Lots of substances may not need to be tested if they occur frequently in nature as we can assume that life has already mitigated the problems that they may or not cause. If we start to widely distribute these naturally occurring substances, then we need to re-examine what effects they may have (e.g. lead occurs naturally, but putting it into the air produced a very harmful effect on human development).
If it's a new substance that doesn't already occur in meaningful quantities, then we need to be very careful before we start putting it into water supplies as that has the potential to disrupt a wide variety of life and habitats. To merely consider it not harmful due to lack of testing is really foolish.
I don't see your point.
Lots of substances may not need to be tested if they occur frequently in nature as we can assume that life has already mitigated the problems that they may or not cause. If we start to widely distribute these naturally occurring substances, then we need to re-examine what effects they may have (e.g. lead occurs naturally, but putting it into the air produced a very harmful effect on human development).
If it's a new substance that doesn't already occur in meaningful quantities, then we need to be very careful before we start putting it into water supplies as that has the potential to disrupt a wide variety of life and habitats. To merely consider it not harmful due to lack of testing is really foolish.