accurately, we really couldn't do epidemiological studies on them," says Swan, a professor in obstetrics and gynecology at the University of Rochester School of Medicine and Dentistry.

Swan recently completed a startling study showing that baby boys born to women exposed to certain chemicals in pregnancy are born with smaller penises and feminized genitals. Similar accounts of disfigurement have been reported in dozens of animals including otters, polar bears and turtles.

"It's very important corroborating evidence when we see similar endpoints being affected in humans and wildlife in response to the same chemicals," Swan says. "The finding of smaller penises in otters is interesting because we have smaller penises in our boys who were exposed to diethylhexyl phthalate. They reinforce each other."

Diethylhexyl phthalate is found in polyvinyl chloride or PVC,and "anything soft plastic like rubber duckies and shower curtains and blow-up toys," Swan says.

"It's very strong evidence in my mind that something is definitely going on in our environment that is altering male reproductive development."

Communities heavily polluted with gender-bender chemicals in Canada, Russia and Italy have given birth to twice as many girls as boys, which may help explain the shift in sex ratios worldwide. Normally, 106 boys are born for every 100 girls but the ratio is falling. The U.S. National Institute of Environmental Health Sciences calculated that 250,000 babies who would have been boys have been born as girls instead in the U.S. and Japan alone.

Some phthalates are manufactured in Canada, and many are imported for use or imported as part of a finished product.