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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MP HC sets up judicial commission to probe water contamination in Indore
Indore (PTI): The Indore bench of Madhya Pradesh High Court on Tuesday set up a commission of inquiry comprising a former HC judge to probe the issue of water contamination in city's Bhagirathpura, saying the matter requires probe by an independent, credible authority and "urgent judicial scrutiny".
It also directed the commission to submit an interim report after four weeks from the date of commencement of proceedings.
A division bench of Justices Vijay Kumar Shukla and Alok Awasthi constituted the commission while hearing several public interest litigations (PILs) filed simultaneously regarding the deaths of several people in Bhagirathpura due to the consumption of contaminated water.
The HC reserved the order after hearing all the parties during the day, and released it late at night.
The state government on Tuesday told the HC that the deaths of 16 people in Indore's Bhagirathpura area was possibly linked to a month-long outbreak of vomiting and diarrhoea caused by contaminated drinking water.
The government presented an audit report of 23 deaths from the current gastroenteritis epidemic in Bhagirathpura before the bench, suggesting that 16 of these fatalities may have been linked to the outbreak of vomiting and diarrhoea caused by contaminated drinking water.
The report, prepared by a committee of five experts from the city's Government Mahatma Gandhi Memorial Medical College, stated that the deaths of four people in Bhagirathpura were unrelated to the outbreak, while no conclusion could be reached regarding the cause of death of three other people in the area.
During the hearing, the high court sought to know from the state government the scientific basis behind its report.
The division bench also expressed surprise at the state government's use of the term "verbal autopsy" in relation to the report, sarcastically stating that it had heard the term for the first time.
The HC expressed concern over the Bhagirathpura case, stating that the situation was "alarming," and noted that cases of people falling ill due to contaminated drinking water have also been reported in Mhow, near Indore.
In its order, the HC said the serious issue concerning contamination of the drinking water supply in Bhagirathpura area allegedly resulted in widespread health hazards to residents, including children and elderly persons.
According to the petitioners and media reports, death toll is about 30 till today, but the report depicts only 16 without any basis or record, it said.
It is averred that sewage mixing, leakage in the pipeline, and failure of civic authorities to maintain potable water standards have led to the outbreak of water-borne diseases. Photographs, medical reports, and complaints submitted to the authorities prima facie indicate a matter requiring urgent judicial scrutiny, the HC said.
"Considering the gravity of the allegation and affecting the right to life under Article 21 of the Constitution of India and the need for an independent fact-finding exercise, the Court is of the opinion that the matter requires investigation by an independent, credible authority," it said.
"Accordingly, we appoint Justice Sushil Kumar Gupta, former judge of the Madhya Pradesh High Court, a one-man commission of inquiry into the issues relating to water contamination in Bhagirathpura, Indore, and its impact on other areas of the city," the HC added.
As per the order, the commission shall inquire into and submit a report on the cause of contamination -- whether the drinking water supplied to Bhagirathpura was contaminated; and the source and nature of contamination (sewage ingress, industrial discharge, pipeline damage etc).
The panel will also probe the number of actual deaths of affected residents on account of contaminated water; find out the nature of disease reported and adequacy of medical response and preventive measures; suggest immediate steps required to ensure safe drinking water as well as long-term infrastructural and monitoring reforms.
It will also identify and fix responsibility upon the officers and officials found prima facie responsible for the Bhagirathpura water contamination incident, and suggest guidelines for compensation to affected residents, particularly vulnerable sections.
The commission shall have powers of a civil court for the purpose of summoning officials and witnesses; calling up records from the government department, hospitals, laboratories and civic bodies; ordering water quality testing through accredited laboratories; conducting spot inspections.
All state authorities involving district administration, Indore Municipal Corporation, public health engineering department and Madhya Pradesh Pollution Control Board shall extend full co-operation and provide records as sought by the commission, it said.
The state government shall provide office space, staff, and logistical support to the commission, it said.
During the hearing in the day, the state government also presented a status report to the court in this matter.
According to reports, a total of 454 patients were admitted to local hospitals during the vomiting and diarrhea outbreak, of whom 441 have been discharged after treatment, and 11 are currently hospitalised.
According to officials, due to a leak in the municipal drinking water pipeline in Bhagirathpura, sewage from a toilet was also mixed in the water.
