Low level methylmercury exposure affects neuropsychological function in adults

Edna M. Yokoo, Joaquim G. Valente, Lynn Grattan, Sérgio Luís Schmidt, Illeane Platt, Ellen Silbergeld

Research output: Contribution to journalArticle

Abstract

Background: The neurotoxic effects of methylmercury (MeHg) have been demonstrated in both human and animal studies. Both adult and fetal brains are susceptible to the effects of MeHg toxicity. However, the specific effects of adult exposures have been less well-documented than those of children with prenatal exposures. This is largely because few studies of MeHg exposures in adults have used sensitive neurological endpoints. The present study reports on the results of neuropsychological testing and hair mercury concentrations in adults (>17 yrs) living in fishing communities of Baixada Cuiabana (Mato Grosso) in the Pantanal region of Brazil. Methods: A cross-sectional study was conducted in six villages on the Cuiaba River. Participants included 129 men and women older than 17 years of age. They were randomly selected in proportion to the age range and number of inhabitants in each village. Questionnaire information was collected on demographic variables, including education, occupation, and residence history. Mercury exposure was determined by analysis of hair using flameless atomic absorption spectrophotometry. The neurocognitive screening battery included tests from the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale, Concentrated Attention Test of the Toulouse-Pierron Factorial Battery, the Manual Ability Subtests of the Tests of Mechanical Ability, and the Profile of Mood States. Results: Mercury exposures in this population were associated with fish consumption. The hair mercury concentration in the 129 subjects ranged from 0.56 to 13.6 μg/g; the mean concentration was 4.2 ± 2.4 micrograms/g and the median was 3.7 μg/g. Hair mercury levels were associated with detectable alterations in performance on tests of fine motor speed and dexterity, and concentration. Some aspects of verbal learning and memory were also disrupted by mercury exposure. The magnitude of the effects increased with hair mercury concentration, consistent with a dose-dependent effect. Conclusions: This study suggests that adults exposed to MeHg may be at risk for deficits in neurocognitive function. The functions disrupted in adults, namely attention, fine-motor function and verbal memory, are similar to some of those previously reported in children with prenatal exposures.

Original languageEnglish (US)
Article number1
Pages (from-to)1-11
Number of pages11
JournalEnvironmental Health: A Global Access Science Source
Volume2
DOIs
StatePublished - Jun 4 2003

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methylmercury
Mercury
hair
Hair
Aptitude
village
fishing community
Wechsler Scales
Verbal Learning
Atomic Spectrophotometry
spectrophotometry
mercury
exposure
Intelligence
Occupations
Rivers
Brazil
occupation
brain
Fishes

ASJC Scopus subject areas

  • Environmental Science(all)
  • Medicine(all)

Cite this

Low level methylmercury exposure affects neuropsychological function in adults. / Yokoo, Edna M.; Valente, Joaquim G.; Grattan, Lynn; Schmidt, Sérgio Luís; Platt, Illeane; Silbergeld, Ellen.

In: Environmental Health: A Global Access Science Source, Vol. 2, 1, 04.06.2003, p. 1-11.

Research output: Contribution to journalArticle

Yokoo, Edna M. ; Valente, Joaquim G. ; Grattan, Lynn ; Schmidt, Sérgio Luís ; Platt, Illeane ; Silbergeld, Ellen. / Low level methylmercury exposure affects neuropsychological function in adults. In: Environmental Health: A Global Access Science Source. 2003 ; Vol. 2. pp. 1-11.
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N2 - Background: The neurotoxic effects of methylmercury (MeHg) have been demonstrated in both human and animal studies. Both adult and fetal brains are susceptible to the effects of MeHg toxicity. However, the specific effects of adult exposures have been less well-documented than those of children with prenatal exposures. This is largely because few studies of MeHg exposures in adults have used sensitive neurological endpoints. The present study reports on the results of neuropsychological testing and hair mercury concentrations in adults (>17 yrs) living in fishing communities of Baixada Cuiabana (Mato Grosso) in the Pantanal region of Brazil. Methods: A cross-sectional study was conducted in six villages on the Cuiaba River. Participants included 129 men and women older than 17 years of age. They were randomly selected in proportion to the age range and number of inhabitants in each village. Questionnaire information was collected on demographic variables, including education, occupation, and residence history. Mercury exposure was determined by analysis of hair using flameless atomic absorption spectrophotometry. The neurocognitive screening battery included tests from the Wechsler Memory Scale and the Wechsler Adult Intelligence Scale, Concentrated Attention Test of the Toulouse-Pierron Factorial Battery, the Manual Ability Subtests of the Tests of Mechanical Ability, and the Profile of Mood States. Results: Mercury exposures in this population were associated with fish consumption. The hair mercury concentration in the 129 subjects ranged from 0.56 to 13.6 μg/g; the mean concentration was 4.2 ± 2.4 micrograms/g and the median was 3.7 μg/g. Hair mercury levels were associated with detectable alterations in performance on tests of fine motor speed and dexterity, and concentration. Some aspects of verbal learning and memory were also disrupted by mercury exposure. The magnitude of the effects increased with hair mercury concentration, consistent with a dose-dependent effect. Conclusions: This study suggests that adults exposed to MeHg may be at risk for deficits in neurocognitive function. The functions disrupted in adults, namely attention, fine-motor function and verbal memory, are similar to some of those previously reported in children with prenatal exposures.

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