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.