Anecdotal evidence (I did it and I'm OK) does not diminish the fact that there are significant risks associated with the use of mercury for whatever purpose including lead removal. Yeah, we old guys all played with it as kids. Who knows how that affected our health?
EXACTLY. The effects are not immediate and may take decades to show up. And since the effects are cumulative you may not end up with enough of it in your system to cause a problem until you're older and received enough exposure. By then it is too late - you can't undo it. And it does give off detectable vapors at room temperature. The most common kind of mercury detector used when cleaning up mercury spills is called a Jerome meter and that is how it detects the mercury - by the vapors.
I would venture to say the majority of solvents used to clean your guns vapors are more detrimental to your health than any mercury vapors you might breath under the same conditions.
I would venture to say you are incorrect. 99.9% of anything you take in by absorption, ingestion, or inhalation can be metabolized (broken down and expelled) from your body. Mercury is one of the few substances that can't. Every molecule you take in STAYS in your tissues for the rest of your life.
Anybody remember the Mad Hatter in Alice in Wonderland? Ever wonder what that was all about? Back in the 1800's men's hat were made of felt. Mercury compounds were used in the production process of making felt - especially in the dyes. Over a period of time breathing the vapors the people that made and worked with the felt hats - called hatters - developed dementia and other neurological disorders from mercury poisoning. That's where the expression "mad as a hatter" comes from. People thought that hatters were "mad" (crazy) because of the symptoms of mercury poisoning.
Anybody who wants to know the facts can find them easily enough. Mercury is nothing to trifle with. You may never accumulate enough in your system over the course of your lifetime to cause you any problems. On the other hand you may. Nobody knows - how sensitive you are to it's effects is a major factor, and is a total crapshoot.
I know I've played with it as a kid, and I also know I want to stay away from it as much as reasonably possible now, because once you have had enough exposure to develop health problems from it, the damage is almost irreversible. You may be lucky enough to have a higher than average tolerance for it. You may not. Want to take the chance? I don't.
It isn't a case of use it today and get sick tomorrow. It's effects are CUMULATIVE - as in you won't see them for years - possibly decades - until you have enough in your system that it damages you. If you're supremely confident that you are one of the lucky ones who can tolerate lots of exposure before it affects you, then by all means, have at it superman! Since I can't say that is true for me or mine with any degree of certainty, and exposing myself and my family to it isn't necessary, I'm not going to take that chance personally.
Unless you're shooting case after case of ammo that was produced more than 50 years ago you don't have to worry about exposure from shooting at indoor ranges. Mercury fulminate was pretty much replaced in all ammo primers by the 1950's or 1960's.