Defence

I came across this argument: humans need to be exposed to a certain degree of harmful chemicals, toxic waste, etc to help raise their defences. as an animal, we often forget how amazingly adaptive our bodies are and as the environment changes over time, so do we. - well, I don't know if going back to smoking at this point will help raise my defences for an increasingly polluted world (but I do know that many can use that argument) however, I do remember how the europeans rendered the tribes a "lesser species" (look up eugenics) because of how they literally wiped them out by bringing western disease. while immunity is important, prevention is still better than cure. at this point, raising consciousness works as better defence than voluntarily swimming in the muck.
or should we all just jump in?