Fish consumption, mercury exposure, and their associations with scholastic achievement in the Seychelles Child Development Study

University of Rochester, School of Medicine and Dentistry, Department of Pediatrics, Rochester, NY 14642, USA.
NeuroToxicology (Impact Factor: 3.38). 09/2010; 31(5):439-47. DOI: 10.1016/j.neuro.2010.05.010
Source: PubMed


Studies of neurodevelopmental outcomes in offspring exposed to MeHg from maternal consumption of fish have primarily measured cognitive abilities. Reported associations have been subtle and in both adverse and beneficial directions. Changes in functional outcomes such as school achievement and behavior in exposed children and adolescents have not been examined. We undertook an assessment of school success of children in the Seychelles Child Development Study (SCDS) main cohort to determine if there were any associations with either prenatal or recent postnatal MeHg exposure. The primary endpoints were Seychelles nationally standardized end-of-year examinations given when the cohort children were 9 and 17 years of age. A subgroup (n=215) from the main cohort was also examined at 9 years of age using a regional achievement test called SACMEQ. Prenatal MeHg exposure was 6.8 ppm in maternal hair; recent postnatal exposure was 6.09 ppm at 9 years and 8.0 ppm at 17 years, measured in child hair. Multiple linear regression analyses showed no pattern of associations between prenatal or postnatal exposure, and either the 9- or 17-year end-of-year examination scores. For the subgroup of 215 subjects who participated in the SACMEQ test, there were significant adverse associations between examination scores and postnatal exposure, but only for males. The average postnatal exposure level in child hair for this subgroup was significantly higher than for the overall cohort. These results are consistent with our earlier studies and support the interpretation that prenatal MeHg exposure at dosages achieved by mothers consuming a diet high in fish are not associated with adverse educational measures of scholastic achievement. The adverse association of educational measures with postnatal exposure in males is intriguing, but will need to be confirmed by further studies examining factors that influence scholastic achievement.

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    • "In mammals, MeHg is a strong neurotoxicant, particularly affecting the developing nervous system, and has been associated with neurological problems (Davidson et al., 2010). The cytotoxicity of MeHg has been attributed to disturbance of intracellular Ca 2+ levels, induction of oxidative stress or by disrupting function of proteins and peptides containing cysteine and methionine (Ceccatelli et al., 2010). "
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    ABSTRACT: Selenium (Se) and its derivatives are known to have protective effects against mercury (Hg) toxicity in mammals. In this study we wanted to evaluate whether Se co-exposure affect the transcription of methylmercury (MeHg) toxicity-relevant genes in early life stages of fish. Juvenile Atlantic cod were exposed to regular feed (control), Se-spiked feed (3mg Sekg(-1)), MeHg-spiked feed (10mg Hgkg(-1)) or to Se- and MeHg-spiked feed (3mg Sekg(-1) and 10mg Hgkg(-1), respectively) for ten weeks. Liver tissue was harvested for transcriptional analysis when the fish were weighing 11.4±3.2g. Accumulated levels of Hg in liver of the two groups of fish exposed to MeHg were 1.5mg Hgkg(-1) wet weight, or 44-fold higher than in the control group, while the Se concentrations differed with less than 2-fold between the fish groups. Selenium co-exposure had no effect on the accumulated levels of Hg in liver tissue; however, MeHg co-exposure reduced the accumulated level of Se. Dietary exposure to MeHg had no effect on fish growth. Interaction effects between Se and MeHg exposure were observed for the transcriptional levels of CAT, GPX1, GPX3, NFE2L2, UBA52, SEPP1 and DNMT1. Significant effects of MeHg exposure were seen for DNMT1 and PPARG, while effects of Se exposure were seen for GPX4B and SEPP1A, as well as for DNA methyltransferase activity. The transcriptional results suggest, by considering up-regulation as a proxy for negative impact and at the tested concentrations, a pro-oxidative effect of Se co-exposure with MeHg, rather than an antioxidative effect.
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    • "Longitudinal exposure to mercury was also evaluated in the Seychelles cohort. Mercury was analysed in hair samples from the prenatal period (maternal hair) to age 9 and 17 years (Davidson et al., 2010). A slight decreasing trend was observed from birth (6.8 ppm) to age 9 (6.09 "
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    ABSTRACT: The purpose of this study is to describe the total hair mercury concentrations and their determinants in preschool Spanish children, as well as to explore the trend in mercury exposure from birth to the age four. This evolution has been scarcely studied in other birth cohort studies. The study population was 580 four year old children participating in the INMA (i.e. Childhood and Environment) birth cohort study in Valencia (2008-2009). Total mercury concentration at age four was measured in hair samples by atomic absorption spectrometry. Fish consumption and other covariates were obtained by questionnaire. Multivariate linear regression models were conducted in order to explore the association between mercury exposure and fish consumption, socio-demographic characteristics and prenatal exposure to mercury. The geometric mean was 1.10µg/g (95%CI: 1.02, 1.19). Nineteen percent of children had mercury concentrations above the equivalent to the Provisional Tolerable Weekly Intake proposed by WHO. Mercury concentration was associated with increasing maternal age, fish consumption and cord blood mercury levels, as well as decreasing parity. Children whose mothers worked had higher mercury levels than those with non working mothers. Swordfish, lean fish and canned fish were the fish categories most associated with hair mercury concentrations. We observed a decreasing trend in mercury concentrations between birth and age four. In conclusion, the children participating in this study had high hair mercury concentrations compared to reported studies on children from other European countries and similar to other countries with high fish consumption. The INMA study design allows the evaluation of the exposure to mercury longitudinally and enables this information to be used for biomonitoring purposes and dietary recommendations.
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    • "In some studies boys seem to be more affected (Grandjean et al. 1998, Gao et al. 2007, Davidson et al. 2010), in others girls (Davidson et al. 1998, 2008). There are similar results of experimental studies on laboratory animals exposed to mercury. "

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