Alternative MedicineAnti-ScienceDear Sasquatch

Dear Sasquatch: Are Synthetic Fibers Dangerous to My Health?

Dear Sasquatch,


I have come across information on the internet that says that I should only buy clothing made out of natural material such as cotton. Apparently polyester, rayon, or anything else will give me cancer and/or other health problems or that synthetic fibers are dangerous because they are treated with flame retardants. Is any of this valid?




Dear Allie,

At the heart of this information is the naturalistic fallacy, the idea that anything natural is automatically better for us (healthier, less “toxic,” etc.). We’re not just being told that all synthetic fibers are dangerous (without any discussion of specific chemicals involved, amounts, etc.), but we’re being asked to assume that natural is automatically not dangerous.

This is not true, of course. We all know of various plants, bacteria, etc., that in certain amounts can be toxic. Even substances we don’t expect can be harmful in large enough doses. Potatoes, for example, contain solanidine, a natural alkaloid poison that can build up in your body. Even water can kill you if you drink enough of it within a short enough span of time. The cardinal rule of toxicity—for natural chemicals and synthetic—is that it is always dose dependent.

dunh . . . Dunh . . . DUNH!!!

Many of the scares about carcinogens are related to rodent carcinogens. A study is done in rats, who are given an extremely high dose or a chronic dose over their lifetime (or both), and if they develop tumors, the science is misreported or misunderstood as meaning that the same substance will do the same to us, when it might not do it at all, or if it does, it would need to be at an extremely high dose, one unlikely to occur in our lifetimes.

We are obviously not rats. The studies may be useful for beginning to explore a question about humans but not for drawing conclusions about humans. Even among humans, our reactions to chemicals vary so widely that large numbers of people must be tested (ideally with controlled variables, double-blinding, etc.), and then the studies must be done repeatedly by independent researchers before we can even begin to draw conclusions. Because of this variability, in fact, the safety level set for various chemicals is at a much lower dose/amount than what most people could be exposed to safely.

Feeding synthetic fabrics to rats is dangerous!

On top of this, in part because of the naturalistic fallacy, synthetic chemicals are tested for toxicity far more often than natural chemicals are, even though we have absolutely no reason to believe they are inherently more dangerous (and several reasons to believe the opposite, since they are standardized, studied more rigorously, etc.). So we hear more about synthetics that may be carcinogenic (to a rat at high doses, maybe even a species already highly susceptible to tumors) but don’t hear about the potentially carcinogenic natural chemicals—not because they aren’t carcinogenic but because they aren’t tested.

For example, studies have found several natural carcinogens in coffee, but these are rodent carcinogens, and even if they also cause cancer in humans, odds are the dose you get even if you drink a lot of coffee daily will not be high enough to have this effect in you. The point is that potential carcinogens are everywhere in the natural world.

So when a chemical used to make a fabric fire-resistant is given in extremely high doses to rats, whether those rats develop tumors doesn’t really tell us anything about the trace amounts of that chemical that may be on clothing we wear. We aren’t ingesting a rayon sports bra, and even if we did, we wouldn’t be getting nearly a high enough dose to match what the rats are getting relative to their body weight.

Now, with that said, some studies have looked at humans, such as those who work in plants where they have high exposures to some chemicals. Again, though, even when a correlation is strong, the dose and the means of exposure are not even remotely comparable to our exposure in clothing. These people are exposed to the chemical itself, on the skin or breathing it in, in high, chronic doses. You could enclose yourself in a polyester space suit for the rest of your life and not even come close to the dose, and you wouldn’t be exposed to the same thing, the chemical itself in liquid, gas, or vapor form.

This picture is tragic enough without the threat of cancer.

I have focused on cancer, primarily as an example but also because that seems to be the most specific claim people make about something synthetic causing a health problem, and we can’t really do much to respond to the more general claims without knowing exactly what chemicals we’re talking about and what specific health problems and what evidence the person has to support the link. Even talking about cancer is way too general considering cancer is really hundreds of different illnesses with various different causes. So which cancer is caused by what and how?

We can, however, note that there is no evidence to support the claims that wearing synthetic fibers will cause cancer or other health problems (except, of course, in people with an allergy to the fiber or other substance in the clothing). And we can avoid spending money unnecessarily (even dangerously) based on fear-mongering (often sponsored by the multi-billion-dollar natural products industry). We can also vocally insist that our government not spend our money unnecessarily—money that in some cases could actually go toward genuinely preventing, oh, I don’t know, cancer.

Do you have a question for Sasquatch? Need advice? An answer to a question that’s been puzzling you? Beauty tips? Ask in the comments section or send an email to [email protected]. Skeptical Sasquatch is now on Twitter (@skeptisquatch) and Facebook.

Image credits: Adapted from photos by Howard Walfish, Rain, VJ Beauchamp, David Allen, and Lana L.

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Skeptical Sasquatch is an amateur tabloid photographer and filmmaker, beauty expert, and jetsetter (for security purposes). Tired of all the lies spread about him by cryptoloonologists and various crackpots, he joined Teen Skepchick to speak for himself about the skeptical issues of the day and to add species diversity.

You can find him on Twitter at (@skeptisquatch) and on Facebook (

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