World’s major cities plagued by toxic air

PARIS: Big cities beset with gridlocked traffic, major regions producing coal, pockets of heavy industry encased by mountains — Europe’s air pollution hotspots are clearly visible from space on most sunny weekdays.

All across the continent, tens of millions of people live and work in areas where average air pollution levels are well above the maximum limits recommended by the World Health Organisation.

But the density and type of pollutants vary from town to town, and sometimes from block to block, depending on whether one is next to an expressway or inside an urban island of leafy green.

That variability makes it nearly impossible to say with accuracy which of Europe’s cities have the most befouled air.

But it is possible to pick out hotspot regions, and rank urban areas by type of pollutant.

On maps prepared by the European Environment Agency, Italy’s Po Valley is covered with a wide, stain-like blotch of air pollution from the Ligurian Sea in the west to the Adriatic, held in place by the towering Alps to the north.

Many cities in the valley have among Europe’s highest concentrations of dangerous microscopic particles less than 2.5 microns in diameter, known as PM2.5.

The WHO says these should not exceed, on average, 10 microgrammes per cubic metre of air (10 mcg/m3) per year.

European Union standards are more lenient at 25 mcg/m3, and still several countries regularly overstep this red line.

PM2.5 is a top cause of premature deaths in the EU, some 391,000 in 2016 — 60,000 in Italy alone.

Turin and Milan, meanwhile, are also plagued by high levels of ozone and nitrogen oxides, produced mainly by petrol — and diesel-burning engines.