Endocrine disrupting compounds (EDC) include a diverse range of chemicals derived from industrial, agricultural and domestic processes (IEH, 1999). They include phthalates (used in the manufacture of plastics), alkyl phenols (present in detergents and surfactants), polychlorinated biphenyls (PCB; formerly used in electrical equipment), dioxins (released from incinerators), organochlorine pesticides and organohalogens (used as flame retardants).

The compounds have a wide range of chemical structures but all of them have the capacity to disrupt normal hormonal actions. In some cases they bind to steroid hormone receptors and so they can have weak oestrogenic or androgenic effects while others disrupt thyroid hormones or other physiological functions. Consequently, they may disrupt reproductive or immune function and can be carcinogenic.

Evidence of adverse effects on animal physiology is partly circumstantial and partly based on empirical studies, mostly involving laboratory rodents. Many reports in the literature indicate that reproductive disorders in wildlife species such as pelicans, birds of prey and polar bears are associated with abnormally high concentrations of EDC in their tissues. Furthermore, controlled studies involving the administration of large, arguably pharmacological, doses of EDC to laboratory rodents have demonstrated adverse effects on their reproductive or immune systems. Relatively little work has yet been done to determine the pattern of uptake and bioaccumulation of EDC in domestic species or the effects of EDC on the physiology of these species.