Probably the most familiar everyday use of chlorine is table salt, or sodium chloride. But as one of the major "building blocks" of industrial production, nearly all manufactured products benefit in some way from chlorine.
From the ground up, many homes are constructed and decorated with chlorine-related products like concrete, house paint, fiberglass insulation, and nylon carpeting, as well as vinyl siding, windows, plumbing pipes, and floor tiles.
Chlorine helps make automobiles safer, more efficient, and more comfortable as a component in the manufacture of seat belts, air bags, upholstery, bumpers, floor mats, dashboards and other plastic items, fan and alternator belts, hoses, gaskets, seals, gasoline additives, brake and transmission fluids, anti-freeze, and air conditioning systems.
The modern-day office depends on chlorine for many electronic devices, such as microprocessors, telephones and computer disks, and plastic housings for computers and keyboards.
Even recreational activities depend on chlorine chemistry. Vinyl soccer balls, golf bags, nylon tents and water-proof jackets, wet suits and inflatable rafts, surfboards, tennis rackets, football helmets, and hundreds of toys are just a few of the items that need chlorine for their manufacture.
The most common method of making chlorine is by passing an electric current through a saltwater solution. The solution separates into chlorine and two other useful products: sodium hydroxide -- also known as caustic soda or lye -- and hydrogen.
Every year, approximately 13.6 million metric tons of chlorine are produced in North America.
The greatest volume of North American chlorine, about 40 percent, is used in the production of polyvinyl chloride, PVC, a low-cost, versatile plastic used to construct everything from water pipes and home siding to appliance parts and food storage containers. About 37percent of chlorine produced in North America is used to produce other organic compounds, including basic chemicals needed for manufacturing, and solvents for metalworking, dry cleaning, and electronics. Roughly 4 percent of North American chlorine is used for water treatment. Other inorganic uses of chlorine include producing hydrochloric acid for myriad chemical processes and titanium dioxide, a popular white pigment.
In countless industrial processes, there's simply no cost-effective, safe substitute for chlorinated compounds.
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Chlorine is one of approximately 100 natural chemical elements, the basic building blocks of our planet.
To be useful, an element must be relatively abundant or have extremely desirable properties. Chlorine has both characteristics.
As a result -- over the course of many decades of careful research and development -- scientists have learned to use chlorine and the products of chlorine chemistry to make drinking water safe, destroy life-threatening germs, produce life-saving drugs and medical equipment, shield police and fire fighters in the line of duty, ensure a plentiful food supply and more.
Chlorine chemistry is deeply woven into the fabric of our lives.
In 1774, in his small experimental laboratory, Swedish pharmacist Carl Wilhem Scheele released a few drops of hydrochloric acid onto a piece of manganese dioxide. Within seconds, a greenish-yellow gas arose.
Although he had no idea at the time, he had just discovered chlorine.
The fact that the greenish-yellow gas was actually an element was only recognized several decades later by English chemist Sir Humphrey Davy. Until that time, people were convinced that the gas was a compound of oxygen. Davy gave the element its name on the basis of the Greek word khloros, for greenish-yellow. In 1810 he suggested the name "chloric gas" or "chlorine."
Some of the most effective and economical germ-killers, chlorine disinfectants destroy and deactivate 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.
First used as a germicide to prevent the spread of "child bed fever" in the maternity wards of Vienna General Hospital in Austria in 1847, chlorine has been one of society's most potent weapons against a wide array of life-threatening infections, viruses, and bacteria for over 150 years.
Restaurants and meat and poultry processing plants rely on chlorine bleach and other chlorine-based products to kill harmful levels of bacteria such as Salmonella and E. coli on food preparation surfaces and during food processing.
Chlorine is so important in poultry processing that the US Department of Agriculture requires an almost constant chlorine rinse for much of the cutting equipment. In fact, no proven economical alternative to chlorine disinfection exists for use in meat and poultry processing facilities.
Because it is highly reactive, chlorine is usually found in nature bound with other elements like sodium, potassium, and magnesium. When chlorine is isolated as a free element, it is a greenish yellow gas, which is 2.5 times heavier than air. It turns to a liquid state at -34°C (-29°F), and it becomes a yellowish crystalline solid at -103°C (-153°F).
Chemists began experimenting with chlorine and chlorine compounds in the 18th century. They learned that chlorine has an extraordinary ability to extend a chemical bridge between various elements and compounds that would not otherwise react with each other.
Chlorine has been especially useful in studying and synthesizing organic compounds -- compounds of mostly carbon and hydrogen. All living organisms, including humans, are composed of organic compounds.
The periodic table is the single most unifying concept in chemistry. It is a structured listing of all the known chemical elements. Elements cannot readily be reduced to simpler substances.
In this table, based on the pioneering work of the Russian scientist Dimitri Ivanovich Mendelev who published it in 1869, the elements are arranged in the order of their atomic number – equal to the number of protons in the nucleus of each atom of a given element.
The horizontal rows of the table are called periods. All elements in a period have the same number of layers, or shells, of electrons.
The table's vertical columns are called groups. Elements that occupy one group all have the same number of electrons in their outermost shell. Elements of any particular group tend to have similar chemical properties.
Chlorine opens doors to thousands of social and public health benefits. If you drive a car, use a computer, drink a glass of water, or wear vinyl rain gear, chlorine is working for you. Chlorine chemistry is also used to produce 93 percent of all prescription drugs used in the U.S. Some people are surprised to learn that chlorine works for the environment, too.
Chlorine is an important component in the development and manufacture of materials that make vehicles lighter -- thereby increasing gasoline mileage.
Using crop protection chemicals that depend on chlorine results in high crop yields -- thereby relieving pressures to convert rainforests and other ecologically important lands to agricultural use.
Chlorine even plays an important role in harnessing solar energy -- purifying the silicon found in grains of sand and helping transform them into solar panel chips.
In so many ways, chlorine is part of the bedrock of sustainable development efforts and other central tenets of modern environmental protection.
Without sodium chloride (salt), there would be no life. Life began in the ocean, a largest repository of salt which is derived from the weathering of the continents.
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 plays an essential role in a delicate balancing act: providing for the electrical neutrality and the correct pressure of body fluids, and keeping the acid-base balance of the body.
One result of this balancing act is that the amount of water we retain and concentrations of salt in our bodies 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 and perspiration the body requires salt; and we are usually thirsty after eating salty food.
Human Body: Muscles
Sodium ions play an important role in our body's communication system. The nimbleness of a world class pianist or the dexterity of an Olympian athlete depend on the inner working of the central nervous system. Sodium ions are vital to the transmission of impulses from our brains to our muscles through the complex network of nerve cells.
On the flip side are the chloride ions, which assist in balancing the electrical charges throughout our nervous system.
Human Body: Digestive System
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 available to the body.
Human Body: Immune System
In the immune system, which is charged with fighting off the daily invasion of germs, chlorine is there to lend a hand. When infections take place, hypochlorite -- a chlorine-containing compound which is a well-known disinfectant -- forms in white blood cells. Hypochlorite itself attacks the germs, or helps to activate other agents that do the work.
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Chlorine is a naturally-occurring chemical element, one of the basic building blocks of matter. Scattered throughout the rocks of Earth’s continents and concentrated in its salty oceans, chlorine is an essential nutrient for plants and animals.
Chlorine chemistry provides clean drinking water to millions around the globe. Clean drinking water made possible with chlorine disinfectants is a monumental triumph over the scourges of waterborne disease. And chlorine chemistry is also critical to manufacturing thousands of products that define life in the 21st century, from silicon-based semiconductors to sustainable PVC building materials.
ACC’s Chlorine Chemistry Division supports the Water Quality and Health Council’s efforts to promote proper pool maintenance and healthy swimming behaviors.
WASHINGTON, D.C. (September 13, 2010) – On the heels of the Water Quality and Health Council’s summer-long campaign promoting proper swimming behaviors and pool maintenance, four new studies were published in Environmental Health Perspectives this week that examined chlorinated swimming pools and the potential effects of disinfection byproducts on human health. Disinfection byproducts (DBPs) are chemical compounds that are formed unintentionally when chlorine and other disinfectants used to protect swimmers react with organic matter, including perspiration and urine in water.
Initial media coverage of the reports has suggested swimming in pools may be linked to cancer and asthma—statements unsupported by current scientific evidence.
Judith Nordgren, Managing Director of the American Chemistry Council’s Chlorine Chemistry Division, issued the following statement in response to the studies:
“The Centers for Disease Control and Prevention (CDC) calls chlorine a vital part of the first line of defense against bacteria and viruses that can make swimmers sick. Chlorine has been used safely and effectively in pools and spas for decades precisely because it kills most germs within minutes.
“Reporting on the studies, some in the media jumped hastily to suggest alternatives to chlorination for disinfecting swimming pools that might impact public health adversely. Unlike other disinfectants, chlorine provides a residual level that continues to disinfect long after it’s applied, helping to prevent cross-contamination among swimmers. Chlorine is also easy to monitor, and levels can be adjusted based on pool conditions.
“Any science-based research that examines complex pool chemistry is a step forward and can help better manage chlorinated pools. As the authors themselves state, these studies rely on small numbers of swimmers in two Barcelona swimming pools with high bromine levels in the source water. Further research is needed to determine whether these results are applicable to swimming pools in the United States and other places where the bromine levels are lower. Nevertheless, we agree with these authors that ‘people need to work harder to reduce everyone’s exposure’ to disinfection byproducts.
“Ultimately, healthy pools are a shared responsibility. The CDC encourages swimmers to play a key role in keeping pools healthy by showering before swimming and refraining from peeing in the pool. ACC’s Chlorine Chemistry Division supports the Water Quality and Health Council’s efforts to promote proper pool maintenance and healthy swimming behaviors.”
For decades, chlorine has been used safely to help destroy waterborne germs that cause diarrhea, swimmer’s ear, athlete’s foot and other ailments. Learn more from this helpful question and answer.
Swimming is a healthy form of exercise for people of all ages. For decades, chlorine has been used safely to help destroy waterborne germs that cause diarrhea, swimmer’s ear, athlete’s foot and other ailments. Unlike alternative disinfectants, such as ozone and ultraviolet radiation, chorine provides a residual level of protection that continues to disinfect long after it is applied.
Q. Does swimming in chlorinated pools cause cancer?
A. Any link between chlorinated pools and cancer is highly speculative. Scientists continue to study this issue, but in no case have they concluded that swimming in chlorinated pools causes of cancer. Respected public health authorities, including the World Health Organization, the U.S. National Cancer Institute, the U.S. Environmental Protection Agency and Health Canada, have each examined scientific research on swimming and bladder cancer, for example. These groups have each concluded existing data are insufficient to show an association. Other studies examining the effects on DNA of swimming in pools are limited and inconclusive.
Q. Is chlorine in swimming pools a health hazard?
A. Chlorine helps protect health by killing waterborne germs that can make swimmers sick. Independent and respected health authorities agree that chlorine itself poses no known health effects when levels are managed within the recommended range for swimming pool water. Research on swimming pools and potential health effects focuses, not on chlorine, but on substances formed in pool water called disinfection byproducts.
Q. What are disinfection byproducts? Where do they come from?
A. Disinfection byproducts are produced when disinfectants such as chlorine, used to protect against waterborne germs, react with impurities, including perspiration, body oils, urine and lotions introduced into the pool by swimmers. All disinfectants form byproducts, but those formed with chlorine are the most well-studied. One type of disinfection byproduct, chloramines, are irritating substances responsible for swimmers’ red eyes and the strong chemical odor of some pools. Many people mistake the smell of chloramines for a sign that there is “too much chlorine” in the pool. The truth may be the reverse: more chlorine may be needed to help reduce chloramine levels.
Q. So, what can I do to reduce my exposure to these disinfection byproducts?
A. Pool managers have a responsibility to manage pool chemistry appropriately, which helps limit disinfection byproducts. Maintaining sufficient levels of chlorine is essential to protect against waterborne diseases. The goal is to limit the impurities in the water that lead to the formation of byproducts. Swimmers can do their part by showering before swimming and never peeing in the pool, for example. If the levels of impurities in pool water are kept low, the levels of disinfection byproducts will also be low.
Q. I guess I thought the chlorine would “take care” of any pee in the pool. Is that not the case?
A. Chlorine, as well as other disinfectants, reacts with any organic matter in the pool, including urine. If chlorine reacts with urine, it is used up so it is not available to destroy germs. And when chlorine reacts with compounds in urine, DBPs are formed. Bottom line: Don’t pee in the pool.
Q. Is peeing in the pool really that common?
A. A 2009 Water Quality & Health Council survey of 1,000 U.S. adults found that one in five adults admit to peeing in a pool. (How many more did not “own up”? We can only speculate.) Swimmers must understand that such practices affect the quality of pool water. While at the pool, parents can take children on “bathroom breaks” and ensure everyone washes their hands after using the toilet.
Q. Does swimming cause asthma?
A. There is no convincing evidence that swimming in chlorinated pools causes asthma in otherwise healthy people. In fact, physicians often prescribe swimming for their asthmatic patients. They say the benefits of swimming as a healthy form of exercise offsets any potential respiratory risk. Research on swimming pools and asthma center around substances formed in pool water called disinfection byproducts (DBPs), which form when disinfectants, such as chlorine, chemically react with impurities, including perspiration, body oils, urine and lotions introduced into the pool by swimmers. Some DBPs are highly volatile and can lead to noxious odors and irritating conditions, particularly at indoor pools. Properly operated and maintained pools should keep the level of DBPs low, while protecting swimmers from waterborne germs. Swimmers must also do their part by showering before swimming and never peeing in the pool.