Impairments of Endocrine Functions: Causes and Consequences - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 188

disruption effect with environmental chemicals functioning as estrogens. Similar hypoth-
eses have been advanced in relation to an increased risk for breast cancer in women (Falk
et al. 1992; Wolff et al. 1993) and an observed decrease in human semen quality (Carlsen
et al. 1993; Auger et al. 1995). Endocrine disturbances have also been revealed in vari-
ous species of fish, including premature maturity of females, intersexuality (Chapter 9),
and the induction of vitellogenin (VTG). The first observations of abnormalities of thyroid
function resulting from exposure to chemical compounds were made on wild organisms,
mainly birds and fish of the Great Lakes region (Black et al. 1974; Moccia et al. 1986).
Approximately 550 substances are now suspected to have an action on hormones (CEC
2001). More than 100 naturally occurring and synthetic substances have been reported
to have effects on thyroid function or thyroid hormone (TH) metabolism (Pearce and
Braverman 2009).
Wastewater treatment plant (WWTP) effluents are a major source of potential or known
EDCs in the aquatic environment (Gust et al. 2010a; Tetreault et al. 2011; Vajda et al. 2011
and references quoted by these authors). The steroidal natural estrogens 17β-estradiol
(E2), estrone (E1), estriol, and synthetic 17α-ethynylestradiol (EE2) (contraceptive pills), as
well as estrogenic alkylphenols and bisphenol A, have been identified in such effluents.
Pharmaceuticals and personal care products are also wastewater contaminants, the endo-
crine disrupting potential of which is poorly documented since few compounds have been
inventoried or regulated worldwide (Caliman and Gavrilescu 2009). In the Pearl River sys-
tem, south China, the equivalent concentrations of hormonal activities in some sites were
greater than the lowest-observed-effect concentrations reported in the literature, suggest-
ing the potential for adverse effects on local aquatic organisms (Zhao et al. 2011).
Owing to the importance of sediments on the transport, fate, and bioavailability of
EDCs, sediment contamination by EDCs has been investigated in more than 30 countries
(Gong et al. 2011 and literature quoted therein). In the Pearl River system, these authors
have shown that the spatial distributions of 4- tert -octylphenol, 4-nonylphenol, and bisphe-
nol A (BPA), and the steroid estrogens estrone and 17β-estradiol in the sediments were
related to the discharge of domestic and industrial wastewater along the river system.
In 54 coastal sediment samples collected from nine locations off central-southern Chile,
Bertin et al. (2011) have shown that total estrogenic loads (estrone, 17β-estradiol, estriol,
17α-ethinylestradiol) were correlated with the size of human populations served by local
sewage plants. Steroid estrogens in sediments can be directly bioaccumulated by benthic
species of invertebrates and fish but are also transferred through the food web (Bertin
et al. 2011 and literature cited therein). An abundant literature exists on the sources and
environmental fates of numerous contaminants that were already of interest to ecotoxi-
cologists before their endocrine disrupting potential was discovered (pesticides, PCBs, fire
retardants, cadmium) (Eisler 2007).
It is thus necessary to have good estimates of EDC exposures, and for this purpose we
have chemical techniques and state-of-the-art biological tests to be detailed below. Because
many molecules are suspected to behave as EDCs, it is impossible, for both technical and
cost-effective reasons, to determine the concentrations of all such compounds. Moreover,
chemical analyses do not provide information about the toxicity of complex mixtures of these
compounds, and it is in mixtures that they nearly always occur in the environment. Another
possible approach is to reveal the presence of EDCs with in vitro and in vivo tests designed
to identify estrogenic, antiestrogenic, androgenic, antiandrogenic, and thyroid effects (e.g.,
Jugan et al. 2007; Kinani et al. 2010; Terrien et al. 2011). Toxicity identification evaluation (TIE)
methods have been recently adapted for the detection of EDCs in environmental samples.
When the presence of EDCs is revealed in a sample (water, effluent, sediment, or biological