Mention information that health workers derive by measuring BOD of a water body.

BOD or Biochemical Oxygen Demand is the amount of dissolved oxygen in a water body, required by microorganisms for the aerobic breakdown of organic matter in the water. Its value for a water sample provides an index for testing the water quality. Health workers derive the degree of pollution of the water sample: the high value of BOD corresponds to a greater number of aerobic microbes and organic matter in a water sample/body indicating poor quality of water for consumption. While a low BOD indicates clean water (<1mg pure water).