Although no longer so common in our environment it is estimated that over half a million children in the USA have dangerously high levels. The Victorians used mercury compounds in ointments and as a cure for diseases such as syphilis but they were also quite capable of dishing it out to their children as a cure for constipation. Experts rate it as being between 1000 and 5000 times more toxic than lead. The UK is a curious case, most countries are eliminating amalgam in dentistry, some even paying citizens to have their old stoppings replaced, however the British state discourages removal. There are probably economic reasons for this.
Symptoms are too numerous to mention.
We have had several people posting tips on health who say that having their fillings removed made a dramatic difference. Cadmium A serious poison that is not any longer a major problem. The metal was until quite recently used as an anti-corrosion coating. Like Aluminium it is known to cause a type of damage to brain cells that are characteristic of Alzheimer's Disease. Not a heavy metal but definitely to be avoided.