From a species-health perspective, doses between the teratogeneic/mutagenic level and the lethal level are more dangerous than dose that simply kill everyone. Dead individuals do not prevent healthy, fertile, and possibly resistant individuals from replacing them, whereas sterile individuals will displace future breeders until they die.
If you want to eradicate a population, you stop the breeding and not the breathing.
If you want to eradicate a population, you stop the breeding and not the breathing.