COVID-19: Most homemade masks block large cough droplets, even as single layer, says study
Washington: Scientists examined the effectiveness of common household fabrics used in homemade masks in blocking droplets generated by coughing and sneezing, and have found that they are considerably protective even as a single layer.
While earlier studies have focussed on the transfer of tiny, nanoscale aerosol particles through masks, the researchers from the University of Illinois at Urbana-Champaign in the US said speaking, coughing, and sneezing generates larger droplets -- about one millimeter in diameter -- that can carry virus particles.
They said the larger droplets pose a problem as they can squeeze through the pores of some fabrics if they have sufficient momentum, and break into smaller droplets and become airborne.
In the study, published in the journal Extreme Mechanics Letters, the scientists filled the nozzle of an inhaler with distilled water seeded with easy-to-find ultra small fluorescent particles -- which happens to be the size of a novel coronavirus particle.
The inhaler forced the water through the nozzle when puffed, and generated high-momentum droplets that collected on a plastic dish placed in front of the inhaler, the study noted.
The researchers repeated this process with the various materials placed over the collection dishes to test their ability to block the particles.
"We count the number of nanoparticles landing on the dish using a high-resolution confocal microscope. We can then use the ratio of the number collected with and without the fabric to give us a measure of droplet-blocking efficiency," said study co-author Taher Saif.
However, the scientists said for an individual to feel compelled to wear a mask, the material must not only be able to block the droplets, but also be comfortable and breathable.
"A mask made out of a low-breathability fabric is not only uncomfortable, but can also result in leakage as the exhaled air is forced out around contours of a face, defeating the purpose of the mask and providing a false sense of protection," Saif said.
"Our goal is to show that many common fabrics exploit the trade-off between breathability and efficiency of blocking droplets -- large and small," he added.
The scientists tested the breathability and droplet-blocking ability of 11 common household fabrics, including new and used garments, quilted cloths, bedsheets and dishcloth material, using a medical mask as a benchmark.
They then characterised the fabrics in terms of their construction, fiber content, weight, thread count, porosity and water-absorption rate.
Their analyses revealed that droplets leave the inhaler at about 17 metres per second (mps) while those released by speaking, coughing and sneezing have velocities within the range of 10 to 40 (mps).
"We found that all of the fabrics tested are considerably effective at blocking the 100 nanometer particles carried by high-velocity droplets similar to those that may be released by speaking, coughing and sneezing, even as a single layer," Saif said.
"With two or three layers, even the more permeable fabrics, such as T-shirt cloth, achieve droplet-blocking efficiency that is similar to that of a medical mask, while still maintaining comparable or better breathability," he added.
The researchers believe the new experimental platform may offer a way to test fabrics for their blocking efficiency against the small and larger droplets that are released as people breathe, or cough.
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Karnataka Milk Federation enters Delhi-NCR, offers competitive pricing on Nandini products
New Delhi, Nov 21: Karnataka Chief Minister Siddaramaiah on Thursday launched the Karnataka Milk Federation's (KMF) Nandini brand milk products in the Delhi-NCR market, pricing them marginally lower than competitors to gain a foothold in the region.
The cooperative will retail four cow milk variants, curd, and buttermilk from Friday, with competitive pricing that undercuts established players like Mother Dairy and Amul.
Cow milk will be sold at Rs 56 per litre, full Cream Milk at Rs 67 per litre, Standardised Milk at Rs 61 per litre, Toned Milk at Rs 55 per litre, and curd at Rs 74 per kg.
"We have surplus milk in the state. KMF along with Mandya Milk Union will market surplus milk of 3-4 lakh litres per day in Delhi-NCR," Siddaramaiah told reporters after launching the products.
The federation currently collects 100 lakh litres of milk daily, with local consumption at 60 lakh litres, leaving a surplus of 40 lakh litres for expansion into new markets.
However, the Chief Minister acknowledged the challenges of transporting milk over 2,500 km, which takes 50-54 hours.
There is a need to find new markets for surplus milk and gradually the KMF should be able to sell 5-6 lakh litres per day in Delhi-NCR, he added.
KMF Chairman LBP Bheemanaik assured that milk quality would be maintained during transit.
The federation has already partnered with 40 dealers in the Delhi-NCR region to facilitate sales, he added.
With a robust infrastructure of 26.76 lakh milk producers, 15,737 dairy cooperative societies, and 15 district milk unions, KMF has a turnover of Rs 25,000 crore and exports dairy products to over 25 countries.
State Animal Husbandry Minister K Venkatesh and Agriculture Minister N Cheluvarayaswamy were present at the product launch.
ದೇಶದ ಹಾಲು ಉತ್ಪಾದನೆಯಲ್ಲಿ ಗುಜರಾತ್ ಮೊದಲ ಸ್ಥಾನದಲ್ಲಿದ್ದರೆ, ಕರ್ನಾಟಕ ಎರಡನೇ ಸ್ಥಾನದಲ್ಲಿದೆ.
— Siddaramaiah (@siddaramaiah) November 21, 2024
ದೆಹಲಿ ನಗರದಲ್ಲಿ ಕೆ.ಎಂ.ಎಫ್ ಮತ್ತು ಮಂಡ್ಯ ಹಾಲು ಒಕ್ಕೂಟಗಳು ಸೇರಿಕೊಂಡು ವಿವಿಧ ಶ್ರೇಣಿಯ ಹಾಲನ್ನು ಮಾರುಕಟ್ಟೆಗೆ ಬಿಡುಗಡೆ ಮಾಡಿವೆ. ದೆಹಲಿಯ ನಿವಾಸಿಗಳಿಂದ ನಂದಿನಿ ಉತ್ಪನ್ನಗಳಿಗೆ ಅತ್ಯುತ್ತಮ ಸ್ಪಂದನೆ ದೊರೆಯಲಿದೆ ಎಂಬ ವಿಶ್ವಾಸ ನನಗಿದೆ.… pic.twitter.com/yUmTQknGzD
