Hormone-like chemicals in plastics, pesticides and other products pose "significant concern for public health," possibly causing infertility, cancer and malformations, a medical society announced Wednesday.
There is strong evidence that chemicals that interfere with the hormone system can cause serious health problems, according to a scientific report from the Endocrine Society, now meeting in Washington, D.C. Although scientists still have many questions about the chemicals, the report says that it's important for people to take a "precautionary approach" by reducing their exposures.
Hormone-disrupting chemicals include bisphenol A, or BPA, often used in plastic baby bottles and the linings of metal cans.
The new report is the latest in a growing number of statements from scientific groups warning of potential harm. Although the Food and Drug Administration says BPA is safe, Canada last year declared the chemical to be toxic. The USA's National Toxicology Program last year also expressed "some concern" over BPA's effects on the brain, behavior and prostate gland in children before and after birth. In 2007, a group of 38 leading researchers published a statement noting serious risks from BPA.
The Endocrine Society decided to release the scientific statement - the first it has ever issued - because these chemicals "affect everyone," says society president Robert Carey. The report notes that 93% of Americans tested have been exposed to BPA.
Carey says the society wants to provide accurate information to lawmakers and regulators. Beyond summing up the latest science, the report also catalogues what doctors don't yet know and lists the sort of research that still needs to be done.
The report notes that hormone-disrupting chemicals behave differently than other toxins. For most toxins, the danger is in the dose, with larger doses posing more risk than small ones, says Andrea Gore, an author of the new statement from the University of Texas at Austin.
Because the body is exquisitely sensitive to hormones, Gore says, even small doses can cause serious problems, especially if babies are exposed during critical development windows, such as before birth. For hormones, the timing of exposure is often far more critical than the amount.
Disturbingly, the damage from hormone-disrupting chemicals can sometimes be passed on to future generations, Gore says.
Scientists at the annual meeting presented new studies on BPA, as well, including one linking the chemical to abnormal heart rhythms in rats and mice. That finding supports a September study in The Journal of the American Medical Association linked BPA to an increased risk of heart disease and diabetes in humans.
Another new study found that people are likely exposed to greater doses of BPA than are considered safe by the FDA. And a third study, showing that BPA causes permanent changes in the DNA of mice, helps doctors understand how this damage is passed on to offspring, says author Hugh Taylor of Yale University School of Medicine. Taylor says his small study supports research showing that prenatal exposure to BPA could permanently change the way the body responds to estrogen.
An industry group, the American Chemistry Council, said in a statement that it agrees scientists need to do more research. But the council notes that a group called the International Union of Pure and Applied Chemistry found there have been no "conclusive" studies proving that the chemicals cause disease.
But Taylor says there is reason for pregnant women to be cautious, even if much of the research so far is in animals.
"You can never do these studies in women," Taylor says. "You can't intentionally give someone high doses, especially in pregnancy."
Taylor says that the small number of human studies, including one linking high BPA levels to miscarriages, suggest that humans react the same way to BPA as animals.
"I don't think anybody is saying this is the most toxic stuff known to man," Taylor says. "But are we doing something that could affect our children into the next generation?"