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New Delhi, Jul 18: The Covid-19 lockdown-led reduction in air pollution levels across five Indian cities, including Delhi and Mumbai, may have prevented about 630 premature deaths, and saved USD 690 million in health costs in the country, according to a new study.

Scientists, including those from the University of Surrey in the UK, assessed the levels of harmful fine particulate matter (PM2.5) from vehicles and other sources in five Indian cities -- Delhi, Mumbai, Kolkata, Chennai and Hyderabad -- since the beginning of the lockdown period.

The study, published in the journal Sustainable Cities and Society, compared these lockdown PM2.5 figures from 25 March up until 11 May, with those from similar periods of the preceding five years, and found that the measure reduced pollution levels in all these places.

According to the scientists, during this period, the levels of these harmful air pollutants reduced by 10 per cent in Mumbai, and by up to 54 per cent in Delhi.

"The percentage reduction for the other cities ranged from 24 to 32 per cent, which was slightly smaller than the measured values for Delhi and Mumbai," the scientists noted in the study.

"While the reduction in PM2.5 pollution may not be surprising, the size of the reduction should make us all take notice of the impact we have been having on the planet," said Prashant Kumar, a co-author of the study from the University of Surrey.

The scientists said these reductions in PM2.5 were comparable to those reported in other cities across the world, such as in Austria's capital Vienna (60 per cent), and Shanghai (42 per cent) in China.

They also calculated the monetary value of the reduced mortality due to air pollution and found that the lowered levels of PM2.5 may have saved 630 people from premature death, and USD 690 million in health costs in India.

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According to the researchers, the present lockdown situation offers observational opportunities regarding potential control systems and regulations for improved urban air quality.

They said an integrated approach might help in understanding the overall impacts of Covid-19 lockdown-style interventions and support the implementation of relevant policy frameworks.

"This is an opportunity for us all to discuss and debate what the 'new normal' should look like - particularly when it comes to the quality of the air we breathe," Kumar said.

New Delhi, Jul 21: The Centre has written to all states and union territories warning against the use of N-95 masks with valved respirator by people, saying these don't prevent the virus from spreading out and are "detrimental" to the measures adopted for its containment.

The Director-General of Health Services in the Ministry of Health, in a letter to the Principal Secretaries of health and medical education of states, said it has been observed that there is "inappropriate use" of N-95 masks, particularly those with valved respirator, by the public other than designated health workers.

The DGHS referred to the advisory on the use of homemade protective cover for face and mouth available on the website of the Ministry of Health.

"It is to bring to your knowledge that the use of valved respirator N-95 masks is detrimental to the measures adopted for preventing the spread of coronavirus as it does not prevent the virus from escaping out of the mask. In view of the above, I request you to instruct all concerned to follow the use of face/mouth cover and prevent inappropriate use of N-95 masks," DGHS Rajiv Garg said in the letter.

The government had in April issued an advisory on the use of homemade protective cover for face and mouth, asking people to wear it, particularly when they step out of their residences.

The advisory stressed such face covers must be washed and cleaned each day, as instructed and states that any used cotton cloth can be used to make this face cover. 

The colour of the fabric does not matter but one must ensure that the fabric is washed well in boiling water for five minutes and dried well before making the face cover. Adding salt to this water is recommended, it said.

It also listed the procedures of making such homemade masks, asking to ensure it fits the face well and there are no gaps on the sides.

It urges people to wash hands thoroughly before wearing the face cover,  switching to another fresh one as the face cover becomes damp or humid, and never reusing it after single use without cleaning it. 

"Never share the face cover with anyone. Every member in a family should have separate face cover," the advisory stated.