Health & Medical Environmental

Dietary Predictors of Maternal Prenatal Blood Mercury Levels

´╗┐Dietary Predictors of Maternal Prenatal Blood Mercury Levels

Abstract and Introduction

Abstract


Background: Very high levels of prenatal maternal mercury have adverse effects on the developing fetal brain. It has been suggested that all possible sources of mercury should be avoided. However, although seafood is a known source of mercury, little is known about other dietary components that contribute to the overall levels of blood mercury.

Objective: Our goal was to quantify the contribution of components of maternal diet to prenatal blood mercury level.

Methods: Whole blood samples and information on diet and sociodemographic factors were collected from pregnant women (n = 4,484) enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). The blood samples were assayed for total mercury using inductively coupled plasma dynamic reaction cell mass spectrometry. Linear regression was used to estimate the relative contributions of 103 dietary variables and 6 sociodemographic characteristics to whole blood total mercury levels (TBM; untransformed and log-transformed) based on R values.

Results: We estimated that maternal diet accounted for 19.8% of the total variation in ln-TBM, with 44% of diet-associated variability (8.75% of the total variation) associated with seafood consumption (white fish, oily fish, and shellfish). Other dietary components positively associated with TBM included wine and herbal teas, and components with significant negative associations included white bread, meat pies or pasties, and french fries.

Conclusions: Although seafood is a source of dietary mercury, seafood appeared to explain a relatively small proportion of the variation in TBM in our UK study population. Our findings require confirmation, but suggest that limiting seafood intake during pregnancy may have a limited impact on prenatal blood mercury levels.

Introduction


Concerns about adverse health effects of mercury exposure during fetal development stem in part from well-documented episodes of mass mercury poisoning from consuming food items grossly contaminated with mercury released into Minamata Bay in the 1950s and from consumption of wheat seed treated with mercury-based fungicides in the 1970s (D'ltri and D'ltri 1978). There have been reports of adverse reproductive effects of mercury, including infertility and miscarriage (Choy et al. 2002; Harada 1995), and of prenatal exposure being positively associated with blood pressure in children at 7 years of age (Sorensen et al. 1999), but the major concern has been the possible effect of prenatal mercury exposure on the brain of the developing fetus (Holmes et al. 2009). However, little research has been done on chronic exposures at low doses. In a cohort study conducted in the Faroe Islands (Grandjean et al. 1997), where seafood exposure was mainly from pilot whale consumption, 979 children were tested at 7 years of age and results compared with cord blood mercury levels; higher mercury levels were associated with subtle deficits in verbal development in language, attention, and memory. On the basis mostly of these findings, the U.S. National Research Council (NRC 2000) established a reference dose level of 5.8 ╬╝g/L of mercury in cord blood. Although advisories intended to reduce fetal exposure to mercury have concentrated on reducing maternal consumption of seafood (U.S. Food and Drug Administration 2004), adverse associations between prenatal maternal seafood consumption and childhood cognition have not been replicated by studies conducted in the Seychelles (Davidson et al. 1998, 2008, 2010), the United Kingdom (Hibbeln et al. 2007), Denmark (Oken et al. 2008), the Faroe Islands (Choi et al. 2008), and the United States (Lederman et al. 2008).

The primary goal of the present study is to evaluate the assumption that seafood consumption is a major contributor to maternal blood levels of mercury. We take advantage of a major British birth cohort survey (ALSPAC; Avon Longitudinal Study of Parents and Children), which collected blood samples and dietary and sociodemographic information from 4,484 mothers in early pregnancy. The main questions to be addressed are a) How much does seafood contribute to prenatal blood mercury levels? and b) How much do other dietary sources contribute to prenatal blood mercury?

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