Delhi Air Pollution: October air fouler than last 2 years

NEW DELHI: Delhi’s air quality index in the first two weeks of October was worse than in the same period in 2018 and 2019, according to CPCB data. The average AQI for Delhi from October 1 to 14 was 212 (poor), a significant rise from last year’s 159 (moderate) in the same fortnight and 207 (poor) in 2018. The capital also logged a high AQI of 300 (poor) this past fortnight against a high of 270 in 2019 and 262 in 2018. Experts feel early harvest remains burning and the poor end to the monsoon season may have contributed to this unseasonal spike.

CPCB data, however, shows 2020 was cleaner in comparison with the same period in 2017, 2016 and 2015. The comparison though could be less than accurate since Delhi had just six air quality monitoring stations in 2015 and 2016 and 17 in 2017, while there are 35 functional air monitoring stations across the city today.


Kuldeep Srivastava, scientist at the India Meteorological Department (IMD) and head of Regional Weather Forecasting Centre in Delhi, attributed the early rise in pollution levels to an early withdrawal of the monsoon relative to 2019, coupled with complete lack of rain from September 8 onwards. “The monsoon withdrew from Delhi this year on September 30, but there was dryness in the atmosphere because the capital last received rainfall on September 8 with 18.8 mm rain. Rain helps settle down pollutants, so this did not happen this year. Besides, the wind speed during the nights was almost nil this week and pollutants could not be dispersed,” said Srivastava.

Last year, the monsoon withdrew from Delhi on October 10 and the city had received 47.3mm rainfall on October 4.

Historical data shows Delhi generally starts recording an increase in pollution with a drop in the temperature and as stubble burning picks up pace from the second week of October. This year, fires to get rid of harvest remnants were seen on satellite imagery from as early as the first week of September, with field fires in Punjab at an all-time high, if data for this period for the last five years from 2016 is considered.

VIIRS satellite data from 2016 onwards shows a spike in farm fire counts in the last week of September and the first week of October, with 50-100 counts per day recorded in 2017. However, this year the average count of such stubble burning incidents per day crossed 150 in the last week of September and ranged between 150 and 200 counts in the first week of October.

Anumita Roy Chowdhury, executive director (research and advocacy) at Centre for Science and Environment, said, “The capital’s air was cleaner from October 1 to 14 in 2019 and 2018 than this year. This is due to meteorological factors and onset of early crop burning in 2020. The local pollution profile now needs to be checked to determine how and why it was different this year compared with the last two years.”