Academic journal article Environmental Health Perspectives

Arsenic Exposure and Motor Function among Children in Bangladesh

Academic journal article Environmental Health Perspectives

Arsenic Exposure and Motor Function among Children in Bangladesh

Article excerpt

BACKGROUND: Several reports indicate that drinking water arsenic (WAs) and manganese (WMn) are associated with children's intellectual function. Very little is known, however, about possible associations with other neurologic outcomes such as motor function.

METHODS: We investigated the associations of WAs and WMn with motor function in 304 children in Bangladesh, 8--11 years of age. We measured As and Mn concentrations in drinking water, blood, urine, and toenails. We assessed motor function with the Bruininks-Oseretsky test, version 2, in four subscales--fine manual control (FMC), manual coordination (MC), body coordination (BC), and strength and agility--which can be summarized with a total motor composite score (TMC).

RESULTS: Log-transformed blood As was associated with decreases in TMC [[beta] = -3.63; 95% confidence interval (CI): -6.72, -0.54; p < 0.01], FMC ([beta] = -1 68; 95% CI: -3.19, -0.18; p < 0.05), and

BC ([beta] = -1.61; 95% CI: -2.72, -0.51; p < 0.01), with adjustment for sex, school attendance, head circumference, mother's intelligence, plasma ferritin, and blood Mn, lead, and selenium. Other measures of As exposure (WAs, urinary As, and toenail As) also were inversely associated with motor function scores, particularly TMC and BC. Square-transformed blood selenium was positively associated with TMC ([beta] = 3.54; 95% CI: 1.10, 6.0; p < 0.01), FMC ([beta] = 1.55; 95% CI. 0.40, 2.70; p < 0.005), and MC [beta] = 1.57; 95% CI: 0.60, 2.75; p < 0.005) in the unadjusted models. Mn exposure was not significantly associated with motor function.

CONCLUSION: Our research demonstrates an adverse association of As exposure and a protectiveassociation of Se on motor function in children.

KEY WORDS: arsenic, Bangladesh, bodily coordination, fine motor control, manganese, motorfunction, neurotoxicity, selenium. Environ Health Perspect 119:1665-1670 (2011). http://dx.doi.org/10.1289/ehp.1103548 [Online 8 July 2011]

Epidemiologic evidence of neurotoxicity associated with arsenic (As) exposure from occupational sources or via drinking water is well documented (Hafeman et al. 2005; Mukherjee et al. 2003; Rahman et al. 2001; Tseng et al. 2006). In the past decade, studies from China (Wang et al. 2007), Mexico (Calderon et al. 2001; Rosado et al. 2007), India (von Ehrenstein et al. 2007), and Taiwan (Tseng et al. 2006) have also demonstrated evidence of an impact on cognitive development, reflected in lower intelligence scores, deficits in long-term memory, and delayed linguistic abstraction among children exposed to As from drinking water. We previously described lower intellectual functioning among children exposed to low to moderate levels of drinking water As (WAs) in two separate studies in Bangladesh (Wasserman et al. 2004, 2007). Recent studies have also reported evidence of manganese (Mn)-induced neurotoxicity in children (Bouchard et al. 2007; Wasserman et al. 2006; Wright et al. 2006). For instance, we observed deficits in intellectual functioning among children exposed to elevated Mn in drinking water in Bangladesh (Wasserman et al. 2006), and in Korea children with higher blood Mn (BMn received lower intelligence test scores (Kim et al. 2009). In a small study of U.S. children living on a former mining site, those with higher hair As and Mn performed less well in cognitive tests (Wright et al. 2006).

Until now, most epidemiologic studies have focused on impaired cognitive function as a measure of neurotoxicity in children exposed to As. Other developmental outcomes, such as motor function, have largely been ignored. Several reports have noted evidence of As-induced neurotoxicity, including peripheral neuropathy, in adults (Hafeman et al. 2005; Mukherjee et al. 2003). A recent cross-sectional study of Taiwanese adolescents reported adverse associations between WAs and several measures of motor and sensory nerve peripheral conduction (Tseng et al. …

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