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. 2012 Jan;120(1):126-31.
doi: 10.1289/ehp.1003300. Epub 2011 Sep 1.

Associations of early childhood manganese and lead coexposure with neurodevelopment

Birgit Claus Henn  1 , Lourdes Schnaas, Adrienne S Ettinger, Joel Schwartz, Héctor Lamadrid-Figueroa, Mauricio Hernández-Avila, Chitra Amarasiriwardena, Howard Hu, David C Bellinger, Robert O Wright, Martha María Téllez-Rojo
Affiliations

Associations of early childhood manganese and lead coexposure with neurodevelopment

Birgit Claus Henn et al. Environ Health Perspect. 2012 Jan.

Abstract

Background: Most toxicologic studies focus on a single agent, although this does not reflect real-world scenarios in which humans are exposed to multiple chemicals.

Objectives: We prospectively studied manganese-lead interactions in early childhood to examine whether manganese-lead coexposure is associated with neurodevelopmental deficiencies that are more severe than expected based on effects of exposure to each metal alone.

Methods: Four hundred fifty-five children were enrolled at birth in an longitudinal cohort study in Mexico City, provided blood samples, and were followed until 36 months of age. We measured lead and manganese at 12 and 24 months and assessed neurodevelopment at 6-month intervals from 12 to 36 months of age using Bayley Scales of Infant Development-II.

Results: Mean (± SD) blood concentrations at 12 and 24 months were, respectively, 24.7 ± 5.9 μg/L and 21.5 ± 7.4 μg/L for manganese and 5.1 ± 2.6 μg/dL and 5.0 ± 2.9 μg/dL for lead. Mixed-effects models, including Bayley scores at five time points, showed a significant interaction over time: highest manganese quintile × continuous lead; mental development score, β = -1.27 [95% confidence interval (CI): -2.18, -0.37]; psychomotor development score, β = -0.92 (95% CI: -1.76, -0.09). Slopes for the estimated 12-month lead effect on 18-month mental development and 24- through 36-month psychomotor development scores were steeper for children with high manganese than for children with midrange manganese levels.

Conclusions: We observed evidence of synergism between lead and manganese, whereby lead toxicity was increased among children with high manganese coexposure. Findings highlight the importance of understanding health effects of mixed exposures, particularly during potentially sensitive developmental stages such as early childhood.

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Conflict of interest statement

This research has not been formally reviewed by the U.S. EPA. The views expressed in this document are solely those of the authors, and the U.S. EPA does not endorse any products or commercial services mentioned in this publication.

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1
Scatterplots and regression lines of 12-month blood lead (BPb) and 18-month MDI among children with 12-month blood manganese (Mn) in quintiles 1–4 (A) and quintile 5 (B).
Figure 2
Figure 2
Scatterplots and regression lines of 12-month blood lead (BPb) on 24-month PDI among children with 12-month blood manganese (Mn) in quintiles 1–4 (A) and quintile 5 (B).
See this image and copyright information in PMC

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