And once they do enough animal testing, they can figure out a reasonable estimate for the danger.
And they've probably done enough for that.
The real barrier here is whether it's considered safe enough to let people volunteer, not just whether they can estimate the level of safety.
There's a big range of experiments where informed consent is possible but it's not allowed because it's too dangerous. I think this testing is probably in that range. And anything in that range is not a matter of "capital E Evil". Evil is when you're not getting consent, or similar.
