Ambient Air Quality in Delhi

Ambient air quality monitoring conducted at different locations for a period of 24 hours in Delhi revealed that suspended particulate matter (SPM), respirable particulate matter (RSPM) and carbon monoxide are in high concentrations at all the monitoring stations. Sulphur dioxide has been recorded within prescribed limit at all the locations while Nitrogen dioxide was within limit at ITO, S.P.Marg, R.K.Puram Crossing, Dr. Jakir Hussain Marg, Windsor Place, Pusa Road, Janpath, Rashtrapati Bhawan, Ridge Area, Badli Industrial Area and Shahjada Bagh. The values of nitrogen dioxide exceeded at Connaught Place and Race Course. Air pollutants were found to increase between 8 AM to 11 AM and 4 PM to 9 PM. Ambient noise level was also found higher than the prescribed limit at all the locations during peak traffic hours.

Benzene Monitoring (By Passive Sampling Method) in Delhi and Kanpur

CPCB has been monitoring benzene in ambient air at seven locations in Delhi comprising residential, industrial and commercial areas. The monthly average values observed at all the locations vary between 16 to 35 microgrammes per cubic metre. Overall mean benzene concentration for all seven locations has been calculated as 26 microgrammes per cubic metre. This is 1.6 times higher than the United Kingdom's Annual Running Mean Standard of 16 microgrammes per cubic metre.

The monthly average values observed in Kanpur varies between 7 to 41 microgrammes per cubic metre. Overall mean benzene concentration for all five locations in Kanpur was calculated as 22 microgrammes per cubic metre, which is 1.4 times higher than the United Kingdom's Annual Running Mean Standard.

Benzene monitoring was carried out using BTEX Analyzer (Benzene, Toluene, Ethyl benzene, o,m,p-Xylene) at ITO and at CPCB premises. Higher levels were observed at ITO.

Levels of Benzo(a)Pyrene in Delhi

Measurements for Benzo(a)pyrene in ambient air particulate samples collected at six locations in Delhi indicate that the annual average ranged between 1.0 ng/m3 to 5.3 ng/m3 from 1997 to 1999. The recommended standard for concentration of B(a)P in ambient air is 10 ng/m3. The concentration of B(a)P during winter season was generally higher as compared to monsoon and summer. Low concentration of B(a)P was recorded during summer possibly due to photo-oxidation and meteorological conditions favouring the dispersal of B(a)P. During monsoon, rain and washout are possible reasons for the low B(a)P.

Ambient Noise Level and Air Pollution during Deepawali

Ambient noise level monitoring was carried out at various locations in Delhi, i.e. Patel Nagar, AIIMS, Connaught Place, India Gate, Lajpat Nagar, Mayur Vihar, New Friends Colony and East Arjun Nagar on occasion of Deepawali festival. The ambient noise levels were above the prescribed limits but were slightly lower at few locations as compared with the previous year's data.

Ambient air quality monitoring was also carried out at ITO intersection, Ashok Vihar, East Patel Nagar and Pusa Road. SO2 levels were higher in the evening on Deepawali day and pre-Deepawali day. NOx and CO levels were observed lower on the Deepawali day as compared with the pre-Deepawali day.

Monitoring of PM10 (RSPM) in Kanpur

Ambient air quality monitoring of PM10 in Kanpur was conducted. Status of PM10 is being worked out with reference to developing a control strategy for PM10 under the World Bank Assisted Programme. The monitoring of PM10 is being conducted with the objective to determine status of PM10 in ambient air of Kanpur and to assess the content of sulphate in PM10. The monitoring was started a 6 locations in Kanpur in July 2000 by CPCB and in September 2000 by the National Environmental Engineering Research Institute (NEERI) at three locations. The Uttar Pradesh Pollution Control Board is measuring PM 10 at 3 locations in Kanpur since April 2000. The frequency of monitoring has been maintained twice in a month, and the following parameters were planned for monitoring: RSPM, SO2 and Sulphate. The maximum & minimum concentrations of RSPM & SO2 at different locations monitored are presented below:





Average RSPM (m g/m3)
Average SO2 
(m g/m3)
Civil Lines 
Gol Chouraha 
Kidwai Nagar 
Deputy Ka Parao 
Lajpat Nagar 
Bara Chouraha 
Agricultural University

The values of SO2 are within norms but RSPM exceeds far in excess of the prescribed norms.

Quality Assurance for Air Quality Measurements

The Central Pollution Control Board has set up a dynamic dilution system (Ring Test Facility) to produce gas mixtures of any desired concentration and composition. The primary objective of developing this system is to conduct quality assurance programme for participating laboratories as well as to calibrate continuous monitoring analyzers. Participation in the quality assurance programme helps the laboratory in achieving compatibility of results and to validate the method being adopted for the measurement. CPCB has been conducting the quality assurance programme for State Pollution Control Boards since 1999. During March 2000, officials from seven State Pollution Control Boards took part in AQC programme for measurement of sulphur dioxide and nitrogen dioxide by wet chemical methods. On analysing the results, it was observed that the performance of 90% of the participating laboratories was satisfactory.

Figure 1: RSPM (Annual Average) in various Cities in India during 1999

Levels of Respirable Suspended Particulate Matter (RSPM) in Selected Cities

The RSPM levels in residential and industrial areas in selected cities are presented in Figure 1. RSPM levels exceeded the National Ambient Air Quality Standards (NAAQS) (annual average) in residential areas of all the monitored cities. Also, RSPM levels exceeded the NAAQS (annual average) in industrial areas of all the monitored cities except Visakhapatnam, Cochin, Mumbai and Chennai. The Respirable Suspended Particulate Matter violated 24 hourly average RSPM Standard at all the monitored locations except Industrial estate, Visakhapatnam. The trend in annual concentration of RSPM at BSZ Marg, (ITO Intersection) New Delhi is depicted in Figure 2. RSPM levels exceeded the NAAQS (annual average) during 1998, 1999 and 2000 at BSZ Marg, New Delhi.

Since the target sampling of 24 hours in a day could not be fulfilled at all the locations due to the power failures etc., the values monitored for 16 hours and more are considered as representative values for assessing the ambient air quality for a day. The target frequency of monitoring twice a week, 104 days in a year could not be met in some of the locations, in such cases, 40 and more days of monitoring in a year is considered adequate for the purpose of data analysis.

Figure -2 Annual Mean Concentration of RSPM at B.S.Z Marg (ITO Intersection) New Delhi

Trends of Sulphur Dioxide (SO2) Levels in Delhi

The trend in annual mean concentration of SO2, at Bahadurshah Zafar Marg. (ITO Intersection), New Delhi is shown in Figure 3. The annual mean concentration of SO2 did not exceed the NAAQS (annual average) during all years of monitoring. Decreasing trend in SO2 levels is observed which is attributable to low sulphur diesel introduced in Delhi.

Figure 3: Trend in Annual Average of SO2  at BSZ Marg (ITO Intersection), New Delhi

Trends in Nitrogen Dioxide (NO2) levels in Delhi

The trend in annual mean concentration of NO2 at BSZ Marg (ITO Intersection), New Delhi is depicted in Figure 4. Decreasing trend in NO2 levels is observed, which might be due to prohibition in plying of more than 15 - year old commercial vehicles in Delhi.

Figure 4: Trend in Annual Average of NO2 at BSZ Marg
(ITO) Intersection, New Delhi

Trends of Suspended Particulate Matter (SPM) in Delhi

The trend in annual mean concentration of SPM at BSZ Marg (ITO Intersection) is shown in Figure 5. SPM levels exceeded the NAAQS (annual average) during all the years.

Trends in Carbon Monoxide (CO) levels in Delhi

Trends in annual mean concentration of CO at BSZ Marg (ITO Intersection), New Delhi is shown in Figure 6.

Air quality, with regard to Sulfur Dioxide (SO2), Oxides of Nitrogen (NO2) and Suspended Particulate Matter (SPM) in industrial and residential locations in various cities/town was monitored during the reported period and evaluated on the basis of Exceedence Factor (EF) in terms of low, moderate, high and critical.

Figure 6: Annual Average Concentration of CO(mg/m3) at BSZ Marg (ITO), New Delhi

Air Quality Index for Public Information

An Air Quality Index (AQI) has been developed in collaboration with the Indian Institute of Technology, Kanpur based on the dose-response relationship of various pollutants. A minimum number of three pollutant parameters (Suspended Particulate Matter (SPM), Sulphur Dioxide (SO2) and Nitrogen Dioxide ( NO2) are essential to calculate the AQI. Any additional information on other pollutants such as Respirable Particulate Matter (RSPM or PM10), Carbon Monoxide (CO) and Ozone (O3) are included to calculate conclusive and complete value of AQI. The developed index is classified in five categories: Good (0-100), Moderate (101-200), Poor (201-300), Very poor (301-400) and severe (401-500).

To present the AQI to general public through mass media (e.g. TV, Internet, Newspaper, radio etc.), a website has become functional (http://home.iitk.ac.in/~mukesh). The website is capable of producing online and historical AQI values for any specified city and location with potential health effects. The special feature of the website is multiple windows system with animation to facilitate inter/intra city comparison of air quality.

Preparation of Environmental Management Plan for Taj–Trapezium Zone (TTZ)

To protect the National Heritage site at Agra and its nearby areas, the Ministry of Environment & Forests had formed an Authority for prevention and control of pollution in the zone. Alongwith pollution prevention activities by other organisations, CPCB took up the activity to prepare the Environmental Management Plan for the entire Zone. The work was initiated in September 2000 and is expected to be concluded by March 2002. The assigned activity is in progress with financial assistance from the World Bank.

The work has been divided in two phases viz. City level Planning and Regional Level Planning. In the city level planning, among other activities, the thematic maps in respect of drainage, water resources, road network, tourist places, solid waste, environmental resources maps have been prepared. In case of Regional Planning Forest, Natural drainage, Contour, Tourist site, settlement and heritage site maps etc. have been prepared. For analysis of the data and its digitization, Geographical Information System (GIS) is proposed to be used.

Air pollution and Human Health

In collaboration with the All India Institute of Medical Sciences (AIIMS), a project has been initiated on the effect of ambient air quality on human health in Delhi. Preliminary survey indicated that CO levels in blood among smokers, factory workers and petrol pump workers are higher and symptoms related to adverse impact on respiratory, cardio-vascular and nervous system were observed.

Important Activities in Air Quality Evaluation and Pollution Control

  • Review of the present air quality monitoring network is under progress. There is a proposal to increase the number of monitoring stations.
  • Report on "Air Quality Status of the city of Delhi" was prepared.
  • Report on "Air Quality Status and Trends in India" was prepared and published
  • CPCB Website (http://www.cpcb.nic.in/) regularly updated with respect to weekly air quality data of ITO intersection, Delhi
  • Measurement of 15 polyaromatic hydrocarbons in ambient air of Delhi has been undertaken
  • Monitoring of ambient ozone at ITO intersection, New Delhi is continued
  • Two fixed and one mobile continuous automatic ambient air quality monitoring stations operated in Delhi, where SPM, SO2, NO2, NOx, CO are recorded
  • Seven stations in Bangalore were monitored for measurement of RSPM, SPM, SO2 and NOx at important traffic intersections of Bangalore City.
  • Pollutants like SPM, RSPM, SO2, NOx, PAH and lead were monitored at 13 traffic intersections in Calcutta.