BENGALURU, India (AP) — For people across South Asia, especially in northern India, Diwali celebrations coincide with the return of hazardous winter air, raising concerns about how to celebrate safely. Winter also brings severe smog to parts of Pakistan and China, where warmer air can act as a lid, trapping colder air and pollution near the ground. In eastern Europe, burning coal and wood to heat homes also adds to winter pollution. Western Hemisphere countries, meanwhile, face their own as...