When you shampoo your hair in the morning, you aren't grabbing a jar of synthetic fragrance chemicals and scrubbing your hair clean. Likewise, you aren't chasing your daily apple with a shot of pesticides. Yet that's how the Environmental Protection Agency (EPA) currently determines "safe" levels of exposure to chemicals—by determining the highest levels of chemicals that cause harm and assuming anything less than that is OK.
That outdated mode of thinking could be changing. The agency has announced that it will be working with other government agencies to determine whether they should begin testing how endocrine-disrupting chemicals affect us when we're exposed at extremely small doses—figuring out, for example, what the lingering levels of those pesticides on your apple are really doing to you and how small amounts of synthetic chemicals used in personal care products could be triggering allergies or even cancer.
Endocrine disruptors are chemicals that interfere with the body's endocrine system, which controls levels of hormones like testosterone, estrogen, and insulin, which are produced by various organs. Over the past decade, hundreds of studies have been published in academic and peer-reviewed journals showing that very low doses of these chemicals can interfere with the endocrine system, disrupting the way it manages all those hormones. These studies found that endocrine disruptors, which include the pesticides on your apple, the bisphenol A used to create the lining of your canned soup, and the phthalates used to make the artificial fragrance in your favorite body lotion, may be contributing to diabetes and other metabolic disorders, infertility, breast and prostate cancers, and learning disabilities, which can be caused by thyroid-hormone dysfunction.
What Is a "Hormone Disruptor" Anyway?
However, when the EPA conducts its safety tests currently, its scientists use a high-dose test, says Laura Vandenberg, PhD, a postdoctoral fellow of biology at the Center for Developmental and Regenerative Biology at Tufts University in Massachusetts. The agency looks for what are considered "insensitive" endpoints, for instance, whether the chemical can cause death or birth defects. By contrast, low-dose testing looks for more subtle changes that can indicate bigger problems, she says, such as whether mothers are nursing properly, if a female's mammary glands are more sensitive to cancer, or if an animal develops insulin resistance, a precursor to diabetes. Vandenberg and 11 other prominent researchers published a landmark three-year-long study in March 2012 pointing out the urgent need to revise chemical-testing methods to better determine these small-dose effects.
"The results of high-dose testing are used to calculate a safe dose for humans," Vandenberg says, "but that dose is never actually tested!" And people wind up getting exposed to levels of chemicals that could be dangerous, she adds. "You could think a dose is safe because it doesn't kill you or make you lose all of your body weight, but it could induce an allergic response or make you more susceptible to cancer, or change the development of a baby's brain."
That's what it appears the EPA might change, and none too soon. A decade ago, the EPA asked the National Toxicology Program to review this very issue. The conclusion then? "There was sufficient evidence for low-dose effects for a number of endocrine disruptors," says Vandeberg. Ten years on, the EPA hasn't changed its testing methods, so there's no guarantee this new analysis will yield significant changes.
Filed Under: HORMONE DISRUPTORS AND OBESOGENS
Published on: December 13, 2012