Some of the best brains in the field of air quality management from across the world met in an international workshop organised by Centre for Science and Environment in Delhi to develop two tools of critical importance in air quality management.

The exercise of developing methodologies for building two basic tools of air quality management for Delhi an air quality index and an emission inventory was launched at an international workshop, in the capital recently. The workshop was attended by experts from the US, Sweden, India, Pakistan, Bangladesh and Nepal. The Indian participants included representatives from Central Pollution Control Board (CPCB), Delhi Pollution Control Board (DPCC), National Environmental Engineering Research Institute (NEERI), Indian Institute of Petroleum (IIP), Automotive Research Association of India (ARAI) and Indian Institute of Technology (IIT), Delhi. Three days of hard deliberations produced a blue print for future actions.

The Challenges
An AQI is used to inform the public of the daily air pollution levels and their effects on the health of different groups of people like asthmatics, children, elderly and also to healthy. However, developing an air quality index for Delhi presented unique problems. It could not just adopt any model being used other countries.

The first step in developing an AQI is to identify the various problem pollutants and to decide how to convey to the public the various effects the different levels pollutants have on their health. But Delhi has the unique problem of a number of pollutants shooting high above the permissible limit on any given day. The question that loomed large was how to capture the health effects of the high levels of the mixture of these pollutants.

Which pollutants should be monitored?
Only three pollutants are monitored regularly at all sites in Delhi —sulphur dioxide, nitrogen dioxide and suspended particulate matter. The experts, however, made it clear that an AQI should be able to capture the health risk from pollution levels comprehensively and for that the range of pollutants monitored be increased to include pollutants like carbon monoxide, ozone and PM10. They also pointed out that the levels of all pollutants should be reported to the public daily.

What about toxic air pollutants?
Another question, hotly debated during the discussions was whether to include toxic air pollutants like benzene in the AQI. It is now well known that concentration of benzene, a known carcinogen, in Delhi’s air is extremely high. However, the experts suggested that a cancer risk map of Delhi should be prepared based on the annual average concentration of benzene, rather than announcing its daily levels, as according to the World Health Organisation there is no level below which it can be considered safe.

Notably, the experts found that if the AQI of USA, which has six descriptor categories, explaining the corresponding health effects, is applied to the pollution levels of Delhi, most of the days will turn out to be of unhealthy air quality, if not worse. Thus, they felt it is more important to capture the health effects at various levels of pollution exceeding the permissible limit rather than focussing on the levels below the limit. Therefore, they recommended that the AQI should have 5 categories, of which 2 categories should be below and 3 above the standards and that the descriptors to be used for these categories should be health-based like good, unhealthy, very unhealthy and critical.

What purpose will an AQI serve?
However, besides serving advisory purpose for the public, the workshop also pointed out that AQI could also serve as a tool for two major purposes. First, to educate people and galvanise them in to action. Experience in Western countries has shown that once people are made aware of the severity of the problem, they take up the initiative by putting pressure on politicians and administrators to bring down the emissions and to make policy level changes. Second, it can be used as a yardstick to declare pollution emergency. Experts like Kirk Smith, Professor of Environmental Health Sciences at University of California, Berkeley, and Shankar Prasad, Community Health Advisor to the Chairman of California Air Resources Board, arguing strongly in favour of having pollution emergency measures pointed out that emergency measures should be on two levels voluntary and mandatory. However, the levels at which pollution emergency should be declared and what the measures should be was left open to be discussed and developed.

But is an AQI enough to capture the risk air pollution poses to the health of people? Some of the experts thought otherwise. Therefore, in addition to the AQI they came up with another kind of index which can capture the long-term health effects of both criteria and toxic air pollutants. To deal with these chronic effects, the group suggested to create a Chronic Pollutants Index (CPI).

Where do all these pollutants come from?
But it is not enough only to know about the daily or monthly levels of pollution. For any air pollution control policy to be effective it is absolutely essential to know where these pollutants come from. This needs a detailed listing the various sources of air pollution and the emissions from them in a given time frame, for instance, a month or a year. This is what an emission inventory does. It is relatively easy to identify the sources of pollutants, but the most important part is to know which source is contributing how much of a particular pollutant. Only then can one formulate an action plan to control the emission of that pollutant.

What is the way ahead?
During the discussions, it became clear that the whole exercise needed to be started from scratch. But what does that mean in Delhi’s context? According to Linda Murchisson, chief of the emission inventory branch, California Air Resources Board, preparing an emission inventory is a step by step process.0 It involves identification of the sources of pollution and the pollutants of concern, their distribution and trend in emission and then identify and track if existing control policies are effective in controlling pollution.

However, preparing such an inventory for Delhi will be highly resource intensive. Therefore, the expert group felt the best way would be to have two approaches — long-term and short-term. While the short-term exercise will be to develop a preliminary inventory in one to two years’ time by way of doing rapid survey and using existing emission factors for calculating emissions, the long-term exercise should be very detailed and can take 5 to 10 years.

In absence of credible emissions data for Delhi, it is not possible to use sophisticated models currently being used in the US and Europe. Therefore, a comprehensive pollution inventory exercise for Delhi has to begin with the conventional bottom-up approach, that is survey and actual measurement of emissions. Without actually doing emissions measurement from various sources, it is not possible to find out how much different sources contribute to the total pollution load.

However, to help prioritise this exercise, satellite based emission estimates could be of great help, the experts pointed out. Such an exercise, which is a short-term activity, has the potential of pointing out the rate of emissions from different sources.

Why did we do this workshop?

Despite advances in the scale and scope of urban air quality monitoring in recent years major difficulties persists in getting comprehensive and reliable air quality data in the Indian cities. Monitoring capability is so weak that routine information on all key pollutants is not available to provide a reasonably complete picture of the air quality trends and assess source wise trends in the city. There is need for a system that would take comprehensive stock of air pollution in cities, warn people on a daily basis about the risk, and set future targets for air quality with steady improvements over time. At the moment we are unable to assess properly.

1.  what are the serious and growing air pollutants in a city;
2.  the contribution of different sources to these pollutants and whether or at what speed these sources are growing; and
3.  risk to public health from peak levels on a daily basis.

Nor can we develop pollutant wise action plans for each pollution source for an effective impact. Therefore, the workshop will address the following:

1.  Develop Air Quality index for the city of Delhi
The public is not fully aware of the dangers that it faces on a regular basis. We would like to develop an appropriate index that helps the public to know very clearly what are the problems on a daily basis in a very simple way. As of now we are not sure what kind of index would capture the risk from urban air pollution in a city like Delhi where a number of gases are simultaneously going above the standards. A day when several gases are above the standard is obviously going to be a particularly deadly day and the index should be able to capture that. We would like to build into these indices toxicity indicators as well so that the index should reflect not just the levels but also whether the cocktail of air pollutants is less toxic or more. The toxicity of different air pollutants is obviously different. Once we develop this index we would like to implement a smog alert for the city in which apart from informing people on a daily basis about the air quality in Delhi we would also put pressure on the government to implement pollution emergency measures for an immediate local impact.

3.  Develop pollution inventory for the city of Delhi
We would also like to develop a good inventory of air pollution sources, so that source wise contribution and trend in source wise emissions can be estimated and predicted as also the health effects thereof. The weakest link in our air quality planning is that it is still not possible to arrive at reliable source wise pollution load estimates in the city.