Environmental toxins are disrupting human biology at the most basic level: reproduction. That was the conclusion of researchers at Michigan State University, who found that men with higher levels of exposure to polychlorinated biphenyls (PCBs) were more like to father boys than girls. PCBs are known to cause sex-related defects in animals (although the researchers were quick to explain that boys are not, technically speaking, sex-related defects) and are also linked to cancer and infertility. The study examined men who had high levels of PCBs in their blood due to eating fish caught in the heavily contaminated Great Lakes. Interestingly, PCB levels in mothers did not seem to affect the gender of the child.