BOSTON—Getting too much or not enough manganese may mean infants will be slower to reach neurological milestones, according to a study published in the journal Epidemiology (doi: 10.1097/EDE.0b013e3181df8e52). The researchers in the study said the data are consistent with manganese as both an essential nutrient and a toxicant.
Researchers from the Harvard School of Public Health noted recent evidence suggests low-level environmental exposure to manganese adversely affects child growth and neurodevelopment. These previous studies addressed the effects of prenatal exposure, but little was known about developmental effects of early postnatal exposure.
Therefore, they studied 448 children born in Mexico City from 1997 through 2000, using a longitudinal study to investigate neurotoxic effects of early-life manganese exposure. Archived blood samples, collected from children at 12 and 24 months of age, were analyzed for manganese levels. The researchers also measured mental development and muscular activity associated with mental processes at six-month intervals between 12 and 36 months of age.
At 12 months of age, they found the children who were in the lowest 20 percentile, with blood manganese levels below 20 mcg/L; and those who were in the highest 20 percentile, with levels higher than 28 mcg/L, did not do as well on the mental development tests.
However, as children aged, the connection between manganese levels and brain development diminished, and at 24 months of age, the researchers found no association between manganese and neurodevelopment.
This study was supported in part by the National Institute of Environmental Health Sciences and by a STAR (Science to Achieve Results) Research Assistance Agreement awarded by the U.S. Environmental Protection Agency (EPA).
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