Research finds link between air pollution and road collisions

12.00 | 7 October 2016 | | 6 comments

New research from the London School of Economics and Political Science suggests there is a link between air pollution levels and an increase in traffic collisions.

Published on 3 October, the research found that ‘small increases in the level of nitrogen dioxide in the air’ are correlated with ‘a measurable rise’ in the number of traffic accidents in the UK.

The results, based on data for the period between 2009 and 2014, show that a rise in the average concentration of nitrogen dioxide of just one microgramme per cubic metre is sufficient to increase the average number of accidents each day by 2%, with the biggest effect occurring in cities.

Although the research cannot identify the link, the author of the report, Lutz Sager, suggests it could be down to impairing drivers’ fitness.

Sager’s analysis divided the UK into a grid of 32 areas each covering about 7,700 square kilometres. He calculated that in the area containing west London, which suffers from some of the highest levels of air pollution, a cut of about 30% in the concentration of nitrogen dioxide could reduce the number of road accidents by almost 5%.

Lutz Sager, a researcher at the Grantham Research Institute on Climate Change and the Environment, said: “Although it has already been shown that air pollution adversely affects human health and the ability to carry out mental tasks, this is the first published study that assesses the impact on road safety.

“The analysis identifies a causal effect of air pollution on road accidents, but I can only speculate about the cause of the link. My main theory is that air pollution impairs drivers’ fitness.

“However, other explanations are possible such as air pollution causing physical distractions, perhaps an itching nose, or limiting visibility.

“Whatever the exact mechanisms responsible, the robust finding of a significant effect of air quality on road safety is important given the high cost of road traffic accidents through damage to vehicles and deaths and injuries to people.

“Although this analysis has used data for the UK, I think my findings are relevant to other parts of the world. These additional costs from traffic accidents strengthen the case for reducing air pollution, particularly in congested cities.”

Photo: the British Lung Foundation.



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    I understand that there is a link between pollution and mental performance to some degree. Not beyond possibility that pedestrians’ judgments are impaired potentially leading to dodgy behaviours and actions?

    Who would have thought that lead in petrol would have caused problems not too long ago?
    I was under the impression that the particulates coming out of a diesel engine are amongst the most carcinogenic materials on the planet?

    Nick, Lancashire
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    In my experiment that I have not yet conducted (and never will), I would have linked the use of air conditioning systems in cars to accidents, because air conditioning can reduce fuel economy and thus, increase pollution – and this article “suggests” that pollution are linked to occurrences of accidents, therefore I am somehow right.

    Or it could just be that places where air quality is poor is linked with higher-than-normal levels of urban traffic – and maybe that’s the real factor with increased accident rates?


    David Weston, Corby
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    Rather than assuming that pollution must cause crashes because there is a correlation between the two, couldn’t it be that neither causes the other but that both have a common causal factor? As we know, there are more crashes when roads are busier and there is more pollution when roads are busier – couldn’t it be that congestion is the cause of both more pollution and more crashes?

    Charles, England
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    Hugh – just for clarity, we (the editorial team) have used the word ‘suggests’, not the researchers.

    Nick Rawlings, editor, Road Safety News
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    I’m wary of any report which does no more than ‘suggests’ a link between something. Rather than ignore the obvious causes of collisions which we can all see for ourselves everyday, academics feel the need to find some other rather obscure, tenuous ‘link’ instead.

    Over the last twenty years or so, more and more everyday vehicles have air con which if used in the city, apart from temperature control, will also reduce the pollutants entering into the cabin giving a cleaner climate than if you were outside, which I presume must be beneficial for the driver’s levels of concentration and attentiveness. Did the authors factor that in?

    Hugh Jones, Cheshire
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    Has anyone studied the effects of sneezing whilst driving a car? I have sneezed and it certainly takes the eyes off the road as it always causes one to close one’s eyes. It could be caused by pollutants such as described.

    Anyone who has a diesel car knows, or should know, that it’s not designed to be driven at slow speeds around town all the time. In order to clear the carbon deposits that build up, particularly through the hot gas return valve, the car has to be driven fast and blown out all of the gasses. These pollutants are seen as a black smoke that comes from the exhaust when the foot is put down. Buses and other commercial vehicles have to undergo servicing regularly to prevent a build up and escape of these pollutant gases from escaping.

    So anyone who has been sold a diesel car because they are, say, retired or female and just want a car that runs cheap on fuel and used mainly for the school run or shopping should not be sold a diesel car. An excess build up of these exhaust particles could render the car unusable within 18 months to 2 years, unless it’s used faster on a regular basis.

    Bob Craven Lancs
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