  Pollution has become a major threat in almost all metropolitan cities around
the world. Currently, atmospheric scientists are working on various models that
could help us understand air pollution. In this paper, we have formulated a new
metric tool called Delhi Similarity Index (DSI). The DSI is defined as the
geometrical mean of the trace gases such as ozone, sulfur-dioxide and
carbon-monoxide, which ranges from 0 (dissimilar to Delhi) to 0.9-1 (similar to
Delhi). The limitation of the tool concerning the result of the
nitrous-di-oxide data set is also analyzed. Also, the GIS projections of PM 2.5
role for Indian cities are graphically represented. The DSI results from 2011
to 2014 data show that Bengaluru is in the threshold of becoming as polluted
like Delhi with values varying from 0.8 to 0.9 (i.e. 80-90%) and Jungfraujoch
with a 0.65 to 0.7 (i.e. 65-70%).
