Livestock wastes as a source of estrogens and their effects on wildlife of Manko tidal flat, Okinawa

The Manko tidal flat in the southern part of Okinawa Island is an important visiting and wintering area for migratory birds and was added to the Ramsar Convention Register of Wetlands in 1999. This area used to be an inlet extending to the inner part of Naha Port, but recent reclamation projects have restricted its connection to the East China Sea. As is typical in rural regions of subtropical islands, the inhabitants in the Manko basin raise livestock, especially pigs, without employing sufficient waste treatment methods. As sewage treatment works are considered to be one of the main sources of environmental estrogens in urban areas, the significance of livestock farming as a source of estrogens in rural area is examined in this study. In the present study, total estrogenic activities in water and sediment samples from the Manko tidal flat and its basin were measured using a recombinant yeast screen method. Estrogenic activities (equivalent to 17β-estradiol, E2) were around 10 ng l−1 in water samples and more than 10 μg kg−1 in some sediment samples. In addition, the concentrations of estrone (E1) and E2 in water samples measured using LC/MS/MS indicated a high contribution of environmental estrogens from livestock wastes.