Vehicles move on a road in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)

People walk on a bridge in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)

A passenger train moves through a market in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)

A man rides a bicycle on a road in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)

Vehicles move on a road in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)

A vehicle moves on a road in dense fog in northwest Pakistan's Peshawar, on Dec. 30, 2019. Dense fog blanketed different cities of Pakistan's Punjab and Khyber Pakhtunkhwa provinces, disrupting air and road traffic. (Photo by Umar Qayyum/Xinhua)