Dietary changes in the population seem the first place to look. That or contamination of some kind?
EDIT: or do we simply have better screening now?
EDIT: or do we simply have better screening now?
Yes but we must unpack that. It's not just WHAT you eat (and even then, a 2024 tomato is not a 1950 tomato), it's how it was grown, how it was processed, how it was prepared, etc. Most studies don't even scratch the surface of this
Food additives are a part of that as well and there is some evidence. E.g. gelatin was replaced by carrageenan in most foods which has been shown to trigger colon cancer.
Drinking water is another such. NDMA is a byproduct of water disinfection and industrial processes (in drinking water as a result of chloramine disinfection, and in chlorinated wastewater used for aquifer recharge) and has been shown to trigger colon cancer. 35-40% of the municipally-treated water in the US is now disinfected using chloramine, a percentage which has nearly doubled in the last decade
Can you point where it was shown? I was just checking EFSA and they have not seem to be implying that.
Because of the possible danger, fewer studies have investigated the potential effects in humans.
Findings like these have led the International Agency for Research in Cancer to list poligeenan as a possible human carcinogen.
This means that the agency has reviewed the evidence that poligeenan can cause cancer in animals and concluded that it may have the same effect in humans.
Some scientists are concerned that food-grade carrageenan is also dangerous. This is because various studies, dating back to the 1960s, show that the substance may degrade and become toxic when it mixes with stomach acid.
The medical community is unsure to what extent carrageenan degrades in the digestive system. This means that we do not know if any amount is toxic. It is important to note that no related studies have involved human participants.
Findings of a review from 2017Trusted Source indicated that even non-degraded carrageenan can cause inflammation and bowel disorders, suggesting that this substance may contribute to ulcers and IBD.
However, authors of a 2018 reviewTrusted Source concluded that there is not enough evidence to draw conclusions about the exact health effects of carrageenan.
Anecdotal evidence suggests that eliminating carrageenan from the diet can provide relief from digestive problems, such as bloating and IBD. However, these reports are not the result of scientific research.
As always there are rabbit/turtle/bird situations; it's impossible to say how many of these early detections are of slow-growing benign conditions that left untreated would never pose a threat to quality of life or morbidity or mortality. But because these tests are not done by default, but only in response to some reported symptoms, it is more likely that there is an actual increase in incidence.
It does not appear that this is yet a published study, which might give more data on the prevalence of testing that might in turn give an idea of how much the screening effect contributes.
https://www.cancer.gov/news-events/cancer-currents-blog/2020...
TLDR Strong evidence diet (more sugar, more alcohol, less fiber, highly processed foods in general), western disease, less exercise are contributing factors.
Following colorectal cancer rates of folks who get on GLP-1 agonists (semaglutide) might provide stronger signal.
https://pubs.acs.org/doi/10.1021/acs.est.3c04844
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4637576/
https://www.sciencedirect.com/science/article/pii/S004565352...
For example, in Japan, gastric cancers are already much higher than in the US (like 5x more frequent), and there is evidence it is due to higher salt, smoked foods, H. pylori, genetics, and higher screening. If you are looking for the impact of a specific environmental pollutant, Japan v. US has a great example too: professionals hypothesize that because their cigarettes are equipped with a different kind of filter, Japanese OR of lung cancer due to smoking is like 15, compared to the US's 30-60.
There is likely a combination of trends, and maybe environmental pollutants play a little bit of a role. But you could definitely ban PFAS and microplastics - whatever that means - and still observe obesity rates rising, more sedentary lifestyles, more salt and processed food intake, etc., and maybe you'd get 280% increase in colorectal cancer instead of 325% for the next 20 years. Ultimately you could spend your money investigating PFAS and microplastics, or you could spend it investigating all the soap people put on their assholes, all the weird cosmetics they use on their mouth and face, the horrible shit they eat, or any number of things whose incidence rate is also a chart going up and to the right, but might interact with the colon quite literally more directly.