please indulge me in my making a completely unfounded statement (with which Occam's Razor comes to mind notwithstanding): it has to be related to plastic.
This is incorrect. The article explicitly mentions PFAS as a potential cause.
> So-called forever chemicals like per- and polyfluoroalkyl substances, better known as PFAS, have been linked to other cancers and could also be driving some of the increase in early-onset colorectal cancer.
The increase in pharyngeal cancers may come from oral HPV infections specifically, not "libertine sexual habits" per se. It's only gonna be a few more years to find out, if HPV is related to the increase in colon cancers in young people, since the broad vaccination of teenagers is going for some time by now.
I think, it's also worth considering the fallout of the AIDS scare messing with statistics here. PrEP, education on and treatment options for HIV may have caused people (including heterosexual) to use less protection in recent years, unfortunately, since other STIs are less scary and stigmatized. I doubt rates of oral and anal sex have increased that much.
While this is true, size matters and a lot of that plastic is only now entering our food chain due to degradation.
Also plastic usage has massively increased compared to the 50s and 60s. Especially things like plastic fiber fast-fashion clothing shedding microplastic particles during wear and washing. Then there is synthetic polymers as cosmetic and personal care ingredients. Plastic bottle and pipe usage increased too, I think.
