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Chapter 1: Air pollution in our changing world The London smog of 1952, in which up to 12,000 people died, 1 was a defining event in air quality management; it brought about the Clean Air Acts and the start of 3 decades of concerted actions to control public exposure to air pollution. Today, life in the UK is very different from how it was in the 1950s. Much more than legislation has changed since this time, with various social, fuel and technology transitions driving a huge change in outdoor air pollution – changing old pollution sources and introducing new hazards into our breathed environment. Concerns about black smoke and air acidification (sulphur dioxide, SO 2 ) from coal burning have been replaced by new concerns about particle pollution and nitrogen dioxide (NO 2 ) from transport, and the air pollution that forms through chemical reactions between other pollutants in the atmosphere. With new knowledge that pollutants can remain in the air for days or even weeks, air pollution has moved from being a local problem to one that requires source control at city, regional and even international scales. Each year in the UK the equivalent of around 40,000 deaths can be attributed to outdoor air pollution linked to exposure to fine particulates and NO 2 (see Chapter 6). 2,3 Box 1: Six US cities that changed our knowledge of modern air pollution By the 1990s, the pollution and mortality peaks linked to wintertime smog seemed consigned to history; the Clean Air Acts and the advent of natural gas heating had displaced solid fuel from our cities. In 1974, US scientists 4 began following the lives of 8,111 people across six US cities. Of these people, 1,490 had died by 1991, but these deaths were not spread evenly. Having accounted for factors including smoking rates, education level, diabetes and workplace pollution exposure, the worst-affected city had a death rate around 30% greater than that of the least-affected city. Across the six cities, the difference in death rates was found to be associated with airborne particle pollution; this was not from air pollution experienced during short smog episodes, but rather from long-term exposure to everyday pollution concentrations. Although the pollution mixture had changed, long-term exposure to modern air pollution was exerting a heavy health burden, leading to the conclusion that modern pollutants needed better control, not just during smog episodes but every day. Returning to the same people 8 years later, researchers 5 were able to repeat and confirm the earlier findings with respect to particle pollution and survival, but with one important difference: those cities with improved air pollution saw improved survival rates, suggesting that at least part of the air pollution health effects might be reversible and that improvements in air pollution can lead to better city-wide health outcomes. 1.1 Changes to transport Changes to transport systems and habits were a defining movement of the last half of the 20th century. In the 1950s, car ownership was beyond the reach of the majority of families; today, many families regard car ownership as an essential part of life, providing mobility and access to jobs, shops and leisure. Between 1949 and 2012, a massive investment in roads and road vehicles led to a tenfold increase in the distance travelled in the UK (Fig 1). This 'freedom' has not been universally accepted as a good thing. 4 © Royal College of Physicians 2016

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