Manganese exposure from drinking water and children's academic achievement
Highlights
► We examined the association between water manganese (WMn) and school achievement. ► Achievement scores of school children in mathematics and languages were collected. ► A 6.4% score loss in mathematics for WMn above the WHO standard was observed.
Introduction
Health effects of chronic manganese (Mn) exposure in both occupational (e.g. welding) and environmental settings are reported in adults. In children, exposure to Mn is likely from environmental sources with exposure levels lower than in adults. Despite lower levels of exposure, several studies report cognitive, neurobehavioral and neuropsychological health effects in children (Bouchard et al., 2007, Bouchard et al., 2011, Ericson et al., 2007, Khan et al., 2011, Kim et al., 2009, Menezes-Filho et al., 2009, Takser et al., 2003, Wasserman et al., 2006, Wright et al., 2006). The memory deficits that often accompany exposure in both children (He et al., 1994, Wasserman et al., 2006) and adults (Bowler et al., 2007, Chang et al., 2009, Chang et al., 2010, Lucchini et al., 1995, Lucchini and Zimmerman, 2009) suggest consequences for children's academic achievement. While cognitive ability is certainly related to academic achievement, early-school academic achievement may be more predictive of functional capacity such as success in later stages in school (Duncan et al., 2007, Hooper et al., 2010, Romano et al., 2010).
Although lowered academic achievement in languages, math, science and other disciplines has been related to children's exposure to lead (Chandramouli et al., 2009, Miranda et al., 2007, Zahran et al., 2009) associations between Mn exposure and measures of children's school performance have less often been reported. In an ecological study in China, Mn-exposed children were found to have significantly lower school performance in mathematics and language (Zhang et al., 1995) compared to children in a non-exposed village.
In Bangladesh, especially in rural areas, people rely on groundwater as the only source of fresh drinking water. However, both naturally occurring Mn and arsenic (As) in groundwater have been recognized as threats to rural public health. Since 2000, a team of health, earth and social scientists at Columbia University has carried out a large collaborative projects in Araihazar, Bangladesh. In this region, independent health effects of both Mn and As on children's intelligence have been documented (Wasserman et al., 2004, Wasserman et al., 2006, Wasserman et al., 2007).
This study examines the associations between Mn and/or As and academic achievement among 8–11 year old children with wide ranges of As and Mn exposures. We also examine the joint effect of Mn and As on children's academic achievement to explore possible effect modification (Kim et al., 2009, Wright et al., 2006).
Section snippets
Overview
This cross-sectional study is a component of an ongoing, prospective elementary school-based intervention study for lowering arsenic exposure from drinking water in Araihazar, Bangladesh. The study area is adjacent to a previously described study area for a larger cohort study of adults (Ahsan et al., 2006) consisting of three unions of Araihazar upazilla located about 25 km southeast of the capital city Dhaka. Araihazar has an area of 183 km2 and contains 12 unions, the smallest administrative
Sample characteristics
Characteristics of included children are described in Table 1. More female students than male students were included. On average, children had attended school for approximately a lifetime total of 30 months, although they were currently attending classes as second through fifth graders. About half the parents had no formal education. Participants were exposed to expectably high levels of As and Mn in drinking water: mean WAs and WMn concentrations were 13 and 3 times the WHO standards of 10 and
Discussion
We found a statistically significant negative association between WMn (dichotomized at the WHO standard) and mathematics achievement test scores that persisted upon adjustment for sociodemographic variables, such as parental and maternal education. WMn was negatively associated with language scores although the associations were not statistically significant. High WMn (>400 μg/L) was more strongly associated with mathematics achievement as compared with language achievement and this difference
Conclusions
In Bangladesh, the problem of groundwater contaminated with As has received enormous public health attention because of the diversity of adverse health effects associated with such exposure. It is now clear that many of these same regions have excessive concentrations of Mn in the well water. However, elevated levels of Mn have received very little attention from the government and development agencies. The British Geological Survey found 35% of the samples collected from various parts of the
Conflict of interest statement
The authors declare that they have no actual or potential competing financial interests.
Acknowledgements
This work was supported by National Institute of Environmental Health Sciences grants P42 ES 10349 and P30 ES 09089, and a training grant (5D43TW005724) from the Fogarty International Center.
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