Occurrence and endocrine effects of agrichemicals in a small Nebraska, USA, watershed.

The Bow Creek watershed (Nebraska, USA) is dominated by the production of beef cattle and row crops; therefore, surface waters are likely to receive runoff containing steroid hormones and pesticides. The goal of the present study was to determine the occurrence and endocrine effects of agrichemicals in this watershed. To accomplish this, four sites within the watershed-Pearl, Bow, and East Bow Creeks and a site at the confluence with the Missouri River-were selected. In June of 2008, polar organic chemical integrative samplers (POCIS) were deployed at each site, whereas in June of 2009, water and sediment samples were collected. Caged fathead minnows (Pimephales promelas) were deployed at all of the selected sites in both years. Analysis of these samples revealed that steroid hormones were not present; however, pesticides were present in POCIS extracts and water samples. In general, the amount of pesticides was higher in POCIS retrieved from Pearl and Bow Creeks than in POCIS from East Bow Creek and the confluence. This variation between sites appeared to be related to row crop density, as row crop land cover surrounding the Pearl and Bow Creek sites was higher than that surrounding the East Bow and confluence sites. To determine the endocrine effects of agrichemicals within this watershed, the hepatic mRNA expression of vitellogenin and estrogen receptor α (ERα), as well as the gonadal expression of P450 aromatase A, was determined for the caged minnows. Females deployed at East Bow Creek and the confluence experienced decreases in the expression of ERα, suggesting that these females had been defeminized; however, this defeminization could not be attributed to any of the pesticides detected at these sites.

The anti-estrogenic activity of sediments from agriculturally intense watersheds: assessment using in vivo and in vitro assays.

The goal of the current study was to determine whether sediments from agriculturally intense watersheds can act as a potential source of anti-estrogenic endocrine-disrupting compounds. The specific objectives of the current study were to determine (1) whether female fathead minnows (Pimephales promelas) experience alterations in endocrine function when exposed to sediments collected from agriculturally intense watersheds and (2) if these sediments display anti-estrogenic activity in an in vitro assay. In addition, sediment samples were analyzed for the presence of steroid hormones and pesticides associated with local agricultural practices. To accomplish this, sediments and water were collected from three sites within two agriculturally intense Nebraska watersheds (Bow Creek and the Elkhorn River). In 2009, minnows were exposed to sediment and/or water collected from the two Bow Creek sites (East Bow Creek and the Confluence) in the laboratory, while in 2010, minnows were exposed to sediment and/or water from East Bow Creek, the Confluence and the Elkhorn River. Following the 7-day exposure period, the hepatic mRNA expression of two-estrogen responsive genes, estrogen receptor α (ERα) and vitellogenin (Vtg) was determined. In 2009, females exposed to Confluence sediments, in the presence of laboratory water or Confluence water, experienced significant reductions in ERα expression relative to unexposed and Confluence water-exposed females. The defeminization of these females suggests the presence of a biologically available anti-estrogenic compound in sediments collected from this site. In 2010, sediments were assessed for anti-estrogenic activity on days 0 and 7 of the exposure period using a 4-h yeast estrogen screen. Lipophilic extracts (LEs) of day 0 sediments collected from the Confluence and the Elkhorn River induced significant reductions in the estrogenic reporter activity of treated yeast cultures suggesting the presence of a lipophilic anti-estrogenic compound in these extracts. Chemical analysis revealed the presence of a variety of steroid hormones, including those associated with the production of beef cattle (i.e. ß-trenbolone, α-zearalanol and α-zearalenol), in sediments indicating that compounds utilized by local beef cattle operations are capable of entering nearby watersheds. Overall, the results of this study indicate that an environmentally relevant anti-estrogenic compound is present in sediments from agriculturally intense watersheds and that this compound is bioavailable to fish. Furthermore, the presence of steroid hormones in sediments from these watersheds provides evidence indicating that steroids are capable of sorbing to sediments.