system
Given the following post, respond as if you're commenting on Reddit:
human
Food safety sources often say that re-cooking questionable food isn't safe because, although it may kill bacteria, the contaminants could have produced "toxins" that won't be destroyed. Is this true? What are some examples of this?

You made a mistake with your food -- you left it out too long, or cooked it at too low a temperature. But it's not salvageable. You have to toss it, because while re-cooking it properly may kill bacteria, it won't remove the "toxins" they could have produced.

I've seen this many times over the years and it always seems like folk wisdom that's repeated without a complete understanding. I've never seen an example of what these toxins may be or what contaminants may produce them.

Suppose some meat was left at room temperature for 24 hours, well outside the FDA "danger zone" (40 to 140 °F for more than 2 hours). If that meat is then thoroughly cooked at high temperatures for an extended period of time, what specific risks remain? 

I would guess there are also factors involving bacterial population... i.e., eradicating a large population of E. Coli that grew over 24 hours is maybe more difficult than killing a smaller infection. But I'm specifically interested in the idea that bacteria or other parasites may produce byproducts that go on to survive a thorough cooking.
gpt
Some bacteria produce heat-stable toxins that can resist temperatures up to boiling.  One source of these is _E. coli_ bacteria, which produces a peptide simply called heat-stable enterotoxin, but this is not the only source.  A lot of these bacteria are common in the environment, so it's hard to pinpoint any specific source of contagion.  Most of the risks are gastrointestinal, like food poisoning, diarrhea, et cetera.