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Calcium is a grey silvery hard metal.[1] It is the fifth most abundant element in the earth's crust, making up more than 3 percent of the crust. Pure calcium does not occur in nature; instead, calcium binds with other elements to form calcium compounds like limestone, gypsum, fluorite, and calcium carbonate (CaCO3). In the Periodic Table, calcium's symbol is Ca and its atomic number is 20. It is classified as an alkaline earth metal.


Calcium carbonate is the basis of cement.[2]

In the Environment

Calcium is an important nutrient in the soil as plants need it to grow.[3] All soil contains calcium.

In Sewage Sludge

In the Targeted National Sewage Sludge Survey, a 2009 test of 84 samples of sewage sludge from around the U.S., the EPA found calcium in every sample in concentrations ranging from 9,480 to 311,000 parts per million.[4]

Human Exposure

Humans consume calcium in their diets, particularly in diary products and leafy green vegetables.[5] Some people may also take calcium supplements.

Health Effects

Humans have more calcium in their bodies than any other mineral, and over 99 percent of the body's calcium is stored in the bones and teeth.[6] However, there is also calcium in blood, muscle, and fluid between cells. The body uses calcium to help muscles and blood vessels expand and contract, to secrete hormones and enzymes, and to send messages through the nervous system. The amount of calcium the human body needs changes as the body ages.

Articles and resources

Related SourceWatch articles


  1. WebElements: Calcium, Accessed August 30, 2010.
  2. WebElements: Calcium, Accessed August 30, 2010.
  3. John E. Sawyer, "Soil calcium:magnesium ratios", Integrated Crop Management, April 21, 2003, Accessed August 31, 2010.
  4. Targeted National Sewage Sludge Survey Report, US EPA website, Accessed August 28, 2010.
  5. Calcium: MedlinePlus, Accessed August 31, 2010.
  6. Calcium: MedlinePlus, Accessed August 31, 2010.

External resources

External articles

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