Chlorine, which is widely used for water purification, sanitation, and the manufacture of modern medicines, is essential for human well-being in today’s world. As epidemics of waterborne diseases escalate across Syria in besieged and opposition-held areas, the Syrian government’s systematic withholding of the primary means to decontaminate water in these areas can be considered an indirect weapon of mass destruction. However, although minute quantities of chlorine are life-saving, if too much is inhaled in its gaseous form, it can cause death in under thirty minutes. Recently, the Syrian government has used chlorine directly against civilians as a chemical weapon. Syrian President Bashar al-Assad has thus transformed a principal element of public health into a tool of both disease and terror.
Human life depends on water—clean water. Attempts to purify water are described in ancient Hindu, Sanskrit, and Greek texts, and passing references are even made in the Old Testament.
Yet the means to kill waterborne microbes was lacking until the discovery of pure chlorine in the early nineteenth century. Nowadays, we take a constant supply of safe water for granted, and chlorine has been our principal agent of water purification for well over a century. In the US, it has been mandated to decontaminate drinking water since 1914.
Chlorine, one of the basic elements, was isolated in gaseous form in 1810 by Sir Humphry Davy, and named for its pale green color (khlōros, in ancient Greek). Its ability to decontaminate derives from its oxidizing properties: it rapidly reacts with and inactivates the proteins that hold cells together. In sufficient concentration, it is poisonous to all species of life.1 Chlorine’s potential for industrial sanitation initially went unnoticed because its discovery predated by several decades the germ theory of disease. At that time disease was believed to be caused by miasma: poisonous particles of dead and decaying matter suspended in foul-smelling clouds arising from graves, swamps, and cesspools.
However, the focus on putrid smells as a sign of miasma led to chlorine’s first clinical use. In 1847, Ignác Semmelweis, a Hungarian physician in Vienna, used chlorine to get rid of the stench of death on his hands after handling cadavers before going onto the maternity ward, and he made his residents do likewise. The death rate on his ward plummeted, but his efforts to broadly institute hygienic practices in hospitals were rejected by the medical community, and he was eventually committed to an insane asylum, where he died of overwhelming sepsis two weeks…
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