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Talk of endocrine-disrupting chemicals (EDCs) is everywhere these days. Sometimes referred to as hormone-disrupting chemicals or endocrine-disruptors, they’re in headlines about everything from microplastics to pesticides to cleaning products. But beyond the headlines, the basics are often glossed over.
What exactly are EDCs? How are they acting in our bodies to cause problems? And what, if anything, can we do about them?
As an endocrinologist, I am asked these questions by my patients nearly every day. I’ve put together a primer to provide some foundational information you can call on when you are reading about EDCs in the media.
What are endocrine-disrupting chemicals?
EDCs are any one of a vast and diverse group of chemical compounds that interfere with our hormonal function. They can do this in a bunch of different ways, including blocking a hormone from being made or released, blocking the receptors that hormones bind to, and changing how hormones are metabolized.
Hormones are chemical messages sent from one part of our body to another. People often think of reproductive hormones (as in, the ones that are associated with puberty or pregnancy), but that is just one group of hormones in our body. There are dozens more. They tell our heart how quickly to beat, our muscle and fat to take up sugar, and our brain to be alert.
Typically hormones contain instructions that tell their target cells what to do. Hormones target cells throughout our body, including our brain, heart, muscle, bone, gut, fat, and other hormone-producing glands. Because hormones affect tissues throughout our body, EDCs have the potential to have far-reaching effects.
The challenge of researching EDCs
One of the challenges with EDCs is they are very difficult to study in humans. Studies in animals often use very high doses of a single chemical, and it may not be administered to the animal in the same way we encounter that chemical in the world. For example, rats may be fed a chemical that we would typically apply to our skin.
Animal research is valuable, but it is difficult to know if a chemical that turns genes on or off — we call this epigenetics — in c. elegans (a species of round worm) will affect human genes in the same way. Scientists have lots of experience conducting research in rats and mice, but we also know that rats differ from humans in sometimes very important ways. Case in point, rats are predisposed to some types of cancers that are much rarer in humans.
Beyond that, it is nearly impossible to conduct randomized trials in humans. For one thing, many of the effects of EDCs seem to occur in animals when they are exposed in utero. No ethics board would approve a study like that in pregnant people. Even more, we are so bombarded by EDCs in our environment that there are no unexposed study participants to recruit. That makes it difficult to isolate which chemical is having a particular effect and tease apart how different chemicals are interacting with one another.
Instead, we will need to get creative, to look for natural experiments. New Jersey has severely limited the amounts of two EDCs (PFOA and PFOS) in drinking water. Previous research suggests exposure to these EDCs may result in low birth weight. Studying infants born before and after the new limits could give us a better understanding of the effects these chemicals have on a developing fetus.
How are you exposed?
Different groups of EDCs appear to have different effects on our bodies. Let’s consider some of the ways we encounter EDCs and the current evidence for each.
The bottom line here is that, unfortunately, there’s not much we can do to reduce exposure (more on that below), but these are the sources of exposure you’ll hear about most often.
Pesticides
We are exposed to EDCs from pesticides in a few different ways. They can be present on the outsides of fruits and vegetables. Some produce can absorb the chemicals into the flesh of the fruit or seeds they grow. Pesticides also run off farms into the water supply.
Different pesticides contain different EDCs. Some of the most common are organochlorides and organophosphates. Organochlorides activate two hormone receptors, estrogen receptors and androgen receptors (androgens include testosterone and several testosterone-like hormones). In very high concentrations, many times higher than the levels allowed in U.S. drinking water, they can disrupt normal fetal development, endocrine signaling in the brain, and cholesterol metabolism.
Organophosphates can also activate estrogen receptors, but their bigger effect is blocking receptors for the stress hormone cortisol. There is some evidence that in high doses they can alter genes related to reproduction. In both cases, the bulk of the evidence is in animal models — this will be a theme. There is little evidence regarding the effect of pesticides in humans.
There are many other EDCs in pesticides. They largely function in similar ways. Often, pesticides contain a mix of chemicals that can either enhance their endocrine activity, making them more potent, or cancel each other out.
Microplastics
Like pesticides, microplastics contain a whole host of EDCs, including bisphenols and phthalates. As plastics break down, the chemicals can easily leach into water, milk, and other liquids. We get some exposure when we store (and especially heat) foods in plastic containers, but the bulk of our exposure is from the environment. Plastics in landfills break down and release chemicals into our water supply. Unfortunately, exposure is largely unavoidable.
Again, microplastics and the chemicals they release are best studied in animals, in particular rat models. Microplastics have been found to damage the testes of male mammals, resulting in decreased testosterone levels as well as reduced sperm count and motility. In female mammals microplastics in the ovaries have been shown to disrupt the maturation of eggs and ovulation.
There is some evidence in animal models that microplastics can affect the metabolism of carbs and cholesterol. Studies suggest that the chemicals in microplastics may do this by turning on or off genes that control metabolism before an animal is born, and those changes can persist for generations. Alterations in cholesterol metabolism can cause heart disease, liver disease, and cellular damage in the brain.
Cleaning products and other environmental exposure
Think of this category as all the chemicals you encounter in your home and out and about in the world, often by breathing them in. These chemicals often end up in the air we breathe through a process called off-gassing. My favorite example of this is when you buy a new shower curtain liner for the bathroom, and for the next week, every time you enter that small room you are assaulted by the new bathroom smell. Paint, varnishes, upholstery, and mattresses can all off-gas EDCs. Keeping rooms well-ventilated when items are new can help disperse off-gassed EDCs more quickly.
But you might also encounter these chemicals as the fragrance in personal care products and cleaning supplies. We encounter a whole slew of chemicals this way, some of which we already read about above: phthalates, parabens, bisphenols, and PFAS. Again, data suggests that these chemicals may affect sugar and cholesterol metabolism, sperm and egg production, and testosterone and estrogen signalling.
Should you try to reduce your exposure?
It is virtually impossible to reduce your exposure to EDCs in a significant way. Most of our exposure to EDCs come from our food and water supply and the air we breathe — they are virtually all around us, and there is nothing, on an individual level, you can do to meaningfully reduce your exposure.
In my family, we do make small changes — we try to reduce the amount of plastic we bring into our house (especially single-use plastic), use “natural” cleaning products, and buy organic produce whenever possible. But the goal of these changes is not to reduce our exposure, because ultimately, they really aren’t moving the needle much. Instead, we are looking to reduce the amount of EDCs we are contributing to the environment. We also want to send a message that we want products that don’t contain EDCs. Because ultimately, it will take policy change and creative solutions to effectively lower our exposure to EDCs and reverse the effects they may be having on our bodies.
The bottom line
- EDCs are a diverse group of chemicals that affect how hormones are made or released or how hormones act throughout the body.
- We encounter EDCs in a number of ways, including pesticide residue on the outsides of produce, EDCs in our water, and off-gased EDCs inhaled from household products such as cleaning products, durable goods like upholstery, and more.
- EDCs are so prevalent in our environment that it is difficult to study how individual EDCs affect humans. As a result, most of the data we have collected to date is in animals, particularly rats.
- It is impossible to reduce our EDC exposure through individual action. Instead we need policy change and innovation to deal with a problem of this scale.
Log in
I find it odd to claim “it is impossible to reduce your risk of EDC through individual exposure.” Is there data to support that? What about avoiding fragrance products, not heating in plastic containers, buying organic, etc? I’d have to imagine these small changes would add up over the years?
When I stopped using any scents in our home and harsh chemical cleaners, switched to stainless/cast iron, and changed laundry detergent to seventh gen/ecos/dirty labs my hormone levels changed over the period of 6 months. Anecdotal, but easy to replicate for others who are interested in trying. Now any time I’m around any artificial scent I almost immediately get a headache. That’s not normal.