You might not like my answer at all, and I don't want to get all analytical on you....but I used to have the fear of lead poisoning. To be honest, the fear is not what is important, rather what is important is what kind of pathology the fear points to.
For me, the fear of lead was the fear of losing my intelligence. That being said, i had a whole spectrum of fears related to that problem and they didn't go away until i started to confront that issue head on....i.e. to not be afraid of losing/not placing as much value on my intelligence.
The truth is, even if you overcome you phobia of mercury and asbestos, that fear will only transform into some other phobia until you address the underlying issue.