Well, the mercury can cause cancer so I'd go after your builder if it was a new house or who ever did your home inspection if it's a older home. Assuming you had a home inspection. I'd have the other houses checked too both for mercury and maybe even asbestos. Both can cause cancer.
8th house deals with other people's money, inheritances, etc. Mercury in the 8th would tend towards lots of communication with other people about these subjects; you might find yourself asked to straighten out people's estates, etc......
