Sitting in a traffic jam really IS bad for you: Motorists breathe in 40% more deadly pollutants when sat at red lights

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Sitting in a traffic jam is enough to send even a calm person's blood pressure soaring.

But new research has found it could be even worse for your health than previously thought.

Being stuck at a red light exposes motorists to deadly pollutants which could seriously damage health, scientists warn.

They found pollution levels inside cars are up to 40 per cent higher in queues and at a busy junctions. 

And fans which draw in air from outside could be adding to the danger. 

Car emissions take longer to disperse in built-up areas and end up accumulating in the air at traffic lights and junctions, scientists say

The World Health Organisation (WHO) has warned outdoor air pollution is as carcinogenic to humans as smoking.

It is expected to kill more than 6.5 million people a year worldwide by 2050 - twice the current number, a study has found.

Globally, the problem causes around 3.3 million premature deaths annually - mainly in Asia.

The premature deaths are due to two key pollutants - fine particulate matter known as PM2.5s - and the toxic gas nitrogen dioxide, both produced by diesel cars, lorries and buses. 

The pollutants affect a person's lung capacity and growth, and are linked to ailments including lung cancer and heart disease. 

And emissions created by traffic queues take more time to disperse, especially in built-up areas.

They end up accumulating in the air at traffic lights, a known pollution hot spot for pedestrians and road users.

But contrary to popular belief, it is drivers who are the most affected.

Researchers from the University of Surrey found those who have their windows open breathe in seven times more PM10 - pollutants up to 10 micrometres in diameter -  than pedestrians at junctions.

Particles of this size can be inhaled deep into the lungs and can also become trapped in the nose, mouth or throat.

From here, they can then be absorbed into the blood and have a negative effect on the body.

The study monitored pollution levels at traffic lights and inside a car under five different ventilation settings over 3.7 miles (6km), passing through 10 different junctions.

However there is a simple solution.

Motorists caught up in queues can slash the levels of pollutants inside their vehicle by more than three-quarters by simply closing the window and switching off the fan.

Drivers should also leave more space between bumpers so exhaust fumes have greater chance to disperse, the researchers say.

They found the safest option is to put fans onto the setting where they re-circulate air within the car, without drawing polluted air in from outside.

Ventilation fans which draw in air from outside could be adding to the danger, experts believe

Lead researcher Dr Prashant Kumar, said: 'Travelling time has increased over the years in the UK and elsewhere, indicating a growing need for accurate exposure assessment during daily commuting.

'Our recent study has shown in some cases as low as 2 per cent of the commuting time spent at traffic intersections could contribute as high as 25 per cent of the total commuting exposure to particle number concentrations (PNCs).

'If the fan or heater needs to be on, the best setting would be to have the air re-circulating within the car without drawing in air from outdoors.' 

Dr Kumar showed last year drivers stuck at traffic lights were exposed up to 29 times more harmful pollution particles than those driving in free flowing traffic.

The latest findings were published in the journal Environmental Science: Processes & Impacts.