UV light could make common disinfectants safer

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More than 400 common disinfectants currently in use could be made safer for people and the environment and could better fight the novel coronavirus (COVID-19) with the simple application of ultraviolet-C (UVC) light, according to a new study published in the journal Cutaneous and Ocular Toxicology.

Benzalkonium chloride (BAK) is the most common active ingredient in many disinfectants regularly used in hospitals, households, and food processing plants to protect against a wide range of viruses and bacteria, including all strains of SARS-CoV-2, the virus that causes COVID-19, but its toxicity means that it can't be used in high concentrations. It also means that products containing BAK are harmful to humans and the environment.

For the study. researchers discovered that the chemical's toxicity could be fully neutralized using UVC when tested on cultured human corneal cells. While an important ingredient for a disinfectant's efficacy, BAK is a severe human skin and eye irritant. The chemical's high toxicity limits the ability to use products with a high concentration of BAK to better protect against harmful viruses and bacteria. High levels of BAK residue are also harmful to the environment, proving especially toxic to fish, aquatic invertebrates, and birds.

After exposing a BAK solution to germicidal UVC lamps, they applied the solution to cultured human corneal cells for five minutes and analyzed for cell metabolic activity and viability. The BAK solutions were completely neutralized by UVC as the solutions no longer harmed the cultured human corneal epithelial cells.

"With concerns about the spread of COVID-19, people are utilizing products with BAK as an active ingredient more than ever," said Manlong Xu, PhD, lead author of the study and a clinical research fellow in the University of Alberta's Department of Ophthalmology and Visual Science. "For many industries, there is the demand to improve the efficacy of standard disinfection procedures, while also keeping in mind any potential negative impact on the environment."

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