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A lungful of pollutants

A study of air pollution at MIDC Marol and Saki Naka conducted by IIT Bombay shows that air pollution in the area may be much worse than is suggested by official figures.

Travelling by an auto or non-airconditioned car through Saki Naka is an ordeal on the best of days. Fumes of exhaust gas from lorries and buses are blown directly into your face and it requires an effort to breathe.

But official figures of pollution don't confirm this experience. They show that while pollution in the area is higher than the standards recommended by the World Health Organisation (WHO) or the National Ambient Air Quality Standards (NAAQS) laid down by the Ministry of Environment & Forests, it isn't much higher. Are residents of the area exaggerating the extent of pollution? Or is something wrong with the pollution figures? Now a study by the Centre for Environmental Science & Engineering (CESE) of the Indian Institute of Technology, Mumbai suggests that official figures are to blame. The study was headed by Professor (Mrs) R.S. Patil of the centre.

When air pollution is monitored by the municipal corporation it is through apparatus mounted on the terraces of municipal buildings. The apparatus is usually at a height of 10 metres from the ground and the resultant figurse make up what is called the Ambient Air Quality (AAQ).

But pollution can vary sharply over a small area and at different times. The CESE study therefore decided to focus on air pollution at the residences and work areas of people at two sites: the BSES Receiving Station at MIDC, Marol and the Regional Telecom Training Centre at Saki Naka. The study was an intensive one that focused on "the air that people breathed" at their homes and places of work. Pollution at the work and residence was measured and people were asked to wear pollution-measuring devices throughout the day. The conclusions of this intensive study are startling.

Take for instance pollution caused by respirable particulate matter (RPM) which is the main cause of trouble for most of us. The WHO pollution standard lays down a limit of 70 micrograms per cubic metre and the NAAQS lays down a limit of 100 micrograms per cubic metre. The CESE's study shows the ambient air concentration of PM10 (particles with a size greater than 10 microns) ranges from 17 to 320 micrograms per cubic metre with an average of 153 micrograms/cubic metre. In other words, pollution is about 50% higher than the NAAQS standard and 100% more than the WHO standard.

But this ambient air quality is measured several metres above the ground. The air that people actually breathe at ground level is much worse than this. Thus the average RPM concentration at work sites and residences was 320 micrograms/cubic metre at MIDC and 340 micrograms/cubic metre at Saki Naka. These figures confirm what all of us know my practical experience: that the air at these places is absolutely unfit to breathe. The personal exposure to RPM is 3.3 times the limit prescribed by the NAAQS and 4.6 times the limit presribed by the WHO.

The results for another pollutant, nitrogen dioxide, confirms this conclusion: that the air people breathe is much worse than is suggested by ambient air quality measurements. Thus the nitrogen dioxide concentration measured at the ambient air quality measuring station was even less than the recommended standard. But the personal exposure was much higher than the standard.

The effects of air pollution on people's health depend closely on the period for which they are exposed to it. Those who spend a lot of time on the road are worst affected followed by those who work or live close to a busy road or traffic junction. The good news is that pollution can fall sharply even at small distances away from a road. For instance, although traffic policemen are subjected to carbon monoxide exposure higher than the limit, concentrations of this noxious chemical fall to less than detectable limits even 5 to 10 metres away from a road.

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