<prompt> Soiling index is used for Quaity assessment of:-WaterAirSoilNoise  <response>: AIR POLLUTION INDICATORS; CO2, CO, SO2, NO2, Air pollution index Soiling index Coefficient of haze SPM Overall best air pollution indicator Overall best chemical indicator is SO2. Best biological indicator of air pollution - LICHENS. Air pollution monitoring - CPCB.Central pollution control board 