title: Iron status as a covariate in methylmercury-associated neurotoxicity risk.
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.
authors.affiliation: 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.
authors.forename: Márlon de Freitas
authors.initials: Mde F
authors.lastname: Fonseca
authors.affiliation: 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.
authors.forename: Sandra
authors.initials: S
authors.lastname: De Souza Hacon
authors.affiliation: 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.
authors.forename: Philippe
authors.initials: P
authors.lastname: Grandjean
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, 401 Park Drive, Landmark Center Room 3-110 East, Boston, MA 02215, USA.
authors.forename: Anna Lai
authors.initials: AL
authors.lastname: Choi
authors.affiliation: 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.
authors.forename: Wanderley Rodrigues
authors.initials: WR
authors.lastname: Bastos
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D000818:Animals; D001938:Brazil; D002648:Child; D016000:Cluster Analysis; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D005399:Fishes / Q000378:metabolism; D006197:Hair / Q000737:chemistry; D006801:Humans; D007501:Iron / Q000378:metabolism*; D016014:Linear Models; D008767:Methylmercury Compounds / Q000633:toxicity*; D008875:Middle Aged; D009498:Neurotoxins / Q000633:toxicity*; D011247:Pregnancy; D018570:Risk Assessment; D045483:Rivers / Q000737:chemistry; D055815:Young Adult
chemical_list: D008767:Methylmercury Compounds; D009498:Neurotoxins; D007501:Iron
keywords: Amazon; Fertile women; Fish consumption; Iron stores; Mercury; Negative confounding