It's the first Friday of December 1952 and Winston Churchill has just been re-elected prime minister. The rationing of tea has finally come to an end and Londoners are looking forward to Christmas. After weeks of cold, breezy weather, the winds suddenly die and a thick fog envelops the capital. People stoke fires to keep warm, and smoke from homes, trains and factories starts to build. By Monday night, 700 people are admitted to hospital suffering from choking and coughing fits and heart problems.
For five days, there is no wind and the black smoke, sulphur dioxide and sulphuric acid from coal-burning gets thicker. And still the fires burn. From the open coal fires in every home to the vast columns of smoke belching out of Battersea, the lives of Londoners had grown utterly dependent on the fuel that was killing them in huge numbers. By Christmas, some 4,000 people, mainly the old and very young, are thought to have died in what is quickly dubbed the "Great London Smog."
In the 55 years since the smog, air quality in our cities has improved dramatically. On the worst days of the smog, each cubic metre of air in London carried 4 grams of soot and 3 grams of sulphur dioxide. Today, sulphur dioxide levels are 1,000 times lower, particles 100 times lower: air quality in our cities is probably better than it has been for 200 years. Yet air pollution is still thought to bring forward the deaths of 1,000 Londoners a year and to knock about a year off the average lifetime in the southeast. By contrast, there are about 220 road deaths in London each year.
Improvement in air quality over the last 50 years is largely the result of regulation. But that regulation has often been introduced many years after evidence of harm first came to light. The Clean Air Act of 1956 came only after the horrendous consequences of the Great Smog, despite a century of evidence of air pollution's harmful effects in cities. In the 1960s, evidence emerged that children's IQs were reduced by lead poisoning from vehicle exhaust, but lead additives in petrol were only finally outlawed in 2000. And we are now into the second decade of evidence of harm from ultra-fine particles and polycyclic aromatic hydrocarbons, but we are still waiting for effective measures to control them.
Our approach to air pollution is still dominated by a Great Smog mindset. Air pollution is considered primarily to be a problem caused by local polluters, whether power stations, bonfires or heavy-goods vehicles. And urban pollution is considered to be all-pervasive in a city's environment once emitted; no account is made for the substantial variations in air quality that people experience in urban micro-environments, or for action individuals can take to reduce their own exposure to that pollution.
But air pollution is increasingly transnational in nature, with measurable amounts of pollution reaching Britain from Europe, the US and even Asia. Within Europe, the ozone smog that regularly forms over the continent is carried to Britain on easterly winds—there have been about 40 moderate episodes of this nature since April this year. Long-range ozone episodes are expected to increase in years to come with the rising levels of the greenhouse gas methane and falling levels of nitric oxide from vehicle exhausts. Particulate pollution, which is much more threatening to health than ozone, can also be carried from central Europe. A severe episode of this occurred in late March 2007, when air pollution in London breached the official "very high" designation.
Similarly, individuals can experience transient levels of air pollution that are much higher than the typical hourly measurements. Air pollution can accumulate in stagnant pools in street canyons, while highly congested environments are often not properly accounted for in pollution inventories. In addition, cyclists and joggers dramatically increase their exposure by breathing heavily, increasing the amount of pollution ingested by up to 20 times.
Public policy must start to focus on trans-boundary air pollution. For several decades the US has operated a market in air pollution permits to control long-range pollution between states. A similar system could be implemented in Europe, with structural funds used to assist polluters in the poorest EU nations. But while we wait for such structural measures, it is essential to reduce exposure to the pollution that's already there.
One example is airTEXT, a trial pollution alert system now operating in London (full disclosure: I manage the service). This informs people when air pollution in their area is forecast to reach moderate levels. Other simple measures include moving congested traffic away from high-density pedestrian zones, like London's Piccadilly, Shaftesbury Avenue and Oxford Street, where a plethora of bus routes are forced down a series of narrow streets with large numbers of shoppers and tangible air pollution. Locating the exhausts of buses and goods vehicles at roof height could significantly reduce exposure. And encouraging health authorities to co-operate with local authorities on managing air pollution and the exposure of those with severe asthma or cardiovascular problems would strengthen the hands of planners when considering major developments that are likely to lead to massive increases in local traffic and therefore pollution.
It is a great achievement that our air is cleaner now than since the beginning of the industrial revolution. But there's more to do if we are to tackle the health effects of air pollution in our cities.
