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Winter inter smog: Not just a Delhi-NCR problem, says CSE

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New analysis finds winter smog envelopes whole of northern India; pollution levels in otherwise cleaner small towns match or exceed the levels reported in Delhi-NCR

Winter smog and the accompanying severe air pollution is a problem that is usually associated with the Delhi-NCR region – but a latest analysis by Centre for Science and Environment (CSE) has found that when pollution spikes during winter, entire northern India experiences smog episodes.

“This analysis has put a spotlight on the cities of Punjab, Haryana, Uttar Pradesh, Rajasthan, Delhi and NCR to understand the synchronised pattern of pollution during winter when atmospheric changes entrap pollution across the region. This shows even smaller cities with lower annual average levels, record pollution levels that are as bad or even worse than Delhi. This demands action at scale and speed across all key sectors of pollution in the larger region,” says Anumita Roychowdhury, executive director, research and advocacy, CSE.

“This analysis has covered 137 continuous ambient air quality monitoring stations (CAAQMS) spread across 56 cities in the six states. Even though air quality monitoring is limited and data for a large part of the northern India is underreported, available evidence clearly points to the magnitude of the regional problem,” says Avikal Somvanshi, programme manager, Urban Lab, CSE.   

Analysis methodology

This analysis, a part of the air quality tracker initiative of the Urban Data Analytics Lab of CSE, is based on real-time data available from the current working air quality monitoring stations in north India. A huge volume of data points have been cleaned and data gaps have been addressed based on the USEPA (United States Environmental Protection Agency) method. Meteorological data for the analysis is sourced from the Palam weather station of the India Meteorological Department (IMD). Fire count data is from NASA’s Fire Information for Resource Management System, specifically the Visible Infrared Imaging Radiometer Suite (VIIRS). Estimates of contribution of farm stubble fire smoke to Delhi’s air quality is sourced from the Union Ministry of Earth Science’s System of Air Quality and Weather Forecasting and Research (SAFAR).

For the purposes of this analysis, the northern region has been divided into five sub-regions. These include Punjab and Chandigarh, NCR (includes Delhi and 26 other cities/towns that fall within NCR), Haryana (excluding cities already included in NCR), Uttar Pradesh (excluding cities in NCR), and Rajasthan (excluding cities in NCR). This is an assessment of annual and seasonal trends in PM2.5 concentration for the period January 1, 2019 to November 30, 2021. Says Somvanshi: “This helps us understand the pollution profile across the northern states and locates Delhi within the larger context of north India related to seasonal variations and annual trends in particulate pollution.”

Seasonal and annual pollution patterns in key cities of north India

During smog episodes, pollution levels in smaller towns that are otherwise cleaner exceed the levels reported in Delhi: Most smaller towns have considerably lower annual average PM2.5 levels — but during early winter when the smog engulfs the entire region and farm stubble fires spike it further, smaller towns report levels comparable to Delhi. For instance, cities like Vrindavan, Agra and Firozabad have comparatively lower annual average PM2.5 than Delhi. But during the early winter of 2021, their weekly average PM2.5 levels exceeded that of Delhi. While the annual average level of Delhi is 97 microgramme per cubic metre (ug/m3), that of Agra is 78 ug/m3 — 20 per cent lower. But during early winter this year, the weekly average PM2.5 level in Agra was 282 ug/mand exceeded by 5 per cent that of Delhi (which stood at ug/m3). Similarly, weekly average of Vrindavan has been ug/mand that of Firozabad, ug/m3. Ghaziabad and Noida had the worst weekly averages this winter.   

Early winter smog is synchronised across the region, but lasts longer in Delhi-NCR: Normally, the smog episodes of November synchronise across the northern region. But they linger longer only in Delhi, NCR and Uttar Pradesh during rest of the winter. Atmospheric changes during winter that lead to inversion, calm conditions, change in wind direction, and seasonal drop in ambient temperature entraps pollution across north India. This is further tripped into severe category by smoke from farm fires and Diwali firecrackers during November.

Air quality improves from ‘severe’ to ‘poor’ and ‘moderate’ categories in cities of Punjab and north Haryana after the stubble fire season, but it remains in the ‘very poor’ category in NCR and UP till February. In fact, air quality in these two sub-regions do not clean up to satisfactory levels until the arrival of monsoon. Rajasthan cities also show an impact of the smoke but to a lesser degree, with relatively less polluted air during rest of the winter.  

Number of days with air quality in ‘very poor’ and ‘severe’ categories is significantly higher in cities of NCR and UP: Delhi and NCR cities lead the chart for the most ‘severe’ days in 2021. Ghaziabad topped the list, recording 108 days of ‘very poor’ and ‘severe’ air quality until November. Delhi recorded 94 days with ‘very poor’ or ‘severe’ air quality this year until the end of November. Faridabad and Gurugram recorded 75 days and 73 days of ‘very poor’ and ‘severe’ days, respectively. UP cities outside NCR including Kanpur recorded 73 days of ‘very poor’ and ‘severe’ levels; Lucknow had 68 days; and Agra, 57 days. They are not much behind Delhi-NCR.  Even in larger Haryana, a small city like Hisar has recorded 74 days of ‘very poor’ and ‘severe’ air quality in 2021 so far. However, if all the months and seasons (from January to November) is considered for the year 2021, the 24-hour standard for PM2.5 has been met in most cities in the region for more than half of the year (recorded mostly during monsoon and summer). Cities in the arid regions of Rajasthan, Haryana and Punjab have — on an average — recorded lesser days with good air quality compared to cities in the plains of UP. Chandigarh and Punjab cities have the most numbers of satisfactory and good air quality days.

Delhi-NCR and cities of Uttar Pradesh are more vulnerable to the pollution build-up: While the whole of north India is vulnerable to the pollution build-up, the overall annual average of Delhi and NCR is among the highest in the region. Also, the average of the urban concentration in UP outside NCR is 8 per cent higher than in NCR (includes Delhi and 26 other cities/towns that fall in NCR). Delhi has lower annual average than several cities of UP. This year (2021), Ghaziabad has been the most polluted city in the region with the average of 2021 going as high as 110 ug/m(up till November 30). Moradabad is the most polluted city outside NCR with a PM2.5 level of 96 ug/m3.

Haryana (excluding NCR sub-region) was the third most polluted state with a PM2.5 average of 62 ug/m— Yamuna Nagar was its most polluted city, with an annual average of 86 ug/m3. Rajasthan, with an average of 57 ug/m3, was lower than others. Jodhpur has been the dirtiest city in the state with a PM2.5 level of 74 ug/m3 during early winter of 2021. Punjab, which is the hotbed of farm stubble burning, has the lowest sub-regional PM2.5 level of 48 ug/m3. Mandi Govindgarh was the most polluted city in the state with PM2.5 level at 62 ug/m3. Chandigarh with PM2.5 level of 37 ug/mwas the cleanest city in whole of north India. Bhatinda, Panchkula, Palwal, Varanasi and Ajmer were comparatively the least polluted cities in their respective sub-regions. Average PM2.5 levels in 2021 (up till November 30) has already crossed the regional 2019 annual average in Punjab and Rajasthan, indicating worsening of air beyond pre-covid levels in these two states.

Longer term trends in urban concentration of PM2.5 in most cities of northern states is downward, though high: Based on the data available for the limited number of cities in north India, it is possible to construct a trend in urban air quality in Delhi-NCR, UP, Haryana, Punjab and Rajasthan. This points to a declining and stabilised trend, though the annual average levels are still way above the national ambient air quality standard for PM2.5 in most monitored cities of the sub-regions. The high annual average levels also explain why pollution build-up is so high during winter.

Advantage of prolonged monsoon lost quickly with the onset of winter: PM2.5 rose by 2.4-5.4 times from a clean monsoon level in November among the sub-regions. Air quality deteriorated the most in UP, where PM2.5 level rose by 5.4 times from the monsoon average of 28 ug/mto reach 151 ug/m3 in the month of November. The NCR, with a November average of 179 ug/m3, was the most polluted sub-region. Air quality deteriorated by 3.6 times in Haryana, 2.8 times in Punjab and 2.4 times in Rajasthan between monsoon and November. During November, Ghaziabad (271 ug/m3) in NCR was the most polluted in the region. Patiala (109 ug/m3) in Punjab, Hisar (220 ug/m3) in Haryana, Vrindavan (185 ug/m3) in UP and Kota (121 ug/m3) in Rajasthan were the most polluted cities in each of the sub-regions. Chandigarh was the least polluted city in the region with a November average of 45 ug/m3

Industrial towns remain vulnerable throughout the year, even during monsoon: The heavy and prolonged monsoon this year brought down PM2.5 levels substantially across the region. The overall concentration in UP cities (outside NCR) registered the lowest sub-regional level at 28 ug/m3 followed by Punjab at 32 ug/m3. NCR, Haryana and Rajasthan had 38 ug/m3 each. Even though the monsoon reduced overall pollution in the region, the levels in industrial cities were comparatively higher than other cities during monsoon. Mandi Govindgarh (43 ug/m3) in Punjab, Yamuna Nagar (52 ug/m3) in Haryana, Bhiwadi (57 ug/m3) in NCR, Moradabad (53 ug/m3) in UP, and Jodhpur (51 ug/m3) in Rajasthan had levels higher than the state averages.

Problem of farm fire remains obstinate: Farm fires are one of the biggest episodic events during winter. Two levels of analysis have been carried out – the daily trend in fire count and the trend in average Fire Radiative Power (FRP) reported by NASA satellites. FRP is the rate of emitted radiative energy by the fire at the time of observation that is reported in MW (megawatts). FRP is considered a better measure of emissions from bio-mass burning as intensity of FRP indicates the quantum of biomass burned. This has bearing on emissions and intensity of smoke and pollution. This year, Punjab has noted the maximum number of fires with a combined count of 76,518 during October and November. Haryana recorded 11,015 incidences, UP 5,187, Rajasthan 2,466 and Delhi 52. But the average FRP of fire incidences in Punjab during October-November 2021 stood at 7.9 MW — highest in the region; Rajasthan was 6.3 MW; Haryana 5.5 MW; UP 3.6 MW; and Delhi, 1.3 MW. Not only has the overall fire count in Punjab been high, but also the quantum of the biomass burnt.

Long-term trend shows that average FRP in Punjab has been increasing since 2017 and this season’s average is highest since monitoring started in 2012. This, coupled with overall increase in fire count in Punjab, may have also contributed to the increased severity of smog this year. Both fire count and average FRP have been declining in Haryana since 2016; but this year, doubling of fire count with minor increase in FRP as well has been noted. The fire count in UP and Rajasthan are insignificant compared to Punjab and Haryana. But both have reported three-fold more instances of fire during summer compared to winter. However, in summer, meteorological conditions allow more efficient pollution dispersion.

Nitrogen dioxide (NO2) levels rise two-fold during November indicating impact of vehicles and industry: There is a significant increase in amount of NO2 in air during November compared to October and September. NO2 comes entirely from combustion sources and significantly, from vehicles. UP cities (outside NCR) have registered 3.7 times increase in NO2 levels between September and November. NCR cities saw a two-fold rise; Punjab and Rajasthan cities had a 2.5 times increase; while Haryana cities witnessed a 2.8 times jump.

Diwali continues to be a mega pollution event: Despite the restrictions on bursting firecrackers, Diwali night still got extremely toxic (see the full analysis for details).

Individual cities of the north need substantial cuts to meet clean air standards: Amritsar, Jalandhar and Patiala need to cut their annual average PM2.5 by at least 15-20 per cent; Ambala by 31 per cent; Hisar, Lucknow, Kanpur and Agra by at least 50 per cent; Varanasi by 35 per cent; and Jaipur and Jodhpur by 25 and 45 per cent, respectively. Only Chandigarh meets the standards.

The way forward

Says Roychowdhury: “The stark evidence from the northern region underscores the urgent need for harmonised action in all states to ensure access to clean fuels and technology in industry and power plants, massive scaling up of public transport, walking and cycling infrastructure and enhanced municipal services for complete segregation of waste and recycling. This requires committed funding and a compliance framework.”

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