Every November, Lahore wakes up to the same grey sky. Cars drive with headlights on at noon and almost every house has someone coughing. Most people call it دھند, the winter fog. However, what fills the air in Punjab each winter is something far more harmful. The smog meaning in Urdu is سموگ, and it is described as دھوئیں اور دھند بھری فضا, air filled with smoke and fog. Smog is a thick layer of smoke, dust and toxic gases that mixes with fog and stays close to the ground. This guide explains what smog is, why it forms, how…