New Delhi's air quality deteriorates in winter, when cooler air traps pollutants close to the ground. (EPA Images pic)NEW DELHI: India began annual measures on Thursday to tackle toxic air pollution in New Delhi, a megacity of 30 million people regularly ranked among the world's most polluted capitals.

Delhi's air quality deteriorates in winter, when cooler air traps pollutants close to the ground.

Major sources include coal-fired power plants, traffic, construction and farm stubble burning in neighbouring areas.

The Delhi government on Wednesday announced a ban on open rubbish burning and ordered food stalls to stop using coal or firewood.