Screening of endocrine disruption activity in sediments from the Uruguay River

Sediment constitutes an important sink of endocrine disruptor compounds; however, the potential of sediments to act as a source of endocrine disruptors should be more extensively investigated. The main objective of this study was to determine whether exposure of immature common carp to Uruguay River sediments undergo physiological and endocrine alterations. The lower Uruguay River watershed supports intensive agricultural and forest production, receives municipal sewage discharge and industrial effluent, and a new large pulp mill was constructed in 2006. A 30-day semi-static assay was performed using sediments from four sites along the Uruguay River and compared with an unexposed group in dechlorinated water as a negative control. We focused on two upstream and two downstream sites of a new elemental chlorine free pulp mill. The results showed that plasma vitellogenin levels increased in fish along the river and significant differences were found between the exposed and unexposed groups. Condition factor and gonadosomatic index were not different; however, a significant difference in hepatosomatic index was observed in fish exposed to sediment from an industrial site. A significant reduction in primary spermatocyte accumulation was observed in the exposed group compared with that in the control group, and some individuals exposed to sediments from industrial sites presented with testis-ova. Our results suggest that Uruguay River sediments act as an important source of estrogenic compounds that could be responsible for the alterations observed. Future studies are needed to identify the causal agents and determine exposure routes.