Cloth masks, particularly those with several layers of cotton fabric, may reduce transmission of deadly COVID-19 as it can block droplet and aerosol contamination of the environment, according to a new research.
According to scientists, most virus transmission occurs via larger particles in secretions like droplets, generated while sneezing, coughing, or even speaking and some are created when water evaporates from these droplets, turning them into aerosol-sized particles.
According to the review research, published in the journal Annals of Internal Medicine, every virus-laden particle retained in a mask is not available to hang in the air as an aerosol or fall to a surface to be later picked up by touch. However, study first author Catherine Clase from McMaster University said that there is no direct evidence about whether wearing a mask made of any material outside a health-care setting reduces transmission of COVID-19.
Clase explained that the point of wearing masks is that not all virus-laden particles retained in a mask will be available to hang in the air or fall to a surface to be later picked up by another person. “Although no direct evidence indicates that cloth masks are effective in reducing transmission of SARS-CoV-2, the evidence that they reduce contamination of air and surfaces is convincing and should suffice to inform policy decisions on their use in this pandemic pending further research,” the researchers noted.
After examining a century of evidence including recent data during the study, researchers found strong evidence suggesting that cloth masks can reduce contamination of air and surfaces. Based on the review research, Clase said cloth masks can block even aerosol-sized particles.
She said a mask made of three layers (muslin-flannel-muslin) reduced surface contamination by 99 per cent, total airborne microorganisms by 99 percent, and bacteria recovered from aerosol-sized particles by 88 to 99 per cent.
The researchers also noted that a commercial mask which is made of four-layer cotton muslin can reduce all particles by 99 per cent, compared with 96 per cent to 99 per cent for contemporary disposable medical masks. Even for aerosols, Clase and her team believe that cloth masks are comparable with medical masks.
Filtration of single-layer cloth varies with it types and may vary in the range of 10 to 40 per cent range for scarf, sweatshirt, and t-shirt. Scientists added that increase the number of layers may increase efficiency.
The researchers said, citing previous studies, that some combinations of cloth such as cotton-flannel, block more than 90 per cent of particles. Clase said that increasing the number of layers will give more protection, both inward and outward, but at the same time, it will become harder to breathe.
She added that people with breathing difficulties and children under two may not find these masks comfortable.
She believes that more research is needed into the best materials and design of cloth masks, to help the many people who are sewing masks to protect people in their community. “Given the severity of this pandemic and the difficulty of control, we suggest that the possible benefit of a modest reduction in transmission likely outweighs the possibility of harm,” Clase said.
