Air pollution is deadly – in fact a recent study found that, on average, it cuts human lifespans by three years, which is higher than the global effect on lifespan caused by smoking. Yet the coronavirus pandemic and subsequent lockdowns enforced by governments across the world has led to cleaner air in many places. We've looked at the 15 most and 15 least polluted countries in the world according to the 2019 World Air Quality Report produced by air pollution tracking organization IQAir. We've quoted the figures they collated on the concentration of harmful PM2.5 particles in micrograms per cubic meter (µg/m³), with a higher number denoting a higher level of pollution. But we've also examined how the current global situation may have reduced these figures, using both current IQAir pollution data and reports. Click or scroll through to find out more on the countries with the dirtiest and cleanest air then and now.