A report in Bengaluru's Deccan Herald today says that "...Air pollution in Bengaluru dropped by an average 28% during the Covid-19 lockdown".The report cites a study on PM 2.5 levels that decreased during the lockdown as an indicator of air quality improvement.
It is not scientific to conclude that a decrease in one air quality indicator (AQI) results in overall air quality improvement or reduction in air pollution. This is because PM2.5 is just one AQI parameter used to measure the air quality level in India. Other pollutant levels need to be tracked to know whether their levels have decreased or not. This include Ozone, oxides of Nitrogen, Sulphur Dioxide, PM 10, and Ammonia.
A report by the Centre for Science and Environment says that Ozone levels saw a spike in many cities that were supposedly clean during the lockdown. The same report states that Bengaluru had an average PM2.5 level of 45% during the lockdown and NOx level have increased by 38%. This further casts doubts on the data quoted by Deccan Herald.
The Deccan Herald report also does not state the pre-lockdown level of PM2.5 in Bengaluru and the new reduced levels.
Most importantly, there was a partial lockdown in Bengaluru from March 13, whereas the data is quoted from March 23 when a full lockdown was imposed in the city. That, I feel. can lead to erroneous data.
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