This epidemiological study of atmospheric air pollution and incidence of bronchial asthma and the severity from mild to severe was conducted in our asthma clinic at Vellore district covering the areas of Vaniyambadi, Ambur, Pernambut, Vellore and Ranipet. The objective of the study was to identify the air pollutants and their concentrations and their effects such as the mild, moderate and severe forms of bronchial asthma and the prevalence rate among the children, adolescent, adults and old age population during the period of 2006 to 2009. The children were affected 10 – 15%, adolescent about 15% , adults about 20-25% and old age about 8-12% were found .Almost all the persons affected by mild type were reversible to normalcy after inhalation of bronchodilators; severe form of bronchial asthma response to moderate state.50% of severe form of bronchial asthma(status asthmaticus) died during the period of study. Simple test like peak flow meter identified the affected persons and the spirometry study proves the severity.