The environment estrogen concentration in the rivers flowed into Harimanada Sea in Hyogo Prefect, was measured. 17α- and 17β- estradiol which were hormone discharged from human and domestic animals were measured. In addition, estron which was a decomposition product of these estradiols was also measured. 17α-estradiol is a sex hormone which derives from the cow. Since the pastureland and cattle shed with the cow exists in the upstream in the river, the quantity of 17α-estradiol detected near the downstream of rivers was little by the biodegradation. However, it was confirmed to reach the concentration in which the estrogen concentration affects the fish near the outfall of the sewage-treatment plant in the Senba river
