Germany has launched a scheme to retrofit its diesel public buses with exhaust-scrubbing systems, and introduce charging points to encourage drivers to switch to e-cars. Still, environmentalists say that's not enough. They want all diesel vehicles — including private cars — retrofitted, or taken off the road.

Milan, one of Italy's most polluted cities, has banned cars from its downtown area during certain hours. Other cities in Italy and abroad have experimented with similar schemes, for example permitting only cars with odd or even license plates on the road at given times in order to limit the amount of traffic.

The Macedonian capital of Skopje is battling with pollution levels up to 15 higher than permitted by the EU — though it's not yet a member state, so isn't facing fines. Macedonia's smog problem is largely down to burning coal and emissions from aging, inefficient industry and vehicles. To get people to leave their dirty old cars at home, the government has introduced free public transport.

One street in London exceeded the EU's annual nitrogen dioxide limit on January 30 — less than a month into 2018. Actually, this is an improvement — it's the first time in a decade the British capital has kept within the annual limit for more than six days. Mayor of London Sadiq Khan has announced he wants to alert the city's schools on days when pollution is particularly bad.