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Air quality index (AQI) or air pollution index (API) is commonly used to report the level of severity of air pollution to public. A number of methods were dev eloped in the past by various researchers/environ mental agencies for determination of AQI or API but there is no universally accepted method exists, which is appropriate for all situations. Different method uses different aggregation function in calculating AQI or API and also considers different types and numbers of pollutants. The intended uses of AQI or API are to identify the poor air quality zones and public reporting for severity of exposure of poor air quality. Most of the AQI or API indices can be broad ly classify as single pollutant index or multipollut ant index with different aggregation method. Every indexing method has its own characteristic strengths and weaknesses that affect its suitability for particu lar applications. This paper attempt to present a review of all the major air quality indices developed worldwide.Key words: Air pollution, Air quality index, Health, Environmental factors, Literature review IntroductIonAir pollution is global environmental problem that influences mostly health of urban population. Over the past few decades, epidemiological studies have dem onstrated adverse health effects due to higher ambient levels of air pollution. Studies have indicated that rep eated exposures to ambient air pollutants over a pro longed period of time increases the risk of being sus ceptible to air borne diseases such as cardiovascular disease, respiratory disease, and lung cancer (WHO, 2009). Air pollution has been consistently linked to substantial burdens of illhealth in developed and devel oping countries Bruce et al., 2000;Smith et al., 2000; WHO, 1999;Schwartz, 1994).Globally, many cities continuously assess air quality using monitoring networks designed to measure and record air pollutant concentrations at several points deemed to represent exposure of the population to these pollutants. Current research indicates that guide lines of recommended pollution values cannot be regar ded as threshold values below which a zero adverse response may be expected. Therefore, the simplistic comparison of observed values against guidelines may mislead unless suitably quantified. In recent years, air quality information are provided by governments to the public comes in a number of forms like annual reports, environment reviews, and site or subject specific anal yses/report. These are generally having available or access to limited audiences and also require time, inter est and necessary background to digest its contents. Presently, governments throughout the world have also started to use realtime access to sophisticated database management programs to provide their citizens with access to sitespecific air quality index/air pollution index and its probable health consequences. Thus, a more sophisticated tool has been developed to commu nicate the health risk of ambient concentrations using air pollution index (API) or air quality i...

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The rapid urbanization in Delhi has resulted in a tremendous increase in the number of motor vehicles with the increase in population and urban mobilization. The vehicular traffic is now recognized as one of the main sources of air pollution in Delhi and has noticeable impact on air quality. The emission of criteria pollutants namely Carbon Monoxide (CO), Nitrogen Oxide (NOx) and Particulate Matter (PM) due to vehicles is estimated through the International Vehicle Emission (IVE) model, which includes the different driving modes of vehicles and meteorological parameters. The estimated emissions of Carbon Monoxide (CO), Nitrogen Oxides (NOx) and Particulate Matter (PM) due to different types of vehicles in the year 2008–09 are found to be 509, 194 and 15 tons/day respectively. The diurnal variation of emissions of air pollutants shows two peaks, which are fortunately matching with the morning and evening office hours. The emissions of CO and NOx due to personal cars (PCs) are found to be about 34% and 50% respectively, and the emission of CO due to 2 W (2- Wheeler) is about 61%. Similarly, the Heavy Commercial Vehicles (HCVs) are contributing PM about 92%. The analysis of fuel-wise emission of pollutants reveals that CO is mainly contributed by petrol, and NOx and PM are contributed by diesel. It is also noticeable that CO, NOx and PM emissions at ITO, one of the busiest traffic intersections of Delhi, are approximately 15, 6 and 0.5 tons/day respectively, which are found to be the maximum followed by Kashmiri Gate (ISBT), Nizamuddin etc. The present vehicular emissions inventory has been compared quantitatively with previous studies of Delhi. The present vehicular emission inventory has also validated using US environmental protection agency’s (USEPA’s) AERMOD model with observed concentration at different locations in Delhi. However, the present study shows that the air quality of Delhi has been degraded due to high level emissions of criteria pollutants.