Neurotoxicity Research

, Volume 36, Issue 4, pp 827–835 | Cite as

Verbal Memory and Learning in Schoolchildren Exposed to Manganese in Mexico

  • Z. García-Chimalpopoca
  • D. Hernández-BonillaEmail author
  • M. Cortez-Lugo
  • C. Escamilla-Núñez
  • A. Schilmann
  • H. Riojas-Rodríguez
  • S. Rodríguez-Dozal
  • S. Montes
  • L. A. Tristán-López
  • M. Catalán-Vázquez
  • C. Rios
Original Article


Manganese (Mn) is an essential nutrient for cellular function, but in high concentrations, it is neurotoxic. Environmental exposure to Mn has been associated with cognitive effects in children. This study aimed to assess the effect of environmental exposure to Mn on verbal memory and learning in schoolchildren residents from two municipalities in the state of Hidalgo, Mexico. Cross-sectional studies were conducted in 2006 and 2013 with a total of 265 schoolchildren of 7 to 11 years old. Children’s Auditory Verbal Learning Test-2 (CAVLT-2) was used to assess verbal memory and learning. Mn exposure tertiles were defined according to hair manganese (MnH) levels determined by atomic absorption spectrophotometry. Linear regression models were used to estimate the association between MnH levels and CAVLT-2 scores. The models were adjusted by potential confounders. The lowest and highest exposure tertiles were defined below and above MnH levels of ≤ 0.72 and ≥ 3.96 μg/g, respectively. Mn exposure was significantly associated with an average of 5- to 9-point decrease in learning curves and summary CAVLT-2 scores in the highest tertile. This study adds to the evidence of decreased verbal memory and learning in schoolchildren environmentally exposed to manganese.


Hair manganese Mining area Verbal memory Verbal learning Schoolchildren 





Gamma-aminobutyric acid


Central Nervous System


Children’s Auditory Verbal Learning Test-2


Hair manganese


Micrograms per gram




Blood lead


Micrograms per deciliter




Grams per deciliter



Our special thanks to all families who participated in this study, and the teachers of the elementary schools “Gral. Ignacio Manuel Altamirano” and “Belisario Dominguez” for all the assistance offered. We thank SJ. Velázquez-Juárez for the design of the study area map. We thank the support of the children’s environmental health Mexico thematic network to publish this paper (CONACyT-Mexico project number 271626).

Funding Sources

This project received funding from the International Development Research Centre (IDRC) project number 100662 and the Consejo Nacional de Ciencia y Tecnología (CONACYT) project number 141385. The funding agencies have not participated in the methodological design of this research.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Bioethics and Research Committees

This study was approved by the Bioethics and Research Committees of the National Institute of Public Health from Mexico.

Informed Consent

Informed consent was obtained from all individual participants included in the study.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Z. García-Chimalpopoca
    • 1
  • D. Hernández-Bonilla
    • 1
    Email author
  • M. Cortez-Lugo
    • 1
  • C. Escamilla-Núñez
    • 1
  • A. Schilmann
    • 1
  • H. Riojas-Rodríguez
    • 1
  • S. Rodríguez-Dozal
    • 1
  • S. Montes
    • 2
  • L. A. Tristán-López
    • 2
  • M. Catalán-Vázquez
    • 3
  • C. Rios
    • 2
  1. 1.Environmental Health DepartmentNational Institute of Public HealthCuernavacaMexico
  2. 2.Neurochemistry DepartmentNational Institute of Neurology and NeurosurgeryMexico CityMexico
  3. 3.Clinical Epidemiology DepartmentNational Institute of Respiratory DiseasesMexico CityMexico

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