By which term does the EPA refer to the range of toxic response or exposure?

The term "variability" is used by the EPA to describe the differences in toxic responses or levels of exposure seen across different populations or individuals due to factors such as genetics, age, health status, and environmental influences. This concept is crucial in environmental health because it acknowledges that not everyone reacts the same way to a particular substance; some individuals may be more sensitive or resistant to toxins based on the factors mentioned. Understanding variability helps in assessing risks and developing safety standards that protect the most vulnerable members of the population.

In contrast, the other options refer to different concepts; "capacity" might relate to the overall potential of an environment to handle contaminants, "range of exposure" could imply a spectrum without explicitly addressing interindividual differences, and "toxic potential" typically refers to the inherent ability of a substance to cause harm. None of these terms encapsulate the idea of differences in responses due to variability among individuals or populations as effectively as the term "variability" does.