CPCB Clarifies Air Quality Index Discrepancies During Diwali
Central pollution board explains methodology differences causing AQI reporting gaps during peak events.
1Addressing Public AQI Confusion
The Central Pollution Control Board recently addressed public scrutiny regarding air quality data discrepancies during Diwali. While official government applications reported severe levels near 400, private platforms displayed figures exceeding 1000. This divergence sparked accusations of data opacity, prompting the board to clarify its core reporting mechanics and design methodology.
2Communication Over Raw Data
The CPCB emphasizes that the National Air Quality Index is primarily a communication tool designed to convey health implications rather than raw, second-by-second volatility. By utilizing cumulative exposure duration as outlined in the 2009 standards, the system prioritizes long-term health risks over momentary spikes caused by episodic events like firecrackers.
3Methodology of Weighted Averages
Unlike private platforms that often track instantaneous hourly readings, the official Indian model relies on weighted 24-hour or 8-hour averages. This approach ensures that individual health statements remain the focus. During extreme pollution episodes, the board notes that specific hours may be excluded to maintain the integrity of daily averages.
4Rationale for 500 Ceiling
The index is intentionally capped at 500 to represent the highest level of health concern. The board explains that values exceeding this threshold do not change the assigned 'Severe' category or the associated health warnings. This design feature aligns with international practices, including the methodology utilized by the US EPA.
5Sensor Technology and Calibration
Discrepancies often arise from the use of low-cost sensors by private entities, which lack the rigorous calibration and quality assurance required by the 2009 standards. These sensors often produce data that cannot be directly compared to the government's quality-assured network, which is designed for consistent, long-term public health monitoring.
6Time-Lag Effect in Reporting
The CPCB highlights a distinct time-lag effect inherent in its model. While private apps may show higher values during sharp hourly peaks, they often report lower figures when concentrations fall. Conversely, the official index continues to reflect the cumulative exposure of the preceding 24 hours, providing a more stable health indicator.
7Expansion of Monitoring Network
To improve data coverage, the board has significantly expanded its infrastructure over the last decade. The number of Continuous Ambient Air Quality Monitoring Stations increased from 30 in 2014-15 to 634 currently. Specifically, the network in Delhi grew from 10 stations to 59, enhancing the overall reliability of regional air reporting.
8Rejection of Manipulation Claims
The board explicitly rejects accusations of data manipulation or under-reporting during high-pollution events. Officials maintain that differences in AQI values are strictly attributable to variations in measurement techniques and mathematical models. The focus remains on providing actionable health information rather than tracking every momentary fluctuation in ambient air quality.
Original article: NDTV – India — CPCB Clarifies Air Quality Index Discrepancies During Diwali