Does London have the worst air quality in Europe?

2nd May 2012

Boris Johnson campaign, Official Website, 20 April 2012 

Following the April 19 mayoral debate on Sky News, Boris Johnson's campaign published a press release detailing alleged false claims made by his main rival Ken Livingstone.

One such claim was that London has the worst air quality in Europe, something which Boris's side have now strongly disagreed with. The claim was countered twice on the incumbent's campaign website, but with different figures. Ken's campaign waded in again with a rebuttal of them. 

But is it Boris or Ken who is lost in the smog?

Analysis

The Better Off With Ken website describes why the Back Boris website may have got their own fact-check wrong:

"For this 'false claim' the Conservative campaign have used real-time air quality figures as a demonstration that there are other worse cities in Europe. Air quality is dependant on a number of factors, including whether or not it has rained in the last 24 hours. In a recent study by the European Environment Bureau, London was ranked among the worst cities in Europe, scoring an F"

The source Ken's campaign seem to be using is from a study conducted with the European Environment Bureau.

The study grades and rates several major Western European cities according to their emission reduction success and whether they are taking measures to actively improve air quality. Specifically it takes into account:

1. Emission reduction success

2. Low emission zones/bans of high emitters

3. Public procurement

4. Non-road mobile machinery

5. Economic incentives

6. Mobility management

7. Promotion of public transport

8. Promotion of walking and cycling

9. Participation and transparency

The terms of the study immediately bring up questions as to whether this is really a useful indicator of "air quality". Most of the categories that factor into the grading relate to what the government are actually doing in terms of promoting greener policies rather than a scientific analysis of how poor the air actually is.

London is also not at the bottom of the rankings. At '58 per cent' London is doing better than Rome, for instance, with a 38 per cent rating. However it does score an F, the lowest score in their simplified rating system, alongside six other European countries.

In addition it should be remembered that the sample involves only 17 Western European cities - not all of Europe. For these reasons, the source doesn't seem to be a useful indicator of air quality nor does it show that London has the worst in Europe.

There was, however, research in 2010 which indicated that London could be one of the worst polluted places in Europe, as measured by King's College London's London Air website, a resource linked with City Hall's air quality work.

So where do Boris's statistics come from? The link provided on their campaign page takes you to the EU website Air Quality in Europe which, as Ken's campaign state, provides real-time data on air quality across Europe from roadside monitoring stations.

As of 2pm today, the emissions data is as follows:

There are severe limitations on checking the data since the findings are updated every few hours. A cursory glance suggests that Stockholm, for instance, is currently showing worse emissions, but this isn't enough to conclude that it has worse air quality.

Update (1/5/2012)

Full Fact originally concluded that neither candidate had provided a sufficient basis to prove their point, and stands by this conclusion.

Following the publication of this article we have been pointed to further research compiled by the Campaign for Clean Air in London with data aggregated by the European Environment Agency.

The research uses data from several thousand Air Quality monitoring stations across European capital and principal cities - similar to the data from the real-time London Air Quality Network website. This research aggregates the data to calculate the annual average levels of pollutants detected by the stations.

The data for London comes from the Marylebone Road monitoring station specifically, which was chosen as it is a 'super site' which the UK Government uses as a benchmark to report its air quality data to the European Environment Agency.

[Clean Air in London]

The chart above shows data from 2010 on the levels of nitrogen dioxide (NO2) detected by each station, for the top 20 worst stations. London's Marylebone Road is the fourth worst among the cities included in the measure for NO2 levels (one proxy of air quality) and the worst of EU capital cities.

[from Clean Air in London]

However it is worth bearing in mind that the stations also monitor the concentrations of 'particulate matter' (PM10) which is also a valid proxy for air quality. On this measure, while London's levels are relatively high, they are far from Europe's worst - the above chart shows (which features four major cities) that Paris, for instance, has higher concentrations.

But what is most interesting is to examine what has changed over the years, since London may well be likely to have higher concentrations given its population and heavy transport usage.

The research also indexes London's Air Quality since 1996 (with provisional 2010 figures) for several gases. Using NO2 again, we can see a broadly stable level since 2005, although a long-term marginal decline compared to the 1990s.

[from London Air Quality Network]

Conclusion

The annual average data from the monitoring stations shows that there is a reasonable basis for claiming London has the worst air quality in Europe, although there are a number of qualifications. By this measure, London was the worst capital city for NO2 concentration in 2010, although not quite the worst compared to other principal cities.

For particulate matter (PM10) levels, London performs better based on the data from the Marylebone Road super site but is still relatively poor overall.

It obviously depends on which measures you consider most important, which is very much open to the reader's interpretation. However the data provided here shows that, while London strictly does not have the 'worst' air quality in Europe there are reasonable bases for claiming it is among the worst or even the worst among Europe's capital cities, based on these measures from monitoring stations.

Unfortunately, neither of the candidates provided such detail when making their claims.