Neuropsychological alterations in mercury intoxication persist several years after exposure

Zachi, Elaine Cristina; Taub, Anita; Faria, Marcília de Araújo Medrado; Ventura, Dora Fix

doi:10.1590/S1980-57642009DN20200003

Abstract

Elemental mercury is a liquid toxic metal widely used in industry. Occupational exposure occurs mainly via inhalation. Previously, neuropsychological assessment detected deficits in former workers of a fluorescent lamp plant who had been exposed to elemental mercury vapor and were away from exposure for several years at the time of examination.

Objectives: The purpose of this work was to reexamine these functions after 18 months in order to evaluate their progression.

Methods: Thirteen participants completed tests of attention, inhibitory control, verbal/visual memory, psychomotor speed, verbal fluency, visuomotor ability, executive function, semantic knowledge, and depression and anxiety inventories on 2 separate occasions.

Results: At baseline, the former workers indicated slower psychomotor and information processing speed, verbal spontaneous recall memory impairment, and increased depression and anxiety symptoms compared to controls (P<0.05). Paired comparisons of neuropsychological functioning within the exposed group at baseline and 1.5 years later showed poorer immediate memory performance (P<0.05). There were no differences on other measures.

Conclusions: Although the literature show signs of recovery of functions, the neuropsychological effects related to mercury exposure are found to persist for many years.

Key words:
mercury; occupational exposure; cognition disorders; neuropsychological tests; mood

Resumo

Mercúrio metálico é um metal líquido e tóxico com ampla aplicação industrial. A exposição ocupacional ao metal ocorre principalmente por inalação. Previamente, comprometimento em várias funções neuropsicológicas foi constatado em ex-trabalhadores de fábrica de lâmpadas fluorescentes que haviam sido expostos ao vapor de mercúrio e estavam afastados da fonte de exposição por vários anos no momento do exame.

Objetivos: Reexaminar estas funções após 18 meses, com a finalidade de verificar a possível progressão do comprometimento.

Métodos: Treze participantes foram submetidos a testes de atenção, controle inibitório, memória verbal e visual, funções executivas, conhecimento semântico e inventários de depressão e ansiedade.

Resultados: Na linha de base, os ex-trabalhadores mostraram lentificação psicomotora e no processamento de informações, déficit de memória verbal espontânea, além de maiores sintomas de depressão e ansiedade comparados com controles (P<0,05). Comparações pareadas do grupo exposto na linha de base e 18 meses após indicaram pior desempenho em memória imediata (P<0,05). Não houve diferença nas demais medidas.

Conclusões: Embora a literatura mostre indícios de recuperação das funções, os efeitos neuropsicológicos relacionados ao mercúrio podem persistir por muitos anos.

Palavras-chave:
mercúrio; exposição ocupacional; cognição; testes neuropsicológicos; humor

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References

¹ Faria MA. Chronic occupational metallic mercurialism. Rev Saúde Pública 2003;37:116-127.
² Rodriguez ZC, Rodriguez JEL. Metallic mercury intoxication. Bol Asoc Med P R 1982;74:380-382.
³ Kishi R, Doi R, Fukuchi Y, et al. Subjective symptoms and neurobehavioral performances of ex-mercury miners at an average of 18 years after the cessation of chronic exposure to mercury vapor. Mercury Workers Study Group. Environ Res 1993;62: 289-302.
⁴ Kishi R, Doi R, Fukuchi Y, et al. Residual neurobehavioural effects associated with chronic exposure to mercury vapour. Occup Environ Med 1994;51:35-41.
⁵ Zachi EC, Ventura DF, Faria MAM, Taub A. Neuropsychological dysfunction related to earlier occupational mercury vapor. Braz J Med Biol Res 2007;40:425-433.
⁶ Mathiesen T, Ellingsen DG, Kjuus H. Neuropsychological effects associated with exposure to mercury vapor among former chloralkali workers. Scand J Work Environ Health 1999;25:342-350.
⁷ Letz R, Gerr F, Cragle D, Green RC, Watkins J, Fidler AT. Residual neurologic deficits 30 years after occupational exposure to elemental mercury. Neurotoxicology 2000;21:459-474.
⁸ Frumkin H, Letz R, Williams PL, et al. Health effects of long-term mercury exposure among chloralkali plant workers. Am J Ind Med 2001;39:1-18.
⁹ Bast-Pettersen R, Ellingsen DG, Efskind J, Jordskogen R, Thomassen Y. A neurobehavioral study of chloralkali workers after the cessation of exposure to mercury vapor. Neurotoxicology 2005;26:427-437.
¹⁰ Wechsler D. Wechsler Memory Scale Revised - User's manual. San Antonio: The Psychological Corporation; 1987.
¹¹ Spreen O, Strauss E. A compendium of neuropsychological tests. New York: Oxford University Press; 1991.
¹² Lafayette Instrument Corporation USA. Grooved Pegboard Instruction: Owner's Manual. [S.l.], IN: Lafayette Instruments. 1979.
¹³ Wechsler D. Wechsler Adult Intelligence Scale Revised - User's manual. New York: Psychological Corporation; 1981.
¹⁴ Heaton RK, Chelune GJ, Talley JL, Kay GG, Curtis G. Wisconsin Card Sorting Test (WCST) - Manual revised and expanded. Odessa: Psychological Assessment Resources; 1993.
¹⁵ Cunha JA. Escalas Beck - manual. São Paulo: Casa do Psicólogo; 2001.
¹⁶ Biaggio AMB, Natalício L. Inventário de ansiedade traço-estado - manual. Rio de Janeiro: CEPA; 1979.
¹⁷ Ventura DF, Simões AL, Tomaz S, et al. Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil. Environ Toxicol Pharmacol 2005;19:523-529.
¹⁸ Costa MF, Tomaz S, Souza JM, Silveira LCL, Ventura DF. Electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication. Environ Res 2008;107:132-138.
¹⁹ Barboni MTS, Costa MF, Moura ALA, et al. Visual field losses in workers exposed to mercury vapor. Environ Res 2008; 107:124-131.
²⁰ Feitosa-Santana C, Barboni M, Oiwa NN, et al. Irreversible color vision losses in patients with chronic mercury vapor intoxication. Vis Neurosci 2008, 25: 1-5.
²¹ Ventura DF, Costa MTV, Costa MF, et al. Multifocal and full-field electroretinogram changes associated with color-vision loss in mercury vapor exposure. Vis Neurosci 2004;21: 421-429.

Publication Dates

Publication in this collection
Apr-Jun 2008

History

Received
22 Apr 2008
Accepted
21 May 2008

This is an open-access article distributed under the terms of the Creative Commons Attribution License

[1] ¹ Faria MA. Chronic occupational metallic mercurialism. Rev Saúde Pública 2003;37:116-127.

[2] ² Rodriguez ZC, Rodriguez JEL. Metallic mercury intoxication. Bol Asoc Med P R 1982;74:380-382.

[3] ³ Kishi R, Doi R, Fukuchi Y, et al. Subjective symptoms and neurobehavioral performances of ex-mercury miners at an average of 18 years after the cessation of chronic exposure to mercury vapor. Mercury Workers Study Group. Environ Res 1993;62: 289-302.

[4] ⁴ Kishi R, Doi R, Fukuchi Y, et al. Residual neurobehavioural effects associated with chronic exposure to mercury vapour. Occup Environ Med 1994;51:35-41.

[5] ⁵ Zachi EC, Ventura DF, Faria MAM, Taub A. Neuropsychological dysfunction related to earlier occupational mercury vapor. Braz J Med Biol Res 2007;40:425-433.

[6] ⁶ Mathiesen T, Ellingsen DG, Kjuus H. Neuropsychological effects associated with exposure to mercury vapor among former chloralkali workers. Scand J Work Environ Health 1999;25:342-350.

[7] ⁷ Letz R, Gerr F, Cragle D, Green RC, Watkins J, Fidler AT. Residual neurologic deficits 30 years after occupational exposure to elemental mercury. Neurotoxicology 2000;21:459-474.

[8] ⁸ Frumkin H, Letz R, Williams PL, et al. Health effects of long-term mercury exposure among chloralkali plant workers. Am J Ind Med 2001;39:1-18.

[9] ⁹ Bast-Pettersen R, Ellingsen DG, Efskind J, Jordskogen R, Thomassen Y. A neurobehavioral study of chloralkali workers after the cessation of exposure to mercury vapor. Neurotoxicology 2005;26:427-437.

[10] ¹⁰ Wechsler D. Wechsler Memory Scale Revised - User's manual. San Antonio: The Psychological Corporation; 1987.

[11] ¹¹ Spreen O, Strauss E. A compendium of neuropsychological tests. New York: Oxford University Press; 1991.

[12] ¹² Lafayette Instrument Corporation USA. Grooved Pegboard Instruction: Owner's Manual. [S.l.], IN: Lafayette Instruments. 1979.

[13] ¹³ Wechsler D. Wechsler Adult Intelligence Scale Revised - User's manual. New York: Psychological Corporation; 1981.

[14] ¹⁴ Heaton RK, Chelune GJ, Talley JL, Kay GG, Curtis G. Wisconsin Card Sorting Test (WCST) - Manual revised and expanded. Odessa: Psychological Assessment Resources; 1993.

[15] ¹⁵ Cunha JA. Escalas Beck - manual. São Paulo: Casa do Psicólogo; 2001.

[16] ¹⁶ Biaggio AMB, Natalício L. Inventário de ansiedade traço-estado - manual. Rio de Janeiro: CEPA; 1979.

[17] ¹⁷ Ventura DF, Simões AL, Tomaz S, et al. Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil. Environ Toxicol Pharmacol 2005;19:523-529.

[18] ¹⁸ Costa MF, Tomaz S, Souza JM, Silveira LCL, Ventura DF. Electrophysiological evidence for impairment of contrast sensitivity in mercury vapor occupational intoxication. Environ Res 2008;107:132-138.

[19] ¹⁹ Barboni MTS, Costa MF, Moura ALA, et al. Visual field losses in workers exposed to mercury vapor. Environ Res 2008; 107:124-131.

[20] ²⁰ Feitosa-Santana C, Barboni M, Oiwa NN, et al. Irreversible color vision losses in patients with chronic mercury vapor intoxication. Vis Neurosci 2008, 25: 1-5.

[21] ²¹ Ventura DF, Costa MTV, Costa MF, et al. Multifocal and full-field electroretinogram changes associated with color-vision loss in mercury vapor exposure. Vis Neurosci 2004;21: 421-429.