Anindya Upadhyay Jessica Shankleman Bloomberg

As New Delhi suffers through a surge in the most harmful type of smog -- a toxic stew that makes India's capital one of the most polluted in the world -- Beijing offers lessons in how another troubled city made progress clearing the air.

As New Delhi suffers through a surge in the most harmful type of smog -- a toxic stew that makes India's capital one of the most polluted in the world -- Beijing offers lessons in how another troubled city made progress clearing the air.