The Indian city of Mumbai, formerly Bombay, is home to one of Asia's largest slums and endures among the worst air quality on earth. Half the city's population lacks running water or electricity, and the smoke from countless wood-burning cooking fires joins with the acrid haze from two-stroke auto rickshaws, diesel buses, and coal-fired power plants to all but choke the city. Breathing Mumbai's air, reports the Lonely Planet travel guide, is equivalent to smoking 20 cigarettes a day. Comparable air quality wraps New Delhi, Bangalore, and 69 of India's 70 principal cities year-round, according to a 1997 study by India's Central Pollution Control Board.
