Disinfectants The good, bad and plain ugly!
Disinfectants – What you should know if you are responsible for cleaning your house or company
Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially not resistant bacteria spores; it is less effective than sterilization, 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, 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.
Sanitizers 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.
A perfect disinfectant would also offer complete and full sterilization, without harming other forms of life, is inexpensive, and non-corrosive. Unfortunately, ideal disinfectants do not exist. Most disinfectants are also, by nature, potentially harmful (even toxic) to humans, animals and the environment. Most modern household disinfectants contain Bitrex, an exceptionally bitter substance which is 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.
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).
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 can increase in number very quickly, which enables them to evolve rapidly. Should some bacteria survive a chemical attack, 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.
For this reason, some question the wisdom of impregnating cloths, cutting boards and worktops in the home with bactericidal chemicals.
- Air disinfectants
- Oxidizing agents
- Accelerated Hydrogen Peroxide,
- Peracetic acid
- Lactic acid
- Performic acid
- Potassium permanganate (KMnO4)
- Potassium peroxymonosulfate,
- Quaternary ammonium compounds
- High-intensity shortwave ultraviolet light.
- Common sodium bicarbonate (NaHCO3)
Measurements of effectiveness
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.
A less specific measurement of effectiveness is the EPA classification into 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 FDA.
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.
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), 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).
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 odour; it is not effective against Giardia lamblia and Cryptosporidium; 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" (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.
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. 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 labelled concentration.
Where one does not want to risk the corrosive effects of bleach, 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.
The use of some antimicrobials such as triclosan, particularly 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.
So now you know most everything there is to know about cleaning and disinfectants and the combination of both.
The million dollar question is: Are you comfortable with the concept that there are so many risks to be familiar with, that you are going to damage the environment, that you will potentially harm people or put their health at risk?
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