Air pollution exceeds WHO levels in 90% of UK, and may cause increase in traffic accidents, says UK study

Air pollution appears to be causing an increase in traffic accidents, according to a new study published by the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science.

An analysis by researcher Lutz Sager 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 United Kingdom.

Sager’s results, based on data for the period between 2009 and 2014, show that a rise in the average concentration of nitrogen dioxide of just 1 microgramme per cubic metre is sufficient to increase the average number of accidents each day by 2 per cent, with the biggest effect occurring in cities.

Only a few days ago, data released from the World Health Organization (WHO) indicates that over 90 per cent of the UK’s population lives in areas where levels of air pollution exceed WHO limits, according to a new air quality model released by WHO. The model was developed in collaboration with an international team of scientists led by the University of Bath, United Kingdom and represents the most detailed outdoor (or ambient) air pollution-related data ever reported by WHO.

However DEFRA's air quality index for the UK this week says that 'Air pollution levels are expected to remain generally Low to end the week'.

Who is right? Can they all be right?

Air pollution increases the risk of respiratory and cardiovascular diseases, stroke, lung cancer, acute respiratory infections and other diseases. Major sources of outdoor air pollution include transport, burning of waste and household fuel, coal-fired power plants, and industrial activities. Globally, it is estimated that 3 million deaths a year can be attributed to outdoor air pollution.

Back at LSE, Sager’s analysis divided the UK into a grid of 32 areas each covering about 7700 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 per cent in the concentration of nitrogen dioxide could reduce the number of road accidents every day by almost 5 per cent.

Sager 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.”

He added: “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 every day. Although this analysis has used data for the United Kingdom, 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.”

Air pollution can result from many different pollutants, including carbon monoxide, nitrogen dioxide, sulphur dioxide, small particulate matter and ozone. Many of these pollutants are caused by the same source.

Sager said: “My analysis suggests that the causal effect of air pollution on road traffic accidents measured in this study more likely stems from nitrogen dioxide or other pollutant gases rather than particulate matter.”

The results of the study are published as a working paper, and will be submitted to a journal for publication.