>We knew since the 1950s (maybe before) that tobacco was bad.
I think the first disclaimers came in the 60s.
>We still do not know today whether micrograms of Hg are causing any harm!
Yes, we do.
Less than one gram of Hg is lethal. That means that
ONE MICROGRAM multplied with factor x is lethal.
We know that certain amounts of Hg cause bodily harm, far less than
one gram. So ONE MICROGRAM multiplied with factor y is hazardous.
We do not want to know what factor x is. We want to know what factor y is.
As long as we do not know we are speculating. Guessing. Until factor y is
established 'beyond reasonable doubt' there should be a moratorium on
jamming this into the mouth of people.