Molecular alcohol was fist isolated and discovered by an Iranian scientist, Al-Razi, in the late 800’s. In everyday speaking, alcohol is often referred to ethanol, which is found in alcoholic beverages. Rubbing alcohols are often a solution of 70% isopropyl alcohol in 30% water, which are used in industrial and healthcare applications as surface disinfectants and hand wash sanitizers.
Alcohols are generally volatile and evaporate easily in open air. The oxidative reactivity of alcohols, more commonly referred to as combustibility, is high regardless of their molecular structure, thus making alcohols to be highly flammable and unsafe to be used near heat sources and sparking devices. Health effects of alcohols are also severe, depending on the type of alcohol a person is exposed to. Ethyl alcohol (in alcoholic beverages) is the safest type even if it is known to cause intoxication in high doses while other types of alcohol can cause serious health effects. In general, most alcohols are classified as volatile organic compounds which are agents known to cause concerns with respect to air quality and if released into the environment in large quantities can cause environmental and aquatic toxicity.
The exact method of action for alcohols’ efficacy is unknown; however there are three general mechanisms that are believed to be responsible for alcohols’ germicidal actions: 1) Protein denaturation (in simple terms, a change in structure like how boiled eggs become hard when cooked), 2) Lytic action (destruction of cells), 3) Interference with cellular metabolism (affect the ability of cells to perform the functions necessary to survive). Alcohols are known to be both bactericidal and bacteriostatic; for example ethanol is bacteriostatic at 10%, but it is required to be at least 30%-40% to act as bactericide. Alcohols can also inactivate fungi, mycobacteria, and viruses with less activity towards non-enveloped viruses. They are however ineffective against bacterial endospores In fact, spores can survive in high concentrations of alcohols for years. One of the main disadvantages of alcohols is their fast evaporation rate and the fact that they do not remain long enough on the surface to sufficiently inactivate pathogenic microorganisms. Ethanol and isopropanol at 60-80% take about 1 to 5 min to disinfect as per standard disinfection test methods; however they dry on the surface in less than 20-30 seconds. Shorter exposure (usually < 30 seconds) of pathogens to alcohols would often result in incomplete germicidal activity. Below a few often-used short chain alcohols and their antiseptic properties:
• Methyl Alcohol: Also known as methanol is considered to have the least antimicrobial activity and is therefore the least used. Methyl alcohol also opposes high toxicity levels to humans due to its neural damaging properties.
• Ethyl Alcohol: Also known as ethanol is mostly effective against live vegetative bacteria. Presence of 30 to 40 percent water is a key to ethanol’s germicidal activity.
• Isopropyl Alcohol: Also known as isopropanol, is the isomeric form of propanol that is often used for surface disinfection. Propanols (three-carbon alcohols) are the largest alcohol molecules that can be dissolved in water in any ratio. Having a larger molecular weight than ethanols, propanol and isopropanol have faster/higher germicidal activity than ethanol, however twice as toxic to humans.
Here’s how we would score alcohol on the key decision making criteria:
• Speed of Disinfection – B to C
o Contact times range from minutes to hours depending on the concentration, type of alcohol used and organism to be inactivated
o Due to the ready evaporation of alcohol, contact times need to achieve disinfection cannot be attained without reapplication
• Spectrum of Kill – B to C
o Similar to the speed of disinfection, performance in this criteria is tied to the in-use concentration and type of alcohol used
• Cleaning Effectiveness – D
o Alcohols are not efficient cleaners as they do not have detergency properties, however, some alcohols can dissolve both polar and non-polar substances, like salts and greases
• Safety Profile – C
o Alcohols are classified as combustible and flammable chemicals that are unsafe to be used near heat sources and sparking devices
o Health effects of alcohols are also severe, depending on the type of alcohol a person is exposed to
• Environmental Profile – B to C
o Alcohols are classified as volatile organic compounds which are agents known to cause concerns with respect to air quality and if released into the environment in large quantities can cause environmental and aquatic toxicity
o In low concentrations they are considered degradable when released to the environment
• Cost Effectiveness – B to C
o Alcohol is a commodity that is readily available in concentrated formats, however, is generally purchased as a Ready-To-Use Solution
**For more in-depth scientific information about Alcohol and other disinfectant chemistries, stay tuned to www.infectionpreventionresource.com