SIMPLE ECONOMICS:

Here is just a partial list of the things, short of death rates, we know are affected by air pollution. GDP, with a 10 per cent increase in pollution reducing output by almost a full percentage point, according to an OECD report last year. Cognitive performance, with a study showing that cutting Chinese pollution to the standards required in the US would improve the average student's ranking in verbal tests by 26 per cent and in maths by 13 per cent. In Los Angeles, after $700 air purifiers were installed in schools, student performance improved almost as much as it would if class sizes were reduced by a third. Heart disease is more common in polluted air, as are many types of cancer, and acute and chronic respiratory diseases like asthma, and strokes. The incidence of Alzheimer's can triple: in Choked, Beth Gardiner cites a study which found early markers of Alzheimer's in 40 per cent of autopsies conducted on those in high-pollution areas and in none of those outside them. Rates of other sorts of dementia increase too, as does Parkinson's. Air pollution has also been linked to mental illness of all kinds - with a recent paper in the British Journal of Psychiatry showing that even small increases in local pollution raise the need for treatment by a third and for hospitalisation by a fifth - and to worse memory, attention and vocabulary, as well as ADHD and autism spectrum disorders. Pollution has been shown to damage the development of neurons in the brain, and proximity to a coal plant can deform a baby's DNA in the womb. It even accelerates the degeneration of the eyesight.

A high pollution level in the year a baby is born has been shown to result in reduced earnings and labour force participation at the age of thirty. The relationship of pollution to premature births and low birth weight is so strong that the introduction of the automatic toll system E-ZPass in American cities reduced both problems in areas close to toll plazas (by 10.8 per cent and 11.8 per cent respectively), by cutting down on the exhaust expelled when cars have to queue. Extremely premature births, another study found, were 80 per cent more likely when mothers lived in areas of heavy traffic. Women breathing exhaust fumes during pregnancy gave birth to children with higher rates of paediatric leukaemia, kidney cancer, eye tumours and malignancies in the ovaries and testes. Infant death rates increased in line with pollution levels, as did heart malformations. And those breathing dirtier air in childhood exhibited significantly higher rates of self-harm in adulthood, with an increase of just five micrograms of small particulates a day associated, in 1.4 million people in Denmark, with a 42 per cent rise in violence towards oneself. Depression in teenagers quadruples; suicide becomes more common too.

Stock market returns are lower on days with higher air pollution, a study found this year. Surgical outcomes are worse. Crime goes up with increased particulate concentrations, especially violent crime: a 10 per cent reduction in pollution, researchers at Colorado State University found, could reduce the cost of crime in the US by $1.4 billion a year. When there's more smog in the air, chess players make more mistakes, and bigger ones. Politicians speak more simplistically, and baseball umpires make more bad calls.

In 2019, a comprehensive global review by the Forum of International Respiratory Societies found that air pollution damages every organ, indeed virtually every cell, in the body. Nanoparticles of pollution have been found inside the brainstems of even the very young. But you don't have to wait until birth to see the effects of breathing particulate matter. The impact begins in the womb, damaging the development of lungs and shortening future lives. In 2019, a small-scale study at Hasselt University found particles of black carbon in every single placenta examined, including those from mothers who lived in areas where the air was thought to be clean, with thousands of particles found in every cubic millimetre. For those who worry about microplastics in the flesh of fish, this is a yet more invasive category of intrusion. Of course, there are also microplastics in the air. They've been found in placentas too.

That​ everything is worse in the presence of pollution means that everything should be better in its absence. And, as best we can tell, it is. According to the National Resources Defence Council, the US Clean Air Act of 1970 is still saving 370,000 American lives every year - more than would have been saved last year had the pandemic never arrived. According to the NRDC, a single piece of legislation delivers annual economic benefits of more than $3 trillion, 32 times the cost of enacting it - benefits distributed disproportionately to the poor and marginalised.

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