Endocrine-Disrupting Chemicals and Their Environmental Impacts - Organic Pollutants: An Ecotoxicological Perspective - page 275

In that study there was an inverse correlation between reproductive performance and
severity of gonadal intersex (Jobling et al . 20 02b).
The phenomenon of estrogens in WWTW effluents is not unique to the United
Kingdom and occurs more widely in Europe [Germany (Hecker et al . 2002), Sweden
(Larsson et al. 1999), Denmark (Bjerregaard et al . 2006), Portugal (Diniz et al .
2005), Switzerland (Vermeirssen et al . 2005), and the Netherlands (Vethaak et al .
2005)] and in the United States (Folmar et al . 1996), Japan (Higashitani et al . 2003),
and China (Ma et al . 2005). The level of estrogenic impact seen in fish in U.K. rivers,
however, appears to be greater than for elsewhere in Europe, and globally. Why this
is the case is not known, but it may relate to the fact that often a considerable propor-
tion of the flow of rivers in the United Kingdom is made up of treated WWTW efflu-
ent; 10% WWTW effluent is a common level of contamination, and for some rivers
it is more normally 50% of the flow. In extreme cases in the United Kingdom, and
generally in the summer months during periods of low rainfall, treated wastewater
effluent can make up the entire flow of the river.
15.4.4 a T r a z i in e a n d a b in o r m a l i T i e s i n f r o g s
Globally, many amphibian populations are suffering drastic declines (Wake 1991;
Houlahan et al . 2000). Causation ascribed to these declines include effects on envi-
ronmental conditions induced by climate change, introduction of alien predators,
overharvesting, habitat destruction, the increase of various diseases, and effects of
UV light on embryo development (Alford et al. 2007; Gallant et al. 2007; Skerratt et
al . 2007; van Uitregt et al . 2007). In some cases chemical exposures have been impli-
cated, but not proved. As an example, in some parts of the United States, deformities
seen in frog populations, in which individuals either lack or have additional limbs,
have been associated with exposure to PCBs that can interfere with normal thyroid
hormone and/or retinoic acid signaling and function. Controlled laboratory studies
have shown that some PCB congeners can induce some of the limb abnormalities
seen in the wild (Gutleb et al . 2000; Qin et al. 2005); however, these effects are
only induced at exposure concentrations exceeding those normally seen in the wild.
In fact, the case for limb deformities in frogs is becoming an increasingly complex
story and causative agents ascribed are now wide-ranging and include the chytrid
fungus, parasitic trematodes, UV radiation and a wide range of chemical contami-
nants (Meteyer et al. 2000; Loeffler et al. 2001; Johnson et al. 2002; Ankley et al .
2002; 2004; Davidson et al . 2007).
More controversially, endocrine disruption as a consequence of exposure to the
herbicide atrazine (2-chloro-4-ethylamine-6-isopropylamine-s-triazine), one of the
most widely used herbicides in the world, has also been hypothesized to explain
various adverse biological effects in frog populations in the United States. Exposure
to atrazine in the laboratory at high concentrations, far exceeding those found in the
natural environment, has been reported to induce external deformities in the anuran
species Rana pipiens, Rana sylvatica, and Bufo americanus (Allran and Karasov
2001). Studies by Hayes et al. have suggested that atrazine can induce hermaphrodit-
ism in amphibians at environmentally relevant concentrations (Hayes et al. 2002;
Hayes et al . 2003). Laboratory studies with atrazine also indicated the herbicide