Keeping six feet apart may not be enough to protect people from COVID-19 during windy weather

Keeping six feet — two metres — apart may not be enough to protect people from COVID-19 during blustery weather, a study has warned. 

Researchers found that saliva droplets can travel more than 16 feet (five metres) in just five seconds if there is a slight breeze of just around 2.5 miles per hour (4 kph).

The findings have been released amid a debate over the amount of distance people need to be putting between each other in order to keep safe from coronavirus.

Former Conservative Party leader Iain Duncan Smith has today called for the Prime Minister to consider lowering the two-metre rule as to ‘get the economy moving’.

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‘The droplet cloud will affect both adults and children of different heights,’ said applied physicist Dimitris Drikakis of the University of Nicosia in Cyprus.

‘Shorter adults and children could be at higher risk if they are located within the trajectory of the travelling saliva droplets.’

Saliva is a complex fluid, one which — when released by a cough — travels from a person’s mouth suspended in the bulk flow of the surrounding air.

Many factors affect how saliva droplets travel, including the size and number of droplets, how they interact with one another and the surrounding air as they disperse and evaporate, as well as the humidity and air temperature.

To study how saliva moves through air, the researchers created a simulation that predicted the state and journey of every single droplet released from the mouth of a person when they cough.

The model considered the effects of humidity, dispersion force, the interactions between molecules of saliva and air and how the droplets ultimately change from liquid to vapour and evaporate.

Each analysis involved the crunching of equations to cover over a thousand saliva droplets — solving roughly 3.7 million equations in total.

‘Each cell holds information about variables like pressure, fluid velocity, temperature, droplet mass, droplet position, etc,’ said paper author and physicist Talib Dbouk, also of the University of Nicosia.

‘The purpose of the mathematical modelling and simulation is to take into account all the real coupling or interaction mechanisms that may take place between the main bulk fluid flow and the saliva droplets, and between the droplets themselves.’

‘This work is vital, because it concerns health and safety distance guidelines [and] advances the understanding of spreading and transmission of airborne diseases,’ added Professor Drikakis.

Former Conservative Party leader Iain Duncan Smith today called for the Prime Minister to reconsider the two-metre rule in order to ‘get the economy moving’.

The MP suggested that the UK is the ‘only country in Europe’ using the two metre distance, with Germany, Poland and the Netherlands practising 1.5 metre separation.

Despite Sir Iain’s claim, however, a number of European countries are also practising two-metre social distancing, including Switzerland, Spain and Italy.

The World Health Organisation, meanwhile, has proposed maintaining a minimum of ‘1 metre (3 feet) distance between yourself and others.’

The researchers’ findings, however, suggest that all of the above rules may be inadequate to keep people safe on windy days without face coverings.

The full findings of the study were published in the journal Physics of Fluids.