Chandigarh air remains ‘very poor’ for 2nd day

Tribune News Service

Chandigarh, December 26

Average air quality index (AQI) for the second consecutive day today remained in the “very poor” category in the city, reportedly due a cumulative effect of pollution.

While the average AQI level stood at 326 around 8 pm in the city, the reading at the continuous ambient air quality monitoring station (CAAQMS) at Sector 22 was 345. The CAAQMA, Sector 53, bordering Mohali, recorded the highest AQI level of 336 at 8 pm and Sector 22 logged 267 (poor).

An increase in AQI causes breathing discomfort to most people on prolonged exposure. The AQI between 301 and 400 is considered ‘very poor’ and can cause respiratory illness on prolonged exposure. Yesterday, the average AQI in the city was recorded at 305 around 9 pm.

An official of the Chandigarh Pollution Control Committee said they were analysing the situation.

On Sunday, for the first time in this season, the average AQI of the city recorded 205 due to changing weather, vehicular emissions and incidents of farm fires in the neighbouring areas.

Dr Ravindra Khaiwal, Professor of Environment Health, Department of Community Medicine, PGI, said: “This sustained period of unhealthy air quality levels in Chandigarh is likely to be a cumulative effect of pollution build-up rather than just reflective of a single day’s activity or conditions.”

Several factors are responsible for high AQI values to represent a cumulative build-up, such as certain pollutants like particulate matter can remain suspended in the air for days together in the absence of strong winds/rainfall that help dissipate them.

So when conditions inhibit dispersion for several consecutive days, previous days’ emissions remain trapped in the air shed.

Many key sources such as vehicles and biomass burning don’t necessarily have significant day-to-day fluctuations. So their daily emissions contribution gets added onto existing pollution loads. Over 10 days, these stable emissions consolidate and accumulate into high ambient pollution concentration rises, he says.

“Meteorology continues to remain unfavourable for dispersion as winter sets in over northern parts of India. Stagnant and cool air close to the ground prevents venting out the pollution,” he said.

In addition, festive activities could exacerbate this cumulative build-up effect. Increased vehicular traffic and related congestion during festive time (Christmas-long weekend) could spike daily tailpipe emissions, he said, adding that higher energy demand for lighting, heating, cooking, etc, boosts industrial/power plant operations.

Thermal inversions also become stronger in winter nights thereby concentrating pollution near the ground level.

“This sustained unfavourable meteorology, combines with relatively consistent emissions from key sources along with marginal periodic spikes from festivals/other anthropogenic activities, all are culminating into the very poor AQIs,” he added.

Pollution build-up to blame

Dr Ravindra Khaiwal, Professor of Environment Health, PGI, said: “This sustained period of unhealthy air quality levels in Chandigarh is likely to be a cumulative effect of pollution build-up rather than just reflective of a single day’s activity or conditions.”

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