Calcium is not an air pollutant, and only trace amounts exist in the air, where it exists only in combination with other elements. In the lab, elemental calcium reacts violently with water, and it reacts slowly with oxygen or nitrogen in the air to form a harmless oxide or nitride. It is an essential element for most life and is a primary constituent of bones, teeth and cell walls in animals.
Some of the most common sources of dietary calcium include dairy products, nuts, beans, some green leafy vegetables and lentils. Insufficient dietary calcium can lead to osteoporosis, while excess dietary calcium can lead to kidney stones.
Calcium compounds are the primary cause of scale build-up on bathroom fixtures, in pipes and in hot water heaters. Many professionals recommend that homeowners use water softeners or periodically drain their hot water heaters to mitigate these problems.
Calcium, the fifth most abundant element in the Earth's crust, is an alkaline earth metal, most commonly found in limestone, gypsum and fluorite. It was discovered by Sir Humphrey Davy in 1808 and named for the Latin word "calx," which means "lime." Today, it has many uses in industry, especially in the production of cement and mortar.