Yoga pants contain the only known substance that 'probably' does not cause cancer

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A big new study just linked cell phones to cancer — though really, there’s nothing to freak out about for now.

The study talks about rats and didn’t actually show that cell phones are making cancer more likely in people.

But sometimes it seems like everything might cause cancer, doesn’t it? Bacon, alcohol, the sun, red meat, sugar… the list goes on.

By some definitions, that’s true. The World Health Organisation’s International Agency for Research on Cancer (IARC) began categorising substances based on their likelihood of causing cancer in 1970.

Since then, they have categorized 989 different substances — and only one has made it into Group 4, the “probably not carcinogenic to humans” category.

That one that is probably not a carcinogenic substance? Caprolactam. The chemical is a precursor to nylon and “used in stretchy yoga pants and toothbrush bristles,” notes Reuters.

That’s not to say caprolactam is harmless. Short-term exposure “may result in irritation and burning of the eyes, nose, throat, and skin in humans,” and “[h]eadaches, malaise, confusion, and nervous irritation” have also been observed, according to the US Environmental Protection Agency (EPA). “Chronic (long-term) exposure of workers to caprolactam has been observed to cause peeling of the hands and some eye, nose, and throat irritation,” the EPA says.

The majority of substances IARC has evaluated — a full 501 of them — fall under Group 3, meaning they just can’t be classified as to their abilities to cause cancer in humans. These substances include caffeine, isopropyl alcohol (not what you drink), and diazepam, the generic name for Valium. Substances fall into this category if there’s not enough evidence to say that they cause cancer or probably don’t cause cancer — the old “more research is needed” rationale.

But pretty much everything else either possibly causes cancer (cell phone use, pickles, coffee); probably causes cancer (red meat, frying food, working as a hairdresser); or definitely causes cancer (smoking, drinking booze, being exposed to either the sun or to radioactive materials in nuclear weapons).

There are a couple of things that are important to note here. Just because something is classified as definitely causing cancer doesn’t mean everything in that category is an equal risk.

The sun can cause cancer but some small degree of sun exposure is healthy. Bacon can cause cancer but it doesn’t increase risk by much — it’s very negligible. Being directly exposed to radioactive strontium-90 is always bad.

And when it comes to things that “possibly” cause cancer, like pickled vegetables or cell phone use, “possible” is just a designation that means there might be some slight evidence but for the most part, the average person doesn’t have much of a reason to worry about these things. Researchers frequently say that something might cause cancer or that there’s too little evidence to say it’s safe.

But it’s incredibly rare to say that something is probably not cancer-causing. Except caprolactam. That one is probably safe. Probably.

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