> There are chemicals that can kill you with a couple milligrams or less.

Obviously, but they are pretty straightforward things.

This chemical that causes Parkinsons is quite different, it has a complicated method of actually becoming active, and seems to target a very specific part of the brain. Unlike those other chemicals, this one is not something you could predict by simply looking at it.

Which is my point - the straightforward, or easily predicted chemicals we already are cautious about. The issue is the complicated or unexpected ones, the ones with very delayed effects.