when removing them with a dental drill without high speed suction(normal loud suction every dentist would use when removing amalgam/silver fillings). Funny part is the few dentists who use scare tactics to get people to change their perfectly functional and safe amalgam fillings are the ones who are most likely going to charge a fortune to drill them out and replace them.
That's not to say amalgam fillings don't have some drawbacks (they can expand over time and stain the teeth a bit and can cause small cracks in the teeth due to expansion, they can fracture), but as far as a low cost, low technique sensitive, long lasting material that is excellent for high cavity risk patients due to its antimicrobial effect at it's margins) that has been around since Napolean, it rocks. The military loves Amalgam fillings and many military dentists become artists with the stuff.