Are These Chemicals Making Us Sick?
With BPA and phthalates, there's nothing like the smoking-lung cancer connection, but there are lots of smoking guns. The research is still in its early days, and much of what we know comes from work with animals. Also, not all phthalates have been linked to health problems. But many prominent scientists believe these chemicals may cause a range of problems related to our hormones:
- Lower sperm counts and other reproductive abnormalities: Since the late 1990s, after Hunt found that mice in BPA-contaminated cages developed egg abnormalities, she and dozens of other researchers have linked the chemical to reproductive problems in rodents, including lower sperm counts and abnormal eggs. Phthalates, too, may cause reproductive problems. In 2006, when Harvard researchers studied 463 men seeking treatment at a fertility clinic, the scientists reported that men with higher levels of certain phthalates in their urine had lower sperm counts and sperm motility, as well as damage to sperm DNA, all of which affect the ability to impregnate a partner.
In one of the most important human studies so far, Swan measured phthalates in 85 pregnant women in three U.S. cities Los Angeles, Minneapolis, and Columbia, MO. In that 2005 study, women with the highest phthalate levels were most likely to give birth to sons with smaller penises, smaller testes, and "reduced ano-genital distance" (the space between the testes and the anus). In other words, these baby boys were somewhat de-masculinized, which could signal impaired semen quality and decreased fertility later on. "The results were dramatic," Swan says. "We were surprised by how strong the link was. And, based on animal studies, we're concerned about possibly serious health consequences for these boys as they get older."
- Early puberty: "We think girls are maturing younger and younger," says Mount Sinai's Dr. Galvez, "and we're now trying to find out if endocrine disruptors play a role." Her center is involved in a large study that is tracking 1,200 girls, currently ages 6 to 8, for five years. But there are already clues. In Puerto Rico, researchers have been studying girls who have developed breasts at extremely young ages (before 8, and most starting before 2). Their 2000 study showed that these children had phthalate levels, on average, almost seven times higher than those in a control group of girls. While the researchers stress that this correlation does not prove there's a link, their report concludes, ominously, that "if the hypothesis holds true, premature sexual development in Puerto Rico may prove to be an unfortunate example of the impact of endocrine-disrupting environmental chemicals at a critical stage of human development."
- Cancer: Early puberty, in turn, has been linked to an increased risk of breast cancer. BPA, too, causes precancerous growths in lab animals, both prostate and breast abnormalities. But in humans it's hard to prove cause and effect with 100 percent certainty, says Andrea Gore. "We're exposed to so many things, and our mothers ate and drank this or that and 50 years later we get breast cancer," she says. "How can you go back and say, 'It must be this chemical?'"
- Obesity and diabetes: In one study of adult men, those with higher-than-average phthalate levels tended to have a larger waist circumference and increased insulin resistance, precursors to diabetes. In a study of mice, the ones fed BPA were more likely to give birth to offspring who became obese.
- Neurobehavioral abnormalities: In a lengthy review article, published in 2007, researchers reported that low doses of BPA during development affect brain structure, function, and behavior in rats and mice.
Next Page: What government agencies have found
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