That's a pretty dumb argument since it leaves the opinion of what a threshold of "poison" is to one side of such a conflict. "They" might rather not be poisoned at all, but that's not a right especially with toxins that are normally present in the environment, sometimes in high concentrations.
One of the real world arguments against the EPA is that it frequently establishes levels of toxins which are far lower sometimes by orders of magnitude than what are required to poison you, sometimes considerably lower than the natural levels of the toxin. And that it does so in a way that frequently ignores cost of compliance.
The EPA also has a variety of tools at its disposal which violate basic constitutional principles (ex post facto laws such as Superfund, punishment without being charged for a crime via wetland regulations, etc).