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 which 50% of the test subjects 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.
Environmental standards and legislation
Environmental quality standards according to the water framework directive
Annual average concentration in marine surface waters: 0,2 µg/l
Maximum allowable concentration in marine surface waters: 0,45 µg/l. However, allowable concentrations may rise up to 1,5 µg/l in areas with a lot of dissolved CaCO3.
Case studiesPCB and heavy metals in beached sperm whales
- Kennish, M. J. (1996): Practical Handbook of Estuarine and Marine Pollution, CRC Press 524 pp
- Biology of marine birds. Schreiber, E.A. & Burger, J. (Eds). 2002. Boca Raton, Florida: CRC Press. 722 pp.
- eds.J. Vos, G. Bossart, M. Fournier, and T. O'Shea, 2004; New perspectives: Toxicology and the environment. Toxicology of marine mammals, New York: Taylor & Francis. 643p
- Clark, R,B., 1999. Marine pollution. Oxford University press, Fourth edition, pp 161