According to the data available with Hindustan Times, since May 2015, July has been the “cleanest” month in terms of air quality with two “good” days and not even one “bad” day.

“In July 2017, there were two good days, where air quality index stayed between 0 and 50. There were 17 satisfactory days, when the AQI (air quality index) was 51-100, while the remaining 12 were moderate (AQI between 101 and 200). This has been primarily because of the good monsoon rain this season in and around Delhi-NCR,” Dr Dipankar Saha, additional director and head of the Air Laboratory at the CPCB, said.

According to the CPCB, Delhi did not have even a single day of good AQI for the past 26 months till June. However, July 30 and July 31 recorded the AQI at 43 and 47. The AQI on Wednesday (August 2) was in the satisfactory range at 92.

A Delhi Pollution Control Committee official said the data shows that if you improve your neighbourhood, the air will improve.

“Even though it is not raining in Delhi all the time this monsoon, surrounding areas across north India have received substantial rain. Because of this, long range transport of pollutants from outside Delhi is minimal. Around 20%-30% pollution gets reduced because of this,” the official said.

According to him, humidity is also high which naturally makes sure that the fine particulate matters go down. “Because of the monsoon, there is lot of moisture in the air. This is also another reason for this decrease in pollution levels. The weather conditions across July, which was not too hot and on the cooler side, also aided the good air quality,” the official said.

Delhi, a city of 20 million people, is among the world’s most polluted cities according to the World Health Organisation. It has been struggling to clean up a toxic cocktail of dust, smoke and gases from its air. The condition worsens every autumn and winter as the city, buffeted by farmers burning crop stalks in neighbouring states and atmospheric changes, records higher levels of air pollution.