Context: Recently, a Supreme Court bench had sharp words for authorities in Haryana, Punjab and Uttar Pradesh for failing to control the practice of stubble-burning on farms, which contributes to air pollution in Delhi at the beginning of every winter. 

• The Bench directed authorities to take measures, including asking the Delhi government and the Central Pollution Control Board (CPCB) to submit a comprehensive plan on setting up “smog towers” in the capital.

About Smog Towers

• It is a structure designed to work as a large-scale air purifier, fitted with multiple layers of filters which trap fine dust particles suspended in the air as it passes through them.
• The air is drawn through fans installed at the top of the tower, passed through filters, and then released near the ground.
• The large-scale filters expected to be installed in the towers in Delhi would use carbon nano-fibres as a major component.
• The first such tower was erected in 2015, in Rotterdam, Netherlands, created by Dutch artist Daan Roosegaarde.

Scenario of Air Pollution in New Delhi

• The air pollution in the national capital has been an issue of concern for quite some time as Delhi and its suburbs have ranked among the most polluted cities in the world frequently since 2014.
• The pollution levels in Delhi increase dramatically during winter with nearly 10 times above the limits prescribed by WHO.
• The major sources of emissions are construction work, industrial and vehicular pollution in and around the city remain more or less consistent.
• An assessment by the CPCB shows that Delhi’s air quality has been improving every year since 2016, even as it remains above acceptable limits.

Effectiveness of Smog Towers

• The towers would create “clean air zones” in the city which would reduce 50% of the particulate matter load.
• The smog towers may not be useful for the whole city, but they can be useful in creating ‘clean air area’ zones in different parts of the city.
• In an open field in calm weather, it can reduce particulate matter of 10 micrometres (PM10) up to 45%, and PM2.5 levels up to 25% in an area of 20 metres around the tower.