Did you know that the level of atmospheric pollution in large swathes of India is between two to five times higher* than the acceptable limit set by the World Health Organisation? What makes matters worse is the fact that air, sometimes referred to as the mad medium, recognises neither borders nor walls; factors such as wind, convection currents, land and sea breeze, all play a role in dispersing pollutants near and far. This is why it is imperative to control air pollution at the source, before any pollutant gets released into the atmosphere. And measurement is an integral part, often the first step, of any effort to control air pollution.

Recognising this, the government revised the National Ambient Air Quality Standards (NAAQS) in November 2009, in order to expand its scope. Although Ambient Air Quality has been monitored for over 25 years now, till a couple of years back the emphasis was on the three criteria pollutants, namely Respirable Particulate Matter (RSPM or PM10), Sulphur Dioxide (SO2), and Oxides of Nitrogen (NOx). The revised standards applicable across the country (see table) include several new parameters, from Fine Particulate Matter (PM2.5) to Benzene and Benzo-Pyrene. Such additions underscore the realisation that much of the urban air quality deterioration can be traced to vehicular sources.

While the revised NAAQS is a much-needed step, a lot more needs to be done. A realistic assessment of air quality across a large country like India requires a collaborative effort by governmental and private stakeholders. This is why large industries are being asked to set up Ambient Air Monitoring stations in the vicinity of their plants, mines and the like, to keep track of the potential sources that can cause deterioration in the air quality.

Industries, on their part, will need to develop a strategy in order to monitor NAAQS' expanded set of 12 parameters in a cost-effective manner. Here's a look at the tools/equipment that can help make the task easier:

Monitoring PM10 and PM2.5: The data from almost all Indian cities where particulates have been measured often shows high values and a rising trend. This makes particulate pollutants perhaps the most important concern. The inclusion of parameters such as heavy metals (lead, arsenic, and nickel) and Benzo-pyrene in the NAAQS implies that monitoring the concentration of particulates alone is not enough. It is as important, if not more so, to assess and quantify the presence of toxic constituents of the particles.

Such quantification requires a physical sample of the particles, which has to be collected and sent for detailed chemical analysis. Clearly, then, sampling instruments will have to be used, which provide a field sample of particles (PM10 and PM2.5) present in the atmosphere.

Monitoring Gaseous Pollutants: Pollutants such as SO2, NOx, and Ammonia can be easily monitored by simple instruments that absorb the pollutant in a suitable chemical reagent. Then, colorimetric lab analyses help determine the concentration of a specific pollutant, say, SO2. For a developing country like India, this is the most cost-effective and practicable method - it requires simple infrastructure and basic skill levels for equipment handling and maintenance.

Monitoring Benzene, Ozone and Carbon Monoxide (CO): These pollutants are mainly traceable to vehicular sources and are essentially an urban phenomenon. As all of them are rather toxic, their monitoring must be implemented even though the instrumentation required is expensive and, at present, needs to be imported. In addition to the analyzers, investments are required in the air-conditioned space, as well as power backup and calibration systems that require skilled handling.

A word of caution for those procuring expensive, imported equipment: Check the credentials of the supplier to ascertain whether he is equipped to provide service support for the specialized hi-tech equipment.

While the initiative taken by the Central Pollution Control Board (CPCB) to enhance the scope of NAAQS is a laudable effort they need to clarify whether ALL the 12 parameters need to be monitored at every location. Take for instance SO2, data from several years confirms that at many places in India SO2 levels are barely detectable: should we continue to insist on monitoring SO2 at these places. Perhaps our resources can be better allocated to pollutants that are at a more critical concentration or are more toxic.

* Source: Journal of Geophysical Research

(Mr Rakesh Agarwal is the Managing Director of Envirotech Instruments Pvt Ltd, (www.envirotechindia.com) an Indian company specialising in providing Air Pollution Monitoring Instruments appropriate to the country's needs)