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Introduction
Air pollution is a serious worldwide public health problem. The shortterm health impacts of air pollution have been studied extensively since the London fog in the mid20th century and the subsequent series of dramatic episodes in industrialised countries (Boyd, 1960). However, the magnitude of effect estimates varies across cities and countries (Analitis et al., 2006; Katsouyanni et al., 2001; Samet et al., 2000a), hindering interpretation and generalisation of the causal association between air pollution and health. Some investigators have attempted to explain the heterogeneity of effect estimates among regions in terms of different levels of air pollutants (Samoli et al., 2001), characteristics of pollutants (Samoli et al., 2005), specific city characteristics (Samoli et al., 2007), and potential confounders including temperature and humidity (Aga et al., 2003; Zeka et al., 2005). After decades of industrialisation, air pollution has become a major environmental issue for both developed and developing countries. Poor air quality has both acute and chronic effects on human health (Yang et al., 2004, Afroz et al., 2003). The relationship between environment and the development is one of the most burning issues of the present times. Developmental activities e.g. industrial transportation, constructional work etc cause degradation and drastic changes in every component of environment namely, hydrosphere, lithosphere, atmosphere and biosphere through pollution. Air pollution has emerged in the past few decades as the most crucial problem to mankind.
In recent years, a large number of studies on health impacts due to air pollution have been undertaken in developing countries (Anonymous, 1980). The public health implications of the emission of CO, O3, toxicants and particulates are substantial (Davies, 1998, Utel Warren and Sawyer, 1998). Among air pollutants, particulate matter (PM) is a ubiquitous and its especially a major problem due to its adverse health effects, Visibility reduction and soiling of buildings (Hamilton and Mansfield, 1991, Seinfield, 1975; Williamson,1973).
In the present paper, an attempt was made to represent the overall ambient air quality in choudwar and its adjoining areas. The environmental impact of major industries like ferroalloys, thermal power plant and steel industry apart from other small scale industries like rolling mill and carpet manufacturing unit are studied.
Air Pollution Indices:
An environmental index is a tool, which is used to report the overall environmental status and trends based on a specific standard (Thom and Ott, 1996). It was developed on the lines of health index (USEPA, 1972, 1973) and measured by the degree of human suffering. Each AQI category makes it easier for the general public to understand how clean or polluted the air is. To evaluate overall air pollution due to various pollutants is complex. It consists of an ill defined mixture of several pollutants from different sources (Canter, 1997). Overall air pollution measures can be used to give meaningful assessment of air pollution to the common man. They also enable one to evaluate the alternative air pollution control policies or control equipment which, for instances, can reduce the level of certain pollutants while increasing the levels of others. AQI can represent the overall air quality status in a better way since the cumulative effect of all the pollutants and the related standard can be taken into account (Lohani, 1984). As a result we can obtain an equation, which transforms the parameter values by means of numerical manipulation into a more simple and precise form. The index of specific pollutant is derived mainly from the physical measurement of pollutants like SPM, RSPM, SO2 and NO2. There are several methods and equations used for determining the AQI (Inhaber, 1974). The Oak Ridge National Air Quality Index (ORNAQI) can be considered for the relative ranking of an overall air quality status at different locations of the study area.