Methylene blue applied to N95 respirators and medical masks for SARS-CoV-2 decontamination: What is the likelihood of inhaling methylene blue?

Here Comes the Sun—Methylene Blue in Combination with Sunlight Sanitises Surgical Masks Contaminated with a Coronavirus and a Tenacious Small Non-Enveloped Virus

“…Methylene blue is routinely applied directly to mucous membranes in the treatment of maxillary sinusitis [22] and has further been used as a treatment of infected wounds both in human [38] and veterinary medicine [39]. In addition, ultraviolet spectroscopy analyses testing the amount of methylene blue that may leach off surgical masks and be inhaled by a wearer during the course of a ten-hour healthcare provider work shift, recently demonstrated that methylene blue does not leach off surgical mask (or other PPE) materials even at high concentrations; following the application of 50-fold the amount of methylene blue used in our present study, no detectable methylene blue was observed, thus providing safety evidence for the use of MBS for SM decontamination [40]. Both SM integrity and fit have been shown to be maintained following multiple cycles of methylene blue-based decontamination [18], further supporting the safety of this method.…”

Personal protective equipment research and innovation in the context of the World Health Organization COVID-19 R&D Blueprint program

“…Kabra et al 16 focused on medical masks and Revolution-ZERO environmentally sustainable fabric masks, and showed that methylene blue effectively decontaminated both these types of mask when contaminated with SARS-CoV2 at concentrations above 5 mM and10 mM, respectively. Finally, in order to assess the safety of reusing medical masks and respirators decontaminated with methylene blue, Lendvay et al 17 undertook a laboratory investigation of the amount of methylene blue inhaled by wearers. They concluded that at 500-times the amount of methylene blue needed to decontaminate N95 respirators and medical masks, there was no residual inhalational risk of methylene blue following treatment, thus providing safety evidence for the use of methylene blue for SARS-CoV-2 decontamination.…”