Air pollution is a serious public health issue. Ninety percent of the world’s population now lives in areas where air quality is considered to be below World Health Organization (WHO) standards (1). This amounts to an average nine-month reduction in life expectancy, worldwide.
Studies are now indicating that air pollution can be linked to a whole range of health issues beyond respiratory diseases. There is also a growing body of evidence linking poor air quality to reduced crop production (2, 3).
Although it is still challenging to gauge the full extent of the consequences of air pollution, governments around the world are starting to recognize the seriousness of this problem, introducing measures to curb pollution.
The UK government, for example, has asked several cities, including London, to introduce clean air zones, and the US Environmental Protection Agency (EPA) has set continuingly stricter national standards for particulate matter levels since 1971 (4).
China is a notable example of the air quality challenge. It is a country where rapid industrialization has resulted in serious pollution problems (5). The Air Pollution Action Plan, which China introduced in 2013, has already been successful in improving air quality in some parts of China and was recently updated in 2018 to include more cities.
However, considerable progress is still needed, and PM2.5 particles (those ≤2.5 µm) are of particular concern, not just in respiratory health but in a wider context.