With cities in India and Pakistan ranking among the world's most polluted, new technologies must be adopted to tackle dangerous levels of winter smog, environmentalists urge.

With cities in India and Pakistan ranking among the world’s most polluted, new technologies must be adopted to tackle dangerous levels of winter smog, environmentalists urge.

According to the Swiss IQ Air index, Lahore in Pakistan and Delhi in India have the highest levels of fine particulate matter in the air, known as PM2.5, of any city—the only two to be rated as “hazardous.”

Lahore, the provincial capital of Punjab, tops the index, with pollution reaching levels ten times higher than those in Shanghai early this week. The pollution is so bad that the huge gray clouds blanketing the region can be seen from space as satellite imagery from NASA Worldview shows.