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Chemosphere. 2014 Apr;100:89-96. doi: 10.1016/j.chemosphere.2013.12.053. Epub 2014 Jan 8.

Iron status as a covariate in methylmercury-associated neurotoxicity risk.

Author information

1
Instituto Fernandes Figueira, Fundação Oswaldo Cruz, Av. Rui Barbosa 716, Flamengo, Rio de Janeiro, RJ 22250-020, Brazil; Department of Environmental Health, Harvard School of Public Health, 401 Park Drive, Landmark Center Room 3-110 East, Boston, MA 02215, USA. Electronic address: marlon@iff.fiocruz.br.
2
Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz, Av. Brasil 4365, Manguinhos, Rio de Janeiro, RJ 21040-900, Brazil. Electronic address: sandrahacon@gmail.com.
3
Department of Environmental Health, Harvard School of Public Health, 401 Park Drive, Landmark Center Room 3-110 East, Boston, MA 02215, USA; Institute of Public Health, University of Southern Denmark, J.B. Winsløws Vej 17A/2, DK-5000 Odense C, Denmark. Electronic address: pgrand@hsph.harvard.edu.
4
Department of Environmental Health, Harvard School of Public Health, 401 Park Drive, Landmark Center Room 3-110 East, Boston, MA 02215, USA.
5
Laboratório de Biogeoquímica Ambiental Wolfgang Christian Pfeiffer, Universidade Federal de Rondônia, Rodovia BR 364 Km 9,5 Sentido Acre, Zona Rural, Porto Velho, RO 76801-974, Brazil. Electronic address: wanderbastos@yahoo.com.br.

Abstract

Intrauterine methylmercury exposure and prenatal iron deficiency negatively affect offspring's brain development. Since fish is a major source of both methylmercury and iron, occurrence of negative confounding may affect the interpretation of studies concerning cognition. We assessed relationships between methylmercury exposure and iron-status in childbearing females from a population naturally exposed to methylmercury through fish intake (Amazon). We concluded a census (refuse <20%) collecting samples from 274 healthy females (12-49 years) for hair-mercury determination and assessed iron-status through red cell tests and determination of serum ferritin and iron. Reactive C protein and thyroid hormones was used for excluding inflammation and severe thyroid dysfunctions that could affect results. We assessed the association between iron-status and hair-mercury by bivariate correlation analysis and also by different multivariate models: linear regression (to check trends); hierarchical agglomerative clustering method (groups of variables correlated with each other); and factor analysis (to examine redundancy or duplication from a set of correlated variables). Hair-mercury correlated weakly with mean corpuscular volume (r=.141; P=.020) and corpuscular hemoglobin (r=.132; .029), but not with the best biomarker of iron-status, ferritin (r=.037; P=.545). In the linear regression analysis, methylmercury exposure showed weak association with age-adjusted ferritin; age had a significant coefficient (Beta=.015; 95% CI: .003-.027; P=.016) but ferritin did not (Beta=.034; 95% CI: -.147 to .216; P=.711). In the hierarchical agglomerative clustering method, hair-mercury and iron-status showed the smallest similarities. Regarding factor analysis, iron-status and hair-mercury loaded different uncorrelated components. We concluded that iron-status and methylmercury exposure probably occur in an independent way.

KEYWORDS:

Amazon; Fertile women; Fish consumption; Iron stores; Mercury; Negative confounding

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