What is it about?
The COVID-19 pandemic has underscored the critical need for effective surface disinfection to control infection. Previous experimental studies evaluating various HOCl-based disinfectants have primarily focused on their antimicrobial properties. Even at high concentrations, these formulations were applied directly to wounds to maximize antimicrobial effects. Dry fogging systems have been developed to achieve effective nonvital surface treatment with HOCl and ensure maximum germicidal action over a large area in a short time. These systems disperse fine droplets of disinfectant, allowing penetration into inaccessible areas. The Biocidal Products Committee (BPC) of the European Chemicals Agency (ECHA) has approved aqueous HOCl solutions releasing 200-300 ppm active chlorine to disinfect hard surfaces in the EU. Although some previous studies have highlighted potential health risks and tissue damage from HOCl mist exposure (such as DNA damage, lipid peroxidation, and protein oxidation), no studies have been conducted on the genotoxicity and cytotoxicity of HOCl-based aerosol disinfectants at high concentrations in human fibroblasts.
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Why is it important?
Therefore, an important question is whether it is safe to disinfect surfaces in the presence of the operator using hypochlorous acid at 300 ppm or 500 ppm. To answer this, we conducted experiments treating human primary fibroblasts with an aerosol of HOCl. We used primary (non-immortalized) human fibroblasts, which may be more sensitive to HOCl exposure in a dry fog. Fibroblasts are the primary cells of connective tissue and a crucial component of the skin, the human body's primary barrier against infectious pathogens. We assessed cell morphology, viability, apoptosis, and DNA damage after exposure to dry HOCl fog or aqueous aerosol. Our study revealed that quadruple exposure of human fibroblasts to aerosolized HOCl at 500 ppm for 9 minutes induced significant cytotoxic and genotoxic effects. In contrast, exposure to aerosolized HOCl at 300 ppm for 3 minutes did not cause similar damage.
Perspectives
Further research is needed to determine the exact HOCl concentrations and exposure times required for safe use as a fogging disinfectant. Future studies should extend our analysis by assessing long-term effects that better mimic real-world disinfection scenarios. Additionally, in vivo studies are necessary to understand HOCl's effects on human tissues fully. This could involve animal models or carefully controlled human exposure studies to investigate the in vivo response to HOCl aerosol.
Elżbieta Trafny
Military University of Technology
Read the Original
This page is a summary of: The HOCl dry fog–is it safe for human cells?, PLoS ONE, May 2024, PLOS,
DOI: 10.1371/journal.pone.0304602.
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