In a study in the\u00a0Journal of Hospital Infection<\/a><\/strong>, researchers assessed the ability of a variety of nontraditional mask materials to protect a person from infection after 30 seconds and after 20 minutes of exposure in a highly contaminated environment.<\/p>\n When the researchers compared wearing masks to wearing no protection during 20-minute and 30-second exposures to the virus, they found that infection risks were reduced by 24-94% or by 44-99% depending on the mask and exposure duration. Risk reduction decreased as exposure duration increased, they found.<\/p>\n Masks from best to worst<\/b><\/p>\n “N99 masks, which are even more efficient at filtering airborne particles than N95 masks, are obviously one of the best options for blocking the virus, as they can reduce average risk by 94-99% for 20-minute and 30-second exposures, but they can be hard to come by, and there are ethical considerations such as leaving those available for medical professionals,” says lead author Amanda Wilson, an environmental health sciences doctoral candidate in the community, environment, and policy department in the Mel and Enid Zuckerman College of Public Health at the University of Arizona.<\/p>\n The next best options, according to the research, are\u00a0N95\u00a0and\u00a0surgical masks\u00a0and, perhaps surprisingly, vacuum cleaner filters, which can be inserted into filter pockets in cloth masks.<\/p>\n The vacuum filters reduced infection risk by 83% for a 30-second exposure and 58% for a 20-minute exposure. Of the other nontraditional materials evaluated by the researchers, tea towels, cotton-blend fabrics, and antimicrobial pillowcases were the next best for protection.<\/p>\n Scarves, which reduced infection risk by 44% after 30 seconds and 24% after 20 minutes, and similarly effective cotton t-shirts are only slightly better than wearing no mask at all, they found.<\/p>\n \u201cWe knew that masks work, but we wanted to know how well and compare different materials\u2019 effects on health outcomes,\u201d says Wilson, who specialises in quantitative microbial risk assessment.<\/p>\n Exposure time is key<\/strong><\/p>\n Wilson and her team collected data from various studies of mask efficacy and created a computer model to simulate infection risk, taking various factors into consideration.<\/p>\n \u201cOne big component of risk is how long you\u2019re exposed. We compared risk of infection at both 30 seconds and 20 minutes in a highly contaminated environment,\u201d she says.<\/p>\n Other conditions that impact risk of infection are the number of people around you and their distance from you, she says.<\/p>\n The size of virus-transporting droplets from sneezes, coughs, or even speech is also a very important factor.<\/p>\n Larger, heavier droplets carrying the virus drop out of the air faster than smaller, lighter ones. That\u2019s one reason distance helps reduce exposure.<\/p>\n \u201cAerosol size can also be affected by humidity,\u201d Wilson says. \u201cIf the air is drier, then aerosols become smaller faster. If humidity is higher, then aerosols will stay larger for a longer period of time, dropping out faster.<\/p>\n That might sound good at first, but then those aerosols fall on surfaces, and that object becomes another potential\u00a0exposure route.\u201d<\/p>\n The study also shows that the more time a person spends in an environment where the virus is present, the less effective a mask becomes.<\/p>\n \u201cThat doesn\u2019t mean take your mask off after 20 minutes,\u201d Wilson says, \u201cbut it does mean that a mask can\u2019t reduce your risk to zero.<\/p>\n Don\u2019t go to a bar for four hours and think you\u2019re risk-free because you\u2019re wearing a mask. Stay home as much as possible, wash your hands often, wear a mask when you\u2019re out, and don\u2019t touch your face.\u201d<\/p>\n How masks protect you from Covid-19<\/strong><\/p>\n Masks protect the wearer and others in a number of different ways. Wilson says there are two \u201cintuitive ways\u201d that masks filter larger aerosols: mechanical interception and inertial impaction.<\/p>\n \u201cThe denser the fibres of a material, the better it is at filtering. That\u2019s why higher thread counts lead to higher efficacy. There\u2019s just more to block the virus,\u201d she says.<\/p>\n \u201cBut some masks (such as those made from silk) also have electrostatic properties, which can attract smaller particles and keep them from passing through the mask as well.\u201d<\/p>\n The model developed by Wilson and her colleagues included parameters such as inhalation rate\u2014the volume of air inhaled over time\u2014and virus concentration in the air.<\/p>\n \u201cWe took a lot of research data, put it into a mathematical model and related those data points to each other,\u201d Wilson says.<\/p>\n \u201cFor example, if we know people\u2019s inhalation rates vary by this much and know this much virus is in the air and these materials offer this much efficiency in terms of filtration, what does that mean for infection risk? We provide a range, in part, because everyone is different, such as in how much air we breathe over time.\u201d<\/p>\n Wilson also says it\u2019s important for a mask to have a good seal that pinches at nose, and she notes that people shouldn\u2019t wear a mask beneath the nose or tuck it under the chin when not in use.<\/p>\n \u201cProper use of masks is so important,\u201d Wilson says. \u201cAlso, we were focusing on masks protecting the wearer, but they\u2019re most important to protect others around you if you\u2019re infected.<\/p>\n If you put less virus out into the air, you\u2019re creating a less contaminated environment around you. As our model shows, the amount of infectious virus you\u2019re exposed to has a big impact on your infection risk and the potential for others\u2019 masks to protect them as well.\u201d<\/p>\n This article first appeared on the World Economic Forum. You can read the original here<\/a>.<\/em><\/p>\n![\"\"](\"https:\/\/businesstech.co.za\/news\/wp-content\/uploads\/2020\/07\/Masks-2.png\")
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