Interestingly, studies have extracted the fraction containing the mixture of legacy POPs, including the PCBs, and found a correlation between the chemical level of POP biomarkers and the xenoestrogenicity of the serum POP mixture related to the detected level: the xenoestrogenic activity of the Inuit's (high serum PCB levels) and Warsaw study groups (lower PCB levels) elicited high frequency of samples with ER antagonistic and agonistic activity, respectively.
Source: wiktionary