Search tips
Search criteria 


Logo of envhperEnvironmental Health PerspectivesBrowse ArticlesAbout EHPGeneral InformationAuthorsMediaProgramsPartnerships
Environ Health Perspect. 2003 May; 111(5): 719–723.
PMCID: PMC1241481
Research Article

Mercury derived from dental amalgams and neuropsychologic function.


There is widespread concern regarding the safety of silver-mercury amalgam dental restorations, yet little evidence to support their harm or safety. We examined whether mercury dental amalgams are adversely associated with cognitive functioning in a cross-sectional sample of healthy working adults. We studied 550 adults, 30-49 years of age, who were not occupationally exposed to mercury. Participants were representative of employees at a major urban medical center. Each participant underwent a neuropsychologic test battery, a structured questionnaire, a modified dental examination, and collection of blood and urine samples. Mercury exposure was assessed using a) urinary mercury concentration (UHg); b) the total number of amalgam surfaces; and c) the number of occlusal amalgam surfaces. Linear regression analysis was used to estimate associations between each marker of mercury exposure and each neuropsychologic test, adjusting for potential confounding variables. Exposure levels were relatively low. The mean UHg was 1.7 micro g/g creatinine (range, 0.09-17.8); the mean total number of amalgam surfaces was 10.6 (range, 0-46) and the mean number of occlusal amalgam surfaces was 6.1 (range, 0-19). No measure of exposure was significantly associated with the scores on any neuropsychologic test in analyses that adjusted for the sampling design and other covariates. In a sample of healthy working adults, mercury exposure derived from dental amalgam restorations was not associated with any detectable deficits in cognitive or fine motor functioning.

Full Text

The Full Text of this article is available as a PDF (140K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Albers JW, Cavender GD, Levine SP, Langolf GD. Asymptomatic sensorimotor polyneuropathy in workers exposed to elemental mercury. Neurology. 1982 Oct;32(10):1168–1174. [PubMed]
  • Albers JW, Kallenbach LR, Fine LJ, Langolf GD, Wolfe RA, Donofrio PD, Alessi AG, Stolp-Smith KA, Bromberg MB. Neurological abnormalities associated with remote occupational elemental mercury exposure. Ann Neurol. 1988 Nov;24(5):651–659. [PubMed]
  • Barregård L, Sällsten G, Järvholm B. People with high mercury uptake from their own dental amalgam fillings. Occup Environ Med. 1995 Feb;52(2):124–128. [PMC free article] [PubMed]
  • Berlin M, Fazackerley J, Nordberg G. The uptake of mercury in the brains of mammals exposed to mercury vapor and to mercuric salts. Arch Environ Health. 1969 May;18(5):719–729. [PubMed]
  • Berlin M, Blomstrand C, Grant CA, Hamberger A, Trofast J. Tritiated methylmercury in the brain of squirrel monkeys. Arch Environ Health. 1975 Dec;30(12):591–597. [PubMed]
  • Bernard A, Roels HA, Buchet JP, Lauwerys RR. Comparison, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, of urinary proteins excreted by workers exposed to cadmium, mercury or lead. Toxicol Lett. 1980 Mar;5(3-4):219–222. [PubMed]
  • Bittner AC, Jr, Echeverria D, Woods JS, Aposhian HV, Naleway C, Martin MD, Mahurin RK, Heyer NJ, Cianciola M. Behavioral effects of low-level exposure to Hg0 among dental professionals: a cross-study evaluation of psychomotor effects. Neurotoxicol Teratol. 1998 Jul-Aug;20(4):429–439. [PubMed]
  • Brown LJ, Swango PA. Trends in caries experience in US employed adults from 1971-74 to 1985: cross-sectional comparisons. Adv Dent Res. 1993 Jul;7(1):52–60. [PubMed]
  • Buchet JP, Roels H, Bernard A, Lauwerys R. Assessment of renal function of workers exposed to inorganic lead, calcium or mercury vapor. J Occup Med. 1980 Nov;22(11):741–750. [PubMed]
  • Buschke H, Fuld PA. Evaluating storage, retention, and retrieval in disordered memory and learning. Neurology. 1974 Nov;24(11):1019–1025. [PubMed]
  • Cianciola ME, Echeverria D, Martin MD, Aposian HV, Woods JS. Epidemiologic assessment of measures used to indicate low-level exposure to mercury vapor (Hg). J Toxicol Environ Health. 1997 Sep;52(1):19–33. [PubMed]
  • Dodes JE. The amalgam controversy. An evidence-based analysis. J Am Dent Assoc. 2001 Mar;132(3):348–356. [PubMed]
  • Echeverria D, Aposhian HV, Woods JS, Heyer NJ, Aposhian MM, Bittner AC, Jr, Mahurin RK, Cianciola M. Neurobehavioral effects from exposure to dental amalgam Hg(o): new distinctions between recent exposure and Hg body burden. FASEB J. 1998 Aug;12(11):971–980. [PubMed]
  • Echeverria D, Heyer NJ, Martin MD, Naleway CA, Woods JS, Bittner AC., Jr Behavioral effects of low-level exposure to elemental Hg among dentists. Neurotoxicol Teratol. 1995 Mar-Apr;17(2):161–168. [PubMed]
  • Ehrenberg RL, Vogt RL, Smith AB, Brondum J, Brightwell WS, Hudson PJ, McManus KP, Hannon WH, Phipps FC. Effects of elemental mercury exposure at a thermometer plant. Am J Ind Med. 1991;19(4):495–507. [PubMed]
  • Ellingsen DG, Bast-Pettersen R, Efskind J, Thomassen Y. Neuropsychological effects of low mercury vapor exposure in chloralkali workers. Neurotoxicology. 2001 Apr;22(2):249–258. [PubMed]
  • Ellingsen DG, Efskind J, Haug E, Thomassen Y, Martinsen I, Gaarder PI. Effects of low mercury vapour exposure on the thyroid function in chloralkali workers. J Appl Toxicol. 2000 Nov-Dec;20(6):483–489. [PubMed]
  • Fawer RF, de Ribaupierre Y, Guillemin MP, Berode M, Lob M. Measurement of hand tremor induced by industrial exposure to metallic mercury. Br J Ind Med. 1983 May;40(2):204–208. [PMC free article] [PubMed]
  • Fung YK, Molvar MP. Toxicity of mercury from dental environment and from amalgam restorations. J Toxicol Clin Toxicol. 1992;30(1):49–61. [PubMed]
  • Gerbert B, Bernzweig J, Bleecker T, Bader J, Miyasaki C. Risks of the "big three": what dentists and patients believe about dental amalgam, fluoride and HIV. J Am Dent Assoc. 1992 Mar;123(3):82–88. [PubMed]
  • Grandjean P, Weihe P, White RF, Debes F, Araki S, Yokoyama K, Murata K, Sørensen N, Dahl R, Jørgensen PJ. Cognitive deficit in 7-year-old children with prenatal exposure to methylmercury. Neurotoxicol Teratol. 1997 Nov-Dec;19(6):417–428. [PubMed]
  • Hanson M, Pleva J. The dental amalgam issue. A review. Experientia. 1991 Jan 15;47(1):9–22. [PubMed]
  • Hansteen IL, Ellingsen DG, Clausen KO, Kjuus H. Chromosome aberrations in chloralkali workers previously exposed to mercury vapor. Scand J Work Environ Health. 1993 Dec;19(6):375–381. [PubMed]
  • Heinegård D, Tiderström G. Determination of serum creatinine by a direct colorimetric method. Clin Chim Acta. 1973 Feb 12;43(3):305–310. [PubMed]
  • Herber RF, de Gee AJ, Wibowo AA. Exposure of dentists and assistants to mercury: mercury levels in urine and hair related to conditions of practice. Community Dent Oral Epidemiol. 1988 Jun;16(3):153–158. [PubMed]
  • Hursh JB, Greenwood MR, Clarkson TW, Allen J, Demuth S. The effect of ethanol on the fate of mercury vapor inhaled by man. J Pharmacol Exp Ther. 1980 Sep;214(3):520–527. [PubMed]
  • Kaufman AS, McLean JE, Reynolds CR. Sex, race, residence, region, and education differences on the 11 WAIS-R subtests. J Clin Psychol. 1988 Mar;44(2):231–248. [PubMed]
  • Kingman A, Albertini T, Brown LJ. Mercury concentrations in urine and whole blood associated with amalgam exposure in a US military population. J Dent Res. 1998 Mar;77(3):461–471. [PubMed]
  • KLOVE H. CLINICAL NEUROPSYCHOLOGY. Med Clin North Am. 1963 Nov;47:1647–1658. [PubMed]
  • Langolf GD, Chaffin DB, Henderson R, Whittle HP. Evaluation of workers exposed to elemental mercury using quantitative tests of tremor and neuromuscular functions. Am Ind Hyg Assoc J. 1978 Dec;39(12):976–984. [PubMed]
  • Langolf GD, Smith PJ, Henderson R, Whittle H. Measurements of neurological functions in the evaluations of exposure to neurotoxic agents. Ann Occup Hyg. 1981;24(3):293–296. [PubMed]
  • Lauwerys RR, Buchet JP. Occupational exposure to mercury vapors and biological action. Arch Environ Health. 1973 Aug;27(2):65–68. [PubMed]
  • Levine SP, Cavender GD, Langolf GD, Albers JW. Elemental mercury exposure: peripheral neurotoxicity. Br J Ind Med. 1982 May;39(2):136–139. [PMC free article] [PubMed]
  • Mackert JR., Jr Factors affecting estimation of dental amalgam mercury exposure from measurements of mercury vapor levels in intra-oral and expired air. J Dent Res. 1987 Dec;66(12):1775–1780. [PubMed]
  • Mathiesen T, Ellingsen DG, Kjuus H. Neuropsychological effects associated with exposure to mercury vapor among former chloralkali workers. Scand J Work Environ Health. 1999 Aug;25(4):342–350. [PubMed]
  • Miller JM, Chaffin DB, Smith RG. Subclinical psychomotor and neuromuscular changes in workers exposed to inorganic mercury. Am Ind Hyg Assoc J. 1975 Oct;36(10):725–733. [PubMed]
  • Naleway C, Chou HN, Muller T, Dabney J, Roxe D, Siddiqui F. On-site screening for urinary Hg concentrations and correlation with glomerular and renal tubular function. J Public Health Dent. 1991 Winter;51(1):12–17. [PubMed]
  • Naleway C, Sakaguchi R, Mitchell E, Muller T, Ayer WA, Hefferren JJ. Urinary mercury levels in US dentists, 1975-1983: review of Health Assessment Program. J Am Dent Assoc. 1985 Jul;111(1):37–42. [PubMed]
  • Newton D, Fry FA. The retention and distribution of radioactive mercuric oxide following accidental inhalation. Ann Occup Hyg. 1978 Mar;21(1):21–32. [PubMed]
  • Ngim CH, Foo SC, Boey KW, Jeyaratnam J. Chronic neurobehavioural effects of elemental mercury in dentists. Br J Ind Med. 1992 Nov;49(11):782–790. [PMC free article] [PubMed]
  • Palumbo DR, Cox C, Davidson PW, Myers GJ, Choi A, Shamlaye C, Sloane-Reeves J, Cernichiari E, Clarkson TW. Association between prenatal exposure to methylmercury and cognitive functioning in Seychellois children: a reanalysis of the McCarthy Scales of Children's Ability from the main cohort study. Environ Res. 2000 Oct;84(2):81–88. [PubMed]
  • Piikivi L, Hänninen H. Subjective symptoms and psychological performance of chlorine-alkali workers. Scand J Work Environ Health. 1989 Feb;15(1):69–74. [PubMed]
  • Ritchie KA, Macdonald EB, Hammersley R, O'Neil JM, McGowan DA, Dale IM, Wesnes K. A pilot study of the effect of low level exposure to mercury on the health of dental surgeons. Occup Environ Med. 1995 Dec;52(12):813–817. [PMC free article] [PubMed]
  • Roels H, Gennart JP, Lauwerys R, Buchet JP, Malchaire J, Bernard A. Surveillance of workers exposed to mercury vapour:validation of a previously proposed biological threshold limit value for mercury concentration in urine. Am J Ind Med. 1985;7(1):45–71. [PubMed]
  • Roels H, Lauwerys R, Buchet JP, Bernard A, Barthels A, Oversteyns M, Gaussin J. Comparison of renal function and psychomotor performance in workers exposed to elemental mercury. Int Arch Occup Environ Health. 1982;50(1):77–93. [PubMed]
  • Singer R, Valciukas JA, Rosenman KD. Peripheral neurotoxicity in workers exposed to inorganic mercury compounds. Arch Environ Health. 1987 Jul-Aug;42(4):181–184. [PubMed]
  • Skare I, Engqvist A. Human exposure to mercury and silver released from dental amalgam restorations. Arch Environ Health. 1994 Sep-Oct;49(5):384–394. [PubMed]
  • Smith PJ, Langolf GD. The use of Sternberg's memory-scanning paradigm in assessing effects of chemical exposure. Hum Factors. 1981 Dec;23(6):701–708. [PubMed]
  • Smith PJ, Langolf GD, Goldberg J. Effect of occupational exposure to elemental mercury on short term memory. Br J Ind Med. 1983 Nov;40(4):413–419. [PMC free article] [PubMed]
  • Smith RG, Vorwald AJ, Patil LS, Mooney TF., Jr Effects of exposure to mercury in the manufacture of chlorine. Am Ind Hyg Assoc J. 1970 Nov-Dec;31(6):687–700. [PubMed]
  • Snow WG, Weinstock J. Sex differences among non-brain-damaged adults on the Wechsler Adult Intelligence Scales: a review of the literature. J Clin Exp Neuropsychol. 1990 Dec;12(6):873–886. [PubMed]
  • Steinberg D, Grauer F, Niv Y, Perlyte M, Kopolovic K. Mercury levels among dental personnel in Israel: a preliminary study. Isr J Med Sci. 1995 Jul;31(7):428–432. [PubMed]
  • Takahata N, Hayashi H, Watanabe S, Anso T. Accumulation of mercury in the brains of two autopsy cases with chronic inorganic mercury poisoning. Folia Psychiatr Neurol Jpn. 1970;24(1):59–69. [PubMed]
  • Weiner JA, Nylander M, Berglund F. Does mercury from amalgam restorations constitute a health hazard? Sci Total Environ. 1990 Dec 1;99(1-2):1–22. [PubMed]
  • Woods JS, Martin MD, Naleway CA, Echeverria D. Urinary porphyrin profiles as a biomarker of mercury exposure: studies on dentists with occupational exposure to mercury vapor. J Toxicol Environ Health. 1993 Oct-Nov;40(2-3):235–246. [PubMed]

Articles from Environmental Health Perspectives are provided here courtesy of National Institute of Environmental Health Science