In the 12th week of a human pregrancy, the momentous event of gender formation begins, as X and Y chromosomes trigger biochemical reactions that shape male or female organs. Estrogens carry the process forward in girls, while in boys, male hormones called androgens do.I won't repost the whole article, but for those who like big and scary words, the link above should be good for a week. For the simple and direct among us, I will summarize it: boys exposed to make-up, hair sprays, mousse, nail polish and perfume end up being more effeminate and less 'manly'.
Now scientists have indications the process may be influenced from beyond the womb, raising a fresh debate over industrial chemicals and safety. In rodent experiments, common chemicals called phthalates, used in a wide variety of products from toys to cosmetics to pills, can block the action of fetal androgens. The result is what scientists call demasculinized effects in male offspring, ranging from undescended testes at birth to low sperm counts and benign testicular tumors later in life. "Phthalate syndrome," researchers call it.
Whether phthalates -- pronounced "thallets" -- might affect sexual development in humans, too, is now a matter of hot dispute. Doses in the rodent experiments were hundreds of times as high as the minute levels to which people are exposed. However, last year, federal scientists found gene alterations in the fetuses of pregnant rats that had been exposed to extremely low levels of phthalates, levels no higher than the trace amounts detected in some humans.