Endocrine disruption

A number of toxic compounds, arising from pesticides or various other industrial products have been observed to interfere with the hormone system of different species. These compounds, some of which have been called hormone mimics or ?gender benders? may interfere with synthesis, secretion or action of natural hormones, or may block their removal from the body. Impacts on land have included observations of reduced spermatogenesis, disruptions to thyroid function and steroid metabolism.

In coastal waters, the effects of such compounds have received particular attention in the North Sea, but it should not be assumed that these problems are restricted to this area. Dog whelks have been recorded with ?imposex? where females develop male sex organs and become sterile. The reverse problem has been observed in flounder in UK estuaries, where various feminisation effects have been observed in males, including the development egg-producing tissues and the reduction of the testes.

As a number of these endocrine disrupters are also highly persistent there is a likelihood of build-up in long-lived species, or species which are high up the food-chain. Very high levels of organochlorines have been found in seals and cetaceans in the north Atlantic, including US and European waters, and in the Mediterranean.