Pollution level in the air, and hence the Air Quality Index (AQI) in all the countries is determined by the measurement of concentration of certain criteria pollutants, such as the Particulate Matter (PM10 and PM2.5), CO, NH3, NO, NO2, SO2, O3, Pb, As, and Benzene etc. Of late, certain RSPM (Respiratory Suspended Particulate Matter), namely, PM0.1 (ultrafine particles), which is the same as nanoparticles, have been found to cause much more damage to human health compared to any of the criteria pollutants. Unfortunately, no sufficient research work has been done till date to conclusively establish the extent of their damaging effects on the health of humans and other living beings. This important issue is highlighted in this paper and it is urged out that a systematic and detailed research work is carried out to formulate the standards of ultrafine or nanoparticles for linking with AQI.