Fate of ethinylestradiol in the aquatic environment and the associated effects on organisms of different trophic levels

The accumulation kinetics of an important, highly effective, and persistent xeno-estrogen, 17alpha-ethinylestradiol (EE2), in the aquatic environment were investigated in indicator species representing the different trophic levels of an ecosystem: a primary producer (Desmodesmus suspicatus), a primary consumer of the water phase (Daphnia magna) and one of the sediment (Chironomus riparius), and a secondary consumer (Danio rerio). Algae highly concentrated 14C-EE2 (72 h Calgae/Cwater: 2200 L/kg ww) and transformed it into two more hydrophobic, but less estrogenic products: Br-EE2 and Br2-EE2, identified by GC-MS and high resolution LC-MS. Daphnids and chironomids showed lower bio-concentration factors (BCFs of 50 and 580 L/kg ww). In extracts of both organisms, more hydrophilic conjugates of 14C-EE2 were detected by means of HPLC with radiodetector before and after enzymatic hydrolysis. This observed biotransformation process was in accordance with the fact that both invertebrates quickly eliminated incorporated radioactivity. Accumulation of radioactivity in daphnids was higher in the presence of algae, depending on the cell density and the consequent filtration and food processing rate. Daphnids additionally removed the test compound during moulting. The bioavailability of EE2 for chironomid larvae was strongly reduced in the presence of (standard OECD) sediment giving a biota sediment accumulation factor (BSAF) of 0.7. However, when a nutritionally valuable food source was available, dietary intake added to the overall accumulation (BSAF: 1.4). A BCF of 960 L/kg ww was calculated for male zebrafish. This value is higher than formerly reported in research concerning EE2 concentration in fish. Uptake of conjugated EE2 by male fish through a chironomid diet resulted in similar internal fish contents and blood vitellogenin levels as EE2 uptake via water, whereas fish exposed to contaminated daphnids showed little uptake. From these results, it could be proven for the first time that dietary applied EE2 glucuronide, synthesized by chironomids, can be reconverted to the parent compound in predator fish. EE2 sulphatide (produced in daphnids and chironomids) and EE2 glucoside (daphnids only) seemed recalcitrant to deconjugation in the fish. EE2-derived radioactivity was detected in all analyzed fish tissues including the brain and filet. This is the first study that shows passage of this estrogen by the blood-brain barrier and indicates risks of EE2 uptake for fish consuming human. EE2 (products) were principally and rapidly distributed to the alimentary system of male zebrafish independently of the uptake route. Biliary excretion was the main depuration route next to dermal release. The differences between the water and dietary treatment were quicker transfer of radioactivity to the liver and more gradual storage in the bile in case of EE2 exposure via water compared to after ingestion of metabolites via living prey. Dietary exposed animals eliminated faster after being transported to clear water. This could be explained by the fact that fish only produced the glucuronic acid conjugate of the test compound, i.e. the one product that is subjected to enterohepatic recirculation, slowing elimination down. Water exposed zebrafish were logically not confronted with the more recalcitrant invertebrate products (EE2 sulphatide & glucoside) that dietary exposed animals ingested. The results of the present study show that EE2 has the potential to be transferred via the food chain since it accumulates in biota from the basis of the web. Therefore, it is important to improve and extend monitoring programs including organisms of different trophic levels, sediments, and suspended material. Hence, sewage treatment plants should be improved to keep this substance from release in the environment. The result that algae highly take up the compound might thereby present a cheap and efficient alternative for water treatment in poor countries, which should be subject of further research