Pollution levels in Delhi usually remain low during the time of monsoon, however, this past July has set a new record for the cleanest air quality index (AQI) recorded in the same month since 2017. Data from the Central Pollution Control Board (CPCB) shows that this July, Delhi saw 25 ‘satisfactory’ air quality days in which the AQI remains between 51 to 100. This is the second AQI category after ‘good’ which has a range of 0 to 50.
Since 2017, no July has seen more than 16 ‘satisfactory’ AQI days. Moreover, the average AQI this July was 83, much lower than the previous year’s figure of 134, and also lower than the last cleanest AQI record of 98 in July 2017 — the year since which complete data is available with the CPCB after records began in 2015.
An official from the Central environment ministry said the reason behind cleaner air is a combined result of meteorology, mainly better rainfall, and also fewer people on the roads.
“A moderate lockdown is still in place even as we are unlocking restrictions. The Metro has not started yet… and all the people who left the city before the lockdown may not have come back,” the official said.
“There’s also less traffic congestion on the roads as people are still cautious about stepping out… Moreover, there’s weekend lockdown in neighbouring cities of UP which also has an impact.”
The official also said that air quality of Delhi has been improving every year as a result of long-term pollution control measures.
In terms of meteorology, the city and its suburbs witnessed rainfall for nearly 25 days this July, totalling 236.9 mm, with two spells of heavy showers in which over 65 mm rain was recorded in a day. The rainfall recorded this July was 12% above the normal average of 210.6 mm for the month.
The overall rainfall in July was higher than 199.2 mm recorded in July last year, but lower than 286.2 mm recorded in July 2018.
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre in Delhi, said, “For at least 22 days this July, one weather station or the other in Delhi recorded rainfall. We also had strong winds on some days of 30 to 40 kmph.”
During monsoon, pollution levels usually remain low as rainfall helps pollutants settle down, which otherwise remain suspended in the air
movement of people and traffic congestion in the city, such as the shift to BS VI fuel and vehicles, closure of thermal power stations in Delhi and making industries use piped natural gas
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