Introduction

The 350-400 cubic feet of air an adult breathes every day has already been exhaled by countless others, including non-humans. Air is therefore a tangible reminder of our delicate interdependencies. What we breathe depends intimately on what others do and do not do. Much the same is true of water. People have been able to survive for two weeks without food, but without water you will probably die within days. And all water is recycled, passing through organic systems (and certain organs, let's admit it) that we tend not to think about closely.

Air pollutants are different to carbon emissions, that is, GHGs such as CO2. The five main air pollutants are ‘particulate matter’ (also called ‘particulates’, which can be up to 30 times thinner than the width of a human hair), carbon monoxide, nitrogen dioxide, ground-level ozone and sulphur dioxide:

In developed nations air quality standards have generally been improving over the very decades when carbon emissions have been increasing. According to Defra's (2013) statistics for 1987–2012, ‘urban background’ and roadside particulate pollution have shown long-term improvement, although they remained stable after 2008. From 1990 to 2010, emissions of sulphur dioxide fell by 89 per cent and emissions of nitrogen oxides by 62 per cent. (Urban background ozone pollution has shown a long-term increase, however.) Defra attributes such improvements to the move away from coal to gas in electricity generation, and to the introduction of emission standards for vehicles. Nevertheless, the UK still has one of the worst records in Europe, and in 2013 it was reported that air quality laws would be breached in 15 regions until 2020, with Londoners having to wait until 2025 for pollution to enter legal limits.

Climate change and air pollutants are linked, as we shall see shortly, but while the former can sound abstruse to many people, air pollution has a more immediate, visceral recognition.