Ethics teams would never let you conduct a scientific study of giving some unknown chemical in the food and water of unknowing people to see what effect it had on them.
But if you do it anyway and don't record the results, then it isn't a study, so you don't even need to ask the ethics panel!
Don't forget to do a 2 week study on 6 rats, prove that none of the 6 rats die, and then send those results off to the government to get the chemical approved for use in everything.
Then, if later it does cause harm, you can shield yourself behind the fact you were just following government guidelines and the government approved it.
But if you do it anyway and don't record the results, then it isn't a study, so you don't even need to ask the ethics panel!