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787268 
Journal Article 
Associations of early childhood manganese and lead coexposure with neurodevelopment 
Henn, BC; Schnaas, L; Ettinger, AS; Schwartz, J; Lamadrid-Figueroa, H; Hernández-Avila, M; Amarasiriwardena, C; Hu, H; Bellinger, DC; Wright, RO; Téllez-Rojo, MM 
2012 
Yes 
Environmental Health Perspectives
ISSN: 0091-6765
EISSN: 1552-9924 
120 
1 
126-131 
English 
21885384 
WOS:000299650400036 
Background: Most toxicological studies focus on a single agent, though this does not reflect the real world scenario in which humans are exposed to multiple chemicals. Objectives: We prospectively studied manganese-lead interactions in early childhood to examine whether manganese-lead co-exposure 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 in an ongoing longitudinal cohort study were enrolled at birth 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 six-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, respectively, were 24.7 (5.9) μg/l and 21.5 (7.4) μg/l for manganese; 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 (μg/dl); mental development score: β = -1.27 [95% CI = -2.18 to -0.37]; psychomotor development score: β = -0.92 [-1.76 to -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 among children with high manganese, compared to mid-range manganese levels. Conclusions: We observed evidence of synergism between lead and manganese, whereby lead toxicity was increased among children with high manganese co-exposure. Findings highlight the importance of understanding health effects of mixed exposures, particularly during potentially sensitive developmental stages such as early childhood. 
coexposure; early childhood; lead; manganese; metals; neurodevelopment