Important context in the article:

"The data showed that the age-adjusted incidence rate fell from 55.2 per 100,000 in 2000 to 36.7 in 2022, then rose to 38.3 in 2023."

If you would like to advance a theory that this is because of a specific environmental change, your theory should cope with the fact that the rate was MUCH higher in 2000 and the rise described here is is 2023. Increased screening is said to be a likely culprit in this case for middle-aged adult prevalence but not for older adult prevalence, because screening has increased somewhat in the middle aged groups.

I am personally dealing with colon cancer, and one of the incredibly annoying things about the awful disease is the number of truly clueless people who use it to advance some culinary agenda they believe in without evidence.

I looked through your comment history to ensure you haven't already answered this. But what made you get tested ? Did you have risk factors ? No problem if you'd rather not share.

Related, I was told by a doctor to get screened after turning 50. But a reasonable self-estimate given all my risk factors puts my chances of having colon cancer at 1 in 10000. A colonoscopy has a false positive of ~2%[0] for my demographic. Meaning if I get a positive result, it's actually ~200 times more likely that I don't have cancer. It's hard to justify a screening given those odds and the 99%+ chance I will waste my time treating and worrying about a disease I don't have. My guess is an insurance company wouldn't cover a colonoscopy for those reasons.

[0]https://pmc.ncbi.nlm.nih.gov/articles/PMC7147410/

Featured article says they are looking into “environmental chemical exposures as a possible culprit”. A rise since 2019 due to “chemical exposure” make food and water pollution, and thus diet, plausible explanations no?

So the processed meat -> colorectal cancer link is actually a textbook example for explaining what statistical & scientific concepts mean.

Processed meat is a known Group 1 carcinogen, in the same category as asbestos, tobacco smoke, and plutonium. Carcinogens are grouped by the strength of scientific evidence on them, not by how hazardous they are. In this case, there are abundant studies with solid methodology that show a link between consuming nitrites in processed meat and a higher risk of cancer, and we also understand how the process works at a molecular level.

This shows how well we understand the link, not how strong the link is. And it turns out that processed meat is a very minor carcinogen. When you average the studies together, the hazard ratio for someone eating 50g of processed meat per day, over an 85 year lifetime, over somebody who eats no processed meat is about 1.18. That means that folks in the former group are about 18% more likely to get colon cancer than folks in the latter group. By contrast, the hazard ratio for cigarette smoking is about 20x (smokers are 2000% more likely to get lung cancer than non-smokers), for asbestos exposure it's about 35-45x (industrial asbestos workers without PPA develop mesothelioma at a rate 3500-4500% greater than the general public), and plutonium exposure is about 7-50x for a single unprotected exposure.

There's a further piece to the statistical puzzle, and that's base rates. Colorectal cancer is relatively rare, with a lifetime incidence (again assuming an 85y lifespan) of about 7%. Combined with the 18% hazard ratio, that means a diet full of processed meats increases your lifetime risk of colon cancer by about 1%. There are far worse activities you could be doing.

https://www.iarc.who.int/wp-content/uploads/2018/11/Monograp...

A related concept is the Prop65 warning labels in California. If you've ever been to the restrooms in the SFO airport, you might notice that there's a warning label of "This restroom contains chemicals known to the State of California to cause cancer." These are pretty ubiquitous, you'll see them everywhere else in California too, like on new cars. Are you going to get cancer just because you transferred through SFO or LAX? No. But the list of chemicals that have scientifically demonstrated carcinogenicity is long, and the good people of California don't really make a distinction between minor risks and major risks.

Whether the known carcinogenicity of processed meats is behind the uptake in colon cancer rates is a separate scientific question. You would need data on processed meat consumption at a population level, over time, to see if that epidemiologically explains the increase we've been seeing. I don't know if this data exists and kinda suspect it would go the other way, but that's what the scientific method is for.

> I am personally dealing with colon cancer, and one of the incredibly annoying things about the awful disease is the number of truly clueless people who use it to advance some culinary agenda they believe in without evidence.

Sorry to hear this, and it's really a shame that whenever health and disease topics show up, every conspiracy theorist comes out from under their rock to try to explain their "theory" to you. Just look at the comment-trainwreck on this HN article. A significant percentage of the comments are "I have a theory that it's [....]" and it's always something mundane, untestable, and vaguely victim-blamey like diet.

> If you would like to advance a theory that this is because of a specific environmental change

It probably is, but it could be anything. For all we know, (joke,) it could be a pesticide with traces present in salads and fresh fruit, or exposure to a cleaning chemical in public transportation.

But the bigger issue is that the people pushing these theories are pushing them on moral reasons; IE, making an unfair claim that colon cancer is on the rise because people have immoral lifestyles. IE, from eating poorly or the multitude of other holier-than-thou lifestyle claims at the tip of their tongue.

Personally, my money is that we find out that regularly holding in farts increases the probability of colon cancer, and that we need a public health campaign to fart in public.