Chairman Bill, in a comment to the last post, deemed hydrogenated fats to be carcinogens.
While I took some issue with the broadness of the statement, I do agree in a broader sense.
At a different level, I believe EVERYTHING causes cancer. You just need more of some things than others.
In a broad sense cancers occur when the body's systems are overwhelmed by a particular compound or radiation. Even shift work is implicated in cancers nowadays. It is a case of the body getting swamped in someway and losing the plot when it comes to cell growth.
Tests in the labs have shown that if you swamp a lab rat's diet with a chemicals it will develop cancers but, in order to speed up the process the labs feed the rats enormous amount of the compound being tested. If you want to see what they went through, make a mix of a food of your choice and include 5% saccharin. Inedible. Now do it all meals for an extended time. Unbearable. No wonder the poor rat developed cancer. But how does swamping a rat's genetic processes translate into the long term effect of low levels of a saccharin on humans?
Bill talked about trans fats in margarines but they are naturally occurring in most fats.
In low levels.
It is generally accepted that smoking causes cancer; this is due to the compounds in the tars. Theoretically these compounds are first cousins of the charring of any plant matter. Smoking marijuana is just as dangerous as tobacco in this sense - different psychoactive substances, same tar.
But burnt plant matter is common in our diet - browned meat, roasted coffee, toast, cakes, biscuits, fries/chips. All theoretically foreign and carcinogens.
I argue that all chemicals, taken in excess for extended time will swamp the system.
I also argue that the system is designed to cope with a multitude of chemicals that are naturally in our food. The analogy would be sand. If I drop a stream of sand on your shoulder, it will bounce off and not be a problem. If I drop a ton of sand on you all at once, it is a big problem.
It is all a matter of recognising and managing risk.