Every resident of London is breathing air that contains dangerous pollutants in concentrations at or above World Health Organisation (WHO) guidelines, it has been revealed.

In most parts of the capital, except some areas of the periphery, levels of fine particulates known as PM2.5 exceed the WHO limit of 10 micrograms (μg) per cubic metre of air by at least half, according to research by the Greater London Authority (GLA).

It means about 94 per cent of Londoners are breathing air that contains an annual average of at least 15μg/m3 of the particulates, the GLA found. But all parts of the city are blanketed by air carrying 10μg/m3 or more.

Sources of PM2.5 include natural dust and ash, domestic fuel burning, and soot produced by the combustion engines of vehicles.

Exposure to air pollution is thought to contribute to tens of thousands of premature deaths every year in the UK. In addition, children who grow up breathing high levels of the tiny PM2.5 particles are more likely to develop asthma and and suffer reduced lung function.

London mayor Sadiq Khan called the GLA’s research “another damning indictment of London’s toxic air”.

Among Mr Khan’s plans to improve London’s air quality are a toxicity charge on polluting vehicles, to be introduced later this month, and an ultra-low emission zone from 2019.