In early January, a toxic cloud of smog settled over Beijing. For nearly a week, it wreathed the city in a choking, yellow haze.
Levels of PM2.5 — microscopic particles that can be absorbed into the lungs and bloodstream endangering human health — peaked at well over 600, more than 20 times the level of daily exposure considered acceptable by the World Health Organization.
Despite the almost apocalyptic conditions, life went on. People practiced tai chi in city parks. Commuters biked to work. Children went to school and played outside. Few wore masks.