In fact, chlorine places in the top ten percent of importance in the creation of all the animal, vegetable and mineral matter that makes up our planet. Considering chlorine's prevalence in so many naturally occurring compounds, it is not surprising that it is also a vital ingredient in many man-made compounds. No two elements are exactly the same, and chlorine's extraordinary usefulness is related to its exceptional ability to bind to other elements and compounds, and to impart its unique properties to form new matter. Because chlorine holds such an important position in our world, we clearly cannot do without it, even if we want to. Like oxygen or hydrogen, chlorine is a natural element and has been an integral part of the universe from the start.
Nature produces chlorine as neutrons from solar radiation strike argon gas in the atmosphere.
Chlorine is also produced as chemical reactions cause the release of chlorine gas from sodium chloride in seas and oceans. More than 1,000 different chlorinated organic compounds are known to occur in nature. These compounds are produced as part of the life cycle of plants, marine organisms, insects, bacteria and fungi, as well as by atmospheric and geological activity. In the human chlorination process, white blood cells engulf invading bacteria with chlorine in the form of hypochlorous acid. People who lack this hypochlorous synthesizing enzyme are highly susceptible to infection, similar to people swimming in a pool without chlorine.