Cadmium is regarded as one of the most toxic metals. It causes sublethal and behavioral effects at lower concentrations than mercury and lead. It causes cancer in animals, and in vertebrates it causes kidney toxicity.  In humans it might also lead to skeletal deficiencies and lung damage.  Environmental concentrations of 5µg/l have affected the reproduction of copepods, decreased the abundance of isopods and depressed the growth of juvenile plaice. Laboratory LC50 (the concentration at wich 50% of the test subject die) toxic levels for copepods were higher than 0,34mg/l. 
Like other heavy metals, cadmium does not have biomagnifying properties. Higher trophic levels accumulate low amounts of cadmium and are able to deal with them efficiently with metallothioneins. Mollusks contain large amounts of cadmium and seem to accumulate them.
See alsoPCB and heavy metals in beached sperm whales
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