From my brief research (yes on the web) it appears that the end product i.e. the tweeter is of negligible risk to us users.

Focal have been using such tweeters for longer than Meridian and are happy that they do not provide a user risk. However the manufacture of these devices is risky and requires great care... should we not be concerned with the employees of the driver manufacturers and not ourselves catching an incurable disease? (Well a different viewpoint.)