A new study by a multidisciplinary team of scientists has recorded high levels of PM 1.0, particulate matter even finer than PM 2.5 that can cause strokes and heart attacks, in the Delhi-National Capital Region in the weeks before and after Diwali.
Over the past few weeks, the explosion of particulate matter pollution caused by the annual crop-burning season has affected air quality across parts of north India. Now, new data from two different studies show that the overall air quality dropped sharply in the weeks leading up to Diwali and immediately after .
The first study found that between 6 and 11 November 2020, almost each day, there was a very high concentration of both PM 2.5 and PM 1.0. The study was done by a team of scientists and researchers from University of Delhi, Jawaharlal Nehru University and Indian Institute of Technology, Delhi, analysed air quality data from a sensor-based network in the NCR before and after Diwali. This new network of around 35 air quality sensors from PurpleAir in Delhi-NCR, Punjab, Haryana and regions of western Uttar Pradesh is part of a Nasa-funded effort led by the US-based non-profit organisation RTI International, in collaboration with IIT-Delhi and other organizations. These findings were particularly worrisome as PM 1.0 can be more damaging than PM 2.5. These are ultrafine particles that are least visible in the air.
The last week of October showed the largest concentration of PM 2.5 of the year in the range of 250-500 microgram per cubic metre. Between 5 and 8 November, it remained in the range of 600-700 microgram per cubic metre. Around 10 November it crossed the 1000 mark. From mid-October to mid-November PM 1.0 levels remained quite high, from 200 to 300 microgram per cubic metre. However, during September it was less than 100. According to an official statement, the increase in these levels of pollution was mainly due to the significant contribution of agricultural waste burning in Punjab and Haryana. Similarly, PM 10 measured almost in similar fashion showed values about 1.5 times larger than the PM 2.5 levels.
A separate analysis of air quality across eight cities by Ambee, an environmental intelligence startup that measures, processes and analyses hyperlocal air quality data in real-time, found that Delhi recorded high levels of pollution, with the average AQI consistently above 250 before and after Diwali, which was on 14 November. The average PM2.5 concentration was above 200.
The air quality across Bengaluru, Delhi, Mumbai, Hyderabad, Chennai, Kolkata, Jaipur, and Pune were analysed for between 9-18 November. Apart from government sensor-based data, Ambee’s on-ground IoT sensors, and open source data, satellite imagery, weather and meteorological data were used to measure air quality.
Bengaluru remained the cleanest with the average AQI between 50-70 and average PM2.5 levels just above 25 throughout the period of analysis. Mumbai’s AQI levels remained at an average of 150 whereas Kolkata’s average AQI increased from 120 to 170 after Diwali. Similarly, Pune recorded a higher average AQI of above 100 after Diwali.
Before Diwali, Chennai’s average AQI was in the moderate category of 110, whereas after the festival, the city saw a drop in pollution with average AQI around 50 due to a spell of rain.
Hyderabad and Jaipur continued to show moderate levels of pollution with average AQI, ranging between 100-130, an official release said.