Water Quality Standards

WHO standards for heavy metals in drinking water and pollution index classification categories

WHO Standards for Heavy Metals

World Health Organization permissible limits for heavy metals in drinking water

Heavy Metal	Symbol	Allowed (mg/L)	Background (mg/L)
Arsenic (As)	As	0.01	0.001
Cadmium (Cd)	Cd	0.003	0.0005
Chromium (Cr)	Cr	0.05	0.001
Lead (Pb)	Pb	0.01	0.01
Mercury (Hg)	Hg	0.001	0.0001
Nickel (Ni)	Ni	0.07	0.002
Copper (Cu)	Cu	2	0.001
Zinc (Zn)	Zn	3	0.01

These standards are based on WHO guidelines for drinking water quality. Background values represent typical natural concentrations in uncontaminated water sources.