Vijay Garg

Delhi air turns poison again

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Delhi is going through its customary, year-end haze of air pollution, when air quality turns toxic. Even after years of enduring this problem, little or nothing has been done to mitigate this annual calamity. Last week, the air quality in Delhi plummeted to its worst levels since January as smoke from smouldering paddy fields in Punjab and Haryana drifted in, marking the beginning of what has been an annual environmental blight that is only predicted to worsen, with more farm fires likely and unhelpful meteorological conditions predicted to persist.

The air quality index (AQI) slumped from an uncharacteristically clean 271 on Wednesday last to 354 on Thursday, according to the 4pm bulletins released on both days by the Central Pollution Control Board. An AQI above 300 is considered “very poor” – the second worst band on the AQI scale. At least two regions in the city, Anand Vihar and Ashok Vihar, had an AQI above 400, which lies in the worst “severe” band. Wind speeds have dropped significantly from October 26 onwards and we are seeing calm wind conditions at night time. Delhi saw calm wind conditions for nearly seven hours between 4.30 am to 11.30 am on Thursday, with this spell playing a significant role in accumulation of pollutants. This was Delhi’s highest AQI in over 10 months; on January 21, it was 365. Forecasts show similar calm conditions are expected to prevail until the end of the month now, largely keeping Delhi’s air quality in the “very poor” category.

Behind the deterioration in Delhi’s air quality was the perfect storm of conditions: the direction of winds changed to northwesterly that fed in a stream of smoke from fires, the number of fires itself spiked in recent days, local winds weakened that help blow away dust and tailpipe gases died down, and the temperature dipped, creating an “inversion” effect that causes pollutants to settle closer to the ground, instead of being dispersed higher into the sky.

In Delhi, vehicles are worst offenders when it comes to pollution. Second comes crop stubble burning in states neighbouring Delhi, which contribute upwards of 30% to the fine particulate matter that clouds visibility, allergises eyes and lungs and, in the case of suspended particulate matter that measures less than 2.5 microns, penetrates deep into the lungs and their tissue. Farmers might, just might, adopt measures other than burning off the stalks that remain on the fields after harvesters have sheared off their bounty of grain, simply out of the goodness of their hearts – if they had the time. But time is a luxury they do not have, in the interval between harvesting the paddy and planting the winter crop of wheat. Until a foolproof, scientific solution comes up, Delhi has to continue to endure the pain.

The writer is retired Principal, educational columnist.


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