Experts debunk Centre’s 10 meters advisory on aerosols

Health experts have debunked the Centres May 13 advisory stating that aerosols one of the key modes of transmission of the novel Coronavirus can travel up to 10 meters They said there is no scientific base to prove such a claimDr Wiqar Shaikh professor of Medicine at Grant Medical College and Sir JJ Group of Hospitals said the advisory stated about aerosols in general and did not specify that SARSCoV2 which causes Covid19 itself travels for 10 metresHe said that an extensive survey of which literature revealed no published or experimental studies to prove that the Coronavirus aerosol indeed travels 10 metres or more Although there have been review articles comments etc in various journals there is no actual research publications to prove as to how far away Coronavirus aerosols can travel in the air he addedAlso Read Aerosols can travel 10 mts physical distancing criticalThe journal Physics of Fluid published a review article on May 19 2020 stating that Coronavirus aerosols can travel more than 2 metres said Dr Shaikh The International Journal of Environment Research in a review article in April 2020 made similar comments The Lancet published a comment on April 15 2021 stating that aerosolised SARSCoV2 can travel more than 2 metres 6 feet However none of these publications provided evidence of any published experimental study that proves the viruslaced aerosol can travel up to 10 metres or more he addedDr Shaikh said that on the contrary the US Centres for Disease Control CDC in an update on May 7 2021 stated that Covid19 infections through inhalation at distances greater 2 metres from an infectious source are less likely than at closer distances The CDC quoted 12 different research publications to prove its pointldquoIt is rather surprising that the central government has put out this advisory without support from any research publication on Covid19 Undoubtedly appropriate behaviour is of paramount importance in a pandemic he saidDr Ketan Vagholkar professor of Surgery at D Y Patil Medical College in Nerul said ldquoAerosols and droplets are both responsible for transmission of airborne viral diseases The distances may vary from a few inches to 10 feet However in a densely populated country it may be difficult to follow a suggested norm of physical distance especially in public places like buses and trainsrdquoldquoA threefeet distance as originally advised should be followed strictly Citizens should avoid crowded areas as much as possible Therefore meticulous use of a proper mask continues to be the best way in preventing infectionrdquo Dr Vagholkar saidAerosol vs droplet spreadldquoWe hear terms like lsquoaerosolrsquo and lsquodropletsrsquo but their precise meaning remains unclear and it is hard to know how to adjust our daily practice so as to avoid generating or getting exposed to Covid19 These are often divided into small invisible aerosols 110 microm size and large visible droplets more than 10 microm Generally during breathing talking coughing sneezing etc aerosol and droplets are generated simultaneously in different proportions Large droplets then drop to the ground before they evaporate causing surface or floor contamination Disease transmission through these large droplets is what we often refer to as ldquodropletcontact spreadrdquo where disease transmission occurs because one touches a surface contaminated by these droplets or gets caught within the spray zone when the patient is coughing Aerosols are so small that buoyant forces overcome gravity allowing them to stay suspended in the air for 1520 minutes or they evaporate before they hit the floor leaving solid particulate aerosol nuclei free to float very long distances for up to 8 hours says Dr Subhash Hira professor of Global Health at the University of Washington and health adviser to several UN and Indian health agenciesDr Hira added ldquoA 1000 microm droplet will fall 1 meter in 03 seconds A 100 microm droplet will fall 1 meter in 3 seconds A 10 microm droplet will take 300 seconds and a 1 microm droplet will take 30000 seconds How long a droplet remains in the air is clearly determined by the ventilation This ventilation becomes a big factor in how far it is able to travel the number of particles or droplets in the inoculum and how many people will get exposed to SARSCOV2 along the pathway Most published experiments have varied results based on multifactorial determinants of airborne transmission Hence public health recommendations are based on metaanalyses of these studies and come up with average distances that the two varieties of airborne transmissions are likely to occur The Indian health ministry recommends that the average distance that large droplets travel is 2 meters surfaces that are contaminated and 10 meters airspaces that are contaminated but does not specify ventilation speed and time that viruses remain afloatrdquoExpert viewDr Jacob John a noted virologist from Vellore said ldquoDroplets fall within one meter not two metres and aerosol travels to two meters not 10 metres If the person shedding virus has unusually heavy virus load as is likely with B16172 then the distance must be considered longer than 2 meters theoretically In closed spaces the meter distances are not important but the virus concentration is In ventilated places there is hardly any risk at 10 meters If all are masked a 2 meters distance is sufficientrdquoldquoViruses do not carry tape measures this one meter two meters and 10 meters are not all or none but dependent on circumstances When everyone is masked one meter is adequate as interindividual distance If the mask is tight fitting then risk of infection is virtually minimalrdquo Dr John added