Half of the world's population is exposed to increasing air pollution, new research has shown.

A team of researchers, led by Professor Gavin Shaddick at the University of Exeter, has shown that, despite global efforts to improve air quality, vast swathes of the world's population are experiencing increased levels of air pollution.

The study, carried out with the World Health Organisation, suggests that air pollution constitutes a major, and in many areas increasing, threat to public health.

Prof. Shaddick said: "While long-term policies to reduce air pollution have been shown to be effective in many regions, notably in Europe and the United States, there are still regions that have dangerously high levels of air pollution, some as much as five times greater than World Health Organisation guidelines, and in some countries air pollution is still increasing".

The World Health Organisation has estimated that more than four million deaths annually can be attributed to outdoor air pollution.

Major sources of fine particulate matter air pollution include the inefficient use of energy by households, industry, the agriculture and transport sectors, and coal-fired power plants.

In some regions, sand and desert dust, waste burning and deforestation are additional sources of air pollution.

For the study, the research team examined trends in global air quality between 2010 and 2016, against a backdrop of global efforts to reduce air pollution, both through short and long term policies.

How is the air quality in your area? Should more be done to address air pollution?