When using these chemicals:
Follow manufacturers’ instructions for proper use of disinfecting (or detergent) products — such as recommended use-dilution, material compatibility, storage, shelf-life, and safe use and disposal.
Examples: acetic acid, citric acid.
Acidic disinfectants damage proteins and change the pH of the environment, thus killing any inhabiting microbes.
Concentrated solutions of acids can be corrosive, cause chemical burns and toxic at high concentrations in the air.
Acids have a defined but limited use as disinfectants- do not kill bacterial spores.
- Acetic acid is usually sold as glacial acetic acid (95% acetic acid) which is then diluted with water to make a working solution concentration of 5% which is non-toxic and non-irritating.
- Acetic acid is typically applied by spraying, misting or immersing an item in a diluted solution.
- Acetic acid has poor activity in organic material.
- Examples: ethanol, isopropanol
- Alcohols are broad spectrum antimicrobial agents that kill microbes by damaging their protein structures.
- Alcohols are used for surface disinfection, topical antiseptic and hand sanitizing lotions. They are rapidly bactericidal against vegetative forms of bacteria; they also are tuberculocidal, fungicidal, and virucidal but do not destroy bacterial spores such as those of Clostridium difficile. However isopropanol is not effective against non-enveloped viruses such as Norovirus.
- Their cidal activity drops sharply when diluted below 50% concentration, and the optimum bactericidal concentration is 60%–90% solutions in water (volume/volume).
- At concentrations of 60-80%, ethanol inactivates:
- Lipophilic viruses (e.g., herpes, vaccinia, and influenza virus)
- Many hydrophilic viruses (e.g., adenovirus, enterovirus, rhinovirus, and rotaviruses, but not hepatitis A virus (HAV) or poliovirus),
- Hepatitis B (HBV),
- Cryptococcus neoformans,
- Blastomyces dermatitidis,
- Coccidioides immitis,
- Histoplasma capsulatum.
- The activity of alcohols is limited in the presence of organic matter.
- Alcohols are highly flammable, and consequently must be stored in a cool, well-ventilated area.
- They also evaporate rapidly, making extended exposure time difficult to achieve unless the items are immersed.
- They can cause damage to rubber and plastic, and can be very irritating to injured skin.
Examples: formaldehyde, gluteraldehyde.
Aldehydes are highly effective, broad spectrum disinfectants, which typically achieve sterilization by damaging proteins.
Aldehydes are effective against bacteria, fungi, viruses, mycobacteria and spores.
Aldehydes are non-corrosive to metals, rubber, plastic and cement.
They are highly irritating, toxic to humans or animals with contact or inhalation, and are potentially carcinogenic.
Personal protective equipment (i.e., nitrile gloves, fluid resistant gowns, eye protection) is required for handling of aldehydes.
- Formaldehyde is a surface disinfectant and a fumigant and can decontaminate wooden surfaces, bricks and crevices of electronic and mechanical equipment.
- Its use must occur in an air tight building, which must remain closed for at least 24 hours after treatment.
- The efficacy of formaldehyde is dependent on relative humidity and temperature; optimum being humidity close to 70% and a temperature close to 57oF.
- As a liquid, formaldehyde is a bactericide, tuberculocide, fungicide, virucide, tuberculocide and sporicide.
- It is a potential carcinogen and OSHA set an employee exposure standard that limits an 8-hour time-weighted average exposure concentration of 0.75 ppm.
- Long-term exposure to low levels in the air or on the skin can cause asthma-like respiratory problems and skin irritation, such as dermatitis and itching.
- Gluteraldehyde is a high level disinfectant at 2% concentration and a chemical sterilant.
- Aqueous solutions of glutaraldehyde are not sporicidal unless the solution is made alkaline by alkalinating agents such as sodium bicarbonate. These solutions have a shelf life of 14 days.
- >2% aqueous solutions of glutaraldehyde, buffered to pH 7.5–8.5 with sodium bicarbonate effectively killed vegetative bacteria in <2 minutes; M. tuberculosis, fungi, and viruses in <10 minutes; and spores of Bacillus and Clostridium species in 3 hours. Spores of C. difficile are more rapidly killed by 2% glutaraldehyde than are spores of other species of Clostridium and Bacillus.
- Microorganisms with resistance to glutaraldehyde have include some mycobacteria (M. chelonae, Mycobacterium avium-intracellulare, M. xenopi) 598-601, Methylobacterium mesophilicum 602, Trichosporon, fungal ascospores (e.g., Microascus cinereus, Cheatomium globosum), and Cryptosporidium.
- 20 minutes at room temperature is considered the minimum exposure time needed to reliably kill Mycobacteria and other vegetative bacteria with >2% glutaraldehyde
- Solutions have greatest efficacy at high temperatures.
- It is highly biocidal even in the presence of organic matter.
- It is non-corrosive to most surfaces.
- It is toxic: acute or chronic exposure can result in skin irritation or dermatitis, mucous membrane irritation (eye, nose, mouth), or pulmonary symptoms, epistaxis, allergic contact dermatitis, asthma, and rhinitis also have been reported in healthcare workers exposed to glutaraldehyde.
- It is quite expensive.
Examples: sodium or ammonium hydroxide, sodium carbonate, calcium oxide.
Alkaline agents work by damaging fats within microbes.
The activity of alkali compounds is slow but can be increased by raising the temperature. Alkalis have good microbicidal properties, but are very corrosive agents and personal protection equipment should be used.
- Sodium hydroxide (lye, caustic soda, soda ash) is a strong alkali used to disinfect buildings.
- It is highly corrosive. Protective clothing, rubber gloves, and safety glasses should be
- worn when mixing and applying the chemical.
- Water and lye should never be mixed as they violently react.
- Sodium hydroxide is corrosive for metals.
- It is an effective Foot and Mouth Disease disinfectant.
- Ammonium hydroxide is diluted and made into household ammonia. It is in many cleaning agents including glass cleaning products.
- It is an effective disinfectant against coccidia oocyts.
- Strong solutions emit pungent fumes.
- This substance is not considered effective against most bacteria.
- General disinfection should follow the use of this compound.
- Sodium carbonate (soda ash, washing soda) has been used in a hot 4% solution (180oF) for disinfecting buildings, which have housed animals with Foot and Mouth Disease.
- It is more effective as a cleanser than a disinfectant since it lacks efficacy against some bacteria and most viruses.
- It has poor activity in the presence of organic material and can be deactivated by hard water.
- It can be irritating and requires protective clothing and is harmful to aquatic life.
- Example: chlorhexidine.
- Biguanides are kill microorganisms by altering cell permeability.
- They have a broad antibacterial spectrum and are sometimes used as antiseptics.
- They are limited in their effectiveness against viruses and are not sporicidal, mycobacteriocidal, or fungicidal.
- Biguanides can only function in a limited pH range (5-7) and are easily inactivated by soaps and detergents.
- These products are toxic to fish and should not be discharged into the environment.
Examples: chlorine or iodine compounds.
These are broad spectrum compounds that are considered low toxicity, low cost and easy to use.
They lose potency over time and are not active at temperatures above 110oF or at high pHs(>9).
Since these compounds lose activity quickly in the presence of organic debris, sunlight and some metals, they must be applied to thoroughly cleaned surfaces for disinfection.
- Chlorine compounds function by damaging microbes protein structure.
- They are considered broad spectrum, being effective against bacteria, enveloped and non-enveloped viruses, mycobateria and fungi.
- At elevated concentrations, chlorine compounds can be sporicidal.
- Sodium hypochlorite (NaOCl) is one of the most widely used chlorine containing disinfectants.
- Commercial chlorine bleach contains 5.25% sodium hypochlorite in aqueous solution and 50,000 ppm available chlorine.
- Biocidal activity is determined by the amount of the available chlorine of the solution.
- Low concentrations (2 to 500 ppm) are active against vegetative bacteria, fungi and most viruses.
- Rapid sporicidal action can be obtained around 2500 ppm, however this concentration is very corrosive and irritating to the mucous membranes, eyes and skin.
- They do not leave toxic residues,
- They are unaffected by water hardness,
- And are fast acting.
- They can remove dried organisms and biofilms from surfaces.
- Sodium hypochlorite at the concentration used in household bleach (5.25-6.15%) can produce ocular irritation or oropharyngeal, esophageal, and gastric burns.
- It is corrosivene to metals in high concentrations (>500 ppm).
- Inactivated by organic matter.
- Can discolour or “bleaches” of fabrics.
- If mixed with ammonia or acid, (e.g., other household cleaning agents) toxic chlorine gas is released.
- Chlorine compounds are rapidly inactivated by light and some metals.
- A hypochlorite solution in tap water at a pH >8 stored at room temperature (23ºC) in closed, opaque plastic containers can lose up to 40%–50% of their free available chlorine level over 1 month.
- Superoxidised water is electrolyzed saline solution.
- The materials required to make the disinfectant, saline and electricity, are inexpensive and the end product (i.e., water) does not damage the environment.
- The main products of this water are hypochlorous acid (e.g., at a concentration of about 144 mg/L) and chlorine.
- As with any germicide, the antimicrobial activity of superoxidized water is strongly affected by the concentration of the available free chlorine.
- It is myobactericidal (effective against M. Tuberculosis), virucidal, fungicidal and sporicidal. In under two minutes freshly generated superoxidized water can inactivate M. tuberculosis, M. chelonae, poliovirus, HIV, multidrug-resistant S. aureus, E. coli, Candida albicans, Enterococcus faecalis, P. aeruginosa) in the absence of organic loading. To kill hepatitis B took seven minutes.
- The solution is nontoxic to biologic tissues and noncorrosive and nondamaging to surfaces.
- Unfortunately, the equipment required to produce the product can be expensive.
These work by damaging microbe protein structure.
They are broad spectrum and considered effective for a variety of bacteria, mycobacteria, fungi and viruses.
Iodines are often formulated with soaps and considered relatively safe.
Concentrated iodine compounds can be irritating to skin, stain fabrics or damage rubber and some metals.
Iodine agents are inactivated by quaternary ammonium compounds and organic debris.
- These are iodine complexes that have increased solubility and sustained release of iodine. They can be used as disinfectants and antiseptics and work by damaging microbe proteins.
- Commercial iodophors are not sporicidal, but they are tuberculocidal, fungicidal, virucidal, and bactericidal at their recommended use-dilution.
- It has not been cleared by the FDA as a sterilant or high-level disinfectant.
- One of the more commonly used iodophors if povidone-iodine. It is good for general use and is less readily inactivated by organic matter than elemental iodine compounds.
- The dilution of iodophors actually increases the free iodine concentration and antimicrobial activity.
- They are non-staining and relatively free of toxicity and irritancy.
Examples: hydrogen peroxide, peracetic acid.
Oxidizing agents are broad spectrum, peroxide based compounds that function by damaging
the proteins and fats of microorganisms.
These agents are irritating and damage clothing when un-diluted.
- Hydrogen peroxide acts by destroying essential cell components.
- For domestic use it is sold in its diluted form (3-10%) whereas industrial use involves concentrated solutions (30% or greater).
- Hydrogen peroxide (at a 5-20% concentration) is considered bactericidal, virucidal (non-enveloped viruses may be resistant), fungicidal and at high concentrations sporicidal.
- Hydrogen peroxide sold as a sterilant is typically 7.5% hydrogen peroxide and 0.85% phosphoric acid. This solution is mycobactericidal after 10 minutes exposure, sporicidal after 6 hours, fungicidal and virucidal in 5 minutes, bactericidal in 3 minutes and it inactivates poliovirus and hepatitis A virus in 30 minutes. 10% Hydrogen peroxide can kill spores of Bacillus species in 60 minutes and spores such as B. Atrophaeus in 30 minutes.
- Under normal conditions, hydrogen peroxide is extremely stable when properly stored (e.g., in dark containers). The decomposition or loss of potency in small containers is less than 2% per year at ambient temperatures.
- Hydrogen peroxide was effective in spot-disinfecting fabrics in patients’ rooms.
- This is a formulation of hydrogen peroxide and acetic acid.
- It is considered rapidly bactericidal, fungicidal, sporicidal and virucidal.
- It damages proteins and makes cell walls permeable.
- Peracetic acid will inactivate gram-positive and gram-negative bacteria, fungi, and yeasts in under 5 minutes at 0.01%. In the presence of organic matter, 0.02%-0.05% is required.
- For viruses, the dosage range is wide (0.0012%–0.2250%, with poliovirus inactivated in yeast extract in 15 minutes with 0.1500%–0.2250%, 3.5% peracetic acid was ineffective against hepatitis A virus after 1-minute exposure, 0.26% Peracetic acid inactivates all test strains of mycobacteria (M. tuberculosis, M. avium-intracellulare, M. chelonae, and M. fortuitum) within 20–30 minutes. With bacterial spores, 0.05%–1% inactivates spores in 15 seconds to 30 minutes using a spore suspension test.
- It has some activity in the presence of organic material.
- It does not produce harmful decomposition products and leaves no residue.
- It can corrode copper, brass, bronze, plain steel and galvanized iron. These effects can be reduced by additives.
- It is unstable, particularly when diluted. A 1% solution will lose half its strength in 6 days.
- Phenols are broad spectrum disinfectants that function by damaging proteins and increasing cell wall permeability of microbes.
- Phenols can be coal-tar derivatives or synthetic formulations.
- Phenols are typically formulated in soap solutions to increase their penetrative powers and at 5% concentrations are considered bactericidal, tuberculocidal, fungicidal and virucidal for enveloped viruses.
- Phenols are not effective against non-enveloped viruses (eg., Adenovirus, Rotavirus, Poliovirus and Rhinovirus) or spores.
- Phenols maintain activity in hard water and in the presence of organic matter and have some residual activity after drying.
- Phenolic disinfectants are generally safe but prolonged exposure to the skin may cause irritation.
- Concentrations over 2% are highly toxic to all animals, especially cats.
- Phenolics are not FDA-cleared as high-level disinfectants.
- Many phenolic germicides are EPA-registered as disinfectants for use on environmental surfaces (e.g., bedside tables, handrails, and bathroom surfaces).
- The use of phenolics in nurseries has been questioned because of hyperbilirubinemia in infants placed in bassinets where phenolic detergents were used.
Quaternary Ammonium Compounds
- Also known as “quats” or QACs, these compounds are cationic detergents that damage microbe proteins.
- QACs are highly effective against gram-positive bacteria, and have good efficacy against gram-negative bacteria, fungi and enveloped viruses.
- They are not effective against non-enveloped viruses or mycobacteria and not sporocidal.
- They but lose their activity at pH less than 3.5.
- QACs are generally inactivated by organic matter, detergents, soaps and hard water- with the exception of some ‘later generation’ QACs (see manufacturers instructions for details on specific solutions).
- QACs are toxic to fish and should not be discharged into water sources (i.e., streams, ponds, lakes).
- Some of the chemical names of quaternary ammonium compounds used in healthcare are alkyl dimethyl benzyl ammonium chloride (over exposure to this has been linked to occupational asthma), alkyl didecyl dimethyl ammonium chloride, and dialkyl dimethyl ammonium chloride. The newer quaternary ammonium compounds (i.e., fourth generation), referred to as twin-chain or dialkyl quaternaries (e.g. didecyl dimethyl ammonium bromide and dioctyl dimethyl ammonium bromide), purportedly remain active in hard water and are tolerant of anionic residues.
- Quaternary ammonium compounds (as well as 70% isopropyl alcohol, phenolic, and a chlorine-containing wipe [80 ppm]) effectively (>95%) remove and/or inactivate contaminants (i.e., multidrug-resistant S. aureus, vancomycin-resistant Entercoccus, P. aeruginosa) from computer keyboards with a 5-second application time. No functional damage or cosmetic changes occurred to the computer keyboards after 300 applications of the disinfectants.
- The quaternaries commonly are used in ordinary environmental sanitation of noncritical surfaces, such as floors, furniture, and walls. EPA-registered quaternary ammonium compounds are appropriate to use for disinfecting equipment that contacts intact skin (e.g., desktop surfaces).
The process of sterilization is mainly used in healthcare for medical and surgical devices. It is generally not necessary for commercial community cleaning. Methods include:
Hydrogen Peroxide Gas Plasma
Peracetic Acid Sterilization
Glass Bead “Sterilizer”.
Vaporized Hydrogen Peroxide
Gaseous chlorine dioxide.
Vaporized Peracetic Acid.