For a region that is the epicentre of crop fire burning, Punjab is exhibiting fairly comfortable levels of air quality index (AQI) while many parts of Delhi NCR, Haryana and Uttar Pradesh are showing elevated air pollution levels.
As par data collated from the Central Pollution Control Board (CPCB) for November 7, cities in Punjab except Jalandhar are all in the satisfactory to moderate category - Amritsar (154), Bathinda (102), Khanna (89), Ludhiana (142), Mandi Gobindgarh (119) and Patiala (66).
Only Jalandhar is in the poor category with AQI count of 217. The joint capital, Chandigarh is at 86 in the satisfactory category of AQI.
These cities are in the vicinity of stubble burning but are showing relatively good AQI counts possibly because the smoke plume is getting a ballast with the wind conditions being northwestern at many times.
Punjab has seen the highest incidence of stubble burning incidents. According to Agriculture Ministry data, there have been 25,366 incidents in the current year, down 8.7 per cent from last year's number of 27,584. Compared to Punjab, such incidents in Haryana are much less, 4,414 in the current year, down from 5,000 last year. In Uttar Pradesh, stubble burning incidents have reduced drastically by 48.2 per cent from 3,133 to 1,622 in the current year.
Vivek Chattopadhyaya, Programme Manager, Air Pollution Control Unit, Centre for Science and Environment (CSE) said: "Due to direction of the wind towards Delhi and stagnation of lower atmosphere, the Indo-Gangetic plane acts as a sink and it coincides with local air pollution and 'parali' burning during winter, therefore air pollution levels rapidly build up. It takes lot of time to clean as atmosphere's capacity to clean itself reduces, as this region is also land locked by Himalaya, Aravali and Vindhya mountain range."
Congress leader Jyotiraditya Scindia said in a recent tweet: "Satellite images suggest that all of Gangetic plains, residing almost half of the population of our country, is locked in a poisonous gas chamber."
Aam Aadmi Party leader Atishi, also in a recent tweet said: "Anyone who thinks smog is a Delhi problem, pls see NASA maps, which show how the smog is spreading in Punjab, Haryana, Delhi, UP, West Bengal and MP. If this is not a national issue, then what is? Is it not time for the Central Govt to solve this yearly national crisis?"
Apart from Delhi, several cities are currently seeing very high air pollution levels. Moradabad in Uttar Pradesh tops the list at AQI of 435 followed by Talcher in Odisha at 413, both falling in the severe air quality zone.
There are many cities falling under the very poor AQI including Patna (338), Sonipat (301), Palwal (310), Muzaffarpur (341), Manesar (328), Lucknow (366), Kanpur (366), Baghpat (352), Panipat (321), Faridabad (312), Ghaziabad (325), Greater Noida (318), and Noida (328). Delhi is also in the same category of AQI.
Pollution may not be just limited to a big city like Delhi with its issues of large population of vehicles and use of diesel generators. There are at least 14 much smaller cities with much higher air pollution than Delhi.
Agriculture burning sources and older vehicles can cause high air pollution in smaller cities.
Sumit Sharma, Director, Earth Science and Climate Change, TERI, said: "There are several reasons which can lead to higher PM2.5 concentrations in smaller cities as well. Proximity to agricultural burning sources, presence of higher share of older vehicles, absence of CNG for automotive, residential, industrial use, burning of waste, and limitations in enforcement and congestion may lead to higher concentration levels in smaller cities.
"Other than these factors, local meteorological factors also influence air pollution levels."
Chattopadhyay of CSE said that cities in north India get affected at the same time.
"Often smaller cities have higher PM levels in air compared to bigger cities, although their respective emission load varies a lot depending upon local sources, although much lower than a city like Delhi," he said.
"Since air pollution is a regional problem all cities in the northern India get affected during the same time. Recently apart from the local sources, crop residue/biomass burning in Punjab, Haryana and UP affects the entire region. For instance in Delhi, biomass burning contribution varies from 2 to about 40 percent but overall much less than 25 percent during the entire winter," he added.