The book Countdown talks about this and the author posits that there is a link. Endocrine disrupting chemicals (EDC's) cause smaller penis sizes, smaller anogenital distance, and homosexual behaviors in reptiles and other animals. Lower sperm counts, lower sperm motility, smaller penis size, and smaller anogenital distance (the most important indicator, oddly) are all also linked in humans, via TONS of studies, to the same chemicals.

She treats the subject very delicately, rightly so, because many people will probably call you a bigot for even asking the question.

From chapter 4 of the book: "In a 2019 article in Psychology Today, Robert Hedaya, MD, a clinical professor of psychiatry at the Georgetown University of Medicine wrote, "It is nothing short of astounding that after hundreds of thousands of years of human history, the fundamental facts of human gender are becoming blurry.""

And in a later passage from the author: "One scientific theory suggests that in utero exposure to EDCs, particularly phthalates, which can lower a fetus's exposure to testosterone, may play a role; these chemicals have been associated with an increased risk of autism spectrum disorders (ASDs) in males. Interestingly, ASD and gender dysphoria, two seemingly unrelated conditions, occur together more often than expected"