MERCURYEXPOSUREFROM DENTALAMALGAM FILLINGS: ABSORBEDDOSEAND THEPOTENTIAL FORADVERSEHEALTHEFFECTS

This review examines thequestion ofwhether adverse health effects areattributable toamalgam-derived mercury. Theissue ofabsorbed doseofmercury fromamalgam isaddressed first. Theuseofintra-oral Hgvapor measurements toesti- matedaily uptake musttake into account thedifferences between thecollection volume andflow rate ofthemeasuring instru- mentandtheinspiratory volume andflow rate ofairthrough themouthduring inhalation ofasingle breath. Failure toaccount forthese differences will result insubstantial overestimation oftheabsorbed dose. Other factors that mustbeconsidered whenmaking estimates ofHguptake fromamalgam include theaccurate measurement ofbaseline (unstimulated) mercury release rates andthegreater stimulation ofHgrelease afforded bychewing gumrelative toordinary food. Themeasured lev- elsofamalgam-derived mercury inbrain, blood, andurine areshowntobeconsistent withlowabsorbed doses (1-3 pLg/day). Published relationships between thenumber ofamalgam surfaces andurine levels areusedtoestimate thenumber ofamal- gamsurfaces that wouldberequired toproduce the30plg/g creatinine urine mercury level stated byWHO tobeassociated withthemostsubtle, pre-clinical effects inthemostsensitive individuals. From450to530amalgam surfaces wouldbe required toproduce the30pg/g creatinine urine mercury level forpeople without anyexcessive gum-chewing habits. The potential foradverse health effects andforimprovement inhealth following amalgam removal isalso addressed. Finally, the issue ofwhether anymaterial caneverbecompletely exonerated ofclaims ofproducing adverse health effects isconsidered.