The Contribution of Dental Amalgam to Urinary Mercury Excretion in Children

Abstract

BackgroundUrinary mercury concentrations are widely used as a measure of mercury exposure from dental amalgam fillings. No studies have evaluated the relationship of these measures in a longitudinal context in children.ObjectiveWe evaluated urinary mercury in children 8–18 years of age in relation to number of amalgam surfaces and time since placement over a 7-year course of amalgam treatment.MethodsFive hundred seven children, 8–10 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral effects of dental amalgam in children. Subjects were randomized to either dental amalgam or resin composite treatments. Urinary mercury and creatinine concentrations were measured at baseline and annually on all participants.ResultsTreatment groups were comparable in baseline urinary mercury concentration (~ 1.5 μg/L). Mean urinary mercury concentrations in the amalgam group increased to a peak of ~ 3.2 μg/L at year 2 and then declined to baseline levels by year 7 of follow-up. There was a strong, positive association between urinary mercury and both number of amalgam surfaces and time since placement. Girls had significantly higher mean urinary mercury concentrations than boys throughout the course of amalgam treatment. There were no differences by race in urinary mercury concentration associated with amalgam exposure.ConclusionsUrinary mercury concentrations are highly correlated with both number of amalgam fillings and time since placement in children. Girls excrete significantly higher concentrations of mercury in the urine than boys with comparable treatment, suggesting possible sex-related differences in mercury handling and susceptibility to mercury toxicity.

Developmental neurotoxicants and the vulnerable male brain: a systematic review of suspected neurotoxicants that disproportionally affect males

“…This finding suggests that Hg toxicity is nonlinear and that chronic Hg exposure may impair excretion and increase retention. Based on the preceding findings, the study's boys retained and accumulated significantly higher levels of Hg than the study's girls over the course of comparable Hg exposures from Hg-amalgam dental fillings (Woods et al 2007). …”

“…Woods et al (2007) found that mean urinary Hg excretion for boys and girls were similar at baseline. However, at about two years after amalgam placement, urinary Hg excretion declined for both genders.…”

“…However, given that the susceptibility genes are numerous and common, the alarming subtext of the report is that children, boys in particular, get neurobehavioral toxicity from routine exposures to Hg, ostensibly from Hg-amalgam dental fillings, which have hitherto been presumed safe. The authors noted that their exposure metric, urinary Hg levels, may include other Hg sources besides amalgam; however, an earlier study by the same team found that urinary Hg levels were correlated with amalgam (Woods et al 2007), and another study found that exposure to fish Hg in this cohort was insignificant (Evens et al 2001); therefore, it is reasonable to conclude that the neurobehavioral impairments are correlated with amalgam exposure. For the boys with the variant(s), significant dose-dependent impairments were found in most of the 23 neurobehavioral tests administered, and the domains most affected were attention, learning and memory, visual spatial acuity, and motor function.…”

A significant relationship between mercury exposure from dental amalgams and urinary porphyrins: a further assessment of the Casa Pia children’s dental amalgam trial

“…This procedure was applied both to baby teeth and adult teeth b Includes only subjects assigned to the dental amalgam group number of amalgam restorations had a significant dose-response relationship with Hg urine levels. Likewise, Woods et al (2007), in a longitudinal study in children, found urinary Hg concentrations were highly correlated with the number of amalgam fillings. Post-mortem studies also show this same dose-dependent central theme.…”

Casting the runes

“…The authors conclude that the integrated daily mercury dose of 7.4 µg for a high amalgam load is well below the tolerable dose of 30 µg (WHO 2003, ATSDR 1999. A recent paper indicated that there may be difference in mercury excretion between boys and girls 8-18 years of age, treated with dental amalgam (Woods 2007).…”