Bad air worse than bad genes for many diseases

The choking blanket of smog that layered Beijing in 2013 was so bad they had to invent a new word for it: “airpocalypse”. But anyone who has spluttered through the vehicle exhaust, construction dust, power plant emissions and crop stubble smoke that regularly cloak Hong Kong, Delhi or Hanoi will know the Chinese capital has no monopoly on bad air.

And the risks go beyond mere discomfort.

Air pollution causes spikes in heart attacks and stroke, triggers hospital admissions for asthma, upsets diabetes control and, for good measure, is a class one carcinogen known to cause lung cancer.

Genetics contributes to each of these, but research led by Philip Awadalla, from the Ontario Institute for Cancer Research in Toronto, Canada, suggests the disease risk from air pollution may have more to do with the genetic changes conferred by those aerial nasties than with the genes your mum and dad gave you.

The researchers analysed the genomes of more than 1000 residents of Montréal, Québec City and Saguenay, cities of Canada’s largest province, the predominantly French-speaking Québec.

The roots of those Québécois were traced back, from their genetic fingerprints, to either French-Canadian ancestry – French settlers who colonised the region prior to the British Conquest of 1759 – or to European bloodlines.

The authors then gathered data on the common air pollutants nitrogen dioxide, sulphur dioxide and ozone, all gases, and particulate matter – solid specks less than 2.5 microns in diameter that, when inhaled, travel to the lung’s deepest recesses.

Participants were also screened for a range of health outcomes, including the stiffness of large blood vessels, which predicts risk of cardiovascular disease, asthma and stroke, liver and lung function, cholesterol levels and white blood cell count.

The results may give pause to enthusiasts of our ever-quickening race to urbanisation.{%recommended 5054%}

Illness was linked much more to air pollution than to ancestry, such that the researchers were able to draw a north-south disease gradient, where sickness increased with population density as you pass south from Saguenay (population, 150,000) to the metropolis of Montréal (1.8 million).

Of all the pollutants, however, sulphur dioxide appears to be the bad boy.

The gas, which smells like a just-struck match and comes mostly from coal-fired power plants, was linked to changes affecting 170 genes that made asthma and cardiovascular disease worse.

In fact, the gas had more of an effect on those outcomes than did smoking, socioeconomic disadvantage, or issues affecting green space and footpaths, suggesting that, as harmful environmental variables go, sulphur dioxide is true royalty.

The findings, which appear in the journal Nature Communications, complement recent research showing air pollution triggers genetic changes linked to chronic obstructive lung disease and lung inflammation. They also raise concerns for visitors to polluted cities about how best to protect themselves.

A well-fitted “N95” air pollution mask is likely to be part of the solution. But prevention is often the best medicine, so it is hard to avoid a discussion of energy mix as a source of pollutants.

On that score, and to misquote a famous Australian politician, there seems a reasonable case that coal may not, at least on certain specific indicators of disease, be good for humanity.

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