Why northern cities have better quality air

Centre for Cities Cities Outlook publication showed that cities, and particularly cities in the south-east of the country, are blighted by poor air quality.

But how does that contrast between northern and southern regions fit with broader changes in the UK in recent years? Centre for Cities researcher Valentine Quinio explores the recent trends.

Manchester. Photo Credit – Big Stock Images

Air quality has undeniably improved over the last sixty years. The London’s Great Smog of the 1950s, which caused an estimated 12,000 deaths in just five days, is a distant memory. Between 1970 and 2010, the emissions of major pollutants such as nitrogen dioxide (NO2) and fine particulate matter PM2.5 dropped by 61% and 76% respectively.

However, this progress has slowed in the last decade, especially when we look at human-made fine particulate matter (PM2.5). In UK cities these PM2.5 concentrations are almost unchanged since 2015.

But this is not a uniform trend. Not only do cities in the north currently have lower absolute levels of PM2.5 concentrations, they have also more successfully reduced air pollution levels compared to cities in the south. This progress has been made despite northern cities having relatively similar initial levels in 2010 (see the map below).

This stark north-south divide suggests that the slow improvement of air quality in the UK as a whole was actually held back by poor progress in the south of the country.

With the exception of two cities, all cities in the north- and in some parts of the Midlands- have cut pollution levels by more than 8.5%. While a large number of them, including all Scottish cities but also Newcastle, Sunderland or Stoke have reduced pollution concentration by more than 20% in the last decade, cities in the south have at best barely improved their air quality, and at worst failed to do so. In cities like Worthing, Portsmouth or Brighton, PM2.5 levels have increased by a respective 12, 9 and 8%

Though the reasons for this are complex, it may be explained by the main sources of fine particulate matter.

At a national level, data from our research on air pollution reveals a drop in the PM2.5 emissions from transport, which halved between 2005 and 2017-from 24,300 tonnes to 12,800 tonnes. However, such progress was almost entirely offset by an absolute and relative increase in pollution stemming from domestic combustion, which includes the currently popular wood burning stoves.

An additional 15,000 tonnes of fine particulate matter were emitted from domestic combustion in the same period, and its share in total PM2.5 emissions increased from 23% to 41%. 

Photo Credit – Centre for Cities

This in itself does not explain the north/south divide. A survey released by Defra in 2016 showed that wood fuel users account for 16% of the population in the South East. This is more than twice the UK average, and four times the share in the North East.

Taken altogether, these two elements might therefore explain why the south of the country lags behind when it comes to air quality: the increase in domestic combustion was disproportionately driven by people living in cities in the south.

All in all, and regardless of potential and diverse explanations, this calls for greater action on fine particulate matter PM2.5.

According to the World Health Organisation, there is no safe level of PM2.5, so all cities and large towns up and down the country must take immediate action to reduce their emissions, including from domestic sources. But given the role of southern cities in creating a disproportionate amount of the UK’s toxic air, special focus needs to be given to reducing their emissions.

If the UK is to meet the WHO guidelines for PM2.5 by 2030, the stronger impetus must come from cities where pollution levels are stagnating.

The upcoming Environment Bill must give local authorities greater power to declare and enforce smoke control areas, and ban wood burning in areas where PM2.5 concentrations are excessively high.

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