Abstract
Groundwater samples were collected in Miyako Island and in the southern part of Okinawa Island from February to November 1999, and their estrogenic activity was measured by means of a recombinant yeast assay. Five out of eight sites in downtown or in the vicinity of residences and two out of fourteen rural sites showed estrogenic activities that ranged from 0.2 to 2.0 ngL-1 (17β-estradiol (E2) equivalent). Further sampling was continued at one site in the downtown of Miyako Island for ten times between July 2000 and June 2001. Correlation between the fluctuation of the estrogenic activity and that of the concentrations of some ions such as Na+ was found at this site. E2 concentration of groundwater samples from Miyako Island in 1999 was also measured by means of ELISA. E2 was detected from all the samples with estrogenic activity.
