Distribution of estrogens, 17beta-estradiol and estrone, in Canadian municipal wastewater treatment plants.

The distribution of female hormones, 17beta-estradiol and estrone, was determined in effluents of 18 selected municipal treatment plants across Canada. Replicate 24-h composite samples were collected from the influent and final effluent of each treatment plant, and the removal efficiency compared to the operational characteristics of the plants. In conventional activated sludge and lagoon treatment systems, the mean concentrations of 17beta-estradiol and estrone in influent were 15.6 ng/l (range 2.4-26 ng/l) and 49 ng/l (19-78 ng/l). In final effluents, the mean concentrations of both 17beta-estradiol and estrone were reduced to 1.8 ng/l (0.2-14.7 ng/l) and 17 ng/l (1-96 ng/l), respectively. 17beta-estradiol was removed effectively, >75% and as high as 98%, in most of the conventional mechanical treatment systems with secondary treatment. The removal of estrone was much more complex with removal varying from 98% to situations where the concentrations in the effluent were elevated above that detected in the influent. The estrogenicity, measured using a transfected estrogen receptor in yeast (YES) assay, was also variable, ranging from high removal to elevations of estrogenicity in final effluent. Although the apparent removals were not statistically correlated with either hydraulic (HRT) or solid (SRT) retention times, plants or lagoons with high SRT were very effective at reducing the levels of hormones. Well-operated plants that achieved nitrification also tended to have higher removal of hormones than those that did not nitrify. Laboratory aerobic reactor experiments confirmed the rapid removal of 17beta-estradiol, estrone, and estrogenicity when exposed to sewage slurries.

Enantiomer-specific activity of o,p'-DDT with the human estrogen receptor.

There is a growing concern that environmental xenobiotics may be affecting human and wildlife health by disrupting normal endocrine function via interaction with steroid hormone receptors. Several of these persistent contaminants are chiral and may have enantiomer-specific biological properties. Previous experiments have demonstrated that (-)-o,p'-DDT enantiomer is a more active estrogen-mimic than the (+)-enantiomer in rats. However, these results have not been extrapolated to other biological systems. This study used a yeast-based assay to assess the enantiomer-specific transcriptional activity of DDT with the human estrogen receptor (hER). (+)-17beta-estradiol, racemic DDT and individual DDT enantiomers were added to yeast cultures and hER activity was measured by quantification of beta-galactosidase. The relative activity of o,p'-DDT was weak compared to estradiol. For o,p'-DDT, the (-)-enantiomer was the active estrogen mimic whereas the hER activity of (+)-o,p'-DDT was negligible. The presence of the (+)-enantiomer at relatively greater concentration decreased the transcriptional activity of (-)-o,p'-DDT. This data demonstrates the need to consider stereochemistry of environmental contaminants and their potential influence on biological responses.