HOW TO CLEAN UP

Four main sources contribute to pollution in our citiestransport, construction, coal-based power plants and agriculture. Here is how we can address them

- M.G. ARUN, ANILESH S. MAHAJAN & AVISHEK G. DASTIDAR

As a thick, poisonous smog engulfed Delhi this November, like so many Novembers before, the air quality level in the national capital deteriorated to its worst ever in eight years. Doctors, too, began reporting an alarming rise in complaints of respiratory disorders. In desperation, the Delhi administration reached out to experts at IIT Kanpur to conduct an experiment that they had long been contemplating of artificial rain. Using the technique of 'cloud seeding', it involves dispersing silver iodide into the atmosphere, which aids the formation of ice crystals in clouds and triggers precipitation. Its use is mostly in dispelling drought in an area, but Delhi wanted to try it-for the first time to clean its air of pollutants. Fortunately, Mother Nature intervened and unexpected showers washed away the smog, restoring some of the air quality. But with its Air Quality Index (AQI), a pollution indicator, continuing to hover at 'hazardous' levels, Delhi kept the cloud-seeding aircraft on standby.

However, while Delhi's smog story is a familiar one, it is by no means the only one in the country. Of the 242 cities for which the Central Pollution Control Board (CPCB) released data on November 14, two days after Diwali this year, the air quality in only 40 was in the 'satisfactory' to 'good' range. On that day, the air quality was 'severe' in three cities, 'very poor' in 32, 'poor' in another 64, and 'moderate' in 106. Bharatpur in Rajasthan was the most polluted, with its AQI of 405 beating Delhi's 377. The smog did not spare India's financial capital either this year, with Mumbai's air quality remaining 'hazardous' for several days. AQI levels are considered 'hazardous' when they breach the 150 mark.