In the outbreak of COVID-19, the extended wear of single-use, disposable respirators was inevitable due to limited supplies. As a respirator is front-line protection against particulate matter, including bioaerosol and droplets, a comprehensive understanding for the reuse strategy is needed. In this study, eight different disinfection methods commonly applied for the reuse of respirators were compared for their influence on the filtration and bactericidal/bacteria removal performance, with in-depth discussion on the cause of effects. Treatments including oven-dry, ultraviolet irradiation (UV), microwaving, laundering with and without detergent, and immersion in hypochlorite, isopropanol, and ethanol were performed to respirators. Immersion in ethanol or isopropanol was effective for inactivation and removal of bacteria, yet such a treatment significantly deteriorated the filtration efficiency in about 20–28%, dissipating the surface charges. Laundering, while effective in removing the attached bacteria, triggered physical damage, leading to a possible reduction of filtration performance. A short-term oven-dry, UV irradiation, and microwaving mostly preserved the filtration performance, yet the drawback lied in the incomplete bactericidal efficiency. This study would contribute to the public health and safety by providing scientific background on the effect of disinfection treatment methods for respirators.

With an increasing use of indoor disinfectants such as chlorine (Cl 2 ) and hypochlorous acid (HOCl), a convenient sampler for estimating exposure to oxidants, such as effective chlorine, is necessary. Here, we developed a personal passive air sampler (PPAS) composed of a redox dye, o ‐dianisidine, in a polydimethylsiloxane(PDMS) sheet. o ‐Dianisidine readily reacts with gaseous oxidants generated by bleach usage, and its colorchanges as the reaction progresses; hence, personal exposure to effective chlorinecould be easily detected by the naked eye,while cumulative exposure could be determined by measuring concentrations of o ‐dianisidine reacting with it. The PPAS was calibrated,and asamplingrate of 0.00253 m 3 h −1 was obtained using a small testchamber. The PPAS was tested with the help of ten volunteers whosepersonal exposure toCl 2 ‐equivalent gas was estimated after bathrooms were cleaned using spray and liquid‐type household disinfection products, and the accumulated exposure‐gas concentrations ranged from 69 to 408 ppbv and 148 to 435 ppbv, respectively. These PPAS‐derived exposure concentrations were approximatelytwoorders lower than those estimated using ConsExpo TM , suggesting a significant overestimation by prevailing screeningmodels,possibly due to the ignorance of transformation reactions.

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Permethrin is one of the most widely used active ingredients in spray-type home insecticides. However, indoor permethrin exposure resulting from the use of home insecticides is not well-characterized, as measured permethrin concentrations in indoor environmental and biological media with a known application rate are scarce.We conducted an intervention study with four participants for seven days. We conducted personal air monitoring and collected 24-h urine samples in which we quantified time-weighted average (TWA) permethrin concentrations in indoor air (C air ) and urinary concentrations of two permethrin metabolites, 3-phenoxybenzoic acid (3-PBA) and cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis/trans-DCCA). We also estimated (1) TWA C air using a simple indoor air model and(2) urinary excreted (UE) mass using a simple excretion model with both estimated and measured TWA C air . Measurements of TWA C air from personal air monitoring were lower than those estimated from the indoor model by a factor of 2.9 to 49.4. The ratio of estimated to measured UE mass ranged 3.5-18.2 when using estimated TWA C air and 1.1-2.9 when using measured TWA C air . Smaller ratios in estimating internal permethrin exposure from personal air monitoring suggest that personal air monitoring could reduce uncertainties in permethrin exposure assessment resulting from the use of spray-type insecticides.

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