A trace element is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). They are classified into two groups; essential and non-essential. Essential trace elements are needed for many physiological and biochemical processes in both plants and animals. Not only do trace elements play a role in biological processes but they also serve as catalysts to engage in oxidation and reduction mechanisms.
The exact definition depends on the field of science:
- In analytical chemistry, a trace element is one whose average concentration is less than 100 parts per million (ppm) measured in the atomic count or less than 100 micrograms per gram.
- In biochemistry, an essential trace element is a dietary element that is needed in very minute quantities for the proper growth, development, and physiology of the organism. The dietary elements or essential trace elements are those that are required to perform vital metabolic activities in organisms. Examples of essential trace elements in animals include Fe (hemoglobin), Cu (respiratory pigments), Co (Vitamin B12), Mn and Zn (enzymes). Some examples within the human body are cobalt, copper, fluorine, iodine, iron, manganese and zinc. Although they are essential, they become toxic at high concentrations. Elements such as Ag, As, Cd, Cr, Hg, Ni, Pb, and Sn have no known biological function, with toxic effects even at low concentration.
- In geochemistry, a trace element is one whose concentration is less than 1000 ppm or 0.1% of a rock's composition. The term is used mainly in igneous petrology. Trace elements will be compatible with either a liquid or solid phase. If compatible with a mineral, it will be incorporated into a solid phase (e.g., nickel's compatibility with olivine). If it is incompatible with any existing mineral phase it will remain in the liquid magma phase. The measurement of this ratio is known as the partition coefficient. Trace elements can be substituted for network-forming ions in mineral structures. Trace elements that are not essential to a mineral's defined composition will not appear in the chemical formula of that mineral.
Trace elements with chronic diseases
Here are several potential diseases that are associated with trace elements. Essential and Non-Essential elements play a crucial role in deciding which chronic illness a person could have. 
- Iron Absorption
- Coronary Heart Disease
- Iron Deficiency Anemia
- Atherosclerotic Cardiovascular Diseases
- Zinc-Copper Interactions
- Dental Caries
- Hypertension and Cardiac Effects
Factors in drinking water
Many variables have an important role to play in how trace elements influence drinking water concentrations.
- Groundwater age
- Federal and State water quality standards
- Mining Areas
- Corrosive Water
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- Soto-Jiménez, Martin (December 2011). "Trace element trophic transfer in aquatic food webs". Hidrobiológica. 21 (3): 239–248. ISSN 0188-8897. Retrieved 5 November 2018.
- Shier, Butler, Lewis, David, Jackie, Ricki (2016). Hole's Human Anatomy Fourteenth Edition. New York: McGraw Hill Education. p. 59. ISBN 978-0-07-802429-0.CS1 maint: multiple names: authors list (link)
- Health, National Research Council (US) Committee on Diet and (1989). Trace Elements. National Academies Press (US).
- "Metals and Other Trace Elements". www.usgs.gov. Retrieved 2020-12-05.