Page 1001 - The Toxicology of Fishes

Estrogenic Effects of Treated Sewage Effluent on Fish in English Rivers 981

A B

Roach
(Rutilus rutilus)

C D

FIGURE 25.8 Feminization of the reproductive duct in juvenile roach (Rutilus rutilus) exposed to the Chelmsford sewage
treatment works effluent. Fish were exposed to series of graded concentrations of treated sewage effluent for 150 days from
50 days post-hatch (dph), and effects on the sex ducts (presence of an ovarian cavity) were determined by histology. (A)
Location of the Chelmsford sewage treatment works in the United Kingdom; (B) mesocosm used to expose juvenile roach
to the Chelmsford effluent; (C) histological section of a male gonad (200 dph) with a feminized duct (ovarian cavity); (D)
percentage of fish with an ovarian cavity exposed to different concentrations of treated sewage effluent. (Adapted from
Rodgers-Gray, T.P. et al., Environ. Sci. Technol., 35, 462–470, 2001.)

the past 10 years investigating for intersex has found that the intersex condition is seen only in fish that
are over 2 years in age (S. Jobling, pers. commun.).
Studies on sexual disruption in wild fish on the European mainland have similarly identified intersex
fish that also appear to have arisen as a consequence of exposure to effluents from sewage treatment
works—for example, Germany, where Hecker et al. (2001) studied bream (Abramis brama); France
(Minier et al., 2000); and Denmark (Christiansen et al., 2000). Sexual disruption in fish in the United
Kingdom has also been demonstrated in coastal waters in the flounder (Platichthys flesus), with inci-
dences of 17% in the Mersey estuary and 7% in the Tyne estuary, but it has not been determined if this
is as a consequence of exposure to STW effluents (Allen et al., 1999; Kirby et al., 2004; Matthiessen,
2003). Differences in the incidence and severity of intersex in wild fish living in contaminated waters
appear to vary widely, and they are likely to depend not only on their level of exposure to EDCs
(determined, at least in part, by the organism’s ecological niche) but also on differences between species
in their sensitivity to the chemicals in question, an issue that has, as yet, received very limited attention.
The findings from wild fish from English rivers strongly support the hypothesis that the concentration
of sewage effluent in a river is a major causal factor in the evolution of intersexuality. Furthermore, as the
majority of the sampling sites in the field studies on roach and gudgeon were several kilometers downstream