The flat rates of peak-hour pollution due to the lockdown proves why strong action is needed to reduce traffic volumes and cut tailpipe emissions to near zero
A deserted Rajpath in New Delhi on March 25. Photo: Vikas Choudhary / CSE As vehicles go off the road after the country-wide lockdown in the wake of the novel coronavirus disease (COVID-19) outbreak, the typical two humps of daily pollution coinciding with morning and evening traffic peak-hours have nearly flattened out in India's big cities.
As cities slow down to fight the pandemic, daily average levels of particulate matter of size less than 2.5 micron (PM2.5) and nitrogen dioxide (NO2) have reduced sharply from the pre-lockdown days by close to more than half in Delhi and the towns of the national capital region (NCR).
A similar trend is evident in other big cities including Mumbai, Kolkata, Bengaluru, Hyderabad and Chennai. But the impact of this overall declining trend is dramatic on daily peak-hour pollution.
This is evident from the new analysis carried out by the Centre for Science and Environment that has assessed hourly trend in PM2.5 and NO2 levels during the day before and after the lockdown and also on the day of the Janata curfew.
This brings out the pronounced effect of traffic on hourly pollution trends. With traffic minimised, hourly trends have plummeted, reducing daily exposures to toxic vehicular pollution.
While overall daily levels of PM2.5 and NO2 concentrations have fallen significantly — by up to 60 per cent in several cities during the lockdown days, the hourly change is also dramatic. Hourly NO2 levels that are strongly associated with vehicles, have dropped more sharply.
Hourly PM2.5 levels that are also influenced by other pollution sources have reduced substantially. For comparison, the average of March 18-19, 2020, have been taken as regular days and the average of March 25-26 as lockdown days. Janata curfew was on March 22, 2020. Real-time data has been sourced from the website of the Central Pollution Control Board.
Normally, on regular days, peak hour pollution during morning and evening traffic hours inflates like a balloon. But after the lockdown and imposition of curfew, the peak hour PM2.5 concentrations have dropped by 57 per cent in Delhi, 69 per cent in Gurugram, 62 per cent in Faridabad and Noida, and 64 per cent in Ghaziabad.
Similarly, peak hour NO2 concentration has dropped sharply — by 64 per cent in Delhi, 66 per cent in Gurugram, 40 per cent in Faridabad, 79 per cent in Noida, and 75 per cent in Ghaziabad.
From studies done by SAFAR and TERI-ARAI in 2018, it is known that vehicles contribute about 40 per cent of the total particulate load in Delhi. According to SAFAR, vehicles contribute about 62.5 per cent of the NOx load and according to TERI-ARAI, 81.3 per cent of NOx load.
The overall impact during the lockdown is hugely substantial. Comparatively, the effect is somewhat lesser on Janata curfew day in Delhi and NCR. This could be due to the shorter duration of Janata curfew (14 hours) that had also shifted the peak hours beyond the curfew hours. It is also reported that people had rushed out for panic buying on that day. But this experience is different in other cities.
What about other cities?
Other cities including Kolkata, Mumbai, Bengaluru, Hyderabad and Chennai also witnessed a drastic drop in peak hour pollution and also daily average levels with some variation. Mumbai was the first one to lockdown and shows a sharper drop. Kolkata has witnessed a higher drop on Janata curfew day, compared to the subsequent lockdown days.
Overall, peak hour NO2 levels during locked-down days show a sharper drop than PM2.5 in all these cities as well. In Kolkata, peak hour PM2.5 reduced by 46 per cent and NO2 by 74 per cent on a lockdown day. Similarly, in Mumbai, it is 52 per cent and 85 per cent respectively; in Bengaluru, it is 42 per cent and 76 per cent respectively; in Hyderabad, 32 per cent and 72 per cent respectively and in Chennai, it is 46 per cent vs 44 per cent.
The take away
Emergency response to the pandemic has induced this change in air quality and hourly concentrations. This does not make a case for crisis-led change. But this experience shows that the measures adopted to fight the new health crisis have somewhat tamed the health risk associated with the ongoing air pollution crisis to give a short breather. This change has been possible due to massive community-wide lifestyle adjustments to practice social distancing.
This proves why we need strong action to reduce traffic volume and phase in a near zero emissions mandate. This crisis-induced change must force us to find and sustain long-term solutions to reduce our vulnerability to toxic risk.
Delhi: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of 37 stations
Delhi: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of 37 stations
Gurugram: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of three stations
Gurugram: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of three stations
Faridabad: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: PM2.5 - average of four stations; NO2 – average of three stations
Faridabad: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: PM2.5 - average of four stations; NO2 – average of three stations
Noida: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of four stations
Noida: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of four stations
Ghaziabad: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of four stations
Ghaziabad: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of four stations
Mumbai: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Mumbai: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Kolkata: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of 7 stations
Kolkata: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Note: Average of 7 stations
Chennai: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Chennai: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Hyderabad: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Hyderabad: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
Bengaluru: Hourly trend in PM2.5 levels on a regular day, after lockdown and as on Janata curfew day
Bengaluru: Hourly trend in NO2 levels on a regular day, after lockdown and as on Janata curfew day
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
.png)
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.