<prompt> Soiling Index is an indicator ofWater pollutionAir pollutionSoil pollutionFood pollution  <response>: Ans. b Air pollution Ref. Park Textbook of Preventive Social Medicine 22ndpg. 683SOILING INDEX Smoke Index is indicator of air pollution.Other indicators of air pollution are: SO2 Grit Dust Measurement Coefficient of Haze Air Pollution IndexNote: The best indicators of air pollution are sulphur dioxide, smoke and suspended particles. 