What in the world: Anti-smog towers

In 2019, anti-smog towers or outdoor air purifiers were floated as an idea for controlling air pollution. Not for the first time.

Before the 2010 Commonwealth Games in 2010, an Italian company installed a $300,000-air-filter in Connaught Place, claiming it to be the cleanest spot in Delhi. There are no numbers to back this up, except for the 2.5 kg of dust collected during its one month of operation. Our estimate for Delhi’s particulate matter pollution is approximately 60,000 tons per year, not including seasonal dust storms and agricultural-clearing emissions. That is 5 million kg per month. Assuming that Connaught Place was the cleanest because of the filter’s operations, we would actually have needed at least 2 million of them to cover the city.

In an opinion piece at the time, Dr. Sarath Guttikunda noted that “installing an air filter in public is more like avoiding the problem and diverting attention away than solving it. Emissions should always be controlled at the source.”

In 2016, we heard about anti-smog towers or outdoor air purifiers again.

As pollution levels climbing up, attention was given to outdoor air purifiers and their possible role in controlling air pollution. NEERI and CPCB announced a plan to install outdoor air purifiers at traffic intersections. There were concerns about the effectiveness of such a solution.

Overall, there are widespread concerns in the scientific community about the effectiveness of such mitigation plans. In China, anti-smog towers were installed in at least two cities- Beijing and Xi’an but were not found to be successful and the idea has been considered to be a failure.

However, an anti-smog tower was proposed to control air pollution in Delhi (note that the anti-smog tower in Xi’an is referenced here!), and the Honorable Supreme Court also suggested this as a solution to air pollution. Separately, Bengaluru announced the plan to install 500 outdoor air purifiers and the Greater Hyderabad Municipal Corporation (GHMC) approved plans to install outdoor air purifiers across the city.

A range of experts agree on this: anti-smog towers are NOT the solution. Emissions need to be controlled at source.

It is costly and works for a limited area like 100 metres, and the pollutants can be easily transported to clean air (area) again. It is not practical to use these (smog-towers) to control air pollution

Dr. Hongliang Zhang, Fudan University

The outdoor purifiers are a distraction. We are saying, focus on the real action of cutting pollution at the source.

Ms. Anumita Roychowdhury, Centre for Science and Environment

It is like trying to air condition a room with the roof off. There is very little evidence they make a difference to concentrations of pollution.

Dr. Alistair Lewis, University of York

Here is an op-ed piece by Dr. Alistair Lewis on anti-smog towers and their inefficiency in controlling air pollution.

Note that there are some studies in the peer-reviewed literature on the efficiency of anti-smog towers (see this and this).

Across India, there has been consistent opposition to the idea to installing outdoor air purifiers or anti-smog towers.

In Bengaluru, members of the civil society responded to the plans for installation of outdoor air purifiers, and argued that the limited resources should be spent efficiently, and on measures that can demonstrably reduce air pollution. At the time, Dr. Guttikunda also argued that “Bengaluru will not breathe better air even with 44,000 air purifiers“.

In December 2019, Care for Air, a Delhi-based advocacy organized published an open letter against outdoor air purifiers to the Supreme Court of India.

Even MoEFCC has argued that roadside air purifiers are not an efficient solution

In November 2019, MoEFCC admitted that “roadside air purifiers and those installed on the top of buses to combat pollution have failed” but the discourse has continued & in fact, has taken an absurd turn recently.

In January 2020, an anti-smog tower was inaugurated in Lajpat Nagar, New Delhi and the Supreme Court recently directed Delhi to install anti-smog towers.

Gautam Gambhir, an MP (BJP) inaugurated an anti-smog tower in Lajpat Nagar. More

In an order in January 2020, the SC asked Delhi government and the Central Pollution Control Board (CPCB) to install anti-smog towers in the city (SC order). More on this here. Two towers were to be setup as a collaboration between University of Minnesota (USA) and IIT-Bombay.

In February 2020, CEEW released their analysis of anti-smog towers and noted that anti-smog towers are not a scalable solution for cleaning up the air.

Fast forward to July 2020 and we are back to talking about smog towers

The Supreme Court has taken up the matter again (more here). It was reported that IIT-Bombay backed out of the collaborative project (more) but as of August 4, 2020), work on one of the towers is set to commence (more) .

In a two-part series on anti-smog towers, Dr. Santosh Harish (CPR) lays out the why this technological solution may not be our best bet for cleaning India’s air (Part I and Part II).

Watch this space for new details in upcoming weeks.

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