I believe it would be most productive to start with the definitions. In the definitions it reads:
“danger to human health or safety” means any unreasonable hazard—existing or potential—that is posed by a consumer product during or as a result of its normal or foreseeable use
Essentially, when we talk about “unreasonable”, we're really trying to get at the notion that there are some consumer products that are inherently dangerous—a chain saw, a kitchen knife, there are others—that we consider to be reasonable dangers because they're part of the utility of the product. In stipulating what, then, would be considered an unreasonable danger, there is already existing, as a result of international standards, a great deal of expertise in industry itself--some of the standards that we've developed. We have implicitly, in our own regulations, to a considerable extent, the definition of what constitutes making sure something is safe. These are all elements of determining whether or not something constitutes an unreasonable danger. Also, through the consultations we're doing on the system for mandatory reporting, we have provided some further elaboration on what would constitute an injury as a result of an unreasonable danger.
So the parameters are well established in the legislation and there is considerable input and advice that we get from the work that goes on in the design industry and in other jurisdictions as well as here.