LAHORE: On Friday morning, heavy fog swapped the areas of Punjab and Khyber Pakhtunkhwa (KP) causing zero visibility at various sections of the motorway. The motorway across various locations was closed due to the visibility problem. According to a spokesperson for the motorway police, M-I from Peshawar to Swabi, M-III from Samundri to Darkhana, M-IV from Abdul Hakeem to Shorkot, M-V from Sher Shah Interchange to Rukanpur, and Swat Motorway from Karnal Sher Khan Interchange to Katlang were closed after fog restricted visibility to zero. After smog disturbing life in Lahore and other parts of Punjab with changing weather conditions, fog has made it difficult to travel in plains owing to visibility issue, which also causes several mishaps during road journey. It is to be mentioned here that brief exposure to smog causes a variety of ailments from minor pains to deadly pulmonary pneumonia and asthma diseases. The smoke produced by automobiles and stubble burning in agricultural areas converts into smog during the month of November with falling temperature. It normally persists when the mean temperature remains in the range of 19-21 degrees Celsius, according to the weather department.