Here’s why air pollution affects mental health

Air pollution has affected humankind since the beginning of civilisation. Paleopathological studies have shown the presence of carbon deposits and other pollutants in the lung of Egyptian mummies.

Following the industrial revolution, air pollution became a visible presence in urban areas, where the combination of domestic and industrial coal burning caused thick and vast smog which provided inspiration for writers and painters of the time. London’s toxic air was a particular fascination to Charles Dickens, who often referred to it as a metaphor of the city’s moral slide into decadence caused by greed and corruption.

Unlike the visible smog of Victorian London, modern pollution that can be found in today’s cities is made of fine particular matter and gases such as sulfur oxides, nitrogen oxides, carbon monoxide – all of which are indiscernible at ground level.

The detrimental effects of air pollution on physical health have long been recognised. In 1952 air pollution in London reached breaking point due to cold stagnant weather conditions that trapped coal burning emissions at ground level for several days. This caused an enormous increase in respiratory and cardiovascular complications, and an estimated 4,000-12,000 deaths.

This public health disaster – which came to be known as London’s Great Smog – led to a set of policies aimed at reducing air pollution. For example, the Clear Air Act (1956) introduced smoke-free areas in which only smokeless fuels could be burned, leading to considerable reductions in respiratory and cardiovascular disease across the city.

In contrast the detrimental impact of air pollution on mental health is a more recent discovery. Since the turn of the century, several studies have reported associations between air pollution and psychiatric disorders. For example, a recent investigation found that the risk of developing depression – the most prevalent mental disorder in the world characterised by with low mood and feeling helpless – is 50 per cent higher in people exposed to greater levels of air pollution. The risk of developing bipolar disorder – where people swing between feeling low and lethargic and feeling very high and hyperactive – is 29 per cent higher.

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