The Covid-19 pandemic continues to dominate headlines with distressing messages about the negative effects on health and the economy. But sometimes a positive message creeps through.

The long months of lockdown and reduced economic activity have reduced emissions of greenhouse gases and air pollutants. In many areas, improved air quality has been hailed as a key side benefit of the crisis.

But as economic activity picks up again, are lower pollution levels really the silver lining of the Covid pandemic?