I don't think, at least at this point, that we would propose changing the definition of “toxic” or “substance”. Someone else may have ideas for how to improve it. It is difficult. You can go to a pure hazard-based one, but that has problems . You can emphasize risk more.
Yes, the word “toxic” does cause confusion, but what you do with it is probably more important than how you define it. It's about making sure that the tool box is appropriate and is used appropriately, given the breadth of that definition. In terms of “substance”, for example, at one time plastic bags were proposed as a substance that should be assessed under CEPA. You could use “refrigerator”.
Yes, it is very broad, for various reasons. You have to keep that in mind when you decide how, within that constraint, you force some actions to occur.