Unprecedented air pollution in the Pakistani city of Lahore has forced authorities to close all primary schools for a week. From Monday, 50% of office workers will also work from home, as part of a "green lockdown" plan. Other measures include bans on engine-powered rickshaws and vendors that barbecue without filters. "This smog is very harmful for children, masks should be mandatory in schools," Punjab Senior Minister Marriyum Aurangzeb said. Lahore, Pakistan's second-largest city, topped the world list of cities with the most polluted air for a second time on Sunday.