[tantalor]

It is rational (you have a cogent reason for doing do) but the reasoning is specious, because you are singling out one specific thing to avoid. If you listed all such substances fitting the criteria "unknown or poorly studied" then you would have to live in a bubble to avoid them all.

[porridgeraisin]

The point is to single out and avoid whatever is realistically possible, for you. Like you said, you would have to live in a bubble to avoid them all!

[Dylan16807]

The goal should be to single out and avoid the most damaging ones, not an effectively random bunch because they were in the news.