It's not about him giving her the safety warning or not, by all means, he should be discussing EVERY safety concern with EVERY employee. But, he didnt.
He singled her out for concern (by name, mind you, and by virtue of the fact that she is the ONLY woman there [and yes, that would stand up as a legal argument in a court of law]) and was concerned for her safety (a woman of childbearing age) OVER being concerned about all his employees livers (and as the OP mentioned, the liver concerns are more more immediate than the reproductive ones. Had someone said those words to me, my next logical thought would be wondering if he was going to take XXX experiments away from me. And I would ge righteously indignant over that.
Not to mention, as later posts by the OP noted, it sounds like he is cherry picking what he discusses as safety concerns. BAD for all employees, IMO. The fact that it was in front of her peers just adds salt to the wound, IMO.
I am not saying she shouldnt have been aware of the safety concerns, or that she (herself) shouldnt have considered them for herself more so than her male counterparts. I am saying that the way her boss expressed his concern was discriminatory.
I am not saying he was malicious in his intent, in fact, I can understand why some older men 'sexually harrass' younger women - in their day their actions were completely normal. It doesnt excuse the behavior, but it does mean that the old dog needs to learn new tricks (whether he likes it or not) if he is making a hostile working environment.
As people we have instincts, and I can completely understand this guys instinct to be concerned over his female employee working with solvents that could affect her (and not others) in XX way. BUT, he needs to learn to address those concerns in a way that isnt potentially limiting for the OP. (note I said potentially. I recognize that no opportunity was actually taken away, but for me, that type of concern is a precursor to those types of actions, IMO)
MarinaDCA, I think we are of like mind on this one.