There is just one thing that is “probably not” carcinogenic to humans, according to an analysis of more than 900 substances and occupations by The World Health Organization’s International Agency for Research on Cancer for their potential to cause cancer in humans.
That thing is caprolactam, a substance used to make synthetic fibers like nylon, which is used in yoga pants, as well as common household items like brush bristles. While even short-term exposure to this substance (like what people who work in factories that use this substance encounter) can cause your eyes and throat to burn, give you headaches and make you confused, it apparently does not cause cancer, the WHO reports.
Using five groups, the WHO classifies substances in terms of their cancer risks to humans. Group 1 is classified as “carcinogenic to humans,” Group 2A as “probably carcinogenic to humans;” Group 2B as “possibly carcinogenic to humans;” Group 3 as “not classifiable as to its carcinogenicity to humans,” and Group 4 as “probably not carcinogenic to humans.” Caprolactam is the only item currently listed in Group 4.
“IARC says you can enjoy your yoga class, but don’t breathe air (Class I carcinogen), sit near a sun-filled window (Class I), apply aloe vera (Class 2B) if you get a sunburn, drink wine or coffee (Class I and Class 2B), or eat grilled food (Class 2A). And if you are a hairdresser or do shift work (both Class 2A), you should seek a new career,” the North American Meat Institute wrote Monday in response to a the WHO report that links consumption of red meat with cancer.
The list of 118 substances and occupations that fall into Group 1 (carcinogenic to humans) include some obvious ones — arsenic, cigarettes, asbestos and plutonium — but also some surprises that many of us encounter every day like estrogen-progestogen oral contraceptives, Chinese-style salted fish and wood dust.
The Group 2A (probably carcinogenic) list of 75 items may also be disturbing to consumers, as it includes red meat, the emissions released when you fry something at hot temperatures and the drink hot mate, as well as the occupations of hairdresser and barber. Group 2B (possibly carcinogenic), which includes 288 items, includes coffee, as well as the occupations firefighter and dry cleaner.
Of course, there are thousands of substances and occupations that do not cause cancer; the WHO list only includes a tiny fraction of substances and occupations. The group with the largest number of items in it was Group 3 — the group in which the WHO says it is not yet possible to classify their carcinogenicity to humans; that means that these items could be safe. Examples of Group 3 items include benzyl acetate, which is found in many essential oils, carrageenans, a thickening agent found in many foods, and crude oil. The WHO also notes that “Significant new information might support a different classification,” of certain items.