Are Metro Cities More Polluted than Industrial Cities?

Are Metro Cities More Polluted than Industrial Cities?

The assumption is that industrial activities are high contributors to air pollution, but recent studies held during the lockdown suggest human activities including transportation may have a far higher impact on air quality. Here we talk about emissions in industrial and metro cities, their impact, and where these findings take us. 

Bengaluru, 22/12/21 - The COVID-19 lockdown over the past months has revealed the extent of human impact on the environment.  

Human activities such as transportation, industrial activity, urbanization etc. have an adverse impact on climate change, and in particular on-air quality. One of the most common pollutants, particulate matter or PM (PM2.5 and PM10), is also among the most dangerous. To study the distribution of PM over the periods of lockdown and before, 8 representative cities (metros and industrial cities) along the Indo-Gangetic Plain have been analyzed.

Impact Upon Different Types of Cities

Air pollution levels in metro cities as opposed to industrial cities were analyzed. Contrary to assumptions, the impact of air pollution on metro cities is far greater than its impact on industrial cities. Recent data from CPCB CAAQMS monitors at metro and Tier II cities shows that average levels of PM2.5 and PM10 during festival periods surpass the pollution levels from industrial cities. Since India has a highly vaccinated population against the COVID-19 virus, there was much increase in vehicular movement and other activities during the festive season. This increased pollution levels in metro and tier-II cities.

Methodology - Air quality data for Indian cities including Mumbai, Kolkata, Ahmedabad, Chandigarh, and Jaipur was sourced from the Central Pollution Control Board (CPCB). 

Cities Selected for Study

To assess the air quality over India during the lockdown in 2020 and 2021, the data for 24-hour average  daily concentrations of pollutants were collected for 2020 and 2021, for the following cities:

Cities

State

Location

Type

Kurukshetra

Haryana

UGP

Metro Tier II

Yamuna Nagar

Haryana 

UGP

Industrial 

Chandigarh

Haryana/Punjab

UGP

Metro Tier II

Asansol

West Bengal

LGP

Industrial

Kolkata

West Bengal 

LGP

Metro Tier I

Ahmedabad

Gujarat

UGP

Metro Tier I

Ankleshwar

Gujarat

UGP

Industrial

Jaipur

Rajasthan

Northwest Arid

Industrial/Metro Tier II

Broad Profile of Selected Cities

Tier

I and II 

Geography

Along Indo-Gangetic Plain

Type

Metros and Industrial Cities 

 

 



Time Profile 

 

2020 (Lockdown 1)

Pre lockdown period

Feb 24 - Mar 24

 

Lockdown period

Mar 25 - May 3

2021 (Lockdown 2) 

Pre lockdown period

Mar 28 - April 28 

 

Lockdown period

April 29 - May 29

 

Note: In 2020, the country saw a complete lockdown of all cities and industries, except those operating essential services. This period witnessed massive reductions in air pollution levels. However, in 2021, cities saw almost a complete lockdown, whereas industries were mostly running albeit with limited production. 

Profile of Pollutants Studied

Particulate Matter - PM2.5 and PM10 

A pictorial representation of particulate matter pollutants - PM2.5 and PM10

 

City Specific Results 

KOLKATA Asansol

Kolkata is a metro while Asansol is an industrial city. Their respective sources of emissions are different, and so are the reductions in pollution levels. 

  • During Lockdown 1 (in 2020), Kolkata saw a 57% reduction in PM2.5 levels and a 61% reduction in PM10 levels. 
  • On the other hand, Asansol saw 47% reduction in PM2.5 and 41% reduction in PM10.
  • During Lockdown 2 (in 2021), the difference is less stark. While Kolkata saw a 46% reduction in PM2.5, Asansol saw a 40% reduction in PM2.5. 

Observation: In this case, pollution reduction was greater in the metro than the industrial city. 

 

PM10 comparison between Kolkata and Asansol before and during the lockdown in 2020 and 2021

PM10 comparison between Kolkata and Asansol before and during the lockdown in 2020 and 2021

 

II

MUMBAI Mahape

The MIDC Industrial area, located in Mahape (Navi Mumbai), has industries ranging from paper mills to heavy machinery. 

  • Mumbai and Mahape show almost equal reductions of PM2.5 and PM10. 
  • There is a slightly higher reduction of pollutants during Lockdown 1, possibly because 2020 saw a complete lockdown compared to 2021.  

Observation: It is possible that industrial emissions are an equal contributor to Mumbai’s air pollution, as vehicular emissions.

 

PM10 comparison between Mumbai metro and Mumbai Mahape before and during the lockdown in 2020 and 2021

 

PM2.5 comparison between Mumbai metro and Mumbai Mahape before and during the lockdown in 2020 and 2021

 

III

CHANDIGARH Yamunanagar – Kurukshetra 

In this belt, Chandigarh is a Tier II metro city, Yamunanagar is industrial, and Kurukshetra is a mix of the two. 

  • During Lockdown 1, Chandigarh recorded the highest decrease in PM2.5 at 38%, while Kurukshetra recorded a PM2.5 reduction of 22% and Yamunanagar recorded a PM2.5 reduction of 17%. 
  • Lockdown 2 in all three cities seemed to be partial, as reductions were non-existent. 

Observation: The metro region recorded a higher reduction than the industrial area. 

 

PM2.5 comparison between Chandigarh, Kurukshetra and Yamunanagar before and during the lockdown in 2020 and 2021

 

PM10 comparison between Chandigarh, Kurukshetra and Yamunanagar before and during the lockdown in 2020 and 2021.

 

IV

AHMEDABAD Ankleshwar

Ahmedabad is a metro and Ankleshwar is an industrial city. 

  • In Lockdown 1, Ankleshwar recorded a PM2.5 decrease of 40%, whereas Ahmedabad recorded a PM2.5 decrease of 46%. 
  • In Lockdown 2, Ankleshwar recorded a PM2.5 decrease of 18% and Ahmedabad recorded a PM2.5 decrease of 34%. 
  • During Lockdown 1, about 950 industrial units were in operation during the pre-lockdown period in Ankleshwar.  Once the lockdown was imposed, only 46 units were open – mainly pharmaceuticals and sanitizer manufacturing facilities.
  • During Lockdown 2, however, it appears that the manufacturing activity picked up and emissions were not significantly different between pre-lockdown and lockdown periods.  

 

PM2.5 comparison between Ahmedabad and Ankleshwar before and during the lockdown in 2020 and 2021

 

PM10 comparison between Ahmedabad and Ankleshwar before and during the lockdown in 2020 and 2021

 

JAIPUR 

Jaipur has a mix of residential and industrial areas. 

  • During Lockdown 1, PM2.5 was reduced by 41% and PM10 was reduced by 35%. 
  • During Lockdown 2, reductions were similar – 36% decrease in PM2.5 and 27% decrease in PM10. 

Observation: This indicates that the restrictions were not implemented completely, and there was no slowing down of economic activity. 

 

CONSOLIDATED FINDINGS

Tier 1 cities saw a higher reduction in pollution than Tier 2 cities. This could be because Tier 1 cities may have had a complete and enforced lockdown, and therefore a vaster reduction in economic activity. 

The reduction of particulate matter is higher in the metro cities that are primarily residential, than in cities that are primarily industrial. 

Industries were probably still operating at reduced capacity through the lockdown, but importantly, the movement of people and goods is a significant contributor to particulate matter. There is tremendous improvement to air quality when economic activity is cut down. 

 

 



Comparison of PM10 levels in Jan 2020 and Jan 2021

Comparison of PM2.5 levels in Jan 2020 and Jan 2021

 

Conclusion 

Evidently, the respite in air pollution over the lockdown has not made enough of an impact on policy. Policymakers need to offer an alternate solution for a livelihood by working with changemakers and advocacy groups to offer sustainable alternatives.  

 

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