Yes
It is used for human consumption as a beverage or in manufactured products such as cheese
Bleach will poison the crawfish, possibly rendering it unfit for human consumption, as well as pollute the environment.
Some mushrooms can indeed cause paralysis. This is because these mushrooms are not meant for human consumption and contain deadly poison.
No, it could not, because the poison was specifically designed to kill rats, and was developed as a rat poison/killer, not a human poison/killer. It would still be considered rat poison, even if the human died from the rat poison.
It's not good for human consumption.
In reality human meat is fit for human consumption. Pretty much any animal (unless poisonous) Is fit for human consumption, so yes, bull shark is fit too.
Cannabalism
no geckos can not spit poison!
what are the factors that determine when a substance is toxic and unfit for human consumption
no
No, humans are not poisonious.
If the meat of the human is poisoned, and the poison does not cook out in the cooking process. Then the cannibals that ingest the human would also ingest the poison.