Impairments of Endocrine Functions: Case Studies - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 232

Monitoring of EDCs using YES or YAS (yeast androgen screen) tests has been conducted
for water and sediment samples in the estuary of the Seine. Potency to elicit a response
is easily compared to the response engendered by the natural hormone, estradiol (or tes-
tosterone), and expressed as estradiol (or testosterone) equivalents present in the sample.
Waters near the discharge of sewage from the Seine estuary contain concentrations of
several tens of nanogram per liter estradiol equivalents, whereas their concentrations in
the waters of the estuary after dilution by sea water fall generally below detection limits.
Most biologically active compounds are associated with suspended matter and possibly
sediment (Peck et al. 2004). Sediment analysis revealed high estrogenic activity in many
samples along the Seine River, highlighting the widespread contamination throughout the
river and estuary. The concentrations vary according to sampling site but suggest an urban
origin for most of the detected activity (Minier et al. 2007).
The biologically active samples were subjected to chemical analysis by high pressure
liquid chromatography and GC-tandem MS (gas chromatography coupled with dual mass
spectroscopy) to identify the main compounds responsible for the measured response.
The active compounds present consist primarily of natural steroids (estradiol, estrone),
synthetic steroids originating from oral contraceptives (ethinylestradiol), and industrial
detergents used in various cleaning products, such as dispersing agents in formulation
pesticides and as an additive in some plastic compounds (alkylphenols) (Gallien-Landriau
2003).
Measurements using the YAS assays also revealed androgenic and antiandrogenic activ-
ities of water and sediment extracts. The latter are measured by using their ability to act
as antagonists of testosterone for the human androgen receptor expressed in yeast cells.
Their potency is compared to flutamide, a well-known antiandrogen. Results show that
very high amounts of antiandrogen compounds can be found in sediments collected in
the Seine estuary. Values range from 0.1 to 10 µg flutamide equivalents/g sediment. The
identities of those compounds are yet to be elucidated, but they might contribute to the
effects on the aquatic fauna.
9.2.3 Xenoestrogen Accumulation in Mussel Tissues
Mussels are aquatic organisms commonly used in monitoring programs because they
accumulate large amounts of lipophilic compounds present in their environment, thus
reflecting the environmental contamination (Phillips 1978). Zebra mussels ( Dreissena
polymorpha ) are used in the upstream part of the Seine estuary (Minier et al. 2006a),
whereas marine mussels ( Mytilus edulis ) are sampled in the marine part of the estuary
(Minier et al. 2006b). After homogenization of tissue and extraction of lipophilic com-
pounds, quantification of estrogenic compounds by the YES assay has highlighted the
occurrence of these compounds across the estuary at concentrations of about 1 to 25 ng
estradiol equivalents per gram of tissue. Concentrations are high in the Seine estuary
(and in many other French rivers), but they fall below detection limits in coastal areas
away from the estuary.
Laboratory experiments have demonstrated that the ability of mussels to bioconcentrate
17β-estradiol in their tissues is particularly high; the corresponding bioconcentration fac-
tors are about 900 for zebra mussels (Peck et al. 2007) and more than 2000 for marine
mussels (Labadie et al. 2007). Figure 9.10 shows the results of an exposure experiment
using the marine mussel M. edulis . Mussels accumulate the natural hormone rapidly in
large amounts but, when placed in an environment free of this hormone, only eliminate
approximately 50% of the accumulated amount. The E 2 efflux is extremely low after a few