Improving Urban Air Quality
Delhi, India

Context

In the last half-century, increasing migration and industrialization have caused a boom in the number and density of mega-cities worldwide. While in 1950 just 54 million people lived in cities with populations larger than 5 million, this number is expected to be more than ten times higher by 2015 ^[3]. Despite tremendous social and technological advances, this rapid growth has come with a heavy price: the confluence of overcrowding with the rise of personal automobile ownership has made air pollution common in these ever-larger urban centers.

Urban areas in topographic basins or valleys where surrounding hills or mountains inhibit air circulation are also prone to the build-up of persistent and high levels of photochemical smog. The health impacts caused by outdoor air pollution have been widely recognized by both national governments and multilateral development organizations as a threat to urban populations, especially in developing countries. People living in large urban areas, especially in developing countries, where the health risks of air pollution may be underestimated and pollution controls lacking, are routinely exposed to concentrations of airborne pollutants that have been shown to cause negative health effects in both the short and long term. Cited as one of the Top Ten Worst Pollution Problems in Blacksmith Institute’s 2008 report, urban air pollution persists as a growing environmental health  issue ^[4].

Site Details

India carries a large part of this heavy burden. In the National Capital Territory (NCT) of Delhi, urban population increased by 51.53 percent between 1991 and 2001 ^[5], and is expected to reach 21 million inhabitants by 2015, making Delhi the 5th largest city in the world ^[6]. In addition to the ecological and industrial problems this poses, Delhi’s communities and government have had to face a dramatic increase in pollutants resulting from the surge in personalized vehicles. Historically the city has relied largely on small, 2 and 3-wheeled vehicles equipped with 2-stroke engines, which emitted more than 70 percent of hydrocarbons and 50 percent of carbon monoxide in Delhi’s air. Overloaded, poorly maintained buses and diesel trucks are also traditional fixtures on the city streets. This combination led to a dramatic rise in pollution from total suspended particles (TSP), which reached a high of 450 μg/m³ in 1996 ^[7].

Exposure Pathways

People are exposed to outdoor air pollution by breathing in pollutants, and by exposing eyes and skin while they are outdoors. Exposure is intensified by vigorous activity, as pollutants are drawn more deeply into the lungs during periods of physical exertion. People who live or work in close proximity to emission sources such as power plants, local industry or highways/major roadways are often exposed to higher concentrations of pollutants for longer periods of time, which elevates their risk of developing acute and/or chronic health problems. Long-term exposure to relatively low levels of pollutants can also cause serious health problems. Cities in developing countries often suffer heavily from outdoor air pollution, due to the heavy use of diesel fuel for transport vehicles, the predominance of coal for power generation, the proximity of urban populations to industrial facilities, and the lack of advanced emission controls for vehicles and industry.

Health Impact

Major health effects associated with outdoor air pollution are typically chronic pulmonary and cardiovascular stress from the fine particles and include increased mortality, respiratory and cardiovascular disease, lung cancer, asthma exacerbation, acute and chronic bronchitis, restrictions in activity and lost days of work.The health effects of outdoor air pollution fall disproportionately on infants, children and the elderly. People with pre-existing health conditions are also significantly affected. Studies indicate that chronic exposure to nitrogen dioxide (NO2) may impair lung development in children and cause structural changes in the lungs of adults. Exposure to ground-level ozone also causes burning and irritation of the eyes, nose and throat, and the drying out of mucous membranes, reducing the ability of the body to resist respiratory infections. Overall, health effects depend on many factors: the pollutant and its concentration in the air, the presence of multiple pollutants, temperature and humidity conditions, and the exposure period of a person to the pollutant, in both the short- and long-term. It is estimated that 7,500 Indians die every year from outdoor air pollution in Delhi alone. A significant reduction in vehicular pollution is key to saving those lives, as well as reducing soaring health care costs. To accomplish these goals, studies have established a target of reducing particulate matter (PM10) by 142 μg/m³ ^[8].

Intervention

Since the early 1990s, India’s Ministry of Environment & Forests (MoEF) has undertaken a multi-pronged approach to solving Delhi’s air pollution problem. Officials recognized early on that vehicles contributed almost two thirds of total pollution figures and initially focused their efforts on converting Delhi’s public transportation fleet to cleaner fuels; the first Compressed Natural Gas (CNG) bus was launched on an experimental basis in 1998. Negotiations between the local and national governments and private contractors culminated in 2001 with the progressive conversion of city buses. Delhi now boasts the largest fleet of CNG-powered buses in the world, and has invested in a suitable network of CNG stations to cater for the demand. While buses account for less than 1% of vehicles on the road, they serve almost half of Delhi’s travel needs ^[9].
CNG’s success in Delhi relied on legal requirements forcing the local government, private operators and individuals to convert to cleaner fuels. Early on, India’s Supreme Court and MoEF introduced emission norms, mandatory inspection and maintenance requirements, and gradually phased out older private vehicles. Through sales tax exemptions and other incentives, the Delhi government helped replace 47,000 older auto-rickshaws and conducted pollution testing on 2.4 million vehicles between 2002 and 2003 alone. Other fuel control measures were introduced: a ban on leaded gasoline, the introduction of EURO I and EURO II emission norms, controls on adulteration of fuel, control of their sulfur content, lowering of benzene content in petrol ^[10]. These measures eventually led to the wide-scale conversion to natural gas and in 2005 the Supreme Court began imposing a pollution tax on diesel buses that had not yet converted to CNG. The revenues generated allowed the city to invest in other pollution control measures throughout Delhi’s agglomeration.
Following MoEF’s recommendation, Delhi’s government initiated an ambitious project to update its transportation infrastructure. The Delhi Metro Network, started in 1998, opened its doors to commuters in 2002 and has since been a model of speed and efficiency. With further expansion phases planned for the upcoming years, the network will reach 500 km of metro lines by the year 2020. The highway network has also been rehauled, notably with the construction of the brand new, 136 km-long Kundli-Manesar-Palwal (KMP) expressway. This ring road has been an important factor in helping decongestion within Delhi itself.

Results

The partnership’s initiatives, and the government’s stringent legal requirements in regard to the major outdoor air pollution contributors yielded good results. After peaking in 1996, vehicular pollution was curbed and levels of the major pollutants began decreasing: between 1998 and 2003, ambient carbon monoxide (CO) decreased by almost half ^[11]; from 1993 to 2000, lead concentrations fell by 75 percent; between 2000 and 2003, as buses were converted to CNG, sulfur dioxide levels (SO2) decreased by 34.8 percent, and particulate matter (PM10) levels, by 7 percent ^[12]. During the same period, however, monitors also observed a 13.7-percent increase in nitrogen dioxide (NO2). This is explained by the dramatic rise in personal vehicles, but also by CNG’s high burning temperatures, which help nitrogen from air react with the oxygen in the combustion chamber, thus resulting in higher NO2 levels than traditional engines. These results are widely considered to show a significant success, even leading one expert to exclaim, “What took 30 years to accomplish, we have done in 5 years.” ^[13] In 2003, Delhi received the Clean Cities International Award by the U.S. Department of Energy for its aggressive efforts in curbing pollution.

Implementing Organizations

India’s Ministry of Environment & Forests (MoEF), the Supreme Court of India, the Delhi Metro Rail Corporation.

Remaining Challenges

Delhi’s development as one of Asia’s main industrial and financial hubs has caused an important increase in population, leading to an explosion in the number of personal vehicles: from less than a million in 1990 to almost 3 million in 2005 ^[14]. This rise will present a formidable challenge to Delhi stakeholders, as vehicular pollution contributes 67 percent of the total pollution in the city. ^[15] In addition, and despite a promising curb in overall vehicular pollution, the Central Pollution Control Board still considers most major pollutants to be above acceptable levels. The high levels of NO2 emitted by CNG, as well as the many other pollutants caused by factors other than vehicles must also be addressed: studies showed that particulate matter (PM10) levels began increasing again in 2003 ^[16]; this increase is related to small industries, domestic coal burning, thermal power plants and natural sources as well as vehicular pollution, but the trend demonstrates the challenges ahead for Delhi’s population. Government agencies and individuals will need to continue re-assessing fast-changing demographics, technologies and industry in order to prevent a return to the catastrophic pollution levels of 1990’s.

Outcomes of Delhi Air Quality Improvement Measures

Source: Auto Fuel Policy, 2002, cited in: United Nations Population Division, World Urbanization Prospects: The 2001 Revision

References

Blacksmith Institute. (2008) Top 10 Worst Pollution Problems. New York, NY.

Chelani, A. B., & Devotta, S. (2007) Air Quality Assessment in Delhi: Before and After CNG as Fuel. Environmental Monitoring and Assessment, 125, 257-263.

Narain, U., & Krupnick, A. (2007) The Impact of Delhi’s CNG Program on Air Quality. Resources for the Future Discussion Paper 07-06. Retrieved 10/05/09 from:
→ http://ideas.repec.org/s/rff/dpaper.html

Ravindra, K. et al. (2006) Assessment of Air Quality in Delhi After the Implementation of Compressed Natural Gas (CNG) as Fuel in Public Transport in Delhi, India. Environmental Monitoring and Assessment, 115, 405-417.

United Nations Environment Program. CNG conversion: Learning from New Delhi. Retrieved 10/05/09 from:
→ http://ekh.unep.org/?q=node/1737

United Nations Population Division, World Urbanization Prospects: The 2001 Revision.

Additional Photos

Efforts to improve air quality in Delhi face an uphill battle given a rapidly growing population and expanding metropolitan area. Credit : Dave Morris

Footnotes

^{[1] Ravindra, K. et al. (2006) Assessment of Air Quality in Delhi After the Implementation of Compressed Natural Gas (CNG) as Fuel in Public Transport in Delhi, India. Environmental Monitoring and Assessment, 115, 405-417.
[2] Chelani, A. B., & Devotta, S. (2007). Air Quality Assessment in Delhi: Before and After CNG as Fuel. Environmental Monitoring and Assessment, 125, 257-263.
[3] United Nations Population Division, World Urbanization Prospects: The 2001 Revision.
[4] Blacksmith Institute. Top 10 Worst Pollution Problems, 2008.
[5] United Nations Environment Program. CNG conversion: Learning from New Delhi. Retrieved 10/05/09 from:
→ http://ekh.unep.org/?q=node/1737
[6] United Nations Population Division, World Urbanization Prospects: The 2001 Revision.
[7] Chelani, A. B., & Devotta, S.
[8] Ravindra, K. et al.
[9] Chelani, A. B., & Devotta, S.
[10] Ibid.
[11] Ravindra, K. et al.
[12] Chelani, A. B., & Devotta, S.
[13] United Nations Environment Program.
[14] Narain, U., & Krupnick, A. (2007) The Impact of Delhi’s CNG Program on Air Quality. Resources for the Future Discussion Paper 07-06. Retrieved 10/05/09 from:→  http://ideas.repec.org/s/rff/dpaper.html
[15] Chelani, A. B., & Devotta, S.
[16] Ravindra, K. et al.}