Just to be the contradicting one, I have never had any exposure to mercury, fillings or otherwise, besides a thermometer break this year. Well and the thimerosal in flu shots. However, people used to play with mercury and ans weren't everywhere then.
I also want to say my brother, nor anyone else, has an an, in my family. We all lived in one spot. I even went to college relatively close. However, I developed one. I am a chem major and work with tons of chemicals, but it shouldn't have that fast of an effect (plus I'm safe while working.)
There has to be something. My doctor was told me mine had been growing for 8-10 years. That's since I was 12-14. My response was "man, I guess my music did ruin my hearing!" (I was kidding, being a musician I never listened to my music that loud with headphones)
Anywho, I wish we could find a cause. Cause a cause means prevention. And prevention means less people having to struggle.