Here's a real study: https://pubmed.ncbi.nlm.nih.gov/29314190/ . It found when frogs were exposed to atrazine (a herbicide) in wastewater runoff, "female minnows were defeminized, whereas male frogs were feminized". Similarly https://www.pnas.org/doi/10.1073/pnas.0909519107 found that "Atrazine-exposed males were both demasculinized (chemically castrated) and completely feminized as adults. Ten percent of the exposed genetic males developed into functional females that copulated with unexposed males and produced viable eggs." So Atrazine can cause frogs to change their gender, and contaminates drinking waters in part of the US (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6164008/), so it's not beyond the realm of possibility that it also influences gender expression in humans to some degree.