Mechanism and epidemiology of bone effects of cadmium.

A slow epidemic of a combination of osteomalacia and kidney damage (itai-itai disease) was first noted in Japan in the late 1940s. During the same period reports of severe bone effects in cadmium-exposed workers in some European factories were published. Cadmium-induced kidney effects and their connection with bone effects were first reported in 1950. Epidemiological and clinical studies in Japan since 1962 have shown that the bone effects develop only at very high cadmium exposures and that persons with low intakes of calcium or vitamin D are particularly at risk. Animal experiments have confirmed that cadmium induces bone effects at high exposures. Six possible mechanisms may explain the cadmium-induced bone effects: (1) interference with parathyroid hormone (PTH) stimulation of vitamin D production in kidney cells; (2) reduced activity of kidney enzymes activating vitamin D; (3) increased excretion of calcium in urine; (4) reduced absorption of calcium from intestines; (5) direct interference with calcium incorporation into bone cells; and (6) direct interference with collagen production in bone cells. The high cadmium exposures needed to produce bone effects may still occur in developing countries, where many people have poor nutritional status and could be vulnerable to such effects.