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Chapter 7: Changing our future 7.1 Introduction Population growth, urbanisation, developments in the way that we travel, our pursuit and use of energy, new approaches to producing and sourcing food, and many other transitions have all delivered benefits for individuals and society. Yet, in combination, such changes have often created unintended new and complicated threats to health and wellbeing. Human beings are now using natural resources at an unprecedented rate and are damaging global systems and processes, on which we all rely for health and wellbeing. 1 Many of the global environmental changes – from depletion of the ozone layer, to ocean acidification, to climate change – can be linked to pollution of the atmosphere by human activity. This emphasises both the fragility and the interconnectivity of global systems and processes. 2,3 The pollutants primarily responsible for climate change often share common sources with the toxic pollutants that damage health in our towns and cities. When we burn fossil fuels in vehicles, in our homes or in industry, health-damaging chemicals (notably SO 2 , oxides of nitrogen including NO 2 , and PM) are released. At the same time, fossil fuel combustion produces gases such as CO 2 and NO 2 , which contribute to warming of the planet. One consequence is that measures to reduce emissions of greenhouse gases through energy efficiency, and most of the options for switching from fossil to other fuels, also reduce local air pollution. Thus, policies and interventions that tackle local air pollution can address climate change, and vice versa. They are said to offer 'co-benefits'. However, there are some policy options that generate 'trade-offs'. For example, as discussed earlier, reducing reliance on fossil fuels by increased burning of biomass (typically biological material derived from recently living plants) may increase particle emissions. Similarly, 'end-of- pipe' options for cleaning flue gases reduce overall energy efficiency and increase the pollutants that they do not specifically target, potentially contributing to both climate change and local air quality problems. Some policy options introduce unexpected complications and can have unanticipated negative consequences. For example, the shift away from petrol and towards diesel for the small engines that power our cars has reduced tailpipe CO 2 emissions. However, critically, the shift to diesel has also contributed to levels of health-damaging airborne particulates in the air of our towns and cities. Notably, too, the Air Quality Expert Group in its 2007 report Air quality and climate change: a UK perspective 4 observed that, while the situation is complicated, the perceived climate benefits of reduced CO 2 in tailpipe emissions are, to an extent, offset by increased refinery emissions of CO 2 due to increased demand for diesel, and the climate-warming effects of black carbon particles that diesel engines emit. Fig 22 provides a simple illustration of how climate change and air pollution policies can interact. 7.2 Different pollutants – different behaviours and effects The public health implications of many different emissions to the atmosphere are considered throughout this report. However, pollutants often differ markedly in their behaviour when introduced to the atmosphere. This is important for whether and how they impact on health and wellbeing and for the types of policy that are required to address the threats. When we think about air pollution in our towns and cities, we naturally focus on local pollutant concentrations and sources, such as busy roads or factories. These are important for people who live and work in the vicinity. However, the challenge from air pollutants assumes different characteristics when they are transported and transformed into secondary pollutants (such as O 3 and secondary particles) during dispersal in the atmosphere, perhaps 94 © Royal College of Physicians 2016

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