Investigating the estrogenic risk along the river Po and its intermediate section.

Different endpoints have been used to investigate the occurrence of estrogenic risk along the Po River, particularly its middle section. An in vitro assay based on recombinant yeast could not detect estrogenic activity in bed sediments of the Italian river or in bile samples of five Cyprinid species, with the only exception being one carp (Cyprinus carpio) captured downstream of the River Lambro, a polluted tributary of the middle River Po. Chemical analyses of fish bile and water samples from the same middle section showed diffuse contamination by moderately low levels of estrogenic chemicals (estrone [E1], 17beta-estradiol, estriol [E3], 17alpha-ethinylestradiol, 4-nonylphenol [NP], 4-tert-octylphenol [tOP], 4-n-octylphenol, and bisphenol A) but they were of limited help in understanding the risk present in the downstream area where intersex barbel were previously found. In contrast, the analyses of River Lambro waters showed that this tributary is a source to the middle River Po of all eight estrogens investigated. Analyses of bed sediments and macroinvertebrates from the same area consistently showed at least two levels of contamination, with the downstream stretch showing higher concentrations of natural steroids (E1 and E3) and xenoestrogens (NP and tOP). Accordingly, new histologic examinations undertaken on young barbel (Barbus sp.) showed intersex gonads only in the individuals captured in the downstream stretch, thereby confirming previous results. Present findings confirm the occurrence of disrupting conditions in the middle River Po and provide the first suggestions of cause-effect relationships.