Health effects of endocrine-disrupting chemicals on wildlife, with specialreference to the European situation

Many wildlife species may be exposed to biologically active concentrations of endocrine-disrupting chemicals. There is strong evidence obtained from l aboratory studies showing the potential of several environmental chemicals to cause endocrine disruption at environmentally realistic exposure levels. In wildlife populations, associations have been reported between reproduct ive and developmental effects and endocrine-disrupting chemicals. In the aq uatic environment, effects have been observed in mammals, birds, reptiles, fish, and mollusks from Europe, North America, and other areas. The observe d abnormalities vary from subtle changes to permanent alterations, includin g disturbed sex differentiation with feminized or masculinized sex organs, changed sexual behavior, and altered immune function. For most reported eff ects in wildlife, however, the evidence for a causal link with endocrine di sruption is weak or nonexisting. Crucial in establishing causal evidence fo r chemical-induced wildlife effects appeared semifield or laboratory studie s using the wildlife species of concern. Impaired reproduction and developm ent causally linked to endocrine-disrupting chemicals are well documented i n a number of species and have resulted in local or regional population cha nges. These include: Masculinization (imposex) in female marine snails by tributyltin, a biocide used in antifouling paints, is probably the dearest case of endocrine disr uption caused by an environmental chemical. The dogwhelk is particularly se nsitive, and imposer has resulted in decline or extinction of local populat ions worldwide, including coastal areas all over Europe and the open North Sea. DDE-induced egg-shell thinning in birds has caused severe population declin es in a number of raptor species in Europe and North America. Endocrine-disrupting chemicals have adversely affected a variety of fish sp ecies. In the vicinity of certain sources (e.g., effluents of water treatme nt plants) and in the most contaminated areas is this exposure causally lin ked with the effects on reproductive organs that could have implications fo r fish populations. However, there is also a more widespread occurrence of endocrine disruption in fish in the U.K., where estrogenic effects have bee n demonstrated in freshwater systems, in estuaries, and in coastal areas. In mammals, the best evidence comes from the field studies on Baltic gray a nd ringed seals, and from the Dutch semifield studies on harbor seals, wher e both reproduction and immune functions have been impaired by PCBs in the food chain. Reproduction effects resulted in population declines, whereas i mpaired immune function has likely contributed to the mass mortalities due to morbillivirus infections. Distorted sex organ development and function in alligators has been related to a major pesticide spill Into a lake in Florida, U.S.A. The observed est rogenic/antiandrogenic effects in this reptile have been causally linked in experimental studies with alligator eggs to the DDT complex. Although most observed effects currently reported concern heavily polluted areas, endocrine disruption is a potential global problem. This is exemplif ied by the widespread occurrence of imposer in marine snails and the recent findings of high levels of persistent potential endocrine-disrupting chemi cals in several marine mammalian species inhabiting oceanic waters.