State of air pollution in Indian cities | Centre for Science and Environment

State of air pollution in Indian cities

    Air quality data generated by the Central Pollution Control Board (CPCB) for 2007 under the National Air Quality Monitoring Programme (NAMP) presents deadly facts about air pollution levels in Indian cities.

Centre for Science and Environment has analysed the official data to assess the state of air quality and trend in Indian cities. The most widely monitored pollutants in India are particulate matter (PM), nitrogen dioxide (NO2), sulphur dioxide (SO2), and on a limited scale carbon monoxide.
Some of the worst forms of air pollutions are found in Indian cities. The Central Pollution Control Board (CPCB) considers air to be ‘clean’ if the levels are below 50 per cent of the prescribed standards for pollutants. During 2007 only 2 per cent cities have low air pollution on the basis of PM10. In about 80 per cent of cities (of a total of 127 cities/towns monitored under the NAMP) at least one criteria pollutant exceeded the annual average ambient air quality standards. This has serious public health implications. There are very few cities, which can be termed clean keeping PM10 levels (respirable particulates) as criteria however over the years SO2 levels have fallen sharply in many cities but the NO2 levels are increasing in many cities.

PM10 trend:
- Almost half of the total cities monitored under NAMP have critical levels of PM10. CPCB classifies cities as critically polluted if the levels of criteria pollutants are more than 1.5 times the standards. Levels up to 1.5 times the standards are labeled high. Levels that reach up to 50 per cent of the standards are moderate. And lower than that is low. In 2007 data of 121 cities has been analysed and only three cities Dewas, Tirupati, Kozhikode recorded low pollution level.

- Indian cities are reeling under heavy particulate pollution with 52 percent of cities (63 cities) hitting critical levels (exceeding 1.5 times the standard), 36 cities with high levels (1–1.5 times the annual standard) and merely 19 cities are at moderate levels, which is 50 per cent below the standard.

- The PM10 levels remain persistently high in the northern region. In the NCR towns Noida, Faridabad including NCT Delhi have high levels of PM10 and in past two years the levels have increased. Only in hill towns such as Shimla, Gajraula and Parwanoo have low PM10 levels. In western and eastern India, there is usually a mixed trend. Eastern cities, including Shillong, Angul, Rourkela and Howrah, show an increasing trend and in the west PM10 levels have declined in some cities like Ahmedabad, Solapur, Nagda and Jamnagar but increased in Mumbai, Kota and Satna.

- In southern India, though the cities generally have lower PM10 levels compared to the northern ones, some cities show an increase. In cities such as Hyderabad, Visakhapatnam, Tuticorin, and Bangalore there is an increasing trend. A sharp declining trend has been noted in Thiruvanthapuram, Kochi and Mysore during 2000-2007 PM10 levels are gradually reducing.

NOx trend:
- NOx (measured as NO2) is emerging as the new national challenge and a growing problem. The NO2 levels during 2007 at seven monitoring stations exceeded the annual average standard in residential areas and NO2 level at one monitoring stations in industrial areas exceeded annual average standard.

- The seven monitoring stations in residential areas that exceeded the standard are located at Town Hall (82 microgram per cubic metre), Sarojini Nagar (65 microgram per cubic metre) in Delhi, Salt lake (66 microgram per cubic metre), Moulali (76 microgram per cubic metre), Minto Park (65 microgram per cubic metre), in Kolkata, Gandhi Maidan (67 microgram per cubic metre) in Patna and Ghuseri (68 microgram per cubic metre) in Howrah. One monitoring stations in industrial areas where annual average standard was exceeded is located at Bandhaghat 91 microgram per cubic metre, (Howrah).

- In North India, cities such as Delhi (where traffic areas record high levels and often exceed the standards), Dehradun, Yamunanagar and Ludhiana show a rising trend. Eastern cities, including Howrah, Kolkata, Dhanbad, Jamshedpur and Jharia, have much higher levels compared to northern cities. In many cities in this region the levels declined up to 2004 however there is an increasing trend observed again in past two years.

- Southern Indian cities show a rising trend especially in Visakhapatnam, Hyderabad and Thiruvanthapuram. Cities in western India are relatively better off with almost constant to declining NO2 levels, though the levels indicate an increasing trend in Mumbai, Nagpur, Nashik, Pune and Chandrapur. Pune after showing high levels till 2003 showed sharp decline till 2005. One of the reasons attributed to lower levels being recorded in Pune is the shifting of the monitoring stations away from heavy traffic sites.

SO2 trend:

- Sulfur dioxide is not considered a problem in India any more. Its levels in most cities are already very low and declining. However, there are still some cities such as Khurja, Nashik, Jamshedpur and Chandrapur have moderate levels, the maximum levels was recorded at Khurja with 45 microgram per cubic meter.

- During 2007 National Ambient Air Quality Standard (NAAQS) (annual average) was not exceeded at any monitoring station in residential and industrial areas. SO2 levels at 79 per cent of the monitoring stations in industrial areas and 93 per cent of the monitoring stations in residential areas were less than 20 microgramme per cubic metre. The highest concentration in residential area was observed at monitoring station located at Nashik and highest concentration in industrial area was observed at monitoring station located at Khurja (UP) during 2007, although SO2 levels at none of the monitoring stations exceeded the annual average standard.

Trend in big cities
In the cities like Ahmedabad, Varanasi, Chennai, Pune, and Kolkata the PM10 levels have reduced in 2007 compared to 2002 levels. However in the cities like Mumbai, Faridabad, Lucknow, Bangalore and Delhi the PM10 annual average levels have increased in 2007 over 2002.  The nitrogen dioxide levels in the cities like Solapur, Ahmedabad, Pune and Kolkata has reduced. According to CPCB, although various interventions have taken place to mitigate ambient NO2 levels but at the same time number of vehicles have increased exponentially. The vehicles are one of the major sources of NO2. Measures taken to mitigate ambient NO2 levels are introduction of improved vehicular technology in the form of Bharat Stage –III vehicles, banning of old vehicles in some cities, improved traffic management etc.


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