373 or 1,747? What was Delhi's actual AQI on Diwali and why did readings differ
Discrepancies between Delhi's official AQI readings and those on private apps during Diwali were caused by different calculation methodologies, specifically the lack of an upper limit in the US-based EPA system. While India's system caps at 500, international platforms can display much higher numbers, leading to public confusion.
Why it matters
Understanding how air quality data is measured is critical for public health awareness and policy response during periods of severe pollution.
NEW DELHI: Social media was flooded with screenshots of air quality apps showing Delhi's Air Quality Index (AQI) touching 1,500 to 1,800 on Diwali night, even as the official figures shared by the Central Pollution Control Board (CPCB) remained below 400.The discrepancy has raised questions about how different platforms calculate air pollution levels and why their readings vary so widely.While India's National Air Quality Index (NAQI), used by CPCB, is capped at 500, several international platforms follow methodologies based on the US Environmental Protection Agency (EPA), which does not impose the same upper limit.But beyond the difference in AQI scores, pollution monitoring data from Delhi showed just how severe the spike in particulate matter was after firecrackers were set off on Diwali night.TOI explains how different AQI methodologies work, why readings vary and what pollution monitoring stations recorded across the capital.How is AQI calculated?The Air Quality Index measures the concentration…
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