Cadmium

About Cadmium

Cadmium is the toxic shadow of zinc. The two sit one above the other in group 12 with nearly identical chemistry — both prefer the +2 state, both form tetrahedral tetraamine complexes — but cadmium accumulates in the kidney cortex with a biological half-life around 30 years. The itai-itai outbreaks in the Jinzū River basin in the 1950s are the textbook case study of why you do not let smelter tailings into rice paddies. Despite the toxicology, cadmium has held onto a few applications that other metals have not been able to displace. Cadmium-yellow (CdS) and cadmium-red (CdS·CdSe) pigments — the colors Monet and van Gogh used straight from the tube — remain the lightfast benchmark for high-temperature plastics and ceramic glazes. CdTe thin-film modules from First Solar are the only non-silicon photovoltaic technology with meaningful market share, hitting cell efficiencies above 22%. NiCd batteries are mostly gone from consumer gear but still dominate aviation backup power because they tolerate -40 °C without flinching. Worldwide supply is almost entirely byproduct cadmium dropped out of zinc roaster flue dust.