This page allows you to compare pollution levels at your selected site to national standards and objectives. The Government has published a series of Air Pollution Indices, one for each of thefive major pollutants, to provide an easily recognisable and straightforward assessment of pollution levels. As the index value increases from 1 to 10, the likelihood of detrimental effects on health increases. Air Quality Objectives have also been set, against which annual pollution levels can be compared. These Objectives allow the authorities to identify which areas require further investigation or action to improve air quality.