Pakistani mothers walk with their children toward school alongside a road amid heavy fog and smog conditions in Lahore on January 17, 2019. - Smog levels spike during winter in southern Pakistan, when air quality often eclipses the World Health Organization's safe levels. Cooler air traps pollutants -- such as from vehicles, building sites and farmers burning crops in regions outside the Indian capital -- close to the ground. (Photo by ARIF ALI / AFP)