Are Smog towers effective? – Explained, pointwise

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Two new smog towers have been recently inaugurated in Delhi. Bengaluru and Chandigarh have also installed smog towers this year. Further, Mumbai’s clean air plan also indicates a financial requirement of ₹25 crore for installing air filtration units at major traffic intersections in the city.

While these efforts indicate that governments are taking cognisance of air pollution, criticism has also been levelled against using quick technological fixes instead of proven solutions to combat air pollution.

Let’s examine the issue in detail.

What is a smog tower?

A smog tower is a structure designed as a large or medium scale air purifier to reduce air pollution.

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It is fitted with multiple layers of air filters and fans at the base to suck the air. After the polluted air enters the smog tower, it is purified by the multiple layers before being re-circulated into the atmosphere. Smog towers work on the principle of HEPA filtration or air ionisation technology to remove PM2.5 particles. That is, air flowing through a smog tower passes through a filter to provide clean air coming out of it.

What are the harmful effects of smog?

Smog causes multiple health problems, such as difficulty in breathing, irritation in the eyes, asthma, reduced immunity to lung infections, and colds that can be fatal in children.

The ozone in the smog also inhibits growth in plants. It can cause widespread damage to crops and forests, and the haze reduces visibility. When inhaled, smog irritates our airways, increasing the risk of serious heart and lung diseases. These health risks are the reason why many cities monitor smog levels.

What is the scale of air pollution in India?

As per the University of Chicago’s Air Quality Life Index (AQLI) report,

India is the most polluted country in the world, with more than 480 million people or about 40% of its population living in the Indo-Gangetic plains in the north where pollution levels regularly exceed those found anywhere else in the world by an order of magnitude.

According to a new report released jointly by UK-based non-profit Clean Air Fund,

Air pollution in India has caused losses of up to Rs 7 lakh crore ($95 billion) annually

According to the World Health Organization (WHO),

India has six of the top 10 most polluted cities in the world, with Delhi on the top of the list.

A 2020 study in The Lancet found

There were 1.67 million deaths in India attributable to air pollution in 2019, including almost 17,500 in Delhi.

What are some issues with the smog towers?

– No scientific evidence: Delhi government claims that the newly installed smog tower in Connaught Place could reduce air pollution levels by 80%. But there is no scientific evidence of smog towers or any other outdoor air filtration units improving air quality in cities. The smog tower installed in China’s Xi’an and another one installed in Beijing did not prove to be effective and were not scaled up.

– Smog towers give citizens a false sense of complacency and assurance, making them feel they are getting air of better quality. This false belief encourages polluting behaviour, as no cost is being imposed on polluters.

Adds to the pollution: A huge number of filters are used in smog towers. Over time these clogged filters find their way to our already overburdened landfills and end up being burnt, thus adding to the pollution.

– Benefits limited to a specific area: The benefits at the surface might be somewhat greater. But cities aren’t sealed boxes, and they have a constant inflow of pollution that needs continuous removal. In other words, only areas located directly downwind of a chimney releasing clean air will see the benefits. 

What has been the global experience?

China– China made a minor show of a 7-metre high anti-smog tower erected in Beijing. It promised to use green energy to clean up 70% of the locality’s breathable particles. However, the concept was trashed by experts for its lack of efficacy in a megacity. So, China’s policy focus shifted to clamping the emissions and reforestation efforts such as great green wall.

Los Angeles– It took similar measures and is now focusing on improving energy efficiency.

What is the way forward?

i). The data on the effectiveness of the newly installed smog towers should be made available publicly for independent evaluation. The government should install calibrated continuous air quality monitors within a 1 km radius of these towers to allow the public to oversee the efficacy and efficiency of this tower.

ii). A better engineering solution to control air pollution is by controlling the emissions at the sources. For example, we can control the emissions in vehicle exhaust by using filters for particles and catalytic converters for gases.

Further, governments must ramp up investments in proven solutions to reduce air pollution.

Policymakers should expand monitoring of air pollution in areas with limited or no air quality monitoring and strengthen forecasting capacity across cities. Of the 132 cities in the country that currently don’t meet the National Ambient Air Quality Standards, 75 do not have a single real-time monitoring station. For areas with no monitoring infrastructure, alternatives like low-cost air quality monitors in combination with satellite observations should be explored to plug the existing data gaps.

Cities should strengthen their air quality forecasting systems by collaborating with scientific institutions that are transparent about their approach and findings. These forecasts should be used in rolling out preventive measures such as travel restrictions, pausing commercial activities or encouraging working from home, on anticipated high pollution days.

– City-level emission inventories must be updated periodically. Until last year, over 75% of our city clean air plans did not contain vital information on emissions from different polluting sources. This data is critical to identify key sources of air pollution and design effective clean air plans as per the local context. While several academic institutions carry out emission inventory and source apportionment studies, these studies should not become a one-time exercise.

– Targeted efforts must be made to improve air quality for urban slum dwellers who have no access to clean cooking energy and use biomass and other polluting fuels for their cooking needs leading to increased household emissions.

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