Delhi is the world’s most polluted city, if the World Health Organisation is to be believed, and the most prominent cause of the grime in the air is its vehicular traffic, if one goes by most sources. But in this oft-repeated narrative, an important strand is being ignored.
Last fortnight, the National Green Tribunal ordered the Delhi government to implement 14 measures to bring the capital’s alarming level of air pollution under control. Almost all of these addressed the very serious problem of Delhi’s traffic.
“No city can take these many cars, particularly in a bowl which traps in the air,” said Ravi Agarwal, director of the non-governmental organisation Toxics Link. “What is significant is that they have given a comprehensive judgement that is aware of the limits of the government. They are holding the system accountable to air pollution and something may come out of it.”
But policymakers may be ignoring another significant source of pollution in Delhi: areas outside the city.
A 2013 study on long-range transfer of airborne pollutants around Delhi suggests that at least half of the particulate matter less than 10 micrometres in diameter, or PM10, in the capital might have been meteorologically borne to it from the areas outside it.
“Our study showed significant transport of PM10 to the city,” said Manju Mohan, a professor at the Centre for Atmospheric Sciences in the Indian Institute of Technology in Delhi. “The transport of PM2.5 must also be significant.” The study, based on a regional chemical transport model, indicates that anywhere between 59% and 89% of PM10 emissions in Delhi might be originating outside the city.
“There are some uncertainties in the model,” said Mohan, “but they are there to give you a gross idea of the level of emissions.”
Outside pollutants
There are several possible sources of outside pollutants. For one, Delhi is next to Ghaziabad, an area that ranks second on the Central Pollution Control Board’s 2013 list of critically polluted industrial areas. A planned city noted for its heavy manufacturing industries, Ghaziabad has a score of 84.13 on the Comprehensive Environment Pollution Index, a scale that measures air, water and land pollution. Its air pollution score, measured in 2012 for the 2013 index, is 69.5.
Also near Delhi is the Najafgarh drain basin, which ranks 18th on the list and has a CEPI score of 73.42 and an air pollution score of 56.8. This region includes Anand Parbat, Naraina, Okhla and Wazirpur.
While Ghaziabad and Najafgarh have large polluting industries, Delhi is also susceptible to smaller units. In an effort to clean up its air in 1996, the Supreme Court banished hazardous and illegal industrial units and brick kilns from the city limits. (This order was still causing unrest till 2001.)
The industries relocated to the outskirts of the city, but still within the National Capital Region and are now among the possible contributors to the pollution.
These include the brick kilns that feed the thriving construction industry in and around Delhi. A 2012 paper by Sarath Guttikunda, a researcher on urban emissions, notes that there were around 1,000 kilns just outside Delhi’s city limits with a daily production capacity of 25,000 bricks. Other polluting and poorly regulated manufacturers include leather tanneries, smelters and metal-working shops, notes Guttikunda.
The long-range spread of pollutants usually depends on the weather, said Mohan, who plans to study their source in her next project. For instance, due to higher levels of moisture, Delhi is particularly polluted in winters and it had a particularly bad spell of smog in 2012. This was caused by a change in wind direction, followed by a period of calm that led to smoke from the annual burning of crop residues in Punjab getting trapped in the city for 12 days.
Poor figures
Despite the proximity of these industries to Delhi, pollution monitoring bodies in the capital, including the Delhi Pollution Control Committee, the System of Air Quality Weather Forecasting and Research, and the Central Pollution Control Board have focused recent studies largely on the impact of pollution arising within the city.
“At the time we were doing the study, there was a view that we do not have this problem so we should not do this study,” said Mohan. “The premise of the project is that there is long-range transport of pollutants – because there is science behind this – but nobody really tried to see how much it is and nobody tried to devise regulatory measures for it.”
The pollution control board does not have exceptional data on air pollution even within the city. In October, the Economic Times reported that the Central Pollution Control Board was relying on faulty machines to measure air quality and that Delhi might be far more polluted than imagined. Other areas in India might be worse off than Delhi.
Mohan said, “While regulations must be imposed on local emissions, astringent control should also be implemented for areas outside Delhi and on regional basis.”
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Last fortnight, the National Green Tribunal ordered the Delhi government to implement 14 measures to bring the capital’s alarming level of air pollution under control. Almost all of these addressed the very serious problem of Delhi’s traffic.
“No city can take these many cars, particularly in a bowl which traps in the air,” said Ravi Agarwal, director of the non-governmental organisation Toxics Link. “What is significant is that they have given a comprehensive judgement that is aware of the limits of the government. They are holding the system accountable to air pollution and something may come out of it.”
But policymakers may be ignoring another significant source of pollution in Delhi: areas outside the city.
A 2013 study on long-range transfer of airborne pollutants around Delhi suggests that at least half of the particulate matter less than 10 micrometres in diameter, or PM10, in the capital might have been meteorologically borne to it from the areas outside it.
“Our study showed significant transport of PM10 to the city,” said Manju Mohan, a professor at the Centre for Atmospheric Sciences in the Indian Institute of Technology in Delhi. “The transport of PM2.5 must also be significant.” The study, based on a regional chemical transport model, indicates that anywhere between 59% and 89% of PM10 emissions in Delhi might be originating outside the city.
“There are some uncertainties in the model,” said Mohan, “but they are there to give you a gross idea of the level of emissions.”
Outside pollutants
There are several possible sources of outside pollutants. For one, Delhi is next to Ghaziabad, an area that ranks second on the Central Pollution Control Board’s 2013 list of critically polluted industrial areas. A planned city noted for its heavy manufacturing industries, Ghaziabad has a score of 84.13 on the Comprehensive Environment Pollution Index, a scale that measures air, water and land pollution. Its air pollution score, measured in 2012 for the 2013 index, is 69.5.
Also near Delhi is the Najafgarh drain basin, which ranks 18th on the list and has a CEPI score of 73.42 and an air pollution score of 56.8. This region includes Anand Parbat, Naraina, Okhla and Wazirpur.
While Ghaziabad and Najafgarh have large polluting industries, Delhi is also susceptible to smaller units. In an effort to clean up its air in 1996, the Supreme Court banished hazardous and illegal industrial units and brick kilns from the city limits. (This order was still causing unrest till 2001.)
The industries relocated to the outskirts of the city, but still within the National Capital Region and are now among the possible contributors to the pollution.
These include the brick kilns that feed the thriving construction industry in and around Delhi. A 2012 paper by Sarath Guttikunda, a researcher on urban emissions, notes that there were around 1,000 kilns just outside Delhi’s city limits with a daily production capacity of 25,000 bricks. Other polluting and poorly regulated manufacturers include leather tanneries, smelters and metal-working shops, notes Guttikunda.
The long-range spread of pollutants usually depends on the weather, said Mohan, who plans to study their source in her next project. For instance, due to higher levels of moisture, Delhi is particularly polluted in winters and it had a particularly bad spell of smog in 2012. This was caused by a change in wind direction, followed by a period of calm that led to smoke from the annual burning of crop residues in Punjab getting trapped in the city for 12 days.
Poor figures
Despite the proximity of these industries to Delhi, pollution monitoring bodies in the capital, including the Delhi Pollution Control Committee, the System of Air Quality Weather Forecasting and Research, and the Central Pollution Control Board have focused recent studies largely on the impact of pollution arising within the city.
“At the time we were doing the study, there was a view that we do not have this problem so we should not do this study,” said Mohan. “The premise of the project is that there is long-range transport of pollutants – because there is science behind this – but nobody really tried to see how much it is and nobody tried to devise regulatory measures for it.”
The pollution control board does not have exceptional data on air pollution even within the city. In October, the Economic Times reported that the Central Pollution Control Board was relying on faulty machines to measure air quality and that Delhi might be far more polluted than imagined. Other areas in India might be worse off than Delhi.
Mohan said, “While regulations must be imposed on local emissions, astringent control should also be implemented for areas outside Delhi and on regional basis.”