Academic journal article Environmental Health Perspectives

Manganese in Drinking Water and Cognitive Abilities and Behavior at 10 Years of Age: A Prospective Cohort Study

Academic journal article Environmental Health Perspectives

Manganese in Drinking Water and Cognitive Abilities and Behavior at 10 Years of Age: A Prospective Cohort Study

Article excerpt

Introduction

Manganese (Mn) is an essential element that functions as a cofactor in a number of enzymes and in certain antioxidants, which makes it important during early life development (Mistry and Williams 2011). The primary source of Mn is the diet, which usually provides the required 3.0 mg/d for pregnant women and 0.52.0 mg/d for children (EFSA 2013). Excess exposure through drinking water is common worldwide (Frisbie et al. 2012; Ljung and Vahter 2007), and there is increasing concern that such exposure may adversely affect the central nervous system, particularly in children (Frisbie et al. 2012; Zoni and Lucchini 2013). Several cross-sectional studies have indicated that elevated Mn concentrations in drinking water (W-Mn) are associated with impaired cognitive abilities, adaptive behaviors, or both in 6- to 13-year-old children (Bouchard et al. 2011; Khan et al. 2011; Oulhote et al. 2014a; Wasserman et al. 2006). Additional studies indicate associations with blood Mn, often with an inverted U-shaped dose-effect relationship (Sanders et al. 2015). However, there appears to be no association between Mn in water and that in blood (Ljung et al. 2009; Rahman et al. 2015).

The timing of exposure may be critical for Mn neurotoxicity because the susceptibility of the brain to toxic insult is known to vary during different phases of development (Grandjean and Landrigan 2014). In addition, exposure may vary over time. Because Mn easily passes through the placenta (Erikson et al. 2007), elevated maternal exposure during pregnancy, combined with increased gastrointestinal absorption (Takser et al. 2004), may lead to excess fetal exposure. Indeed, a few studies have indicated inverse associations between Mn concentrations in umbilical cord blood and child neurodevelopment (Takser et al. 2003; Yu et al. 2014). Similarly, Mn in tooth dentin measured using microspatial analysis, which estimated prenatal and early postnatal exposure, was associated with adverse neurodevelopmental outcomes (Gunier et al. 2015; Mora et al. 2015). In another study that measured Mn levels in pulverized whole teeth, no association of Mn with neurodevelopmental outcomes was observed (Chan et al. 2015). Early childhood may be another critical period of Mn exposure because regulation of intestinal absorption and biliary excretion is not yet fully developed (Erikson et al. 2007). Although breast milk contains very little Mn (Ljung et al. 2009), introduction of food and drinking water may lead to high-level exposure. The present study aimed to prospectively evaluate potential adverse effects of elevated W-Mn, from fetal life to school age, on cognitive abilities and behavior in a large cohort of boys and girls at 10 y of age. Elevated Mn concentrations were found mainly in medium-deep wells, many of which were constructed to decrease exposure to arsenic (As), which was present in many shallow wells (Kippler et al. 2016; Ljung et al. 2009).

Materials and Methods

Study Area and Population

The study involves a large mother-child cohort, covering early pregnancy to 10yofage. The study was initially nested in a randomized food and micronutrient supplementation trial (MINIMat) conducted in pregnant women living in Matlab, in rural Bangladesh (Persson et al. 2012), to evaluate the health effects of early life exposure to As, which occurs frequently in shallow wells (Vahter et al. 2006). The installation of deeper wells, often with the aim to decrease As exposure, has resulted in elevated W-Mn (Kippler et al. 2016; Ljung et al. 2009), which motivated us to evaluate the potential health consequences. The 1,607 singleton children born within the MINIMat trial between October 2002 and December 2003 were invited for follow-up of child growth and development at 10 y of age, and 95% (n = 1,530) agreed to participate. The main reasons for loss to follow-up were parental refusal and out migration.

This study was approved by the ethics review committee at International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) in Bangladesh and by the Regional Ethical Review Board in Stockholm, Sweden. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.