Air pollution in London (and elsewhere)
5 min read
Air pollution in our biggest cities is much worse than most of us have realised. It averages well over twice World Health Organisation (WHO) guidelines and legal limits near many of London’s busiest roads. The most recent data from the European Environment Agency confirmed that London has the highest levels of nitrogen dioxide (NO2), a toxic gas, of any capital city in Europe.
Ambient or outdoor air pollution comprises particles and gases. The particles, which can comprise anything from tiny droplets to diesel soot and tyre and brakewear, are called ‘particulate matter’ and classified by their aerodynamic diameter in microns (one-millionth of a metre which is about one-hundredth of the thickness of a human hair) e.g. PM2.5 and PM10. The gases, which can coalesce and become particles, are mainly NO2, ozone (O3) and sulphur dioxide (SO2).
The WHO says there is little evidence to suggest a threshold below which no adverse health effects would be anticipated for particulate matter or, put another way, there is no safe level of human exposure to it. An ‘Update of WHO air quality guidelines’ (AQG) published in February 2008 said ‘The AQG have always addressed exposures and health effects of individual pollutants or indicators (such as PM10 mass, an indicator of a complex pollution mixture with multiple sources). However, as understanding of the complexity of the air pollution mixture has improved, the limitations of controlling air pollution and its risk through guidelines for single pollutants have become increasingly apparent. NO2 for example is a product of combustion processes and is generally found in the atmosphere in close association with other primary pollutants, including ultrafine particles. It is itself toxic and is a precursor of ozone, with which it coexists along with a number of other photochemically generated oxidants. Concentrations of NO2 are often strongly correlated with those of other toxic pollutants. Its concentration is readily measured but needs interpretation as a potential surrogate for a set of sources and the resulting mixture. Achieving guideline concentrations for individual pollutants, such as NO2, may therefore bring health benefits that exceed those anticipated on the basis of estimates of a single pollutant’s toxicity.’ NO2 is not just a molecule therefore as the Government would have us believe.
Mayor Johnson has estimated that 4,267 early deaths in London in 2008 were attributable to long-term exposure to PM2.5 alone. Latest estimates from the Department of Health show 6.3% to 9.0% of all deaths in London in 2010 were attributable to long-term exposure to PM2.5. Most of these occur as cardiopulmonary deaths. Separately, Clean Air in London has found 1,148 schools and educational places near roads carrying over 10,000 vehicles per day on average after discovering that living or going to school within 150 metres of such roads could be responsible for 15-30% of all new cases of asthma in children and chronic obstructive pulmonary disease in adults of 65 years of age and older.
Legally binding, health based ‘limit values’ for several air pollutants, have been set by the European Union since 1999. London is failing to meet these for PM10 and NO2.
PM10 limit values had to be complied with by January 2005 but the UK obtained unlawfully a time extension until 2011 to comply in London. This time extension has now expired but PM10 limit values, also known as ‘Bad Air Days’, continue to be breached in London e.g. in Marylebone Road and near waste management sites such as Neasden Lane in Brent.
NO2 limit values had to be complied with by January 2010. The UK Government has stated it does not expect to comply with these standards in 15 of 43 zones within the UK before 2020 and in London until 2025. The Government has admitted to the European Commission that some 440,000 Londoners were exposed to unlawful levels of NO2 in 2011 at background locations alone i.e. away from the busiest roads.
Clean Air in London has found that only eight of 43 UK zones complied with legal limits for nitrogen dioxide, a toxic gas, in 2011. Clean Air in London has also identified marginal constituencies where these legal standards are breached.
In Clean Air in London’s view, the current Government is failing to warn people and misleading them with statistics such as: “air pollution has declined significantly in recent decades”; air quality is “good across 99% of the UK”; and “air pollution still reduces life expectancy by an average of six months”.
London experienced the worst ozone smog for six years on the eve of the opening ceremony of the Olympic Games and has had 12 smog episodes in 2012. The Government stopped issuing press releases to warn the public of smog episodes in April 2011 after it became front page news. The UK’s limited monitoring national network can be seen at UK-AIR.
Perhaps more seriously, the UK Government and the Mayor of London have been caught lobbying to weaken air pollution laws in the lead up to the European Commission’s ‘Year of Air’ in 2013.
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