At peak of air pollution on Deepavali, data goes missing at several government monitoring stations in Delhi

The calculation of the Air Quality Index (AQI) relies heavily on the continuous monitoring of specific pollutants, primarily PM2.5 and PM10. The AQI is derived using a moving or running average of hourly concentrations of eight parameters over a 24-hour period. When hourly data is missing, especially during peak pollution events like Deepavali, the mathematical calculation is skewed, resulting in an artificially lowered AQI. The failure of CPCB monitors to record PM2.5 levels beyond 1000 micrograms per cubic metre—which is significantly higher than the World Health Organization (WHO) 24-hour guideline of 15 micrograms per cubic metre—highlights a critical flaw in environmental monitoring infrastructure. This inability to capture extreme peaks means the true severity of the pollution crisis is underrepresented, hindering effective mitigation strategies and public health advisories.

The recurring issue of missing air quality data raises serious questions about transparency and accountability in environmental governance. The Central Pollution Control Board (CPCB), a statutory organisation constituted under the Water (Prevention and Control of Pollution) Act, 1974 and entrusted with powers under the Air (Prevention and Control of Pollution) Act, 1981, is responsible for providing reliable air quality data. The failure to maintain continuous data streams, particularly during known high-pollution periods, undermines public trust. Environmental activists allege this data gap might be a deliberate attempt to fudge data and conceal the actual severity of the pollution crisis rather than addressing the root causes. This situation highlights the need for robust, tamper-proof environmental monitoring systems and greater accountability from regulatory bodies to ensure citizens have access to accurate information regarding their environment, linking back to the fundamental right to a clean environment under Article 21.

Delhi's severe air pollution is exacerbated by its unique geographical location and meteorological conditions, particularly during the winter months. As a landlocked city, Delhi experiences temperature inversion during winter, where cold air traps pollutants close to the ground, preventing their dispersion. When this natural phenomenon is combined with anthropogenic activities like stubble burning in neighbouring states, vehicular emissions, and episodic events like firecracker bursting during Deepavali, it creates a severe public health emergency. The inability to accurately measure and report these peak pollution levels hampers the understanding of the spatial and temporal distribution of pollutants across the National Capital Region. Accurate, continuous data is crucial for developing targeted, geography-specific interventions, such as implementing the Graded Response Action Plan (GRAP), which relies on real-time AQI thresholds to trigger emergency measures.