Contaminant Level (MCL)
Cadmium is a soft, bluish-white metal usually associated with zinc. It's used in the manufacture of batteries, electronics and nuclear reactors. It's plated onto steel to prevent corrosion, and two of its compounds (cadmium sulfide and cadmium selenide) are used to produce pigment for plastics.
Cadmium can enter the environment through a variety of industrial and agricultural operations, and as a by-product of fossil fuel use. General use has declined, and now about 80% of cadmium in the environment comes from nickel-cadmium batteries. Cadmium often enters water as the result of deterioration of galvanized plumbing, fertilizer contamination, and industrial waste in general.
Long term exposure to cadmium may have harmful effects on the kidney, according to the EPA:
Some people who drink water containing cadmium in excess of the maximum contaminant level (0.005 milligrams per Liter) over many years could experience kidney damage.
Cadmium is easily removed from water by reverse osmosis (95 to 98%), by cation exchange (water softener), and by dialysis.
Sources: Enting Engineering Handbook, WHO, Wikipedia, EPA, Photo: WikiMedia, author: Alchemist-hp
(whole house & well units)