By: Susan-Marie Cronkite, PhD.
Chlorine, or Household Bleach
H
ousehold bleach, or chlorine bleach, is a chemical compound manufactured from chlorine, caustic soda and water. The active ingredient in chlorine bleach is sodium hypochlorite [1,2]. Today’s bleach is the end product of centuries of trial, error and scientific discovery in an on-going search for a way to whiten cloth. White fabrics were a status symbol; the whiter the fabrics, and the more you owned, indicated your social standing.
Fabric whitening on a large scale was invented in the 12th century in Holland. It was such a lucrative business that the process was a well guarded trade secret; it was hence necessary for European countries to send their cloth to the Netherlands to be whitened by this secret process. Eventually, the secret leaked out and spread across Europe, arriving in England in 1322 . White fabric was a sign of status because the process took months. Raw cloth was first ‘bucked’ or soaked in a water / lye solution for several days. After the initial soaking, it was washed thoroughly and then spread out flat in grass fields to be baked by the sun. This process, called ‘crofting’, lasted for several weeks. Bucking and crofting were then repeated until the cloth was as white as possible. Finally, the cloth was washed in sour milk or buttermilk to ensure the lye mix was neutralized so the cloth fibers would not be damaged more than necessary by the whitening process. The cloth then underwent a final wash in plain water, was crofted once more and then finally shipped back [3].
Chlorine itself was discovered in 1774 by a Swedish scientist Karl Whilhelm Scheele. A French scientist, Claude Berthollet, discovered that chlorine could be incorporated into the fabric whitening process, reducing the bleaching time to a few hours. He began to manufacture the first bleaching powder in 1789, called “Eau de Javelle” after the city where the product was made – Javel, a small town outside of Paris. A second bleaching powder entered the market in 1799, invented by a Scottish chemist Charles Tennant. These early whitening aids were only available in a powder form; liquid chlorine solutions were not available until WW I [4].
The second property of chlorine bleach as a disinfectant was identified in the 19th century when Louis Pasteur experimented with and promoted ‘germ theory’ (emergent growth of bacteria is not due to spontaneous generation or ‘bad air’ called ‘miasma’, but rather to biogenesis [5]). Pasteur discovered three preventatives to the growth of micro-organisms: the use of filters, the use of heat and the use of chemical solutions [6] . Various scientists, chemists and doctors now began to experiment with available products and the importance of bleach as a disinfectant became clear and it slowly began to be used in early Public and Environmental health [7, 8].
- 1847 — chlorine first used as a germicide to prevent the spread of peurperal fever in the maternity wards of Vienna General Hospital
- 1850 – used by John Snow to disinfect the water supply in London after an outbreak of cholera
- 1895 – first large public use of chlorine bleach in the US when it was used to disinfect drinking water in New York city’s Croton Reservoir
- 1909 – mass production of bleach became possible; bleach became an household product
- 1918 – US Dept of Treasury called for all water to be disinfected with chlorine
- 1960’s – used by NASA as a disinfectant for all space flights, both before and after the flights.
Today, chlorine bleach is seen as the preeminent biocide. It is simple and inexpensive to manufacture, it kills germs, mico-organisms, algae, mold and mildew and its health and environmental affects are very limited if used correctly [9, 10].
The Pros of sodium hypochlorite solutions (aka chlorine bleach or household bleach)
Chlorine bleach has a wide range of uses: swimming pool disinfectant, sewage treatment, sanitizing equipment of all types, algae control, fabric disinfectant in medical, industrial and commercial situations [11]
- as a general biocide, chlorine / chlorine bleach is important in water purification. “Chlorine in water is more than 3 times more effective as a disinfectant against e.coli than equivalent concentration of bromine and more than 6 times more effective than equivalent concentration of iodine” [12]. To purify water, use two drops of 5% chlorine bleach to a quart of water and let stand for 30 minutes before using.
- The use of chlorine bleach has greatly aided public health in developing countries, saving many, many lives. As a good, all purpose and inexpensive disinfectant it is used in hospitals, rural clinics, food production facilities, schools and most importantly, to purify water
- if used correctly, chlorine bleach has a very limited health and environmental impact. Under normal use, household bleach is broken down into salt, oxygen and water and small quantities of AOX by-products (adsorbable organic halides) which are easily degradable, water soluble and not bio-accumulative [13]
And the Cons…. [14, 15]
health effects:
- sodium hypochlorite solutions can be classified as an irritant or as corrosive depending upon the concentration. Dilution directions should always be followed carefully.
- chlorine bleach when mixed with ammonia, rust removers and certain acids creates toxic chloramine gas which can cause severe respiratory irritation requiring medical treatment.
References
[1] How Products are Made: Vol 2, BLEACH. (on line) Available: http://www.madehow.com/Volume-2/Bleach.html. Cited 2009 28 October
[2] Fletcher, Dr. John and Don Ciancone, The Sodium Hypochlorite Story. (on line) Available: http://www.southshoregunitepools.com/resources/htms/naocl.htm. Cited 2009 29 October.
[3] How Products are Made: Vol 2, BLEACH. (on line) Available: http://www.madehow.com/Volume-2/Bleach.html. Cited 2009 28 October
[4] ibid. Cited 2009 28 October.
[5] Louis Pasteur, Wikipedia (on-line) Available: http://en.wikipedia.org/wiki/Louis_Pasteur. Cited 2009 29 October.
[6] Fletcher, Dr. John and Don Ciancone, The Sodium Hypochlorite Story. (on line) Available: http://www.southshoregunitepools.com/resources/htms/naocl.htm. Cited 2009 29 October.
[7] Joseph Lister, 1st Baron Lister. Wikipedia (on-line) Available: http://www.southshoregunitepools.com/resources/htms/naocl.htm. Cited 2009 28 October. http://en.wikipedia.org/wiki/Joseph_Lister,_1st_Baron_Lister. Cited: 2009 29 October.
[8] Chlorine. Wikipedia (on-line) Available: http://en.wikipedia.org/wiki/Chlorine. Cited 2009 29 October.
[9] How does chlorine bleach work?, Howstuffworks.com. (on line) Available at: http://science.howstuffworks.com/question189.htm/printable. Cited Cited 2009 30 October.
[10] Chlorine. Wikipedia (on-line) Available: http://en.wikipedia.org/wiki/Chlorine. Cited 2009 29 October.
[11] Fletcher, Dr. John and Don Ciancone, The Sodium Hypochlorite Story. (on line) Available: http://www.southshoregunitepools.com/resources/htms/naocl.htm. Cited 2009 29 October.
[12] Chlorine. Wikipedia (on-line) Available: http://en.wikipedia.org/wiki/Chlorine. Cited 2009 29 October.
[13] Fletcher, Dr. John and Don Ciancone, The Sodium Hypochlorite Story. (on line) Available: http://www.southshoregunitepools.com/resources/htms/naocl.htm. Cited 2009 29 October.
[14] Ibid. Cited 2009 30 October.
[15] Mrvos, R., Dean B.S. And E.P Krenselok, Pittsburgh Poison Center, Children’s Hospital of Pittsburgh, PA 15213. Home exposures to chlorine/chloramine gas: review of 216 cases. South Med J. 1993 Jun;86(6):654-7. (on line) Available: http://www.ncbi.nlm.nih.gov/pubmed/8506487. Cited Cited 2009 30 October.
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