in bile flow and bile salt excretion, appear to be responsible for the cholestasis. Very high concentrations of estradiol, via its metabolite estradiol glucuronide, are also implicated in cholestasis, for instance in cholestasis of pregnancy. However, the incidence and severity of cholestatic hepatotoxicity appear to be much greater with EE than with estradiol, which is thought to be due to the reactive C17α ethynyl substitution in EE as well as its greatly reduced susceptibility to hepatic metabolism. Whereas abnormal liver function tests (LFTs) are normally found in about 1% of women not on birth control pills or taking lower-dose EE-containing birth control pills, this increases to more than 10% of women taking birth control pills containing 50 μg/day EE or more. With birth control pills containing 50 μg/day EE, alanine aminotransferase (ALT) levels increase by 50%, hematocrit by 19%, and leukocytes by 50%, while gamma-glutamyltransferase (GGT) decreases by 30%. However, the values usually remain in the normal range. In addition to abnormal LFTs, pathological changes in partial liver functions and liver morphology can be observed in half of women on birth control pills with 50 μg/day EE. EE-containing birth control pills have also been associated with a 25- to 50-fold increase in the risk of rare benign liver tumors and a 3- to 6-fold increase in the risk of hepatocellular carcinoma, as well as greater risk of other liver complications. At one time, EE-containing birth control pills were estimated to be responsible for 84% of all drug-related and histologically verified liver damage. However, these risks now are reduced with modern lower-dose EE-containing birth control pills, with contain 35 μg/day EE or less. Uterine cancer The high doses of EE that were used in early COCs were associated with a significantly increased risk of endometrial cancer in certain preparations, for instance those containing the progestogen dimethisterone. Unopposed estrogens like EE have carcinogenic effects in the endometrium and progestogens protect against these effects, but dimethisterone is a relatively weak progestogen and was unable to adequately antagonize the endometrial carcinogenic effects of EE, in turn resulting in the increased risk of endometrial cancer. COCs containing dimethisterone have since been discontinued (with more potent progestogens used instead) and doses of EE in COCs in general have been dramatically reduced, abrogating the risk. In turn, most studies of modern COCs have found a decreased risk of endometrial cancer. Ecological Effects Wastewater contains various estrogens, including