What Is a "Hormone Disruptor" Anyway?

'Hormone-disrupting chemical' is becoming an everyday term. But what does it really mean for your health?

By Leah Zerbe

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It seems like not a week goes by without a study linking a common household product—or its ingredients—to one serious health problem or other. Whether it's BPA in cans causing heart attacks and cancer or fake fragrances in personal care products inducing early puberty in girls, the deluge of what's harming us can be depressing. But all of these studies underline one important fact: Chemicals are introduced onto the market before they're adequately tested for their long-term impacts on human health, and many of them are harmful hormone disruptors.

We turned to expert Laura Vandenberg, PhD, a postdoctoral fellow of biology at the Center for Developmental and Regenerative Biology at Tufts University in Massachusetts. She and her team just published a landmark study in the journal Endocrine Reviews showing that the way we test chemicals for health effects on humans is ineffective and in desperate need of revising. In fact, when it comes to hormone-disrupting chemicals, tiny doses could actually be more harmful than the higher doses commonly tested.

So how can we possibly protect ourselves from the 80,000—often inadequately tested—chemicals on the market? The answer is easy. We need to change testing protocol so that consumers don't have to be chemists to figure out whether or not a bottle of shampoo is safe.

What are hormone disrupting chemicals?
The endocrine system consists of glands located throughout the body whose job is to manufacture hormones that are released into the bloodstream or the fluid of surrounding cells. Different organs contain receptors that recognize and respond to the hormones. It's like members of a symphony working together to create music. Chemicals that interfere with this extremely delicate system cause all sorts of chaos within our bodily systems, kind of like one member of the symphony playing the wrong notes. It throws everything off.

Chemicals commonly found in everyday products are throwing off the endocrine system, causing temporary, and in some cases, possibly permanent, damage. For instance, some chemicals mimic a natural hormone, causing the body to over-respond. Sometimes, the effect is hormones aren't released when they're needed, as in abnormal insulin production. And some hormone-disrupting chemicals block organ receptors that make the endocrine system work properly.

How do hormone-disrupting chemicals affect our health?
The U.S. Centers for Disease Control and Prevention calculates that currently, more than 2 million American women are infertile, with more than 7 million women using infertility services. About 16 million Americans are believed to have diabetes, and more than 20 million are dealing with thyroid disease. All of these ailments have links to hormone disruption. The chemicals in our everyday environment can influence fertility, metabolic syndrome, and thyroid health. These aren't chemicals we are studying just for the sake of science—we are studying them because they can have a serious impact on human health!

Research on hormone-disrupting chemicals has really blossomed over the last decade. Scientists have developed better tools to determine what effects these chemicals might be having on people who are exposed to low levels in their everyday lives. This wealth of knowledge is really coming all at once, which is incredibly exciting to scientists in the field, but can be overwhelming to the general public.

We often hear that the dose makes the poison, but this new research shows small doses could, in fact, be more harmful. How is that possible?
For several years, scientists studying hormone-disrupting chemicals have known that some of these chemicals can have effects at low doses that cannot be predicted based on the effects of high doses. This is because high doses of these chemicals are toxic—they kill animals, or cause serious birth defects. Low doses do not generally kill or disfigure animals, but that doesn't necessarily mean they are safe. Rather than an immediately obvious effect like death, animals exposed to low doses can experience changes that are harder to detect, such as permanent changes in the development of their organs. That means the brain of a boy animal can look like the brain of a girl animal, or an adult female can stop having regular cycles, and therefore lose the ability to get pregnant earlier in life. Or, an exposed animal may metabolize food differently, so even though it consumes the same number of calories as an unexposed animal, it will become obese later in life.

Scientists studying hormone-disrupting chemicals have known for years that low doses of these chemicals can have serious and permanent effects on animals and people. But most of those studies have focused on single chemicals, such as BPA or phthalates. So the conclusion could be that those chemicals are exceptions. This new research suggests that all hormone-disrupting chemicals have effects at low doses. The analysis of more than 800 peer-reviewed studies suggests that chemicals that mimic or block the actions of hormones will act at low doses—in the range that humans are exposed to. Levels that are currently thought to be "safe."

It's on the store shelf, so it must be safe, right?
The kind of toxicology tests that are done for chemical safety involve giving animals large doses and evaluating whether they die or develop obvious problems like birth defects. Safety testers then use the results of those high-dose tests, plus some mathematical calculations, to predict a safe dose. But the low dose that is thought to be safe for humans is usually not tested. And if it is tested, regulators look to see if animals die or have obvious problems. They don't look at the other sensitive, important endpoints like thyroid health, brain development, lifetime fertility, and other health conditions.

What are some of the most dangerous hormone-disrupting chemicals out there?
There are about 900 identified hormone-disrupting chemicals on the market, and they are commonly found in food packaging, plastics, pesticides, cosmetics, detergents, home and lawn care products, industrial pollutants, and other places. Studies in the U.S. find more than 100 hormone disruptors in umbilical cord blood samples, indicating that fetuses and neonates are regularly exposed to many. It is hard to say which are the most dangerous, but so far scientific literature has studied BPA, the pesticide atrazine, dioxin, and perchlorate, a component of rocket fuel found in some water sources. Scientists focused on these chemicals because most humans are exposed to them, and the evidence suggests they aren't safe. There could be worse offenders out there, but the information collected on these well-studied examples can most likely be applied more broadly to other chemicals with similar hormone-disrupting features.

This information may seem overwhelming to someone raising a family. What power does the average consumer have in solving this problem?
It's easy to say, 'This problem is so big, I can't possibly make a difference' and give up. But that simply isn't true. There are small and simple changes that consumers can make to lower exposures to these types of chemicals:

  1. Use greener cleaning products.
  2. Avoiding plastics whenever possible.
  3. Reduce the use of pesticides in their homes and yards.
  4. Eat organic.

But this isn't a problem that can be solved simply by smarter shopping. We need regulators to change their ways, and start testing chemicals at low doses (instead of just calculating a safe dose that is never tested).

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