Delhi shuts schools, halts construction to tackle pollution

India's capital announced a slew of measures Sunday to combat the crippling air pollution that has engulfed the city, including closing down schools, halting construction and ordering that all roads be doused with water to settle dust.

New Delhi, one of the world's dirtiest cities, saw levels of PM2.5 — tiny particulate matter that can clog lungs — soar to over 900 micrograms per cubic meter on Saturday. That's more than 90 times the level considered safe by the World Health Organization and 15 times the Indian government's norms. The severe weekend pollution followed a week of constant gray smog.

Study: Air pollution kills 3.3 million worldwide, may double

Air pollution is killing 3.3 million people a year worldwide, according to a new study that includes this surprise: Farming plays a large role in smog and soot deaths in industrial nations.

Scientists in Germany, Cyprus, Saudi Arabia and Harvard University calculated the most detailed estimates yet of the toll of air pollution, looking at what caused it. The study also projects that if trends don't change, the yearly death total will double to about 6.6 million a year by 2050.