Dental amalgam fillings and the use of technological devices as an environmental factor: Updating the cumulative mercury exposure-based hypothesis of autism

AbstractDental amalgam—a mixture of elemental mercury and a silver-dominated metal alloy—has been the most widely used dental filling material for well over a century. Alternative materials exist but are not well suited for some important applications, and all are more expensive than amalgam. The toxic effects of occupational mercury exposure have long been known, but it was not until about 1980 that serious consideration was given to the possibility that mercury vapor escaping from amalgam fillings might be affecting health, specifically producing subtle effects on the central nervous system. Such effects have been reported among dentists and other dental personnel, whose exposures are well below industrial levels but above those from fillings alone. No large studies have been completed that examine the effects of mercury exposure from dental amalgam fillings. In the face of inadequate evidence on the possible risks of dental amalgam, countries have reacted disparately. Sweden is phasing out amalgam entirely, possibly by the end of 1997. Germany has produced guidelines for limiting its use, other countries have signaled their intention to reduce it, and others—the United States and Canada—have studied the matter but taken no action. Policy differences within Europe have made dental amalgam a test case for the European Community's new medical device regulations. Relatively little epidemiologic research has been initiated to try to answer the question of dental amalgam's possible health effects. An international effort to define and carry out a research agenda to guide public policy is called for.

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Reduced Levels of Mercury in First Baby Haircuts of Autistic Children

International Journal of Toxicology ◽

10.1080/10915810305120 ◽

2003 ◽

Vol 22 (4) ◽

pp. 277-285 ◽

Cited By ~ 116

Author(s):

Amy S. Holmes ◽

Mark F. Blaxill ◽

Boyd E. Haley

Keyword(s):

The United States ◽

Dental Amalgam ◽

Mercury Exposure ◽

Autistic Children ◽

Autistic Group ◽

Hair Mercury ◽

Significant Difference ◽

Childhood Vaccines ◽

Dental Amalgam Fillings ◽

Amalgam Fillings

Reported rates of autism have increased sharply in the United States and the United Kingdom. One possible factor underlying these increases is increased exposure to mercury through thimerosal-containing vaccines, but vaccine exposures need to be evaluated in the context of cumulative exposures during gestation and early infancy. Differential rates of postnatal mercury elimination may explain why similar gestational and infant exposures produce variable neurological effects. First baby haircut samples were obtained from 94 children diagnosed with autism using Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM IV) criteria and 45 age- and gender-matched controls. Information on diet, dental amalgam fillings, vaccine history, Rho D immunoglob-ulin administration, and autism symptom severity was collected through a maternal survey questionnaire and clinical observation. Hair mercury levels in the autistic group were 0.47 ppm versus 3.63 ppm in controls, a significant difference. The mothers in the autistic group had significantly higher levels of mercury exposure through Rho D immunoglobulin injections and amalgam fillings than control mothers. Within the autistic group, hair mercury levels varied significantly across mildly, moderately, and severely autistic children, with mean group levels of 0.79, 0.46, and 0.21 ppm, respectively. Hair mercury levels among controls were significantly correlated with the number of the mothers' amalgam fillings and their fish consumption as well as exposure to mercury through childhood vaccines, correlations that were absent in the autistic group. Hair excretion patterns among autistic infants were significantly reduced relative to control. These data cast doubt on the efficacy of traditional hair analysis as a measure of total mercury exposure in a subset of the population. In light of the biological plausibility of mercury's role in neurodevelopmental disorders, the present study provides further insight into one possible mechanism by which early mercury exposures could increase the risk of autism.

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