Endocrine-Disrupting Chemicals and Their Environmental Impacts - Organic Pollutants: An Ecotoxicological Perspective - page 279

15.6.1 n a T u r a l a n d p h a r m a c e u T i c a l e s T r o g e n s
As illustrated in the case for feminization of fish in U.K. rivers, both natural and
synthetic steroidal estrogens present in the environment are impacting wildlife
adversely. The source of natural estrogens in surface waters is predominantly via
the human population and via discharges through WWTW. Other sources, however,
include both diffuse and point sources from livestock practices, including from poul-
try and cattle farms (Shore et al. 1998; Lange et al. 2002). Concentrations of individ-
ual steroidal estrogens at some point source discharges are sufficient to inhibit sexual
development and function. For a review on steroidal estrogens and their effects in
fish, we would refer the reader to Tyler and Routledge (1998).
15.6.2 p e s T i c i d e s
DDT and its metabolites have been shown to have various endocrine-disrupting
effects, including acting as an estrogen ( o,p ′ -DDT and p,p ′-DDT) and an antian-
drogen ( p,p ′ - DDE). Concentrations in most environments, however, are generally
now at, or below, the no-observed-effect levels. Nevertheless, in developing coun-
tries where DDT-based pesticide use still occurs, concentrations in water sources
have been recorded as high as 10 µg/L, and at these levels they would induce endo-
crine disturbances in exposed animals (Begum et al. 1992). Many other pesticides
have now been reported with endocrine activity (Short and Colborn 1999, reviewed
in Bretveld et al. 2006), and they include other organochlorine pesticides, such as
methoxychlor (its hydroxy metabolites; Thorpe et al. 2001), and lindane and kepone,
which are structurally similar to DDT (Eroschenko 1981). These chemicals can still
be found in surface waters at biologically effective concentrations, and can induce
gonadal developmental aberrations, VTG induction, behavioral changes, such as
exploring and learning responses, and disrupt ionic regulation in fish (Davy et al.
1973; Weisbart and Feiner 1974; McNicholl and Mackay 1975; Begum et al . 1992;
Donohoe and Curtis 1996; Metcalfe et al. 2000). The photosynthesis-inhibiting her-
bicides linuron and diuron, and metabolites of the fungicide vinclozolin are also all
endocrine-active, acting as antiandrogens (Kelce et al . 1994; Thorpe et al. 2001).
Other pesticides reported to have endocrine-disrupting activity, with (anti)estrogenic
and/or (anti)androgenic activity, include some of the pyrethroids, including per-
methrin, fenvalerate, and cypermethrin, albeit weakly (Tyler et al . 2000; McCarthy
et al. 2006; Jaensson et al . 2007; Sun et al. 2007).
15.6.3 pcb s
The estrogenic activity of PCBs was brought to light in 1970, and it was quickly
established that some are also toxic and bioaccumulative to wildlife (Hansen et al .
1971; Hansen et al . 1974) and could impair the reproductive performance capabilities
in a variety of animals (Platonow and Reinhart 1973; Nebeker et al . 1974). The estro-
genic nature of some PCBs has been shown to reverse gonadal sex in turtles (Crews
et al . 1995), and affect uterine development in rats (Gellert 1978). Some of the 209
PCB congeners also have thyroid-disrupting activity (Darnerud et al . 1996), and are