Air pollution: a dark cloud of filth poisons the world’s cities

The number of annual deaths caused by pollution around the world is now greater than malaria and HIV combined, according to a recent study, with scientists warning that fatalities could reach 6 million a year by 2050

During these cold winter days, Anumita Choudhury dare not leave her small second-floor apartment in Delhi's northern suburbs. Elderly now, she has developed asthma. The last time she ventured into the streets of the world's second most populous city she began gasping for breath and had to be helped home by her neighbours.

The story is the same in many of the world's great cities. From Kabul in Afghanistan to Hong Kong and Shijiazhuang in China, and from Lima to Sio Paulo in Latin America, people are increasingly suffering in severe toxic smogs - leaving hospitals and health clinics flooded with people with respiratory and heart problems.