The Mechanisms of Disinfectants and Their Safety, Part 2: Formaldehyde

SMT continues its investigation into different products recommended for disinfection as well as their attendant safety concerns. In part 1, alcohol was found to be ineffective with percentages below 50%. We also learned that it works by denaturing, or changing the shape and structure of vital proteins, and that a quick evaporation time makes surface disinfection difficult. In this installment, we will discuss and discover the chemical formaldehyde.

Formaldehyde may be more widely known as a biological preservative–or as an embalming substance–however, it is also used as a disinfectant in either gas or liquid form. It is mainly used as a water-based solution, 37% by weight commonly known as formalin.

How does formaldehyde kill pathogens?

Formaldehyde deactivates, or kills pathogens by “alkylating the amino and sulfhydryl groups of proteins and ring nitrogen atoms of purine bases.” In more simple terms, alkylation is the transfer of alkyl group from one molecule to another. An alkyl group is a piece of a molecule containing the elements carbon and hydrogen. The transfer of this molecule chemically alters the pathogen’s ability to function properly by disrupting necessary cellular transport and survivability mechanisms.

What are the risks?

While formaldehyde can be an effective disinfectant and biocide, it is accompanied with some serious risks. Formaldehyde is a known carcinogen and thus poses some problems for use. Because of its carcinogenic status, OSHA has set some serious exposure limits. In an 8-hour time period, the weighted average of such chronic exposure must be below 0.75 ppm in the atmosphere. There is also a 15-minute short term exposure limit of 2 ppm.

In addition, long-term exposure can cause skin and respiratory issues. Such issues include asthma-like condition as well as dermatitis and itching. There have even been instances where people have claimed formaldehyde was the cause of miscarriage. For instance, after a 2008 earthquake in Sichuan, China, it is believe that high levels of formaldehyde in the materials used in temporary shelters was to blame for over 100 miscarriages in a single community.

Formaldehyde use percentages

Formaldehyde requires high concentrations in order to be effective. An 8% concentration, or 80,000 ppm is required for the inactivation of poliovirus. A concentration of 4% is necessary for tuberculocidal properties, as well as 2.5% for inactivation of Salmonella Typhi. In some cases, formaldehyde also requires a very high contact time. A solution of 4% needed 2 hours to achieve inactivation of B. anthracis, or the agent of anthrax.

These aforementioned and recommended use percentages are dangerously high, and whereas similar log reduction can be discovered using on fractional concentrations of other commonly known pesticides such as peracetic acid and chlorine dioxide.

If you’d like to learn more about the uses of formaldehyde, or the mode of action for other common disinfectants, visit the following link and enjoy the free download:

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