According to Hanna Instruments , even though zinc is non-toxic to human beings, concentrations higher than 5 mg/L (ppm) can cause a bitter, astringent taste. This level of zinc can result in a milky colour in alkaline water and is irritant to the human digestive system. Zinc in low quantities is a beneficial and necessary element for body growth. Zinc is normally introduced into drinking water through industrial effluents. In addition to drinking water, zinc is measured in surface finishing, boilers and cooling towers, water conditioning and effluent waters.