Disinfection
Encyclopedia : D : DI : DIS : Disinfection
- 'Disinfectant' redirects here. For the Macintosh anti-virus software, see Disinfectant (software).
All disinfectants are also, by their very nature, potentially harmful (even toxic) to humans or animals. They should be treated with appropriate care. Most come with safety instructions printed on the packaging, which should be read in full before using the disinfectant. Most modern household disinfectants contain Bitrex, an exceptionally bitter substance designed to discourage ingestion, as an added safety measure. Those that are used in people's homes should never be mixed with other cleaning products as chemical reactions can occur. They are frequently used in hospitals, dental surgeries, kitchens and bathrooms to kill infectious organisms.
The choice of the disinfectant to be used depends on the particular situation. Some disinfectants have a wide spectrum (kill nearly all microorganisms). (In the UK there was a long running advert for Domestos bleach in which it was claimed that "Domestos kills all known germs Dead!"). Others kill a smaller range of disease-causing organisms but are preferred for other properties (they may not be corrosive, and relatively non-toxic to humans).
The disinfecting properties of sunlight (ultra-violet) are powerful. Basic hygiene, rather than total reliance on chemicals, is important in the fight against bacteria, which generally prefer a warm-moist-dark environment. There are arguments for creating or maintaining conditions which are not conducive to bacterial survival and multiplication, rather than attempting to kill them with chemicals. Bacteria have a very rapid multiplication rate, which enables them to 'evolve' rapidly. Should some bacteria survive a chemical attack, they give rise to the next generation. Thus they are able to develop resistance to hostile chemicals. For this reason, some question the wisdom of impregnating cloths, cutting boards and worktops in the home with bactericidal chemicals. Hygiene in is important in prevention of foodborne illness.
A note on terminology
Disinfectants destroy vegetative microbes (bacteria, fungi) and viruses on surfaces, medical equipment and other man-made objects. Antiseptics disinfect skin. Antibiotics either kill or interfere with the life cycle of bacteria inside the body. Substances which kill bacteria are said to have a bactericidal effect, while those which interfere with cell growth and reproduction are said to be bacteriostatic. Disinfectants and antiseptics are bactericidal (some disinfectants are bacteriostatic at low concentrations): antibiotics can be either bactericidal or bacteriostatic.Sanitation refers to killing 99+ % of germs in applicable situations. Sanitisers are compounds that sanitise.
Common disinfectants
- Chlorine – Used to disinfect swimming pools, and is added in small quantities to drinking water to reduce waterborne diseases.
- Chloramine – Used in drinking water treatment instead of chlorine because it produces less disinfection byproducts.
- Chlorine dioxide – Used as an advanced disinfectant for drinking water to reduce waterborne diseases. In certain parts of the world, it has largely replaced chlorine because it forms fewer byproducts.
- Dettol – Used to disinfect surfaces at home. It kills the majority of bacteria. It is one of the few disinfectants useful against viruses.
- Sodium chlorite, sodium chlorate, and potassium chlorate have little disinfection effect but are used as precursors for generating chlorine dioxide.
- Alcohol – Usually ethanol or isopropanol – Wiped over benches and skin and allowed to evaporate for quick disinfection. Alcohols are more effective combined with water, 70% alcohol is more active than 95% alcohol. Alcohol is not effective against bacterial spores.
- Hydrogen peroxide – Used in hospitals to disinfect surfaces. It is sometimes mixed with colloidal silver. It is often preferred because it causes far fewer allergic reactions than alternative disinfectants. Also used in the food packaging industry to disinfect foil containers. A 3% solution is also used as an antiseptic. When hydrogen peroxide comes into contact with the catalase enzyme in cells it is broken down into water and oxygen. It is the oxygen that kills bacteria. However, as recent studies have show hydrogen peroxide to be toxic to growing cells as well as bacteria, its use as an antiseptic is no longer recommended.
- Iodine – Usually dissolved in an organic solvent or as Lugol's iodine solution. It is used in the poultry industry. It is added to the birds' drinking water. Iodine is rapidly neutralised by the presence of organic material, so surfaces must be cleaned prior to disinfection. Although no longer recommended because it increases scar tissue formation and increases healing time, tincture of iodine has also been used as an antiseptic for skin cuts and scrapes.
- Ozone – a gas that can be added to water for sanitation.
- Phenol and other phenolics – The active ingredient in most bottles of "household disinfectant". It is also to found in some mouthwashes and in disinfectant soap and handwashes. Phenol is probably the oldest disinfectant (used by Lister) and was called carbolic acid in the early days of antiseptics. Phenol is rather corrosive to the skin and sometimes toxic to sensitive people, so the somewhat less corrosive substitute phenolic o-phenylphenol is often used as part of a disinfectant formula. Hexachlorophene is a phenolic which was once used as a germicidal additive to some household products but was banned due to suspected harmful effects.
- Potassium permanganate – Formula KMnO4. Red Crystalline powder. Colours everything it touches. Used to disinfect aquariums. It is also used widely in community swimming pools to disinfect ones feet before entering the pool. Typically, a large shallow basin of KMnO4/water solution is kept near the pool ladder. Participants are required to step in the basin and then go into the pool. It is also used widely to disinfect community water ponds and wells in Tropical countires. It is also used to disinfect the mouth before pulling out teeth. It can be applied to wounds in dilute solution. KMnO4 is a very useful Disinfectant.
- Quaternary ammonium salts (quats) such as benzalkonium chloride are a large group of related compounds. Some have been used as a low level disinfectant. They are effective against bacteria, but not against spores or viruses. Nor are they effective against some species of Pseudomonas bacteria. Quats are biocides which also kill algae and are used as an additive in large-scale industrial water systems to minimize undesired biological growth.
- Hypochlorites – Sodium hypochlorite, often in the form of common household bleach, is used in the home to disinfect drains, and toilets. A dilute form is used under the brand name Milton to disinfect baby bottles. Other hypochlorites such as calcium hypochlorite are also used, especially as a swimming pool additive. Hypochlorite gives off free chlorine and it is the chlorine that is the true disinfectant. Hypobromite solutions are also sometimes used.
- Toluene
- Virkon – A wide-spectrum disinfectant used in labs. It kills bacteria, viruses, and fungi. It is used as a 1% solution in water, and keeps for 1 week once it is made up. It is expensive, but very effective, its pink colour fades as it is used up so it is possible to see at a glance if it is still fresh.
Relative effectiveness of disinfectants
One way to compare disinfectants is to compare how well they do against a known disinfectant and rate them accordingly. Phenol is the standard, and the corresponding rating system is called the "Phenol coefficient". The disinfectant to be tested is compared with phenol on a standard microbe (usually Salmonella typhi or Staphylococcus aureus). Disinfectants that are more effective than phenol have a coefficient > 1. Those that are less effective have a coefficient < 1.See also
External links
- [What Germs Are We Killing? Testing and Classifying Disinfectants]
- [link] Water Disinfection worldwide, technologies, markets, applications and the future to 2015
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.