Actually,.1 microgm/m3 is the toxic threshold. This level results in 4 microgms hg/day.I havent read the study you cited yet. I suspect that they used urinary levels to draw conclusions about daily exposure. Less than 10% of hg is excreted
in urine. Also, the levels in urine dont tell you how much is stored in the kidneys,pituitary etc. Urinary levels are especially poor evidence re. chronic ezposure since as the kidneys become increasingly damaged ,they are less able to excrete hg.
I dont have the cite handy but I read studies showing that hg vapor levels go up by >1000% after chewing gum for fifteen minutes and stay elevated for 90min in people with amalgam. Even when not chewing ,hg levels are several times higher in people with amalgam.Dr Lorscheider did some of the above research.Studies have found hg vapor levels of 80 microgms/m3 after chewing.Remember that .1 microgm/M3 results in 4 microgms/day.
Dr Pleva studied old Amalgams and found that they had lost most of their hg. New Amalgams have around 500,000 microgms/hg.If an Amalgam lost one microgm/day ,after 15 years ,it would still have 99% of its hg instead of 33%. New Amalgams are around 50%hg. Old ones are often only 20% hg while their percentage of other components increases over time. This shows that hg vaporizes off in large amounts.