Endocrine-Disrupting Chemicals and Their Environmental Impacts - Organic Pollutants: An Ecotoxicological Perspective - page 274

estrone (E 1 ; Desbrow et al . 1998; Rodgers-Gray et al . 2000, 2001), together with EE 2
(a component of the contraceptive pill) have been identified as the major contributing
agents in the feminization of wild roach. These natural and synthetic steroidal estro-
gens, derived from the human population, are predominantly excreted as inactive
glucuronide conjugates (Maggs et al . 1983), but they are biotransformed back into
the biologically active parent compounds by bacteria in WWTWs (van den Berg et
al . 2003; Panter et al . 2006). Horse estrogens used in hormone replacement therapy
(Gibson et al . 2005) and alkylphenolic chemicals, derived from the breakdown of
industrial surfactants (see later text), have also been shown to contribute to the estro-
genic activity of some WWTW effluents and are biologically active in fish at environ-
mentally relevant concentrations (Gibson et al. 2005). Alkylphenolic chemicals have
been shown to be especially prevalent in WWTW receiving significant inputs from
the wool scouring industries (Jones and Westmoreland 1998; Sun and Baird 1998).
Laboratory exposures of roach and other fish species to steroidal estrogens and
alkylphenolic chemicals have induced VTG synthesis, gonad duct disruption, and
oocytes in the testis, albeit for the latter effect, at concentrations generally higher
than that found in effluents and receiving rivers (Blackburn and Waldock 1995; Tyler
and Routledge 1998; Metcalf et al. 2000; Yokota et al. 2001; van Aerle et al. 2002;
Hill and Janz 2003). EE 2 is present at considerably lower concentrations in the aquatic
environment than for the natural steroidal estrogens, but it is exquisitely potent in
fish, inducing VTG induction at only 0.1 ng/L EE 2 in rainbow trout ( Oncorhynchus
mykiss ) (Purdom et al . 1994) for a 3-week exposure, inducing intersex in zebrafish
at 3 ng EE 2 /L, and causing reproductive failure in zebrafish for a lifelong exposure
to 5 ng EE 2 /L (Nash et al. 2004). In a recent study in which a whole experimental
lake was contaminated with 5-6 ng EE 2 /L, over a 7-year period there was a complete
population collapse of fathead minnow ( Pimephales promelas ) fishery (Kidd et al.
2007). Adding further to the hypothesis that steroidal estrogens play a major role in
causing intersex in wild roach in U.K. rivers, the incidence and severity of intersex
in roach from a study on 45 sites (39 rivers) found they both were significantly corre-
lated with the predicted concentrations of the E 1 , E 2 , and EE 2 present in the rivers at
those sites (Jobling et al . 2006). Adding further complexity to the story of the femi-
nization of roach in U.K. rivers, and as mentioned earlier, U.K. WWTW effluents are
also antiandrogenic (Johnson et al. 2004), and this activity is likely to contribute to
the feminization phenomenon (Jobling et al., submitted; see Section 15.7).
Importantly, the intersex condition in roach has been shown to affect their ability
to produce gametes, which is dependent on the degree of disruption in the reproduc-
tive ducts and/or altered germ cell development (Jobling et al. 2002a, 2002b). Small
numbers of wild roach occur in affected wild populations that cannot produce any
gametes owing to the presence of severely disrupted gonadal ducts. In the majority
of intersex roach found, male gametes were produced that, although viable, were of
poorer quality than those from normal males obtained from aquatic environments
that do not receive WWTW effluent (Jobling et al . 2002b). Fertilization and hatch-
ability studies showed that intersex roach even with a low level of gonadal disruption
were compromised in their reproductive capacity and produced less offspring than
roach from uncontaminated sites under laboratory conditions (Jobling et al . 2002b).