Updated: September 1, 2021 8:22:37 am
Delhi has not seen a single ‘good’ air day in eight months of this year, going by the Central Pollution Control Board’s (CPCB) Air Quality Index (AQI) bulletins.
According to the National Air Quality Index, AQI in the range of 0 to 50 is considered ‘good,’ 51 to 100 is ‘satisfactory,’ 101 to 200 is ‘moderate,’ 201 to 300 is ‘poor,’ 301 to 400 is ‘very poor,’ and 401 to 500 is ‘severe.’ While ‘good’ AQI has minimal health impacts, AQI falling in the ‘satisfactory’ range can lead to minor breathing discomfort among people sensitive to these changes, ‘moderate’ AQI can lead to breathing discomfort among people with existing heart or lung diseases, and AQI in the ‘poor’ range can lead to breathing discomfort to most people on ‘prolonged exposure,’ as per the CPCB.
In contrast, 2020 saw five days when the AQI fell within the ‘good’ range — four of these days were in August of last year. March 28, 2020, when the nationwide lockdown was in place, also recorded a ‘good’ AQI.
Two days in 2019 fell within the ‘good’ AQI range — also in August. The year 2018 saw no ‘good’ AQI days, while 2017 saw two such days in July.
Going by data from the past five years, the city has witnessed only nine days when AQI has been within the ‘good’ range.
AQI is calculated as a 24-hour average of the concentration values for pollutants at the monitoring location. Eight pollutants are considered while monitoring AQI and a minimum of three of these are necessary to calculate the average figure — PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead.
This year, the average AQI for August, calculated from the CPCB’s daily bulletins, is 106, a dip in air quality compared to the same month in the past two years. The corresponding figure for 2020 was 63, while it stood at 86 in 2019.
However, August this year fared better than the same month in 2018. In 2018, the average AQI for August was 111. The figure for August in 2017 was 102.
In the monsoon season this year, August, which recorded only around nine days of rainfall, has seen better air quality than June and July. The average AQI figure for June this year was 147, while it was 110 for July. The monsoon season witnesses air that is cleaner than the winter and summer months, going by the CPCB’s daily bulletins.
In the last monsoon season as well, August, with an average AQI of 63, recorded better air quality than June with an average AQI of 123 and July with an average of 83.
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