In the face of the new normal we face, what disinfection measures are useful and why? How do disinfectants work?, Toothpaste contains disinfectants, which mainly act on the surface of the gums and dental plaque.
The life expectancy worldwide has increased, according to the United Nations, from 29 years in 1850 to 73 years in 2019 . The most decisive discovery that explains this increase is undoubtedly the ability to fight infections .
The effort has allowed, on the one hand, to identify the origin of many diseases, such as the action of bacteria, viruses, fungi or other forms of microscopic life . And, on the other, develop hygienic practices and medicines to fight infections caused by these pathogens.
This reflection makes perfect sense in the face of the pandemic caused by the SARS – CoV – 2 virus, which causes Coronavirus Disease 19 , abbreviated as COVID – 19. Once the first wave of the pandemic is over, we have to modify our hygienic habits, or at least reinforce them , to prevent new infections as much as possible.
Disinfectants In The Modern World
The media is reporting profusely about it. They tell us how we should act and what measures to take, to disinfect our body and our environment. These explanations are usually practical recipes; what we must do in a simple way, to ensure proper hygiene.
However, in addition to the practical articles, based on the recommendations of the health authorities, other newspaper articles also appear in the media , together with advertisements, on disinfectant practices, products and devices that, although they could have their basis, generate more problems what solutions.
It must be borne in mind that the intention of those who adopt extraordinary measures is the best possible; they want to guarantee maximum disinfection. On the other hand, the advertising intention of certain companies that want to take advantage of the circumstance, is not so much. Even those who advertise their products correctly suffer the suspicion created by the disloyal.
Why is it possible that actions are taken that are not correct? The answer is clear: due to lack of information. A lack, increased by the fear of contagion, and the false belief that by overprotecting ourselves we act better than doing what is officially recommended.
Let's start by reviewing the most relevant terms.
The microorganisms against which to fight, the pathogens or germs , are diverse: bacteria , fungi , viruses , spores , and a fifth class, prions , which are proteins whose folding is wrong, and that are capable of unfolding other proteins and rendering them useless. Viruses and prions are not considered living things, but they cause diseases, some very serious.
Biocide is any product or procedure that destroys all forms of life, not just microorganisms. Three classes are distinguished:
On the one hand, there are sterilants , extreme processes that destroy all forms of life . An example would be high-energy radiation, UV-C or gamma radiation , or chemicals such as ethylene oxide , which are used, for example, to sterilize operating rooms, vaporizing them for a few hours.
Secondly, we have disinfectants , substances that reduce microorganisms present on inert surfaces . We take advantage of the fact that the only form of life present, on these surfaces, is that of pathogens. The best known are bleach or alcohol.
And, thirdly, antiseptics , which reduce the presence of microorganisms on the surface of living tissue . Its application is based on less aggressiveness, since pathogens are the first to undergo treatment, but healthy cells are also affected.
The three exposed categories are non-selective, since they attack all forms of living beings . In many cases, the biocidal agent is the same, whether as a sterilant, disinfectant, or antiseptic; simply change the form of application and the dose.
For example, hydrogen peroxide is used to sterilize closed rooms, including the cabins of commercial aircraft. It is administered as steam , in a concentration of 1 milligram per liter, and sterilizes in about 30 minutes. It can also be used, in liquid form and concentrations between 30 and 90%, as a disinfectant, on materials that are not affected by its corrosive capacity. Finally, in much more dilute concentrations, 3% or less, is used as an oral or dermal antiseptic, to prevent infections in small wounds. Who does not remember suffering more from hydrogen peroxide than from a scrape on the knee? Or the discussions about the preferences between alcohol and hydrogen peroxide? By the way, something that you may have ever wondered: what are the bubbles that appear when hydrogen peroxide is applied to a wound? It is the product of the decomposition of hydrogen peroxide, molecular oxygen gas, O 2 , the same oxygen that we breathe.
On the other hand, there are selective substances , which can be different depending on the pathogen, and are administered as drugs . We refer to antibiotics, antivirals, antifungals, which destroy microorganisms inside our body. The duration and dose of treatment should be adjusted after long clinical studies, to maximize its germicidal action and minimize side effects.
The order in which the categories have been presented is also the order of their aggressiveness, from most to least. I insist that only the latter corresponds to medications, substances that we can ingest to fight infections always under medical prescription .
Bleach, which today is a complex preparation, is the most versatile disinfectant, and perhaps the substance most responsible for the hygienic conditions that characterize modern society.
It is not the goal of this article, but we need to talk about sterilants. The reason is that only in this way can we put disinfectants in proper context, and avoid confusion between them and those.
The most familiar form of sterilization is through the use of steam , between 120 and 135 ºC, through a sealed chamber known as an autoclave . Complete sterilization is obtained in 60 minutes of operation.
Another possibility is by means of hot air , which is also called dry steam , where the temperature varies between 160 and 190ºC, and the application times, between about 12 minutes at 190ºC, and two hours at 160ºC —the lower the temperature, the longer. Other heat treatments are possible, but we do not include them here so as not to make the article too long.
A different possibility is ultrasound , with frequencies between 20 kilohertz and 10 megahertz. Its action is based on the phenomenon of cavitation , where an almost microscopic implosion occurs , inside which temperatures of up to 5000 degrees are reached, during a very short period of time. This thermal and baric shock deactivates microorganisms and pollutants.
When the sample to be sterilized does not withstand high temperatures, methods and substances at room temperature must be used. One of the most effective is the use of radiation, be it the energetic Ultraviolet C, or even gamma radiation, the radiation of higher energy than humans are capable of generating .
This treatment requires completely evacuating the room to be sterilized. For example, biological labs are sterilized using UV-C lamps, but it can only be used under professional supervision.
Another battery of treatments is based on the use of chemical substances . We have already mentioned ethylene oxide or hydrogen peroxide. We will also add nitrogen dioxide, various chlorine oxides, ozone, formaldehyde and peracetic acid . They are all very reactive substances, so the concentration and duration of the treatment is key, as we have already analyzed in the case of hydrogen peroxide.
Finally, there are situations in which what we want to sterilize is delicate, since it does not resist any type of physical or chemical stress. The most important example is in the manufacture of medicines , substances whose conservation is delicate, and their vital sterilization, never better said - can you imagine that the medicines were contaminated with the microorganisms against which they act? -.
In these cases, so-called sterile filtration can be used . This can be microfiltration , based on membranes whose pore is 0.22 microns, or nanofiltration , with membranes whose pore is between 20 and 50 nanometers. Microfiltration retains most bacteria, whereas viruses require nanofiltration.
Proper hand hygiene, with soap and hydroalcoholic solution, eliminates 99.99% of microbes in general, and viruses with a greasy envelope, in particular.
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