our ancestors seemed to have taken air quality more seriously than we do today; for example, in ancient Indian villages, the location of kilns was compulsorily some distance from human habitation. Formal smoke control regulations in several Indian towns date from as far back as the middle of the 19th century. However, the first scientific and regular monitoring of air quality was started only in 1967 by the Nagpur-based NEERI (National Environment Engineering Research Institute). neeri started regular monitoring of air quality at three stations - one each in a prominent industrial, residential and commercial area - in 10 major Indian cities.The parameters monitored included dust-fall, sulphation rate (rate of sulphur production) and emissions of sulphur dioxide (so2), oxides of nitrogen (nox) and suspended particulate matter (spm). spm was further analysed for heavy metals, carcinogens and other specific chemical pollutants. It should be noted, however, that data available represents the years from the mid-'60s to early '90s. It is, therefore, shocking to observe that the deterioration in air quality had set in long ago and the trend only seems to be getting worse.
so2 emissions were considered the most critical pollutants in the neeri study during the 1960s-80s review period. so2 causes bronchial irritation in humans and damage to vegetation even at low concentrations. Higher so2 concentrations could result in acid rains. Mumbai, with its high degree of industrialisation, large number of vehicles and rather adverse topography and meteorology, reported a few incidents of acid rain, and the industrial area of Chamber and its environs earned the epithet 'gas-chamber of Mumbai'. so2 concentrations in ambient air in the 10 cities monitored by neeri shows an apparent decline in five of them after 1980 (See table: Sulphur spurts). This perhaps can be attributed to liquid petroleum gas replacing wood, coal and kerosene as a cooking fuel. But among the 10 cities surveyed, Delhi and Kochi showed a significant rising trend in so2 emissions after 1980, essentially caused by large, unplanned and uncontrolled industrial and urban growth. In the southern cities of Bangalore and Mysore in Karnataka, based on surveys conducted by the Karnataka state pollution control board, the annual average concentrations of so2 were not of significant concern at less than 30 g/m 3 (microgrammes per cubic metre) - half the permitted international limits - except at the Amco Batteries and Graphite India stations in Bangalore, where the level was 30 g/m 3 and 54 g/m 3. respectively.
The spm level was another of neeri's concerns. In all the 10 cities, the annual average spm values exceeded the international criterion of 100 g/m 3; Delhi, Calcutta, Jaipur and Kanpur have posted spm levels three times this level. Comparatively, spm levels were low in Mysore but Bangalore reflected the high averages of its northern counterparts.
The Bhopal gas tragedy in 1984 and the notification of the Air (Prevention and Control of Pollution) Act of 1981 prompted an increase in the monitoring of air quality in urban and industrial areas. The bulk of these were conducted by industrial units, consultants working for environmental impact assessments (eias) in related areas and other research groups. Such monitoring was still very disjointed and unreliable. The Central Pollu- tion Control Board (cpcb) got its act together in 1985 and started the national ambient air quality monitoring (naaqm) network with an initial set-up of 30 stations (See box: On the pollutant hunt). The ambient air quality standard refers to those levels of air quality which would be necessary to protect the general health of the people and vegetation, with an adequate margin of safety.
SO2 concentrations in 10 Indian cities monitored by neeri during 1967-87
|Jaipur||Always<10 ug/m3; showed declining trend after1982; was 5 ug/m3 in 1985; 3ug/m3 in 1987|
|Around 20 ug/m3 till 1980; declining since to below 10 ug/m3 in 1987|
|Mumbai||40-60 ug/m3 untill 1980; declining since; below 30 ug/m3 after 1983; below 20 ug/m3 after 1996|
|Kochi||From below 20 ug/m3 untill 1980 to above 30 ug/m3 since 1985|
|Delhi||From below 25 ug/m3 till 1981 to above 60 ug/m3 after 1985|
|Concerning fluctuated between 20-40 ug/m3|
While there is much talk of the adverse effects of deteriorating air quality on public health, there is little or no scientific data except when it is linked to gas-leaks and other toxic pollutants. Moreover, health records maintained are too unreliable for any scientific analysis or interpretation. If air quality data is available, there is no data on health-impairment and if health surveys are conducted, there is no related data on exposure of the subjects.
Envirotech Instruments Pvt Ltd, a Delhi-based company has conducted several surveys which show distinct correlations between air quality degradation and public health. The surveys were primarily centered in Kanpur (up), Bokajan (Assam), Haldia (wb) and Barauni (Bihar). spm levels above 600 g/m 3 in these cities resulted in higher prevalence of respiratory diseases. Out of 1,000 people exposed in each of these cities, 98 in Kanpur, 156 in Bokajan, 108 in Haldia and 84 in Barauni reported the prevalence of respiratory diseases. Eyes and skin also get affected due to higher spm levels in air. Levels of spm between 300-600 g/m 3 led 103 people out of the 1,000 exposed in Kanpur to complain about irritation in the eye. The number shot up to 412 people when the spm level rose to above 600 g/m 3.
While the ministry of environment and forests (mef) has been keen to undertake notification of standards and then to prescribe stringent limits, it has done little to monitor or ensure compliance. If monitoring is to be undertaken only in industrial and highly polluted areas, why are standards being notified for sensitive or rural areas? The monitoring effort under naaqm should logically be better distributed over different categories. The proposed distribution of operative naaqm stations should be: sensitive areas, 20 per cent; rural areas (non-industrial, population upto 10,000), 30 per cent; large towns, 20 per cent; mining areas, 10 per cent; and industrial areas, 20 per cent.
A comparison between the updated national ambient air quality standards for India by the mef in April 1994 and the naaqm data reveals the following.
l The annual average limits specified for so2 and nox are too liberal. Such values alongside the current urge to globalise, may irreversibly destroy our ecology and environment. If annual average values are to be prescribed, they should be much lower than those in the April 1994 notification. Due to the vast differences in climatic conditions during the year, the annual average is not likely to be more than 30-35 per cent of the 98-percentile 24-hour peak value. Thus the 98-percentile 24-hour value is more than adequate to ensure satisfactory air quality. In fact, the 24-hour values for nox should be revised to 150, 100 and 50 g/m 3 in place of the current 120, 80 and 30 g/m 3 values initially prescribed in the 1984 standards (See table: Setting standards).
l The annual average limits for spm are too stringent and unrealistic for most states and the 24-hour values even more so, if they were to be 98-percentile values. It would be preferable to have separate limits for different parts of the country and to prescribe values which will have practical compliance. Such values should also be applied for respirable particulate matter.
Monitoring should be extended to cover heavy metals and other pollutants not currently listed in the notification. Detailed area-specific plans should be drawn up to achieve compliance with full participation of local communities and ngos.
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