By Simon Birkett, Founder and Director of Clean Air in London - 11th January 2012
Simon Birkett, the founder and director of Clean Air in London, outlines the dangers of air pollution and the 'cover-ups' that have taken place in government over the last few years.
Air pollution is much worse than most of us have realised. It regularly exceeds twice World Health Organisation (WHO) guidelines and legal limits near our busiest roads in London and elsewhere. Only smoking causes more early deaths than air pollution in the UK.
In December 2009, 'Clean Air in London' (CAL) accused the previous government of one of the biggest public health failings or 'cover-ups' by a government in modern history. Perhaps amazingly given the seriousness of the accusation, the Environmental Audit Committee (EAC) has twice since confirmed CAL's findings. In CAL's view, the current government is still failing to warn people and may be 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".
Let's rewind. Ambient or outdoor air pollution comprises particles and gases. The particles are called 'particulate matter' and classified by their aerodynamic diameter in microns e.g. PM2.5 and PM10. The gases, which can coalesce and become particles, are mainly nitrogen dioxide (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. NO2 is a product of combustion processes and is generally found in the atmosphere in close association with other primary pollutants, including ultrafine particles.
In the Great Smog of December 1952 there were 4,075 deaths in London due to short-term exposure to air pollution with more over the following months. The number was easy to calculate through time-series analysis i.e. the number of deaths peaked about two days after air pollution levels peaked. The Committee on the Medical Effects of Air Pollutants (COMEAP) published a report in 1998 on the health impact of short-term exposure to PM10. COMEAP estimated a total of 8,100 deaths 'brought forward' due to PM10 annually among total deaths in urban GB. The same COMEAP report referred to 3,500 deaths brought forward per year due to SO2 in urban areas of GB and between 700 and 12,500 deaths brought forward by O3 in both urban and rural GB during the summer only.
It was not until 1995 and 2000 that huge cohort studies in cities in the United States with different annual mean concentrations of PM2.5 showed the health impact of long-term exposure to air pollution. The results estimated a range of coefficients from 1% to 9% for a 10 microgram per cubic metre (mg/m3) reduction in PM2.5. COMEAP reported on these results in 2001 that using the 1% coefficient, the effects of long-term exposure were about ten-fold greater than the effects of short-term exposure. Based on further scientific evidence, COMEAP in June 2009 recommended, as a best estimate for mortality in the UK, a higher risk coefficient of 6% change in risk of death from all causes with a 10 mg/m3 change in PM2.5.
Mayor Johnson was the first politician to use COMEAP's 2009 advice to publish in June 2010 estimates by ward of 4,267 deaths in London in 2008 attributable to long-term exposure to PM2.5. COMEAP lead the way nationally in December 2010 by estimating, using the language used for alcoholism, obesity and smoking, 29,000 deaths in the UK in 2008 attributable to long-term exposure to PM2.5 at an average loss of life for these people of about 11.5 years. COMEAP and the Mayor's estimates were calculated after eliminating the effect of dozens of other possible risk factors to produce a pure number assuming air pollution is the sole cause of those deaths. In CAL's view, these estimates are much more meaningful to members of the public than 'years of life lost' or an 'average loss of life of six months for everyone in the UK'.
Combining therefore the short and long-term impacts of different pollutants suggests a range of between 29,000 and 53,100 early deaths nationally from air pollution. For the first time, we can compare easily the health impact of long-term exposure to PM2.5 with the Government's estimates for the number of premature deaths attributable to alcoholism (15,000 to 20,000 in England; average men 20 years, women 15 years), obesity (9,000 in England; average nine years) and smoking (87,000 in England; average 10 years) and understand the complexities of these metrics.
The estimates of 4,267 and 29,000 extra or excess deaths are good ones for comparing the effects of air pollution with the effects of other causes such as alcohol, active or passive smoking, obesity, diet etc which are calculated in the same way. However, COMEAP has shown us that because, in practice, individuals experience multiple risks, it is more reasonable to consider that air pollution may have contributed to all 200,000 deaths due to cardiovascular causes in the UK in 2008 (i.e. one in three of all deaths) at an average additional loss of life for these people of about two years.
In conclusion, it is fair to point out there were as many early deaths in London in 2008 due to long-term exposure to PM2.5 as we thought occurred during the Great Smog of 1952 (due to short-term exposure to air pollution when we knew nothing of the long-term effects). Put another way: knowing that there were 4,000 early deaths in the Great Smog of 1952 was enough to 'change the world'; but knowing there were 4,000 early deaths in London in 2008 is now considered by some 'room for improvement'.
It's time for change. London and the UK should be leading the world in the Olympic year in tackling air pollution as we did after the Great Smog of 1952.
This is the first in a series of six articles being written for PoliticsHome by Simon Birkett, founder and director of Clean Air in London, about air quality in the lead up to the London 2012 Olympics.
Other topics are expected to include: legal issues; sources and solutions; Mayoral Manifestos; indoor air quality; and the Olympics. A fuller version of this article, which includes information about morbidity and inequalities and additional references, can be seen on Clean Air in London's website.
