While "mad hatter disease" is certainly a possible outcome of chronic high
level exposure to Hg vapor, the literature indicates that lower levels of
exposure do not result in this type of frank psychological effect. If
exposure to Hg vapor from dental amalgams does result in identifiable adverse
effects (and I agree that the jury is still out), they are most likely to
correspond to the lowest level of effects seen in occupational exposure. The
U.S.EPA has reviewed this literature in support of its Reference Dose (RfD)
for Hg vapor. These adverse effects include sub-clinical hand tremor,
reduction in nerve conduction velocity, sub-clinical changes in autonomic
functions and psychological disturbances characterized by memory and sleep
disturbance. I am aware that there are subjective reports and anecdotal
evidence of a wide range of psychological and physiological effects
associated with exposure to Hg from dental amalgams, but these largely seem
qualitatively and quantitatively inconsistent with the experience from
occupational exposure at higher levels. In any event, I think that Dr.
Haye's assessment overstates the potential hazard by putting it in terms of
mad hatter's disease.
Alan H. Stern, Dr.P.H., D.A.B.T.