Threat of Estrogen Biomagnification in Food Chain Unfounded in Top Predator Fish

[Endocrine (Sexual) Disruption Is Not a Prominent Feature in the Pike (Esox luscius), a Top Predator, Living in English Waters; Environmental Toxicology and Chemistry], 2005; Vol 24 (6):1436-1443

Newswise — Concerned that environmental estrogen may biomagnify in food chains, that is, increase to high concentrations through dietary consumption, researchers have found this not to be the case for pike, a predator fish in English waters. A new study published in the June issue of Environmental Toxicology and Chemistry indicates that estrogen does not inhibit the sexual development of pike.

This is good news, considering the potency of environmental estrogen. The synthetic estrogen ethinylestradiol is detected at potent concentrations 1,000-fold greater than that of any other mimic, affecting fish even at very low concentrations. Ethinylestradiol appears at its most toxic concentrations downstream from major sewage treatment works, where it comes from birth control pills and hormone replacement therapies.

Endocrine-disrupting chemicals such as estrogen can enter a fish through food or from the environment, where toxins in the water pass over the gills and eventually enter the blood. Depending on the nature of the chemical, it may become bioconcentrated in the fish, often reaching concentrations much higher than those in the surrounding water. From there, the chemical may biomagnify either through benthic food-chain transfer or from prey-to-predator transfer.

Biomagnification of chemicals causing pronounced biological effects is evident in the decline of the sparrow and the bald eagle. Consumption of prey that contained relatively low concentrations of DDT caused eggshell thinning and, later, reproductive failure in the adult birds. Additionally, a high percentage of male Mediterranean swordfish have been found to be intersexed, suggesting chemical biomagnification in fish.

Pike was chosen as the investigative species in this study because it is the top predatory fish in English rivers, and chemicals from food are concentrated in its body. Evidence of endocrine disruption in pike also has been reported in the Elsa basin in Spain, where intersexed pike have been found.

Researchers in this study found no evidence of severe disruption in the sampled pike taken upstream and downstream from the sewage treatment works. However, 14% of the fish were intersexed, of which 15 of 16 showed patches of male germ cells among the predominantly female gonadal tissue. The incidence of masculinization was independent of whether the pike had been sampled upstream or downstream.

The study's results show that estrogen may not biomagnify in food chains, and the potentially adverse effects of this endocrine modifier may not be as pervasive as has been feared.

To read the entire study, click here: http://www.allenpress.com/pdf/entc_24_611_1436_1443.pdf

Environmental Toxicology and Chemistry is a monthly journal of the Society of Environmental Toxicology and Chemistry (SETAC). For more information, visit http://www.setac.org.