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Delhi Diwali Air: Numbers Don't Add Up
9 Nov
Summary
- Delhi recorded 812 µg/m³ PM2.5 on Diwali night.
- Official AQI ratings differ vastly from app readings.
- AQI scales vary by country and averaging periods.
On Diwali night, Delhi's Nehru Nagar air monitor recorded 812 micrograms of PM2.5 per cubic meter between 9pm and 10pm. This high concentration resulted in vastly different Air Quality Index (AQI) scores depending on the scale used, with some apps showing figures over 1,000 while official readings stayed in the 400s.
India's National AQI has a 'severe' band starting at 401, but official figures do not go beyond 500, masking actual pollution levels above 380 µg/m³. Scales like the UK's and US's have different thresholds and averaging periods, leading to further discrepancies. The US index, for example, can translate Delhi's 812 µg/m³ reading to 1,469, significantly higher than India's capped scale.
