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Feature Briefing

Air pollution in UK: the public health problem that won’t go away

BMJ 2015; 350 doi: (Published 22 May 2015) Cite this as: BMJ 2015;350:h2757
  1. Nigel Hawkes, freelance journalist, London, UK
  1. nigel.hawkes1{at}

Sixty years after the Clean Air Act, air pollution is back in the headlines. The government has been accused of a failure to act while drivers of diesel cars, who were encouraged to believe they were doing the environment a favour, are now categorised as polluters in chief. Air pollution now kills 29  000 people a year in the UK, according to the headlines. In 2011, the Environmental Audit Committee of the House of Commons said: “The costs to society from poor air quality are on a par with those from smoking and obesity.”1

How has this happened?

Air pollution of all sorts has declined sharply in the past 25 years according to official figures.2 Nitrogen oxide levels have fallen by almost two thirds from their 1990 peak, and particulates have more than halved over the same period. But the decline has slowed, and recent studies of the health effects of these two pollutants have raised the bar. While pollution is actually lower than it used to be, the damage it does is better quantified.

Can it really cost 29 000 lives a year?

The figure comes from a 2014 report by the Committee on Medical Effects of Air Pollutants 3 and relates to particulates—small particles less than 2.5 microns in size, called PM2.5. Using risk estimates calculated by a large American Cancer Society study of several hundred thousand people in US metropolitan areas, the committee concluded that mortality increases 6% for every 10 μg/m3 rise in PM2.5. At 2008 concentrations (8.97 μg/m3) that was reckoned to have an effect on mortality equivalent to 29 000 deaths in the UK at typical ages of death.

There are big uncertainties. The committee estimated a 75% probability that the risk lay between 1% and 12%, so deaths could be as low as 4700 or as high as 51  000. That represents a range of loss of life expectancy at birth of between one month and one year.

As time passes, the science is becoming more robust, according to Ian Mudway of the environmental research group at King’s College London. “It has become more pressing to deal with these issues,” he told a Commons inquiry last year.4 Meeting the current limits for particulates, nitrogen dioxide, and ozone should be seen as “the minimum expectation to protect public health.”

Why is the UK in the dock?

The UK meets all European targets for particulates but falls short in reducing levels of nitrogen dioxide, which has serious, though less well documented, health effects. The European Commission has launched an action against the UK while the UK Supreme Court, in a case brought against the government by the environmental law group Client Earth, has ruled that the UK should draw up a plan by 31 December to cut nitrogen dioxide levels.

The main reason for UK non-compliance is diesel. Diesel engines emit more particulates and nitrogen oxides (NOx) than petrol engines, despite a succession of EU standards designed to clean them up. Particulates are reduced by filters that are fitted to newer vehicles approved under the Euro 5 regulations, but official tests used to measure NOx seriously underestimated the amount the newer vehicles would produce.

Real world NOx emissions from Euro 5 compliant cars approved since 2009 now exceed those on cars approved under Euro 1 regulations in 1992 and “are in the region of five times the limit value” the European Commission has admitted.5 “This has a major impact on concentrations of NO2, ozone, and secondary particles across Europe.” Or, as Mudway put it: “The technology has not delivered.”

The UK has encouraged the use of diesel cars through a favourable tax regime based on carbon dioxide emissions, with the result that in 2011 diesels outsold petrol cars in the UK for the first time. The rapid growth of diesel cars with high NOx emissions was thus the result both of mistaken environmental incentives and the failure of the EU testing regime.

Is the UK alone in missing targets?

No. The EU has 16 cases running against member states for breaches of particulate levels. The case against the UK is the first for NO2 levels. Alan Andrews, a lawyer with Client Earth, says that the UK could have sought an extension to the deadline for meeting the EU standard, as other member states did, but chose not to.

What’s to be done?

The long term answer is cleaner vehicles, such as electric, hybrid, or hydrogen powered. The Euro 6 regulations that came into force last September are tougher but tests to ensure vehicles meet them won’t be introduced until 2017. “We won’t see any improvements before 2018,”Andrews says. It will then take at least a decade for the changing vehicle population to translate those improvements into lower pollution levels.

Short term, enforcing low emission zones can have worthwhile effects. London has had such a zone since 2008. Heavy vehicles that do not meet emission standards either have to clean up or pay £100 or £200 a day, depending on size, to enter the zone. Cars are not currently included but will be when the ultra-low emission zone is introduced in 2020. However, the new zone will cover a much smaller area (the congestion charge area), risking displacing polluting vehicles on to neighbouring streets. Transport for London claims that when all parts of the plan are implemented, NOx emissions in the zone should fall by up to 51%.

Other cities have been reluctant to follow, and there is no national framework. Germany has 50-60 low emission zones, the UK only one, plus three more limited efforts in Oxford, Norwich, and Brighton. A nationally enforceable standard that would oblige heavy goods vehicles and buses to retrofit pollution reducing technology should be the aim, says Client Earth, together with a shift to walking and cycling.


Cite this as: BMJ 2015;350:h2757


  • Competing interests: I have read and understood BMJ policy on declaration of interests and have no relevant interests to declare.

  • Provenance and peer review: Commissioned; not externally peer reviewed.


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