Masks Can Reduce Volume of Cough Clouds, Curb Covid-19 Spread: Indian Study 


A new study by the Indian Institute of Technology Bombay states that face masks can reduce the volume of cough clouds and cut down the spread of the Covid-19 virus.  The study states that the size of cough clouds is seven times smaller when one wears a surgical mask and nearly 23 times smaller with an N-95 mask.

The researchers said their analysis suggests that the first five to eight seconds after a person coughs are crucial for suspending the exhaled droplets in the air.

“The volume of the cough-cloud without a mask is about 7 and 23 times larger than in the presence of a surgical mask and an N95 mask, respectively,” the study states. “The presence of a mask drastically reduces this volume and significantly cuts down the risk of the infection to the other persons present in the room.

“Similarly, the actions which drastically cut the distance traveled by the cloud, such as coughing into the elbow and the use of a handkerchief can reduce the volume of a cough cloud and, therefore, the chances of dispersion of the virus.”

Some medical professionals and researchers say that coughing into the elbow or using a handkerchief cannot entirely substitute for the continuous use of a face mask.

“When someone is carrying the infection, the person will contaminate the air even with normal breathing and talking. Therefore, face masks play a crucial role,” said Amit Agrawal, co-author of the study.

Agrawal said that by not wearing face masks, those carrying the virus continue to rapidly contaminate the air.

“For example, if you are in a closed space with people who are not wearing masks, your chances of getting infected go up,” said Agrawal.

Rajneesh Bhardwaj, author of the research, said,  “Without a mask, it takes about five to eight seconds for a cough or a sneeze cloud to evolve. With a mask, the size of these clouds reduces considerably. This brings down the spread of viruses such as the SARS CoV-2 which causes Covid-19.”

Bhardwaj said his team started researching this aspect soon after the pandemic hit India.

“We used a computer model and experimental data on the velocity of coughs and sneezes for our research,” he said. “The findings will help us in planning the ventilation of closed spaces as we learn to live with the virus.”

The study states that the cough of a Covid-19-infected subject contaminates a large volume of the surrounding air with the virus in the jet-like flow created by the cough.

“In the present work, we estimate this volume of the air may help us design the ventilation of closed spaces and thereby reduce the spread of the disease,” the study noted.

As winter in India and the subcontinent sets in, more people are expected to come down with coughs, colds and other symptoms that may be similar to those of Covid-19. In all cases, faces masks could be of benefit.  While scientists and health officials have emphasized the benefits of wearing face masks, the mandatory use of face coverings has been a matter of debate among some. In the United States, the argument centers on personal freedom and responsibility versus government-imposed mandates.

The World Health Organization has stated that masks are key in helping to suppress transmission of the virus.

“The masks reduce potential exposure risk from an infected person, whether they have symptoms or not. People wearing masks are protected from getting infected. They also prevent onward transmission when worn by an infected person,” the WHO stated.

It said masks should be used as part of a comprehensive approach, including physical distancing, avoiding crowded, closed and close-contact settings, improving ventilation, cleaning hands and covering sneezes and coughs, among other measures.

The WHO stated that within wider environments where the virus is spreading, masks should be worn by the general public in settings where it is not possible to maintain a distance of at least 1 meter (3.2 feet) from others.

“The examples of these settings include indoor locations that are crowded and have poor ventilation, public transport and places of high population density, among others. In enclosed settings, especially where there is poor ventilation, it is also very important to increase the rate of air change, reduce recirculation of air and increase the use of outdoor air,” it said.

Doctors believe masking is the single most important way to break the chain of transmission in densely populated countries such as India.

“A well-fitted mask is more important than a vaccine. People should not unmask while speaking. As masks have to be removed while eating, physical distancing should be maintained strictly,” said Dr. Shashank Joshi, a member of the Covid-19 task force in the western state of Maharashtra, which has recorded the highest number of Covid-19 cases and deaths in the country.

India has over 7.9 million Covid-19 cases as of Oct. 26, with around 120,000 deaths.

The research findings were published by the American Institute of Physics in the journal Physics of Fluids.

(Edited by Uttaran Das Gupta and Judy Isacoff.)

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