The urethra is supposed to emerge at the tip of the penis, but in 1 out of every 300 baby boys, its opening is elsewhere—sometimes just underneath the head, or midway down the shaft, or even at the base of the scrotum. No one knows what causes the defect, called hypospadias, but studies have shown that widespread chemicals called phthalates can reproduce it in rodents. Phthalates are used widely as softening agents in certain plastics, notably PVC, and are also found in some cosmetics, pharmaceuticals, and a wide range of other products.
Scientists classify these chemicals among the "endocrine disruptors," so known for their ability to alter the proper balance of hormones, which play a central role during development. "It's not just bisphenol A that we're concerned about," says Ted Schettler, the lead scientist at the Iowa-based advocacy group called the Science and Environmental Health Network, referring to another endocrine disruptor that has made headlines this spring.
Widespread problem. Human exposure to hormone-disrupting synthetic chemicals, which can leach from a slew of consumer products, is continuous and widespread. The Centers for Disease Control and Prevention found in 2005 that most Americans have traces of hormone-disrupting chemicals in their body. An analysis of the data by the Environmental Working Group, an advocacy organization based in Washington, D.C., concluded that 84 percent of Americans have at least six different phthalates in their urine.
Toxicologists have been studying the effects of various phthalates in animals for decades. Three in particular—diethylhexyl phthalate (DEHP), butyl benzyl phthalate (BBP), and dibutyl phthalate (DBP)—cause a constellation of reproductive defects that includes hypospadias, testicular cancer, reduced sperm quality, diminished penis size, and undescended testicles. The effects, in some cases, seem to extend beyond the male reproductive system. Studies in animals have linked allergic skin lesions and lung malformations to DEHP, which is the most widely produced of the phthalates. And pregnant rodents given high daily doses of DBP tend to lose their fetuses. Not everyone, however, thinks such adverse effects in animals justify concern among people. "Most of the exposures are at doses far higher than what we see in humans," says Marian Stanley, a spokesperson for the Phthalate Esters Panel, an industry group that represents phthalate manufacturers. Major scientific reviews from the National Toxicology Program have concluded the risk the chemicals pose to humans is minimal. Yet, the most concerned scientists counter that emerging evidence does suggest phthalates harm humans. Shanna Swan, an epidemiologist at the University of Rochester, has shown that baby boys born to women with elevated DBP and BBP levels tend to have somewhat demasculinized and slightly smaller genitals. Recent studies in adults have linked high exposure to certain phthalates to low sperm quality and abdominal obesity.
Though these studies don't prove cause and effect, some people find the existing evidence alarming enough to act. Many European countries have banned phthalates in certain toys, and a number of American states are considering similar restrictions. Meanwhile, "phthalate-free" products are popping up in stores and on the Internet—just as bisphenol A (BPA)-free baby bottles and water bottles have. Industry groups say that many of the products people worry most about—including plastic wrap, water bottles, and food containers—do not contain any phthalates.
Still, avoiding phthalates altogether is more difficult than avoiding BPA, since it's not clear which of the panoply of products containing them contribute most to exposure. The chemicals easily move from sources such as vinyl tiles or shower curtains, so phthalates routinely end up in the air, water, and dust.
Pregnant women, children, and couples trying to conceive may have the most to gain from trying to avoid phthalates, scientists say. "The primary risk appears to be to the developing fetus," says Swan.