn't require special disposal procedures, unlike the cadmium method. The U.S. EPA validation study for wastewater has shown that the enzymatic nitrate test method produces equivalent results to cadmium based nitrate testing. The nitrate reductase method has been formatted for many types of analysis, from easy on-site test kits to reagent packs for automated, high-throughput nitrate analysis.
- Hallberg, G.R. (1989) Nitrate in ground water in the United States. In: Nitrogen Management and Ground Water Protection, R.F. Follet, ed., Elsevier, Amsterdam, pp. 35-74.
- Puckett, L.J. (1995) Identifying the major sources of nutrient water pollution. Environmental Science & Technology: 408A - 414A
- Kross, B.C., G.R Hallberg, D.R. Bruner, K. Cherryholmes, and J.K. Johnson (1993) The Nitrate Contamination of Private Well Water in Iowa. Am J Public Health 83:270-272.
- Bruning-Fann, C.S., J.B. Kaneene (1993) The effects of nitrate, nitrite, and N-nitroso compounds on human health: a review. Vet Human Toxicology 35:521-538.
- US EPA Office of Water (WH-550) "Is Your Drinking Water Safe?" EPA 570 9-91-005, Sept. 91. This document is no longer available on epa.gov website.
- Committee on Nitrate Accumulation, Ag. Board, Div. Of Biology & Agriculture, National Research Council (1972) Hazards of Nitrate, Nitrite, and Nitrosoamines to Man and Livestock. In: Accumulation of Nitrate, National Academy of Sciences, Wash., DC, pp. 46-75
- Hyde, G.E., J.A. Wilberding, A.L. Meyer, E.R. Campbell & W.H. Campbell (1989) Monoclonal antibody-based immunoaffinity chromatography for purifying corn NADH:nitrate reductases. Plant Mol. Biol. 13: 233-246.
- Campbell, WH, T Kinnunen-Skidmore, MJ Brodeur-Campbell & ER Campbell (2004) New and improved nitrate reductase for enzymatic nitrate analysis. American Laboratory 22(10): 12. PDF.
- Patton, Charles J., Anne E. Fischer, Wilbur H. Campbell, and Ellen R. Campbell (2002) Corn leaf nitrate reductase: A nontoxic alternative to cadmium for photometric nitrate determinations in water samples by air-segmented continuous-flow analysis. Environmental Science and Technology, 36: 729-35. Abstract.
- Patton, CJ, J Kryskalla, ER Campbell & WH Campbell (2004) Replacing Toxic Cadmium with Environmentally Benign Nitrate Reductase in Automated Continuous Flow and Batch Determinations of Nitrate in Environmental Water Samples: An Overview. PittCon2004, Chicago, IL, March 9, 2004. Abstract: 12000 – 200.
- Campbell, Wilbur H., P Song, GG Barbier (2006) Nitrate Reductase for Nitrate Analysis in Water. Environmental Chemistry Letters, 4: 69-73. Abstract.
- Campbell, Wilbur H., Ellen R. Campbell, Lynn Egan (2006) Green Chemistry Nitrate Determination: An Alternative Nitrate Analysis Method. American Laboratory, February, 2006. PDF.
- Patton, Charles J., et al. (2006) Discrete Analyzer Nitrate Analysis with Nitrate Reductase.