- What functional groups does it have?
- How many functional groups does it have?
- How much electron delocalization does it have?
- How much of that electron delocalization is PAHs?
- Does the molecule participate in redox reactions?
Etc.
Basically check to see which molecules can generate free radicals, strip DNA, convert to dangerous metabolites, etc.
I wish it was as easy as this - while there are known toxicophores/no-go functional groups in medchem, there is going to be a big dearth of data on non-acute (e.g. not hERG, hepatotoxicity, etc) toxicity, which is really what the question is here: what are the marginal risks/rewards from eating existing food X (since we know it's probably not acutely toxic).
Sometimes no bugs are allowed at all, people be getting upset if their pop tarts have bugs in them.
Sometimes it's like some bugs are allowed and just part of it like when I buy organic broccoli at the farmers market and need to soak it to get whatever those things are in there out. Or when I get those little mummified bugs in the bottom of oatmeal tins.
Sometimes it's like the food is literally coated in bugs like all that stuff that's coated on schellac. Which, finally to bring it back to a callback to your point, is both GRAS and also made of bugs.
I also learned today that the harvesting process kills the lac beetles.
I agree with most of what you are saying. However, I think it's valid to also apply heavy scrutiny on new chemicals being added to the food chain. The default being to not allow it if it's not proven safe.
Red dye 3 probably shouldn't have been added to the food supply chain with that criteria but since it's already been there for decades with no strong link to negative outcomes there's little reason to ban it now.