Should we have antibiotic chemicals present in everyday domestic items?
In the first half of the 20th century hospitals were disinfected with lysol (mixture of cresols in soapy water) which gave them their very typical smell. The purpose was to decrease the populations of bacteria in hospitals and to prevent transmission of disease from one patient to another indirectly through furniture, utensils, dirt or dust. At some stage, this may have been a sensible means to restrict the spread of tuberculosis and other transmissible diseases.
However, the history of microbicidal products is full of disasters and tragedies. In the 1960s in a hospital St. Louis, Missouri, pentachlorophenol was used in to disinfect laundry, an obviously improvised use against the express directions printed on the package. Many children were found to have been exposed to pentachlorophenol. About 20 children needed treatment for poisoning, and two of them died.
Today sports shoes are sold, treated with antibacterials so that sweating feet do not smell. There are antibacterial dish-cloths and chopping boards, antibacterial toothpaste, antiseptic detergent for laundry and many other things.
Microbicidal substances may thus bring benefits but also cause harm. What is the balance?
There are two completely different kinds of hazards. The substances can be outright poisonous. Pentachlorophenol has been banned for a long time not only in laundries but in many countries also for use in sawmills where it was used as a timber preservative. Likewise some antiseptic chemicals used in deodorants or soaps have been banned, e.g. hexachlorophene. Thus the use of clearly toxic compounds has been discontinued. Even though there are occasional scares about some chemicals such as triclosan, the risks of direct toxicity are presently really not substantial.
There is another kind of problem, however. Man has no way of truly sterilizing his/her environment, such that it would be completely devoid of microbes (fortunately – a sterile environment would be truly life-threatening). In fact, when we apply antimicrobial compounds, we will kill some of the microbes, but this only creates more space for those which are resistant. Maybe the shoes do not smell quite the same, but that is no guarantee that they are home to fewer microbes. Such disturbance may lead to unpredictable results – undoubtedly we would probably be better off with our own characteristic microbial environment than with some artificial microbial environment we have created by using antimicrobial chemicals.
Another problem is the development of resistance even in those species that were initially sensitive to the antibacterial chemical. Microbes can become more resistant through a mutation or by acquiring resistance genes from other microbes, even from quite different species. This can be a problem later in the future, for example, if a real bactericidal action would be needed due to the outbreak of a disease. Therefore one should disturb bacterial populations as little as possible.
The benefits of antibacterial or other disinfectant substances are greatest when one knows exactly what they are intended to achieve. When taking a blood sample, the skin must be cleaned with antiseptic substance to prevent entry of bacteria through the needle sticking into the blood vessel. This effect is temporary, and the normal microbes are soon back, but by then, the opening is already sealed.
In a hospital, certain areas should be kept as clean as possible and alcoholic solutions or disinfectant detergents may be needed to clean them. Likewise in an institute performing animal experiments it may be necessary to sterilize or disinfect the animal rooms in order to eradicate microorganisms causing animal infections. It is a common feature in all of these operations that one aims to kill all microbes for a short period of time, not simply the pathogenic (disease-causing) microbes. On the other hand, any attempt to keep an environment sterile permanently is doomed from the very onset.
Another restricted but proper way of using antimicrobial substances is as preservatives in certain products. Shampoos, toothpastes and similar products may contain antimicrobial compounds to preserve them in the bottle or tube until used. The purpose is not to cause any antimicrobial effect on the hair that is washed with the shampoo.
Antibacterial or other antimicrobial substances have not been shown to be beneficial for health when used in homes or in usual consumer products. A clean environment can be best achieved by normal hygiene, mostly by using water and soap or ordinary detergents. It is much more important to wash the chopping board immediately after cutting meat than to use a board impregnated with antibacterial materials. Similarly, it is much more important to keep building structures or construction materials dry than to try to prevent microbial growth in buildings by incorporating disinfectants into the walls and floors.
Hygiene is necessary in our present lifestyles, but this means keeping things clean mainly by mechanical means. Antibacterial or other antimicrobial substances should only be used for specific purposes.
Notes and references
- Disinfectants are used for eradication of microbes from non-living objects (utensils, water, waste etc.), antiseptic substances kill microbes locally on skin or mucous membranes. Sterilization means destruction of all microbes and their spores e.g. by autoclaving at 120 °C under pressure or by applying very potent chemicals such as ethylene oxide. Also terms microbicidal or microbe killing substances, bactericidal or bacteria killing substances and antibacterial substances are sometimes used.
- See the chapter "Are cosmetics chemicals?"
- There are two kinds of resistance or tolerance of an antibiotic drug or other antimicrobial chemical by the microbes. Many bacteria are naturally resistant to e.g. penicillin. Bacteria may also acquire resistance either through mutation or by borrowing the necessary gene from another bacterium. Bacteria were skilful users of biotechnology much before man even invented the word. It is to be noted that it is the bacterium that becomes resistant, not the patient. Therefore it is not correct to say that “penicillin does not help me, because I am resistant.” Penicillin helps all right, if the next infection is caused by bacteria sensitive to penicillin.
- See the chapter "Mutagenesis, carcinogenesis and other scary words – what do they really mean?"
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