Vehicles, unclean household fuels major contributors of CO in Delhi, govt study finds

Vehicular emissions and use of unclean household fuels are the major sources of carbon monoxide (CO) in the national capital, a study conducted by the union ministry of earth science and Indian Institute of Tropical Meteorology (IITM) has found.

The study, which focuses on the sources of CO emissions in Delhi and Mumbai, has recorded levels of the pollutant during the Covid-19 lockdown— when restrictions were placed on vehicular movement, industrial operations and other financial activities — and compared it to emissions on regular days when all of these sources were operational and contributing to emissions.

The findings show that in Delhi during the Covid-19 lockdown, the total CO emissions showed an 86.39% reduction compared to regular days, as opposed to a decline of 62.14% reduction in Mumbai. It also showed that the biggest reason behind this reduction, especially in Delhi, was because of restrictions in traffic movement.

In the national capital, the CO emissions from vehicular movement reduced from 31.01gigagram/month (Gg/month) on regular days to just 3.1 Gg/month during the lockdown period. The second biggest contributor of CO in Delhi was the use of unclean household fuels, which contributed to 1.35 Gg/month on usual days. This did not show any change even during the lockdown.

“The major sources of CO in Delhi were transport and household fuels during normal time. Transport was completely shut during lockdown, except for vehicles from law enforcement agencies, emergency services and that of essential supply chains. Not more than 10% of total vehicles were on the road, a data that cross-checks with the total sale of petroleum products,” the findings read.

Carbon monoxide (CO), which is a colourless and odourless gas, is highly toxic and is produced by incomplete combustion of fossil fuels, oil, coal, woods, and natural gas. Scientists said that CO is more harmful than particulate matter, as it has the potential to stay for a longer period in the atmosphere and does not get washed away by rain like PM 2.5 (particulate matter with diameter less than 2.5 micrometres) and PM 10 (PM with diameter less than 10 micrometres).

“Exposure to CO is particularly harmful for the elderly, children and people who are suffering from medical conditions such as heart and lung problems. We have examined the scientific processes responsible for the variability in CO during the Covid-19 lockdown in two of the largest megalopolises of India and the role of transport in influencing its concentration during the lockdown, and to understand the role of biofuel emissions,” said Gufran Beig of System of Air Quality Forecasting and Research (Safar) at IITM, who headed the study.

Beig added, “The CO data was collected from continuous Air Quality Monitoring Stations (AQMS) under the Safar network.”

Another important observation made by the study was the contribution of CO levels in Delhi’s air from neighbouring states. The findings of the study showed that because of the landlocked demography of Delhi and the long lifespan of pollutant, the sources from long-range transport was also adding to the CO levels in the city.

“CO has a long life and hence a significant contribution can come by the long-range transport from surrounding regions. The long-range transport of CO in Delhi, whereas wind reversal combined with emissions from slum clusters in Mumbai played a major role during the lockdown period,” the study said.