Environmental Question #35 [Hormone Disruptors]

Are chemicals that mimic hormones in consumer goods causing widespread health problems?

Courtesy of Reddit user u/M1ST3RJ1P

Q: Are chemicals that mimic hormones in consumer goods causing widespread health problems?

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A: Hormone-like synthetic chemicals have caused health problems for some people, but I would hesitate to call the problem widespread, because the vast majority of people aren't exposed to enough of these materials to cause serious health problems.

To put this question in context, let's look at how hormone-like chemicals behave in the body. Hormones are the signal molecules of the body, you can think of them like letters being delivered in the mail. The cells of the body are all covered in "mailboxes" called receptors, which are shaped to perfectly accept specific hormones, so that if hormone A floats by receptor A the hormone will snap into the receptor, almost like two magnets coming close to each other. That hormone and receptor snapping together tells the cell to follow whatever set of instructions is associated with that hormone. If the hormone is cortisol, the stress hormone, that might tell heart cells to beat faster, for example.

Now this will mix my metaphors a bit, but hormones are often also viewed as locks and keys, since the receptor and hormone are such specific shapes. This is important, because it's how the body avoids sending and receiving mixed signals by mistake. If a hormone accidentally bumps into the wrong receptor, it won't set that receptor off, because the hormone doesn't fit in that receptor, so the hormone will just bounce off. This is very much like if you tried to put your house key into someone else's front door--it just wouldn't work and it might not even fit in the keyhole.

The place where hormone-like chemicals come into play is that they are shaped sort of like various hormones. If you're curious, look below at the chemical structure of 17-beta estradiol (the most common form of estrogen) and bisphenol A (BPA, a plastic additive that used to be very common). You don't need any chemistry training to see they look pretty darn similar--both molecules are about the same size, they have an OH on each end, and they have some chunky ring shapes in the middle. Those molecules look pretty similar to our cells' receptors too. They're so similar in fact that sometimes bisphenol A sets off receptors that are meant for estrogen, but bisphenol A isn't a very good stand-in for estrogen even when it's tricking the body. 

 

         17-Beta Estradiol (estrogen)       Bisphenol A (Plastic Ingredient)

Hormone-like chemicals are similar to hormones, but not the same, so think of them like keys that are all bent out of shape. You can still open a lock with a messed up key, but it will take a lot of tries, and the same is true for hormone-like chemicals in the body. Most hormone-like chemicals are hundreds or thousands of times less likely to set off a receptor than the hormone that they accidentally mimic, so once every thousand attempts that messed up key will open the lock. Fortunately though, our bodies have safety measures in place for if receptors get triggered incorrectly, since this kind of mistake happens naturally sometimes too. Around 50 natural hormones have been discovered in humans so far, and many of them are fairly similar chemically, so hormone receptors being accidentally triggered occasionally isn't a problem most of the time.

This can become a bigger issue when the dose of these chemicals is very high. There are some cases in developing countries where the entire water pipe infrastructure was made of cheap, poorly made plastic that leached large amounts of hormone-like chemicals into the water that people there used for all their drinking and washing. This kind of high level constant exposure can and has caused serious health problems. A misshapen key opening a lock one in a thousand times is no big deal if you only have a few of those keys in your body, but if you have millions of those misshapen keys in your body then they open a lot of locks that shouldn't be getting opened.

In the developed world, the doses of hormone-like chemicals we are exposed to are very low, particularly since all of the public backlash over the past 20 years has caused many of them to be outlawed. There is some credible evidence that people who are exposed to higher than average levels of these chemicals through consuming all their food and drink from plastic containers are at increased risk of certain cancers like breast cancer. In context, I'm not especially worried about it though. It's important to remember that every generation of humans has been poisoned by something in their environment. Second hand smoke causes a much more dramatic increase in cancers than hormone-like chemicals do, including breast cancer, and basically every public space was blanketed in second hand smoke until about 50 years ago. While it is true that we are being subtly poisoned by hormone-like chemicals and other pollutants in our environment, our parents were being poisoned much worse than we are. I think that is cause for a little celebration right before we roll up our sleeves to finish the job by working together to get rid of today's poisons.