When the Covid-19 pandemic forced global lockdowns earlier this year, one positive – if temporary – upside was a reduction in outdoor air pollution.
Between early March and early May 2020, Airthings, a Norway-based manufacturer of smart air-quality monitors, analysed data of their users in the US and Europe and found levels of carbon dioxide and airborne particles called volatile organic compounds (VOCs) increased by 15 to 30% in more than 1,000 homes across several European countries.
Similarly, data collected by Dyson of its registered air purifiers in 11 cities over four continents, found levels of VOCs and nitrogen dioxide (NO2) had risen in people’s homes since lockdown.
"We spend 90% of our time indoors in developed countries, and yet all the focus, when it comes to pollution, is on the 10% of our time that we spend outdoors," says Nicola Carslaw, a professor of indoor air chemistry at the University of York.