Disinfectant

Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects(Dell INSPIRON MINI 9 battery). Disinfection does not necessarily kill all microorganisms, especially nonresistant bacterial spores; it is less effective than sterilisation, which is an extreme physical and/or chemical process that kills all types of life. Disinfectants are different from other antimicrobial agents such as antibiotics(Dell LATITUDE C500 battery), which destroy microorganisms within the body, and antiseptics, which destroy microorganisms on living tissue. Disinfectants are also different from biocides — the latter are intended to destroy all forms of life, not just microorganisms(Dell LATITUDE C600 battery).

Sanitisers are substances that simultaneously clean and disinfect.

Bacterial endospores are most resistant to disinfectants, but some viruses and bacteria also possess some tolerance.

Disinfectants are frequently used in hospitals, dental surgeries, kitchens, and bathrooms to kill infectious organisms(Dell LATITUDE C800 battery).

Properties

A perfect disinfectant would also offer complete and full sterilisation, without harming other forms of life, be inexpensive, and non-corrosive. However, ideal disinfectants do not exist. Most disinfectants are also, by nature, potentially harmful (even toxic) to humans or animals(Dell LATITUDE D400 battery). Most modern household disinfectants contain Bitrex, an exceptionally bitter substance added to discourage ingestion, as a safety measure. Those that are used indoors should never be mixed with other cleaning products as chemical reactions can occur(Dell LATITUDE D500 battery).

The choice of disinfectant to be used depends on the particular situation. Some disinfectants have a wide spectrum (kill many different types of microorganisms), while others kill a smaller range of disease-causing organisms but are preferred for other properties (they may be non-corrosive, non-toxic, or inexpensive) (Dell LATITUDE D600 battery).

There are arguments for creating or maintaining conditions that are not conducive to bacterial survival and multiplication, rather than attempting to kill them with chemicals. Bacteria can increase in number very quickly, which enables them to evolve rapidly. Should some bacteria survive a chemical attack(Dell LATITUDE D800 battery), they give rise to new generations composed completely of bacteria that have resistance to the particular chemical used. Under a sustained chemical attack, the surviving bacteria in successive generations are increasingly resistant to the chemical used, and ultimately the chemical is rendered ineffective(Dell LATITUDE D820 battery). For this reason, some question the wisdom of impregnating cloths, cutting boards and worktops in the home with bactericidal chemicals.

Types of disinfectants

Air disinfectants

Air disinfectants are typically chemical substances capable of disinfecting microorganisms suspended in the air. Disinfectants are generally assumed to be limited to use on surfaces, but that is not the case(Dell STUDIO 1450 battery). In 1928, a study found that airborne microorganisms could be killed using mists of dilute bleach. An air disinfectant must be dispersed either as an aerosol or vapour at a sufficient concentration in the air to cause the number of viable infectious microorganisms to be significantly reduced(Dell VOSTRO 1400 battery).

In the 1940s and early 1950s, further studies showed inactivation of diverse bacteria, influenza virus, and Penicillium chrysogenum(previously P. notatum) mold fungus using various glycols, principally propylene glycol and triethylene glycol(Dell VOSTRO 1500 battery). In principle, these chemical substances are ideal air disinfectants because they have both high lethality to microorganisms and low mammalian toxicity.

Although glycols are effective air disinfectants in controlled laboratory environments, it is more difficult to use them effectively in real-world environments because the disinfection of air is sensitive to continuous action. Continuous action in real-world environments with outside air exchanges at door(Dell XPS M1210 battery), HVAC, and window interfaces, and in the presence of materials that adsorb and remove glycols from the air, poses engineering challenges that are not critical for surface disinfection. The engineering challenge associated with creating a sufficient concentration of the glycol vapours in the air have not to date been sufficiently addressed(Dell XPS M1330 battery).

Alcohols

Alcohols, usually ethanol or isopropanol, are sometimes used as a disinfectant, but more often as an antiseptic (the distinction being that alcohol tends to be used on living tissue rather than nonliving surfaces). They are non-corrosive, but can be a fire hazard(Dell XPS 1340 battery). They also have limited residual activity due to evaporation, which results in brief contact times unless the surface is submerged, and have a limited activity in the presence of organic material. Alcohols are most effective when combined with purified water to facilitate diffusion through the cell membrane(Dell XPS M1530 battery); 100% alcohol typically denatures only external membrane proteins. A mixture of 70% ethanol or isopropanol diluted in water is effective against a wide spectrum of bacteria, though higher concentrations are often needed to disinfect wet surfaces. Additionally, high-concentration mixtures (such as 80% ethanol + 5% isopropanol) (Dell XPS M170 battery) are required to effectively inactivate lipid-enveloped viruses (such as HIV, hepatitis B, and hepatitis C). Alcohol is, at best, only partly effective against most non-enveloped viruses (such as hepatitis A), and is not effective against fungal and bacterial spores(Dell XPS M1710 battery). The efficacy of alcohol is enhanced when in solution with the wetting agent dodecanoic acid (coconut soap). The synergistic effect of 29.4% ethanol with dodecanoic acid is effective against a broad spectrum of bacteria, fungi, and viruses. Further testing is being performed against Clostridium difficile (C.Diff) spores with higher concentrations of ethanol and dodecanoic acid(Dell XPS M1730 battery), which proved effective with a contact time of ten minutes.

Aldehydes

Aldehydes, such as formaldehyde and glutaraldehyde, have a wide microbiocidal activity and are sporocidal and fungicidal. They are partly inactivated by organic matter and have slight residual activity(Dell XPS M2010 battery).

Some bacteria have developed resistance to glutaraldehyde, and it has been found that glutaraldehyde can cause asthma and other health hazards, hence ortho-phthalaldehyde is replacing glutaraldehyde(Dell Inspiron Mini 12 battery).

Oxidizing agents

Oxidizing agents act by oxidizing the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death. A large number of disinfectants operate in this way. Chlorine andoxygen are strong oxidizers, so their compounds figure heavily here(SONY VGP-BPS9A/S battery).

Sodium hypochlorite is very commonly used. Common household bleach is a sodium hypochlorite solution and is used in the home to disinfect drains, toilets, and other surfaces. In more dilute form, it is used in swimming pools, and in still more dilute form, it is used in drinking water(SONY VGP-BPS9/B battery). When pools and drinking water are said to be chlorinated, it is actually sodium hypochlorite or a related compound—not pure chlorine—that is being used. Chlorine partly reacts with proteinaceous liquids such as blood to form non-oxidizing N-chloro compounds, and thus higher concentrations must be used if disinfecting surfaces after blood spills(SONY VGP-BPS9/S battery).

Other hypochlorites such as calcium hypochlorite are also used, especially as a swimming pool additive. Hypochlorites yield an aqueous solution of hypochlorous acid that is the true disinfectant. Hypobromite solutions are also sometimes used(SONY VGP-BPS9A battery).

Electrolyzed water or "Anolyte" is an oxidizing, acidic hypochlorite solution made by electrolysis of sodium chloride into sodium hypochlorite and hypochlorous acid. Anolyte has an oxidation-reduction potential of +600 to +1200 mV and a typical pH range of 3.5––8.5, but the most potent solution is produced at a controlled pH 5.0–6.3 where the predominant oxychlorine species is hypochlorous acid(SONY VGP-BPS9A/B battery).

Chloramine is often used in drinking water treatment.

Chloramine-T is antibacterial even after the chlorine has been spent, since the parent compound is a sulfonamide antibiotic.

Chlorine dioxide is used as an advanced disinfectant for drinking water to reduce waterborne diseases(HP Pavilion DV6-1210SA battery). In certain parts of the world, it has largely replaced chlorine because it forms fewer byproducts. Sodium chlorite, sodium chlorate, and potassium chlorate are used as precursors for generating chlorine dioxide.

Hydrogen peroxide is used in hospitals to disinfect surfaces and it is used in solution alone or in combination with other chemicals as a high level disinfectant(SONY VGP-BPS11 battery). Hydrogen peroxide is sometimes mixed withcolloidal silver. It is often preferred because it causes far fewer allergicreactions than alternative disinfectants. Also used in the food packaging industry to disinfect foil containers. A 3% solution is also used as an antiseptic. However, recent studies have shown hydrogen peroxide to be toxic to growing cells as well as bacteria(SONY VGP-BPL11 battery); its use as an antiseptic is no longer recommended.

Hydrogen peroxide vapor is used as a medical sterilant and as room disinfectant. Hydrogen peroxide has the advantage that it decomposes to form oxygen and water thus leaving no long term residues, but hydrogen peroxide as with most other strong oxidants is hazardous, and solutions are a primary irritant(SONY VGP-BPL12 battery). The vapor is hazardous to the respiratory system and eyes and consequently the OSHA permissible exposure limit is 1 ppm (29 CFR 1910.1000 Table Z-1) calculated as an eight hour time weighted average and the NIOSHimmediately dangerous to life and health limit is 75 ppm. Therefore, engineering controls, personal protective equipment(SONY VGP-BPS12 battery), gas monitoring etc. should be employed where high concentrations of hydrogen peroxide are used in the workplace. Vaporized hydrogen peroxide is one of the chemicals approved for decontamination of anthrax spores from contaminated buildings, such as occurred during the 2001 anthrax attacks in the U.S. It has also been shown to be effective in removing exotic animal viruses(SONY VGP-BPS14 Battery), such as avian influenza and Newcastle disease from equipment and surfaces.

The antimicrobial action of hydrogen peroxide can be enchanced by surfactants and organic acids. The resulting chemistry is known as Accelerated Hydrogen Peroxide and is produced by Virox Technologies Inc(SONY VGP-BPS14/B Battery). A 2% solution, stabilized for extended use, achieves high-level disinfection in 5 minutes, and is suitable for disinfecting medical equipment made from hard plastic, such as in endoscopes. The evidence available suggests that products based on Accelerated Hydrogen Peroxide, apart from being good germicides, are safer for humans and benign to the environment(SONY VGP-BPS14/S Battery).

Iodine is 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. In human and veterinary medicine, iodine products are widely used to prepare incision sites prior to surgery. Although it increases both scar tissue formation and healing time(SONY VGP-BPS14B Battery), tincture of iodine is used as an antiseptic for skin cuts and scrapes, and remains among the most effective antiseptics known.

Ozone is a gas used for disinfecting water. Ozone decomposes relatively quickly, however, in comparison to chlorine, so that tap water chlorination cannot be replaced by ozonation, as the ozone would decompose already in the water piping(SONY VGP-BPS22 battery).

Peracetic acid is a disinfectant produced by reacting hydrogen peroxide with acetic acid. It is broadly effective against microorganisms and is not deactivated by catalase and peroxidase, the enzymes that break down hydrogen peroxide(SONY VGP-BPS18 battery). It also breaks down to food safe and environmentally friendly residues (acetic acid and hydrogen peroxide), and therefore can be used in non-rinse applications. It can be used over a wide temperature range (0-40°C), wide pH range (3.0-7.5), in clean-in-place (CIP) processes, in hard water conditions, and is not affected by protein residues(SONY VGP-BPS22/A battery).

Performic acid is the simplest and most powerful perorganic acid. Formed from the reaction of hydrogen peroxide and formic acid, it reacts more rapidly and powerfully than peracetic acid before breaking down to water and carbon dioxide(SONY VGP-BPS22A battery). Performic acid is the ultimate environmentally friendly oxidising biocide for all disinfection applications.

Potassium permanganate (KMnO4) is a red crystalline powder that colours everything it touches, through a strong oxidising action. This includes staining "stainless" steel, which somehow limits its use and makes it necessary to use plastic or glass containers(SONY VGP-BPL10 battery). It is used to disinfect aquariums and is also widely used 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(SONY VGP-BPS10 battery). Additionally, it is widely used to disinfect community water ponds and wells in tropical countries, as well as to disinfect the mouth before pulling out teeth. It can be applied to wounds in dilute solution(Dell Latitude E6500 battery).

Potassium peroxymonosulfate, the principal ingredient in Virkon, is a wide-spectrum disinfectant used in laboratories. Virkon kills bacteria, viruses, and fungi. It is used as a 1% solution in water, and keeps for one 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(Dell Latitude E6400 battery).

Phenolics

Phenolics are active ingredients in some household disinfectants. They are also found in some mouthwashes and in disinfectant soap and handwashes.

Phenol is probably the oldest known disinfectant as it was first used by Lister, when it was called carbolic acid(Dell Latitude E5400 battery). It is rather corrosive to the skin and sometimes toxic to sensitive people. Impure preparations of phenol were originally made from coal tar, and these contained low concentrations of other aromatic hydrocarbons including benzene, which is an IARC Group 1 carcinogen(SONY VAIO VGN-NR11Z battery).

o-Phenylphenol is often used instead of Phenol, since it is somewhat less corrosive.

Chloroxylenol is the principal ingredient in Dettol, a household disinfectant and antiseptic.

Hexachlorophene is a phenolic that was once used as a germicidal additive to some household products but was banned due to suspected harmful effects(SONY VAIO VGN-NR11S battery).

Thymol, derived from the herb thyme, is the active ingredient in some "broad spectrum" disinfectants that bears ecological claims.

Quaternary ammonium compounds

Quaternary ammonium compounds ("quats"), such as benzalkonium chloride, are a large group of related compounds. Some concentrated formulations have been shown to be effective low-level disinfectants(SONY Vaio VGN-FW31J Battery). Typically, quats do NOT exhibit efficacy against difficult to kill non-enveloped viruses such as Norovirus, Rotavirus, or Polio. Newer synergous, low-alcohol formulations are highly effective broad-spectrum disinfectants with quick contact times (3–5 minutes) against bacteria(SONY Vaio VGN-FW32J Battery), enveloped viruses, Pathogenic Fungi, and Mycobacteria. However, the addition of alcohol or solvents to quat-based disinfectant formulas results in the products' drying much more quickly on the applied surface, which could lead to ineffective or incomplete disinfection. Quats are biocides that also kill algae and are used as an additive in large-scale industrial water systems to minimize undesired biological growth(SONY Vaio VGN-FW17W Battery).

Silver

Silver has antimicrobial properties, but compounds suitable for disinfection are usually unstable and have a limited shelf-life. Silver dihydrogen citrate is a chelated form of silver that maintains its stability. SDC kills microorganisms by two modes of action: 1) the silver ion deactivates structural and metabolic membrane proteins, leading to microbial death(SONY Vaio VGN-FW31E Battery); 2) the microbes view SDC as a food source, allowing the silver ion to enter the microbe. Once inside the organism, the silver ion denatures the DNA, which halts the microbe's ability to replicate, leading to its death. This dual action makes SDC highly and quickly effective against a broad spectrum of microbes(SONY Vaio VGN-FW139E Battery). SDC is non-toxic, non-caustic, colorless, odorless, and tasteless, and does not produce toxic fumes. SDC is non-toxic to humans and animals: the United States Environmental Protection Agencyclassifies it into the lowest toxicity category for disinfectants, category IV(SONY Vaio VGN-FW139E/H Battery).

Other

The biguanide polymer polyaminopropyl biguanide is specifically bactericidal at very low concentrations (10 mg/l). It has a unique method of action: The polymer strands are incorporated into the bacterial cell wall, which disrupts the membrane and reduces its permeability(SONY Vaio VGN-FW465J Battery), which has a lethal effect to bacteria. It is also known to bind to bacterial DNA, alter its transcription, and cause lethal DNA damage. It has very low toxicity to higher organisms such as human cells, which have more complex and protective membranes(SONY Vaio VGN-FW31M Battery).

High-intensity shortwave ultraviolet light can be used for disinfecting smooth surfaces such as dental tools, but not porous materials that are opaque to the light such as wood or foam. Ultraviolet light fixtures are often present in microbiology labs, and are activated only when there are no occupants in a room (e.g., at night) (SONY VAIO VGN-FZ21E Battery).

Common sodium bicarbonate (NaHCO3) has disinfectant properties.

Lactic acid is a registered disinfectant. Due to its natural and environmental profile, it has gained importance in the market.

Measurements of effectiveness

One way to compare disinfectants is to compare how well they do against a known disinfectant and rate them accordingly(SONY VAIO VGN-FZ21Z Battery). 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(SONY VAIO VGN-FZ21J Battery).

A less specific measurement of effectiveness is the United States Environmental Protection Agency (EPA) classification into either high, intermediate or low level of disinfection. High-level disinfection kills all organisms, except high levels of bacterial spores, and is effected with a chemical germicide cleared for marketing as a sterilant by the U.S. Food and Drug Administration (FDA) (SONY Vaio VGN-FW11 Battery). Intermediate-level disinfection kills mycobacteria, most viruses, and bacteria with a chemical germicide registered as a "tuberculocide" by the EPA. Low-level disinfection kills some viruses and bacteria with a chemical germicide registered as a hospital disinfectant by the EPA(SONY Vaio VGN-FW11M Battery).

Home disinfectants

By far the most cost-effective home disinfectant is the commonly used chlorine bleach (a 5% solution of sodium hypochlorite), which is effective against most common pathogens, including difficult organisms such as tuberculosis (mycobacterium tuberculosis) (SONY Vaio VGN-FW11S Battery), hepatitis B and C, fungi, and antibiotic-resistant strains of staphylococcus and enterococcus. It even has some disinfectant action against parasitic organisms.

Positives are that it kills the widest range of pathogens of any inexpensive disinfectant, is extremely powerful against viruses and bacteria at room temperature, is commonly available and inexpensive, and breaks down quickly into harmless components (primarily table salt and oxygen) (SONY Vaio VGN-FW21E Battery).

Negatives are that it is caustic to the skin, lungs, and eyes (especially at higher concentrations); like many common disinfectants, it degrades in the presence of organic substances; it has a strong odor; it is not effective against Giardia lamblia and Cryptosporidium(SONY Vaio VGN-FW21J Battery); and extreme caution must be taken not to combine it with ammonia or any acid (such as vinegar), as this can cause noxious gases to be formed. The best practice is not to add anything to household bleach except water. Dilute bleach can be tolerated on the skin for a period of time by most persons, as witnessed by the long exposure to extremely dilute "chlorine"(SONY Vaio VGN-FW21L Battery) (actually sodium or calcium hypochlorite) many children get in swimming pools.

To use chlorine bleach effectively, the surface or item to be disinfected must be clean. In the bathroom or when cleaning after pets, special caution must be taken to wipe up urine first, before applying chlorine, to avoid reaction with the ammonia in urine, causing toxic gas by-products(SONY Vaio VGN-FW21M Battery). A 1-to-20 solution in water is effective simply by being wiped on and left to dry. The user should wear rubber gloves and, in tight airless spaces, goggles. If parasitic organisms are suspected, it should be applied at 1-to-1 concentration, or even undiluted. Extreme caution must be taken to avoid contact with eyes and mucous membranes(SONY VGP-BPS13Q Battery). Protective goggles and good ventilation are mandatory when applying concentrated bleach.

Commercial bleach tends to lose strength over time, whenever the container is opened. Old containers of partially used bleach may no longer have the labeled concentration.

Where one does not want to risk the corrosive effects of bleach(SONY VGP-BPS13B/Q Battery), alcohol-based disinfectants are reasonably inexpensive and quite safe. The great drawback to them is their rapid evaporation; sometimes effective disinfection can be obtained only by immersing an object in the alcohol(SONY VGN NR11S/S battery).

The use of some antimicrobials such as triclosan, in particular in the uncontrolled home environment, is controversial because it may lead to the germs becoming resistant. Chlorine bleach and alcohol do not cause resistance because they are so completely lethal, in a very direct physical way(SONY VGN NR11Z/S battery).