The Aesthetic Objective for iron in drinking water is 0.3 mg/L and the Aesthetic Objective for manganese is 0.05 mg/L. These are naturally occurring through leaching in the ground.

The taste and smell of iron or maganese at higher concentrations may be noted by users but are not a health risk. They can cause colour, taste and rust flakes in water, stains, and deposits in pipes and tanks. It may also increase the growth of "iron bacteria" which, although unpleasant, is not hazardous to health.