‘Chennai’s air almost as clear as in Europe’

Residents of Chennai finally have got something to cheer about. No, the coronavirus isn’t showing any sign of letting up, but the nationwide lockdown, followed by State-level restrictions, has resulted in a substantial improvement in the average air quality index (AQI) of the city.

According to an analysis by Bengaluru-based environment intelligence start-up Ambee, the average AQI in Chennai during May was around 40, which was not only the lowest in a decade but also one of the best among the key cities that were analysed.

Three phases covered

Ambee’s survey covered three phases pre-lockdown (March 1 to 21), lockdown period (March 21 to May 3), and post-lockdown (May 3 onwards).

“Lockdown had a huge impact on Chennai’s AQI, which dipped to a 10-year low. We have noticed that the pollution is almost as good as some of the European cities,” said Madhusudan Anand, CTO and Co-founder of Ambee, adding that “some places even recorded single digit PM 2.5 and it would have not been possible without the lockdown”.

PM 2.5 refers to atmospheric particulate matter (PM) that has a diameter of less than 2.5 micrometers, which is about 3 per cent of the diameter of a human hair. Exposure to these fine particles can cause short-term to long-term health effects such as asthma and heart disease.

Not just Chennai, other major cities such as Delhi (80), Mumbai (60), Bengaluru (65) and Hyderabad (80) have also witnessed a substantial improvement in AQI in May.

A dip in the AQI signifies improvement in the air quality. According to regulatory standards, AQI in the range of 0 to 50 is classified as ‘good’, 51 to 100 (satisfactory), 101 to 200 (moderately polluted), 201 to 300 (poor), 301 to 400 (very poor), and above 401 ‘severe’.

“Delhi is one of the most polluted cities in the Indo-Gangetic plain. Many people said Delhi can never be under AQI level of 50, but it did come to 30 to 40 levels average in the entire city,” said Anand.

Ambee uses a combination of dispersion modelling, data from more than seven satellites, ground sensors of Pollution Control Board (PCB) and its own sensors to bring granular level information on pollution. Ambee’s technology can be used to gather hyper local data of pollution even at a pin code level.

“According to WHO data, India needs around 4,000 sensors, but we barely have 150 to 160 sensors operational across the country,” said Anand, adding, “so, we are using a combination of low cost sensors, over the edge computing and calibration methodology that will work in all Indian conditions”.

Ambee’s study also revealed a direct correlation between easing of lockdown restrictions and rise in pollution levels. For instance, Bengaluru, which announced a partial unlock on June 1, saw a 30 per cent jump in pollution levels in the first week and 67 per cent in the second week.

According to Ambee’s post-lockdown air quality analysis between June 1 and 21, the average AQI of Chennai (60), Delhi (100) and Hyderabad (60) witnessed deterioration when compared to May, while Mumbai (45) and Bengaluru (50) witnessed improvement, aided by the recent spell of heavy rains.

Anti-allergic medicines

Anand also noted that there has been a reduction in consumption of allergens or anti-allergic medicines in Chennai during this period, and even those suffering from chronic allergy conditions suddenly felt there is good improvement in their health condition.

“We spoke to a few doctors, pulmonologists, general physicians, obstetricians and even paediatricians, and all of them conferred that there has been a huge reduction in OPD, especially on their respiratory side,” he added.

Currently, Ambee is studying the post-lockdown impact on pollution levels as more and more States are moving towards unlocking activities.

“We are in talks with hospitals, research institutions, public health companies and government officials to see if they can share numbers to corroborate with our findings,” added Anand.