J.
G. Vos, National Institute of Public Health and the Environment, Bilthoven,
The Netherlands J.
G. Vos, National Institute of Public Health and the Environment, Bilthoven,
The Netherlands
There is growing concern on possible harmful consequences
of exposure to xenobiotic compounds that are capable of modulating or disrupting
the endocrine system. This concern for endocrine disrupting chemicals (EDCs)
is directed at both wildlife and humans.
Although there are associations between EDCs, so far investigated, and human
health disturbances, a causative role of these chemicals in diseases and abnormalities
possibly related to an endocrine disturbance has not been verified. This concerns
i) the reported general decrease in sperm concentration and semen volume, ii)
the reported increased prevalence in cryptorchidism or hypospadias, ii) the
increase in testicular, prostate and breast cancer recorded during the last
decades, iv) the declining proportion of male new-borns during the last decades.
In wildlife, associations have been reported between reproductive and developmental
effects and EDCs, in particular of the aquatic environment. Effects have been
observed in mammals, birds, reptiles, fish and molluscs from Europe, North America
and other continents. The observed abnormalities vary from subtle transient
changes to permanent alterations, including disturbed sex differentiation with
feminized or masculinized sex organs that may even result in population decline,
changed sexual behaviour, and altered immune function. Crucial in establishing
causal evidence for chemical-induced wildlife effects appeared semi-field or
laboratory studies using the wildlife species of concern. Impaired reproduction
and development causally linked to EDCs are well documented in a number of species
and have caused local or regional population changes. These include: i) masculinization
(imposex) in female marine snails by tributyltin, a biocide used in anti-fouling
paints, ii) in mammals, the best evidence comes from the field studies on Baltic
grey and ringed seals, and from the semi-field studies on Wadden Sea harbour
seals, where both reproduction and immune functions have been impaired by PCBs
in the food chain. Reproduction effects resulted in population declines, whereas
suppression of immune function have likely contributed to the mass mortalities
due to morbillivirus infections, iii) EDCs have adversely affected a variety
of fish species. In the vicinity of certain sources (e.g. effluents of water
treatment plants) and in the most contaminated areas is this exposure causally
linked with effects on reproductive organs which could have implications for
fish populations.
For
future studies on health effects in man and wildlife, major attention should
be given to the causality issue. In this respect, emphasis in wildlife should
be on semi-field or laboratory studies using the species of concern.
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