January 27, 1997

In a new study sponsored by the U.K. Environment Agency, researchers reported that the estrogenically-active substances in sewage treatment works (STW) effluents are predominately natural estrogens. The researchers stated that these hormones "are only significant estrogenic chemicals measured in the effluents."

According to the report, past research conducted by Brunel University and the Ministry of Agriculture, Fisheries, and Food (MAFF) laboratory "confirmed that an estrogenic effect could be caused in male fish [roach] when exposed to domestic sewage effluent, as shown by the synthesis of the egg yolk protein vitellogenin normally found only in females." The researchers recently determined that two female hormones were present at all seven test sites. The hormones were present in a "biologically-active, unbound (free) form and not in the inactive, bound form in which the hormones would have been excreted, suggesting that they had been re-activated within the sewage system and/or the sewage treatment works." The synthetic hormone used in birth control pills, ethinyl estradiol, was below the limit of detection at most sites on most occasions.

Researchers at Brunel and MAFF previously pointed to alkylphenols as potential estrogenically-active substances in these effluents. However, according to the U.K. Environment Agency report, "(n)o other significant estrogenic activity was found, indicating that these hormones constitute the majority of the estrogenic activity within domestic sewage effluent...The earlier observations of estrogenic activity in domestic effluents and some rivers can be attributed to these hormones." The report does note that "the results do not rule out other weakly estrogenic compounds as contributing to the overall effect."

The report also points out that there has been no observed "widespread fish (or other organism) population decline...Indeed, most of the rivers adjacent to the STWs assessed are highly productive."

The results of the study were reported at the Society for Environmental Toxicology and Chemistry (SETAC) meeting in Washington, D.C. in November, 1996. Publication of the completed study is expected in Spring 1997. The U.K. Environment Agency also plans an environmental risk assessment "to evaluate the link between the occurrence of these estrogenic hormones in the environment and the biological effects they may cause, and any effects observed in the wild."