Wiping, cleaning, scrubbing, cleansing, washing, disinfecting, sterilizing - all of these are intended to remove dirt and germs such as fungi, bacteria or viruses from fabrics or surfaces. But how many germs actually and which is the best method? What exactly do the percentages on disinfectants mean and when is an object or surface clean, disinfected and when sterilized? The hygiene experts at UVIS provide the answers.
Our perception of cleanliness, or rather our perception of hygiene, has changed greatly in recent years. Our knowledge about the spread of germs, such as fungi, bacteria and especially viruses through the air and surfaces has grown. But not all terms are clearly defined and not everyone agrees when cleaning is sufficient and when it is better to disinfect or even sterilize.
Cleaning, wiping, disinfecting, sterilizing - what is useful at home?
No one wants or should live in a germ-free environment, because not all germs are harmful to us. Our body and immune system are very well adapted to attacks by small microorganisms, and we also live in symbiosis with many germs, for example in our intestines. Nevertheless, there are areas where it makes a lot of sense to clean, disinfect or even sterilize thoroughly. Let's take the household. Of course, you should keep your own realm clean and clean regularly to prevent germs from spreading and causing infections. But disinfecting or even sterilizing is not absolutely necessary here. You can keep the domestic flood of germs under control very well with household remedies. Germ-free, as some manufacturers propagate it, is not at all necessary, or rather, the same level of cleanliness can be achieved with normal cleaning agents. It often depends on how well you clean, not necessarily on the product.
Many viruses, for example, have a protective layer of fat, which can be very well damaged or even removed with conventional cleaning agents, making the virus unable to survive. Since the concentration of viruses and bacteria at home is usually not so high, normal cleaning agent is sufficient.
And we should not live in a germ-free environment at all. Our immune system, especially that of small children, must learn to defend our body and it can only do that if it is also confronted with germs.
Disinfection – germs are rendered harmless!
Disinfection is useful in more sensitive areas where many people come together and germs can spread quickly, usually through the hands. Disinfection can also keep potential germs at bay when in the vicinity of vulnerable people, such as babies, the elderly or the sick, in order to prevent infections. This is because these groups of people are often very susceptible to infections, which can then become very dangerous. The definition of disinfection is to inactivate germs and contain them in such a way that the number of bacteria, viruses or fungi is so low on a surface or the hands that they can actually no longer cause an infection.
Even in hospitals, serious infections, for example after operations, with so-called hospital germs are not uncommon. Even though great attention is paid to hygiene here, the generous administration of antibiotics in the past, even for minor infections, has led to most bacteria developing resistance. Thus, even minor hygiene deficiencies can have serious consequences, as the infections cannot be treated with medication. Hygiene, and especially hand hygiene, has therefore taken on a whole new significance, since 80 percent of germs are spread via the hands. In sensitive areas, hand disinfection is now the gold standard to prevent infections, in addition to the usual surface disinfection.
Sterilization - germs are flattened!
Sterilization is one step tougher against germs. This is much more aggressive and is used when the germs are not only to be inactivated, but killed, mostly in the medical field. There must be no germs on scissors, syringes or instruments used in the operating room and used in internal body regions to protect patients. An object is considered sterile if the probability of a living germ being present on the object is less than 1:1,000,000 (one million). However, sterile environments also prevail in laboratories, semiconductor production and in optics and laser technology or in the manufacture of medical products. In the so-called clean room, even higher requirements must be met. Not only must all surfaces be sterile, but the air is also cleaned accordingly so that the production processes or examinations taking place there are not distorted or contaminated.
Depending on the resistance of the microorganisms and the material on which they are located, a distinction is made between chemical and physical sterilization processes. Chemical sterilization is usually gas sterilization for heat-sensitive materials. Physical methods include thermal sterilization with steam, for example, irradiation sterilization with UV, X-ray or gamma radiation, and sterile filtration, in which temperature-sensitive liquids are freed from microorganisms with the aid of suitable filters.
Time and again, we also get into contact with sterile products in everyday life, for example when we open a can. The contents are cooked in the factory. To ensure that the soup or vegetables can be kept for a long time, they are sterilized again in an autoclave with steam and under pressure. This kills all germs and the soup or vegetable can be canned for years.
Log levels – the unit of measurement for killing germs
When dealing with the various stages of cleaning, disinfection and sterilization, log levels inevitably come into play. On cleaning agents, a germ reduction of 99.9 percent is sometimes indicated, which corresponds to 3 log. The figure suggests a lot, because it is almost 100 percent, but when you realize that this figure refers to 1 million or even 10 million germs, the germ reduction rate is again relatively low.
Log reduction (logarithmic) is a standard mathematical term that reflects the number of microorganisms eliminated by disinfection, in other words, a way of expressing the kill rate. Assuming 1,000,000 pathogens, a 5 log reduction means that 99.999 percent of the pathogens are killed, leaving ten pathogens.
In science, by the way, no one will ever be carried away to confirm a statement of 100 percent sterility, because one small germ can still be "hidden" somewhere. Only what has been proven may be claimed.
Innovative technologies to kill germs
To get rid of germs, there are various technologies that can be used. On surfaces, after commercial cleaning agents, mostly liquid disinfectants with different degrees of effectiveness are used. Conditionally virucidal or virucidal means that certain or all viruses are inactivated, against bacteria must be bactericidal and against fungi fungicidal indicated on the container. However, the quantity and the exposure time must be observed so that the liquid disinfectant also shows the desired effect of up to 5 log. Disadvantage of this disinfection method, it requires many resources – people who disinfect, disinfectant, wipes, the correct method and a lot of time. With the background of sustainability, this method should be considered critically. In addition, not all surfaces can be disinfected with liquid agents. Electronic devices or certain materials, such as wood, upholstery or fine fabrics, such as silk, should not come into contact with it.
Alternatively, disinfection with UVC light can be used here. This technology is known for decades from water treatment and the food industry. For handrails of escalators the ESCALITE UVC module, which is installed in escalators and continuously disinfects the handrail to 99.99 percent, has been available for several years. Since there are many highly infectious germs on handrails, many users are afraid to touch the handrails, thereby accepting a high risk of falling. This does not have to be the case. For normal surfaces, such as desks, hotel reception areas or treatment rooms in doctors' surgeries, hand-held devices such as the UVIS Surface are now available, with which surfaces can be cleaned of all germs quickly, easily and, above all, sustainably. A study by the University Hospital of Tübingen also shows how effectively UVC light can be used for surface disinfection. In the study, a 6 log reduction of SARS-CoV-2 was achieved. No more germs were detectable, and that without the use of chemicals and disposable wipes.
For a sustainable and lasting reduction of germs on surfaces in public areas, such as shopping centers, public transport or offices, where continuous disinfection is not possible, antimicrobial coatings are used. Immediately after application, these coatings reach up to 5 log for norovirus and 4 log for SARS-CoV-2. Viewed over the entire effective period of up to twelve months, the coating permanently kills 90 percent of the germs. Although this is not equivalent to disinfection, in combination with normal cleaning intervals it reduces the number of germs to such an extent that infection is very unlikely.
In recent years, we have all learned from the pandemic that germs also spread very readily by droplet infection through sneezing or coughing and aerosols. This is where various air filter technologies come into play. Filters such as activated carbon or HEPA filters are well known, but UVC light or plasma are also effective technologies for keeping the air germ-free. It is important to consider where and how a device is to be used and what effect is to be achieved. If allergy sufferers are concerned with the elimination of pollen, the elimination of contagious flu and cold viruses in open-plan offices or canteens may be the reason for purchasing air filtration devices. We have set up a detailed comparison in our article "Room air purifiers - Which device fits my needs?".
In summary: Clean does not equal pure, but often clean is absolutely sufficient. It always depends on which areas need to be cleaned, disinfected or even sterilized. Which technology is then best used should be considered from the point of view of effectiveness but also sustainability.
Fotocredit: Europa Passage Hamburg/Robin Loesch
Published: May 23, 2023