The Mechanisms of Disinfectants and Their Safety, Part 1: Alcohol

When disinfecting your facility–whether it be in a healthcare setting, school, daycare, business or hotel–it is important to consider the safety of the substance used. It is also important to take into account the effect it may have on end users (custodial staff), patrons (business), patients (healthcare), children (school/daycare) and guests (hotels), as well as the environment itself. In this multi-part series, SMT will discuss the mode of action for many types of different disinfectants and the potential risks associated with the use of each.

How does alcohol kill pathogens?

The term alcohol encompasses two forms of the substance: ethyl alcohol and isopropyl alcohol. This type of disinfectant is an effective bactericidal agent against vegetative bacteria, as well as tuberculocidal, virucidal and fungicidal. However, it is generally rendered ineffective against bacterial spores.

The most apparent and feasible mode of action, or how alcohol kills pathogens, is protein denaturation. Denaturation, according to the Elmhurst College’s Virtual Chembook, is “the disruption and possible destruction of both the secondary and tertiary structures.” Alcohol causes this denaturation by destroying hydrogen bonds in the secondary and tertiary protein structures. What this means, essentially, is that the shape and structure of the proteins within the pathogen are changed and their function is halted.

In bacteria cells alone, protein structure and attendant metabolism processes are vital to many different cellular mechanismsand structures, such as flagella and pili, and functions such as swimming, DNA transfer, membrane permeability and surface attachment. When protein denaturation occurs, cells can no longer reproduce or survive and thus the bacteria is rendered inert.

What are the risks?

Although alcohol is a competent disinfectant, there are some hurdles for use as well as risks to the end user and environment. First, most alcohols require concentrations of at least 50%. As far as disinfectants go, this is a very high percentage of volume.

For instance, methyl alcohol can be recommended at 100% and Ethyl alcohol at ranges from 60-95%.  The lowest recommendation is isopropyl alcohol at a concentration of 20%. While this is more acceptable than its counterparts, 20% is still 200,000 parts per million. At these use concentrations, equipment disinfected with alcohol is very susceptible to damage. These substances can swell and damage plastic tubing after repeated use, among other things. In addition, due to these high necessary concentrations, flammability becomes a huge potential risk as well.

Alcohol also presents challenges in surface disinfection. Because of the evaporative nature of the chemical, the solution quickly loses potency. Presentably, therefore, longer contact time is necessary to achieve prescribed bacterial kill rates, especially as compared to more sophisticated disinfectants such as pure chlorine dioxide.

If you would like to know more about the mechanism of disinfection for other chemicals, click the graphic below and enjoy the free download:

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