One of the most effective and economical germ-killers, chlorine also destroys and deactivates a wide range of dangerous germs in homes, hospitals, swimming pools, hotels, restaurants, and other public places. Chlorine's powerful disinfectant qualities come from its ability to bond with and destroy the outer surfaces of bacteria and viruses. It was first used as a germicide to prevent the spread of "child bed fever" in the maternity wards of Vienna General Hospital in Austria in 1846, chlorine has been one of society's most potent weapons against a wide array of life-threatening infections, viruses, and bacteria for 150 years.

Without sodium chloride (salt), there would be no life. Life began in the ocean, the largest source of salt and the origin of all organic material. Through evolution, our bodies learned how to use salt, and its constituent elements such as chlorine, in a number of essential ways. Sodium chloride literally keeps our bodies from drying up, moves our muscles, makes our meals matter, and attacks germs to keep us healthy. Our body's cells exist in a sea of fluid. This extracellular body fluid is mostly water, along with the charged atoms (ions) of sodium and chloride. Chloride and other chlorine compounds play an essential role in a delicate balancing act: providing for the electrical neutrality and the correct pressure for the body fluids, and in keeping the acid-base balance of the body. One result of this balancing act is that the amount of water and concentrations of the salt remain relatively constant over time. We don't dry up nor do we bloat uncontrollably. When changes occur, the balance reasserts itself. For example, after heavy exercise the body requires salt; and we are usually thirsty after eating salty food.

Chloride ions are building blocks of hydrochloric acid, which is essential to our digestive system. Hydrochloric acid made in the stomach has two main purposes: to help destroy germs that arrived with the food; and to help pepsin, an enzyme, break down the proteins found in the food stuffs, ensuring that essential nutrients are made avail- able to the body.

Chlorine in water reacts with living tissues and organic matter causing acute necrosis (cell death) in fish. Most municipal water companies sterilize their water with chlorine or chloramine, a combination of chlorine and ammonia, for safe human consumption. While relatively harmless to humans, chlorine can be deadly to fish. The amount of chlorine in tap water may fluctuate, but it is usually between 0.5 and 2.0 parts per million (ppm).

Sources
Chlorine is found in soils, minerals, plants and animals. Seawater is a huge reservoir of dissolved chlorine weathered from the continents and transported to the oceans by Earth's rivers.

Chlorine is produced industrially from the compound sodium chloride, one of the many salts found in geologic deposits formed from the slow evaporation of ancient seawater. When electricity is applied to a brine solution of sodium chloride, chlorine gas (Cl 2 ), caustic soda (NaOH) and hydrogen gas (H 2 ) are generated according to the following reaction:

Salt + Water ---> Chlorine Gas + Caustic Soda + Hydrogen Gas

Toxicity
Chlorine is a greenish-yellow, noncombustible gas at room temperature and atmospheric pressure. The intermediate water solubility of chlorine accounts for its effect on the upper airway and the lower respiratory tract. Exposure to chlorine gas may be prolonged because its moderate water solubility may not cause upper airway symptoms for several minutes. In addition, the density of the gas is greater than that of air, causing it to remain near ground level and increasing exposure time. The odor threshold for chlorine is approximately 0.3-0.5 parts per million (ppm); however, distinguishing toxic air levels from permissible air levels may be difficult until irritative symptoms are present. Chlorine gas is a pulmonary irritant with intermediate water solubility that causes acute damage in the upper and lower respiratory tract. Elemental chlorine and its derivatives, hydrochloric and hypochlorous acids, may cause biological injury.

In animal models of chlorine gas toxicity, immediate respiratory arrest occurs at 2000 ppm, with the lethal concentration for 50% of exposed animals in the range of 800-1000 ppm. Bronchial constriction occurs in the 200-ppm range with evidence of effects on ciliary activity at exposure levels as low as 18 ppm. With acute exposures of 50 ppm and subacute inhalation as low as 9.0 ppm, chemical pneumonitis and bronchiolitis obliterans have been noted. Mild focal irritation of the nose and trachea without lower respiratory effects occur at 2.0 ppm.

Numerous scientific studies report that chlorinated water is a skin irritant and can be associated with rashes like eczema. Chlorinated water can destroy polyunsaturated fatty acids and vitamin E in the body while generating toxins capable of free radical damage (oxidation). Chlorinated water destroys much of the intestinal flora, the friendly bacteria that help in the digestion of food and which protect the body from harmful pathogens.

Chlorinated water contains chemical compounds called trihalomethanes which are carcinogens resulting from the combination of chlorine with organic compounds in water. These chemicals, also known as organochlorides, do not degrade very well and are generally stored in the fatty tissues of the body (breast, other fatty areas, mother's milk, blood and semen). Organochlorides can cause mutations by altering DNA, supress immune function and interfere with the natural controls of cell growth.

Chlorine has been documented to aggravate asthma, especially in those children who make frequent use of chlorinated swimming pools. Several studies also link chlorine and chlorinated by-products to a greater incidence of bladder, breast and bowel cancer as well as malignant melanoma. One study even links the use of chlorinated tap water to congenital cardiac anomalies.

Toxicity Symptoms
The immediate effects of chlorine gas toxicity include acute inflammation of the conjunctivae, nose, pharynx, larynx, trachea, and bronchi. Irritation of the airway mucosa leads to local edema secondary to active arterial and capillary hyperemia. Plasma exudation results in filling the alveoli with edema fluid, resulting in pulmonary congestion.

Toxicity Limits
The exact levels where chlorine becomes toxic is not clear. About 0.2-0.5 mcg. intake daily is probably safe. Below 0.2 ppm is considered current normal ranges for body chlorine levels. There should not be any inorganic chlorine present in the body.