Prevalence of endometriosis in rhesus (Macaca mulatta) monkeys ingesting PCB (Aroclor 1254): review and evaluation

A total of 80 menstruating rhesus monkeys (Macaca mulatta) were equally and randomly divided among groups receiving 0, 5, 20, 40, or 80 mu g of Aroclor 1254/kg body weight/day during a 6-year toxicological-reproduction study. During the first 3 years of the study, 4 of the treated monkeys became moribund and were euthanized; 3 had endometriosis. This finding suggested a possible link between the PCB treatment and the occurrence of endometriosis. However, neither a laparoscopic examination of the control and high-dose monkeys nor the necropsy data provided evidence for a possible link between the PCB treatment and the observed incidence (37% (6/16) of controls; 25% (16/64) of treated monkeys and/or the severity of the endometrial lesions. Additional clinical and historical data not contained in previous reports are presented to facilitate independent evaluation of the relationship between PCB ingestion and endometriosis. We conclude that the incidence and severity of the endometriosis lesions observed in the rhesus monkeys utilized in this study did not have any relationship with the dosages of Aroclor 1254 they ingested.