While the focus has been on rising levels of particulate matter in Delhi when the city is covered with smog, the concentrations of gases including carbon monoxide, oxides of nitrogen, sulfur dioxide and ozone have also been higher during the smog period this year. , when compared to pre-smog levels, shows an analysis by the Center for Science and Environment (CSE).
For carbon monoxide and ozone, the levels are above the standards set by the National Ambient Air Quality Standards. For sulfur dioxide and nitrogen dioxide, levels have not exceeded standards, but are higher than pre-smog levels. (see box)
The analysis also noted that the contribution of farm fires to PM 2.5 levels in Delhi this year was low. But it states: “Staying on this year’s haze for a long period despite relatively windy local conditions this year may be due to a lack of pollution control measures in the city this year.”
As per the analysis, the daily average contribution of agricultural fires to PM 2.5 levels in Delhi from mid-October to November 8 has been the lowest in the last 4 years. An average of 12% per day has been registered so far, as against 17% per day in 2020, 14% per day in 2019 and 16% per day in 2018. However, this year the peak contribution (48%) is higher than that. Extreme figures for the last two years. But, on November 7, when this contribution was at its peak, PM 2.5 levels, by contrast, fell from 501 µg/m3 on November 5 to 265 µg/m3 on November 7.
“Smoking is certainly a contributing factor. But, this year, on average, it has been lower than in previous years, mostly due to meteorological conditions. However, pollution levels have not decreased despite smoke levels [from farm fires] being less. This suggests that local pollution levels are high and there is a lack of action on the ground…,” said Avikal Somvanshi, program manager, Sustainable Cities Programme, CSE, who is one of the authors of the analysis.
Hence, the Smog episode is believed to be from 4th November. The episode ran from 6 days to 9th November and according to Somvanshi, continues in the same manner as the first smog episodes of 2018 and 2020. Whereas in the analysis only the data till then was considered. On November 9, Somvanshi said that even on November 10, the level of PM 2.5 remained ‘severe’. “If the situation does not improve, it could be overtaken by the 8 days of 2019 smog,” the analysis said.
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