The Central Pollution Control Board (CPCB) has provided an explanation for the data gaps observed during Diwali, stating that hourly air quality calculations do not include particulate matter concentrations above 1,000 micrograms per cubic metre. The CPCB also clarified that sudden increases in pollutant concentrations, such as those caused by firecrackers during Diwali, are usually short-lived and less relevant indicators of adverse health effects.
The Central Pollution Control Board (CPCB) has provided a detailed explanation for the data gaps observed during Diwali, a period when air quality typically deteriorates sharply in Delhi. In a statement, the pollution regulator clarified that its monitoring equipment was originally calibrated to measure particulate matter concentrations up to 1,000 micrograms per cubic metre only.
According to the CPCB, hourly readings beyond this threshold are not included in the computation of air quality calculations. This clarification comes amid reports that more than 20 of Delhi’s 59 air quality monitoring stations had not reported readings on Diwali night.
The pollution regulator also stated that sudden increases in pollutant concentrations, such as those caused by firecrackers during Diwali, are usually short-lived. It added that the National Air Quality Index is designed to account for prolonged exposure to air pollution rather than momentary spikes in pollutant concentrations.
Launched in 2015, the National Air Quality Index calculates hourly AQI readings based on measurements of eight pollutants: particulate matter 2.5, particulate matter 10, carbon monoxide, nitrogen dioxide, sulphur dioxide, ammonia, ozone and lead.
The CPCB further explained that when the National Air Quality Index was introduced, particulate matter analysers were calibrated to measure concentrations ranging from zero to 1,000 micrograms per cubic metre. It also mentioned that when readings exceed this threshold, they are treated as outside the range and not used in the computation of air quality calculations.
The pollution regulator said it was reviewing the methodology in light of advances in monitoring technology and evolving international practices.
Source:
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