Punjab on Tuesday badly hit by smog as Lahore reached to the top of the cities having worst air quality on Tuesday.
New Delhi remained the second most polluted city, while Lahore remained on top on the Air Quality Index in the world.
Mangolias Ulan Bator remained third on the AQI, Kolkata fourth and Dhaka on fifth position with regard to air pollution.
Bangladeshs Dhaka remained fifth most polluted city, Nepals Kathmandu 7th and Karachi 8th on the Index with worst air quality.
According to the reports of international media and a study of the United States National Aeronautics and Space Administration (NASA), burning of crop residue and garbage in northern Indian states causes dangerous hike in environmental pollution in the region.
According to experts, hike in air pollution used to be recorded in the winter. A change in the wind speed, wind direction and sliding minimum temperature increases air pollution.
The air becomes heavier in the winter as compared to summer, causing poisonous particles in the atmosphere to move downwards and making the atmosphere polluted. As a result, a layer of polluted particles, including large amounts of carbon and smoke, covers a city.
The smoke produced by burning crop remnants, factories and burning coal, garbage, oil or tyres enters the atmosphere and the effects of this appear at the onset of winter and remain till the seasons end, experts said.
Thus, air pollution reaches to extremely dangerous levels, severely compromising the air quality.
The AQI is calculated based on five categories of pollution: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.