For the love of air
the exercise of developing methodologies for building two basic tools of air quality management for Delhi - an air quality index (aqi) and an emission inventory - was launched at an international workshop in the capital recently. The workshop was organised by the Delhi-based Centre for Science and Environment (cse), and was attended by experts from the us , Sweden, India, Pakistan, Bangladesh and Nepal.The Indian participants included representatives from the Central Pollution Control Board (cpcb), Delhi Pollution Control Committee (dpcc), National Environmental Engineering Research Institute (neeri), Indian Institute of Petroleum (iip), Automotive Research Association of India (arai), Delhi College of Engineering (dce) and the Indian Institute of Technology (iit), Delhi. In 1997, cse had published a study which showed that Delhi's air pollution claimed one life every hour. But, despite the warning and worsening pollution levels, no action has yet been taken by the government to inform the public of the daily pollution levels and how it affects people's health. The government maintains a silence, while semi-government and independent research organisations make sporadic half-hearted efforts, which only add to the confusion. This is primarily because there are numerous gaps in our knowledge about the sources of the deadly cocktail of pollutants and the quantities emitted in the air everyday. In view of its extended campaign for 'Right to Clean Air', cse decided to take the initiative to assess the ambient air quality through an aqi and the emission levels through an emission inventory. An aqi is used to keep the public informed about the pollution level and its effect on the health of different groups of people like asthmatics, children and the elderly. The result was three days of hard deliberations. And this was only the beginning.
The challenges Developing an aqi for Delhi had its peculiar problems. Models employed by other countries were not found suitable here.
The first step in developing an aqi is to identify the major pollutants and decide how to convey to the public the effects of current levels of the pollutants on health. The general practice the world over is to bring out a daily aqi report on the pollutant which records the highest ambient concentration. But Delhi has the distinction of having a number of pollutants exceeding the permissible limits on any given day. The other issue, therefore, was to be able to provide warnings of the health effects of high levels of a mixture of pollutants simultaneously exceeding their safe limits.
The first task was to identify the pollutants which should be taken into account while preparing Delhi's air quality index? Experts made it clear that the three pollutants - sulphur dioxide, nitrogen dioxide and suspended particulate matter - regularly monitored at all sites by the cpcb, were not enough. For a proper aqi, it is absolutely essential that the range of pollutants monitored be increased to include pollutants like carbon monoxide, ozone and pm10 and that the daily levels of all pollutants be disclosed to the public. According to Joseph Cassmassi, senior meteorologist in the South Coast Air Quality Management District, California, the highest priority should be given to pm2.5 (particulate matter smaller than 2.5 microns), pm10 (particulate matter smaller than 10 microns), carbon monoxide and ozone.
According to the experts, measurement of total suspended particulate matter would serve no practical purpose. Even monitoring pm10 is not enough, they felt. The focus of monitoring particulate matter should shift to pm2.5 because these are fine particles emitted by combustion sources and can penetrate deeper into the lungs, causing more harm than pm10, they pointed out.
Credibility of data
The experts who analysed the air quality data and geographical and meteorological features of Delhi, were puzzled to find that data provided by cpcb shows extremely low levels of ozone in the city. However, when Viney P Aneja, Research Professor at the North Carolina State University, used the air pollution data of Delhi in an air quality model, he found that the ozone level could be as high as 4,000 microgrammes per cubic metre (
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