How the world’s biggest cities are fighting smog
For three days in March 2016, 10 London pigeons became famous. Seeing pigeons take to the sky from Primrose Hill in north London was not unusual in itself. But these pigeons were wearing backpacks. And the backpacks were monitoring air pollution. Once in the air, the backpacks sent live air-quality updates via tweets to the smartphones of the Londoners below. In almost all cases, the readings were not good. London’s air pollution problem has been getting worse for years, and it often rises to more than three times the European Union’s legal limit.