Postnatal exposure to methyl mercury from fish consumption: A review and new data from the Seychelles Child Development Study

University of Rochester School of Medicine and Dentistry, Department of Neurology, Rochester, NY, United States.
NeuroToxicology (Impact Factor: 3.38). 06/2009; 30(3):338-49. DOI: 10.1016/j.neuro.2009.01.005
Source: PubMed


Fish is an important source of nutrition worldwide. Fish contain both the neurotoxin methyl mercury (MeHg) and nutrients important for brain development. The developing brain appears to be most sensitive to MeHg toxicity and mothers who consume fish during pregnancy expose their fetus prenatally. Although brain development is most dramatic during fetal life, it continues for years postnatally and additional exposure can occur when a mother breast feeds or the child consumes fish. This raises the possibility that MeHg might influence brain development after birth and thus adversely affect children's developmental outcomes. We reviewed postnatal MeHg exposure and the associations that have been published to determine the issues associated with it and then carried out a series of analyses involving alternative metrics of postnatal MeHg exposure in the Seychelles Child Development Study (SCDS) Main Cohort.
The SCDS is a prospective longitudinal evaluation of prenatal MeHg exposure from fish consumption. The Main Cohort includes 779 subjects on whom recent postnatal exposure data were collected at the 6-, 19-, 29-, 66-, and 107-month evaluations. We examined the association of recent postnatal MeHg exposure with multiple 66- and 107-month outcomes and then used three types of alternative postnatal exposure metrics to examine their association with the children's intelligence quotient (IQ) at 107 months of age.
Recent postnatal exposure at 107 months of age was adversely associated with four endpoints, three in females only. One alternative postnatal metric was beneficially associated with 9-year IQ in males only.
We found several associations between postnatal MeHg biomarkers and children's developmental endpoints. However, as has been the case with prenatal MeHg exposure in the SCDS Main Cohort study, no consistent pattern of associations emerged to support a causal relationship.

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    • "The data we reported upon here from the ELEMENT cohort may have an important role in the global effort to understand the public health risks of mercury, especially methylmercury exposure from seafood. To date, decisions have mainly relied upon data from two longitudinal birth cohort studies in the Faroe Islands and Seychelles which address neuropsychological outcomes in relation to current, early-life, and developmental exposures to methylmercury and fish consumption (Davidson et al., 2006; Debes et al., 2006; Myers et al., 2009). The studies differ in many regards (e.g., exposure biomarkers, neurodevelopmental tests, timing of tests, co-stressors, participant diet). "
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    ABSTRACT: Background: Mercury is a global contaminant of concern though little is known about exposures in México. Objectives: To characterize mercury levels in pregnant women, children, and commonly consumed seafood samples. Methods: Use resources of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohorts to measure total mercury levels in archived samples from 348 pregnant women (blood from three trimesters and cord blood), 825 offspring (blood, hair, and urine) and their mothers (hair), and 91 seafood and canned tuna samples from Mexico City. Results: Maternal blood mercury levels correlated across three trimesters and averaged 3.4. μg/L. Cord blood mercury averaged 4.7. μg/L and correlated with maternal blood from trimester 3 (but not trimesters 1 and 2). In children, blood, hair and urine mercury levels correlated and averaged 1.8. μg/L, 0.6. μg/g, and 0.9. μg/L, respectively. Hair mercury was 0.5. μg/g in mothers and correlated with child[U+05F3]s hair. Mean consumption of canned tuna, fresh fish, canned sardine, and shellfish was 3.1, 2.2, 0.5, and 1.0 times per month respectively in pregnant women. Mean mercury content in 7 of 23 seafood species and 5 of 9 canned tuna brands purchased exceeded the U.S. EPA guidance value of 0.3 μg/g. Conclusions: Mercury exposures in pregnant women and children from Mexico City, via biomarker studies, are generally 3-5 times greater than values reported in population surveys from the U.S., Canada, and elsewhere. In particular, mercury levels in 29-39% of the maternal participants exceeded the biomonitoring guideline associated with the U.S. EPA reference dose for mercury.
    Environmental Research 09/2014; 135C:63-69. DOI:10.1016/j.envres.2014.08.029 · 4.37 Impact Factor
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    • "In boys aged 5.5 years postnatal exposure to mercury was associated with changes in visual-spatial orientation (Davidson et al. 1998) and at the age of 9 years with school performance (understanding of the text and mathematics) (Myers et al. 2009). In girls aged 9 postnatal exposure to mercury was inversely associated with intelligence quotient (IQ) (Myers et al. 2009) and at the age of 10.7 years with visualspatial orientation (Davidson et al. 2008). "

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    • "Examples include inhalation of Hg vapor from atmospheric sources or from dental amalgam fillings, and, most importantly, ingestion of fish and shellfish contaminated with Hg, primarily methyl Hg (U.S. ATSDR, 1999; Mahaffey et al., 2009). The health effects of dietary Hg have been studied most extensively with respect to neurodevelopment and cardiovascular endpoints (Grandjean et al., 1999; Guallar et al., 2002; Hallgren et al., 2001; Mozaffarian et al., 2011; Myers et al., 2009; Oken et al., 2008). The epidemiologic evidence is mixed in these cases, in part because of differences in relative Hg and omega-3 fatty acids (FAs) in the available dietary fish. "
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    ABSTRACT: It remains unclear whether exposure to low-level mercury (Hg) is associated with impaired renal function, and whether omega-3 fatty acid (FA) intake could affect the association of interest. The current study examined the association of blood Hg and omega-3 FAs with renal function using data from 1046 subjects aged 40 or above from the 2003-2004 National Health and Nutrition Examination Survey. Kidney function was assessed by estimated glomerular filtration rate (eGFR) and occurrence of albuminuria. Logistic regression analyses were applied to assess the association of interest with confounding variable adjustment. The analyses indicated that blood Hg was associated with reduced eGFR (<60mL/min/1.73m(2)) in a dose-response fashion (p<0.05). The association was particularly apparent with adjustment for blood omega-3 FA levels. The adjusted odds ratio for having reduced eGFR was 2.94 (95% confidence interval=1.04-8.33) in the highest tertile of blood Hg as compared with the lowest tertile. There was no significant association between Hg exposure and albuminuria. In summary, this study demonstrates that Hg exposure is associated with increased odds of having lower GFR in the US population aged 40 or above. A statistical association with albuminuria was not apparent. We also observed that omega-3 FA intake may play a preventive role in Hg-induced nephrotoxicity. Additional studies are warranted to determine the sources, exposure routes, and forms of Hg most responsible for observed associations.
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