CSE analyses air quality in cities of south India, finds pollution levels rising post-lockdown

  • CSE analysis of air pollution in regional cities focuses on the states of Karnataka, Tamil Nadu, Andhra Pradesh, Telangana and Kerala
  • Finds that while particulate concentration reduced during lockdown, it spiked with the onset of winter
  • While several bigger cities witnessed a reduction in annual trends in PM2.5, smaller towns and cities have experienced an increase – this reflects the trend in local and regional build-up of pollution
  • Average December PM2.5 level considerably higher in inland cities compared to coastal cities this year
  • Air quality gets more toxic with the onset of winter -- share of tinier PM2.5 in the PM10 particles increases
  • Recent Lancet study (Health and economic impact of air pollution in the states of India: the global burden pf disease study, 2019) shows among southern states, Karnataka has the highest total burden of health costs
  • No room for complacency about relatively lower levels in the southern states compared to India’s northern states, says CSE
  • This reaffirms why air quality management requires regional approach to implement clean air action plans with speed, scale and urgency 

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New Delhi, February 2, 2021: New analysis of winter pollution (until January 26, 2021) in India’s five southern states, done by Centre for Science and Environment (CSE) shows how clean air gains of the lockdown and monsoon periods have been now lost with the reopening of the economy and with the onset of the winter. Even though atmospheric conditions during winter in the south is not the same as that in the Indo-Gangetic Plains in the northern region, trapping of winter pollution is quite high -- especially in inland cities. 

Higher PM2.5 levels is a typical and predictable winter trend when continuous emissions from local sources including vehicles, industry, and construction get trapped due to meteorological changes. A combination of the reopening of the economy and changing meteorology is responsible for high winter pollution levels. 

Says Anumita Roychowdhury, CSE’s executive director in charge of research and advocacy: “This analysis has dispelled the myth about safer air in the south compared to other regions. Health impacts are nearly equally bad. Complacency cannot slow down action. Despite the dramatic reduction in air pollution during the lockdown, pollution has bounced back across the region post-lockdown unmasking the high impacts of local and regional pollution. This demands quicker regional reforms to curb pollution from vehicles, industry, power plants and waste burning to further bend the air pollution curve on a regional scale. This demands speed and scale of action.”   

CSE’s analysis is part of an air quality tracker initiative which has followed changing patterns of air quality trends in different regions of the country. This seeks to understand the impact of the extraordinary year that has just gone by -- 2020 -- that witnessed one of the biggest disruptions in the recent times. This is also an inflexion point at the onset of the new decade. This addresses basic curiosities around the impact of the lockdown, lowering of the regional influence on local air quality, and deeper seasonal patterns that unmask the underlying high trends despite the lockdown phases. 

After assessing the changing trends in the Indo-Gangetic Plains, Delhi-NCR, Rajasthan, Maharashtra and West Bengal, this analysis now unravels the pattern in cities of southern India – a vulnerable but poorly monitored region from the air quality perspective. 

Avikal Somvanshi, programme manager in CSE’s Urban Lab team of the Sustainable Cities programme, says: “Winter is not as harsh in the southern cities. Therefore, the impact of inversion is expected to be limited -- yet pollution build-up has been noted. Even though the average level of PM2.5 for the summer and monsoon months in 2020 is considerably lower than the previous year due to the summer lockdown, the PM2.5 levels this winter have risen beyond that in 2019 in most of the monitored cities, Chennai and Thiruvananthapuram being the only exceptions. The region cannot rely only on the natural advantage of warmer winters and sea breeze to avoid bad air.” 

This detailed data analysis shows that air pollution is a south Indian problem as well. This requires quicker reforms and action in key sectors of pollution – vehicles, industry, power plants and waste management -- to control winter pollution and further bend the annual air pollution curve. 

Data used in the analysis: The analysis is based on publicly available granular real-time data (15-minute averages) from the Central Pollution Control Board’s (CPCB) official online portal Central Control Room for Air Quality Management. 

Real-time data from 36 cities was accessed, but only 21 cities – Hyderabad, Amaravati, Rajamahendravaram, Tirupati, Visakhapatnam, Bagalkot, Chikkaballapur, Chikkamagaluru, Hubballi, Mysuru, Ramnagara, Vijaypura, Yadgir, Bengaluru, Coimbatore, Chennai, Kannur, Kollam, Kozhikode, Kochi, and Thiruvananthapuram -- have been selected for this analysis, because real-time data is available for these cities for whole of 2020. 

CSE has analysed data recorded by 10 air quality monitoring stations in Bengaluru, eight in Chennai, six in Hyderabad, three in Kochi, two in Thiruvananthapuram, and one station each in rest of the cities under the Continuous Ambient Air Quality Monitoring System (CAAQMS) of CPCB. Weather data for Bengaluru, Chennai, Hyderabad, Thiruvananthapuram, and Visakhapatnam has been sourced from the weather stations of India Meteorological Department (IMD) located at the airports in each city. This air quality trend analysis does not include investigation of local sources of pollution. 

Key highlights 

While several bigger cities have witnessed reduction in annual trends in PM2.5, smaller towns and cities have experienced an increase: Only nine out of the 21 cities have data for the complete year of 2019. The 2020 average PM2.5 level in many inland cities in the Deccan Plateau has climbed up to breach the average concentration recorded in 2019. Chikkaballapur in southern Karnataka is the worst performer with 3.9 per cent increase from 2019 level. Tirupati has registered a 1.8 per cent increase. The maximum improvement is noted in Chennai which closed 2020 with a 30 per cent lower PM2.5. Amravati at 24 per cent, Bengaluru at 19 per cent, Visakhapatnam at 16 per cent, and Hyderabad and Rajamahendravaram at 14 per cent are the other best performers in the pool. Thiruvananthapuram has shown an improvement of 5 per cent. For context, Delhi’s 2020 average is 13 per cent lower than its 2019 level. 

Average level of PM2.5 has been lowest during this summer and monsoon due to the lockdown but could not prevent the winter spike: The overall PM2.5 average this summer and monsoon has been predictably lower compared to the previous year largely because of the unprecedented economic disruption during the summer lockdown and phased unlocking. But reopening of the economy coinciding with the onset of the winter trapping of pollution made PM2.5 levels rose starting October. From the respective cleanest week the weekly average of PM2.5 in Hyderabad rose 7 times, in Bengaluru 3 times, Chennai 5 times, Visakhapatnam 14 times, and Thiruvananthapuram 3 times to the dirtiest week. These major cities recorded lesser deterioration than Delhi where weekly air quality worsened 14 times but smaller towns beat the capital. Rajamahendravaram deteriorated 19 times, Bagalkot 18 times, Amravati 17 times, Hubballi 12 times, Kannur and Kozhikode 10 times. 

Andhra Pradesh cities were most polluted in the region with Visakhapatnam, Amravati, and Rajamahendravaram being only cities with weekly average exceeding 100 μg/m3. Mysuru was cleanest city with its worst weekly average only rising to 33 μg/m3. Bengaluru, Chennai, Chikkaballapur, Chikkamagaluru, Coimbatore, Hubballi, Hyderabad, Kannur, Kochi, Kollam, Kozhikode, Rajamahendravaram, Ramnagara, Thiruvananthapuram, Tirupati, and Vijaypura are other cities whose worst weekly average was found to be below 24hr standard i.e. 60 μg/m3

Dirtiest week for Hyderabad, Amravati, Rajamahendravaram, Chikkaballapur, and Yadgir was week ending on 3 January 2021. For Tirupati, Visakhapatnam, Hubballi, Chennai, Coimbatore, Kannur, Kozhizode, Kochi, and Thiruvananthapuram,  the dirtiest week on the week ending on 27 December 2020. Chikkamagaluru and Vijaypura the dirtiest week on the week ending on 8 November 2020. Bengaluru, Bagalkot, Mysuru, Ramnagara, and Kollam the dirtiest week on the week ending on 1 November 2020. Cleanest week for Rajamahendravaram, Tirupati, Visakhapatnam, Bagalkot, Chikkaballapur, Chikkamagaluru, Hubballi, Mysuru, Ramnagara, Vijaypura, Yadgir, Bengaluru, Coimbatore, Chennai, Kannur, Kollam, Kozhikode, Kochi, and Thiruvananthapuram was recorded pre-monsoon in months of April, May, and early June. Rest of the region recorded their cleanest week during monsoon (July, August, and September). The transient change of the lockdown phases could not be sustained without the systemic changes needed to control pollution from vehicles, industry, power plants, and waste. 

Average December PM2.5 level has been considerably higher in inland cities this year: December this year was dirtier across most inland cities in the peninsula. The PM2.5 average this December was worst in Andhra Pradesh with 69 per cent higher in Visakhapatnam, 66 per cent in Tirupati, 43 per cent in Rajamahendravaram and 34 per cent in Amravati compared to December 2019. Karnataka cities recorded dirtier December as well with 33 per cent higher in Chikkaballapur and 8 per cent in Bengaluru. Hyderabad’s December was 7.5 per cent dirtier in 2020 compared to 2019. Chennai and Thiruvananthapuram buck the trend recorded registered 16 per cent and 5 per cent cleaner December respectively compared to 2019.

Air quality gets more toxic with the onset of winter -- share of tinier PM2.5 in the PM10 increases: The share of tinier and finer particles in the overall coarser PM10 concentration determines the toxicity of air. When the overall share of tinier PM2.5 in the overall coarser PM10 is higher, the air is more toxic as the tiny particles penetrate deep inside the lungs and cut through the blood barrier increasing health risk. Interestingly, during lockdown, when the overall suspended coarser particles had settled down reducing the PM10 levels, the PM2.5 had also come down. Bengaluru and Hyderabad have relatively high PM2.5 percentage throughout the year but their monthly peaks are lower relative to coastal metro cities (See Graph 5: Changing share of percentage share of PM2.5 in PM10 among months). The share of PM2.5 in PM10 in Chennai has been identical range as registered in Delhi in 2020 though overall levels are lower. 

Diwali is an issue in southern cities as well: Thiruvananthapuram had dirtier diwali night in 2020 compared to 2019: In 2020 there was 114 per cent higher rise in hourly PM2.5 concentration at Plammoodu station of Thiruvananthapuram between afternoon and night of Diwali that is mostly caused due to firecracker busting. Hourly concentration peaked at 386 μg/m3 in the evening of November 2020, which is the highest hourly concentration recorded in the capital city of Kerala between start of lockdown in March to end of 2020.Bengaluru, Chennai, Hyderabad, and Visakhapatnam too registered abnormal spike in hourly pollution on Diwali night but is was considerably lower compared to spike noted in 2019 Diwali. 

Hyderabad and Visakhapatnam had earlier start of bad air days in 2020 winter: The rolling weekly average rose over the 24hr standard or 60 μg/m3 in Visakhapatnam on October 23 (9 days earlier), and Hyderabad on October 25 (14 days earlier). This winter overall has been 34 per cent dirtier in Visaakhapatnam, 7 per cent in Hyderabad, and 9 per cent in Thiruvananthapuram. Bengaluru registered no change in the seasonal average while Chennai was 20 per cent cleaner. The rolling weekly average didn’t breach the standard in Bengaluru, Chennai and Thiruvananthapuram. 

Number of days with PM2.5 concentration meeting standard was considerably lower this winter in Hyderabad and Visakhapatnam; Bengaluru, Chennai and Thiruvananthapuram saw lesser bad air days: There have been 31 days of poor or worse air days this winter compared to 10 recorded last year in Visakhapatnam. Hyderabad registered a day will poor air quality compared to zero in winter of 2019. Similarly standard days have been lesser by 11 days in Hyderabad, 23 days in Visakhapatnam. Thiruvananthapuram met the air quality standard on all the days of this winter. Chennai and Bengaluru saw reduction in number of days with PM level exceeding the standard but Bengaluru also saw decrease in number of days with good air quality.  

Cyclical ups and down of pollution this winter is less volatile – showing slower rise and fall than pervious winter: This inelastic behavior of PM2.5 levels in southern cities is looking more volatile during this winter with frequent quicker rise and drop. This can be the impact of meteorology. 

Even with comparatively cleaner air during this year, most cities recorded daily spikes similar to those observed in 2019: CSE has compared the annual averages and peak 24hr averages in these southern cities between 2019 and 2020. This shows that the smaller towns even with much lower annual average levels of PM2.5 have experienced almost same or higher maximum daily levels during winter when the entire region got air locked. Andhra Pradesh cities have relatively highest daily peak compared to the rest. 

Need deep cuts

This analysis bears out the need for deeper clean air action in the regions of southern India that otherwise is considered less polluted than the northern belt. But the region will have to work harder to meet not only the national ambient air quality standards but also aspire to meet the health based guidelines of the World Health Organisation to reduce public health risk.  

Says Roychowdhury: “It is clear that the region has to take forward its wins so far and raise the level of ambition to drive action across all key sectors of pollution and in the entire region. Enforce power plant standards across the state, minimise use of coal and other dirty fuels in the industry while improving industrial emissions control systems, scale up public transport and vehicle restraint measures, and manage waste to have a zero waste and zero landfill strategy.”

For more on this, contact Sukanya Nair of The CSE Media Resource Centre at sukanya.nair@cseindia.org, 8816818864