A model to estimate influent and effluent concentrations of estradiol, estrone, and ethinylestradiol at sewage treatment works.

To predict sewage influent and effluent concentrations of the steroid estrogens 17beta-estradiol, estrone, and 17alpha-ethinylestradiol, a review of human excretion was carried out. This included conjugation and metabolism of the natural and synthetic steroid estrogens within the body, together with quantities excreted in the urine and feces by different members of the population. This has been combined with fate and behavior information for conjugated and unconjugated estrogens in the sewage treatment system to enable sewage works influent and effluent concentration predictions to be made. The model has proved to be reasonably accurate when tested against recent measurements of these steroid estrogens in the influent and effluent of sewage treatment works. The model may be used with river dilution ratios to predict which sewage treatment works are most likely to cause the greatest endocrine disruption due to steroid estrogens.