New Delhi. India's capital New Delhi on Friday became the world's most polluted city, surpassing Pakistan's Lahore. The air pollution level has reached a dangerous state, and Delhi, with a population of 20 million, is covered in thick smog and haze. Due to pollution, visibility has also reached a low level in various parts of the city.According to IQAir, a Switzerland-based air quality monitoring organization, Delhi's Air Quality Index (AQI) reached 334 on Friday. This is considered a dangerous level for health. Based on this index, Delhi has become the most polluted among the major cities of the world.However, India's...