Effects of Prenatal Exposure to Mercury on Cognitive and Psychomotor Function in One-Year-Old Infants: Epidemiologic Cohort Study in Poland

Chair of Epidemiology and Preventive Medicine, College of Medicine, Jagiellonian University, Krakow, Poland.
Annals of Epidemiology (Impact Factor: 2). 06/2006; 16(6):439-47. DOI: 10.1016/j.annepidem.2005.06.059
Source: PubMed


The aim of the study is to assess the cognitive and psychomotor status of 1-year-old infants whose mothers were exposed to low, but varying, amounts of mercury during pregnancy.
Mercury levels in cord and maternal blood at delivery were used to assess prenatal environmental exposure to mercury. Bayley Scales of Infant Development were used to assess neurobehavioral health outcomes. The cohort consisted of 233 infants who were born at 33 to 42 weeks of gestation between January 2001 and March 2003 to mothers attending ambulatory prenatal clinics in the first and second trimesters of pregnancy. Enrollment included only nonsmoking women with singleton pregnancies between the ages of 18 and 35 years who were free from chronic diseases.
The geometric mean (GM) for maternal blood mercury level for the group of infants with normal neurocognitive performance was lower (GM = 0.52 mug/L; 95% confidence interval [CI], 0.46-0.58) than that observed in the group with delayed performance (GM = 0.75 mug/L; 95% CI, 0.59-0.94), and this difference was significant (p = 0.010). The GM of cord blood mercury level in the normal group also was lower (GM = 0.85 mug/L; 95% CI, 0.78-0.93) than that observed in the group with delayed performance (GM = 1.05 mug/L; 95% CI, 0.87-1.27), and this difference was of borderline significance (p = 0.070). The relative risk (RR) for delayed performance increased more than threefold (RR = 3.58; 95% CI, 1.40-9.14) if cord blood mercury level was greater than 0.80 mug/L. Risk for delayed performance in the group of infants with greater maternal mercury levels (>0.50 mug/L) also was significantly greater (RR = 2.82; 95% CI, 1.17-6.79) compared with children whose mothers had mercury levels less than 0.50 mug/L.
The results may be of public health importance because delayed psychomotor or mental performance in infants is assumed to be an indicator of later neurocognitive development in children, which may persist into adult life.

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Available from: Wieslaw Jedrychowski, Sep 30, 2014
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    ABSTRACT: This paper estimates the effects of exposure to environmental factors, including lead, mercury, environmental tobacco smoke (ETS), and polycyclic aromatic hydrocarbons (PAH), on child psychomotor development. The study population consists of mother-child pairs in the Polish Mother and Child Cohort Study. Prenatal and postnatal exposure to environmental factors was determined from biomarker measurements as follows: for lead exposure-cord blood lead level, for mercury-maternal hair mercury level, for ETS-cotinine level in saliva and urine, and for PAH-1-hydroxypyrene (1-HP) in urine. At the age of 12 (406 subjects) and 24 months (198 subjects) children were assessed using Bayley Scales of Infant and Toddler Development. There were no statistically significant effects of prenatal exposure to mercury or 1-HP on child psychomotor development. After adjusting for potential confounders, adverse effects of prenatal exposure to ETS on motor development ( β = -2.6; P = 0.02) and postnatal exposure to ETS on cognitive ( β = -0.2; P = 0.05) and motor functions ( β = -0.5; P = 0.01) were found. The adverse effect of prenatal lead exposure on cognitive score was of borderline significance ( β = -6.2; P = 0.06). The study underscores the importance of policies and public health interventions that aim to reduce prenatal and postnatal exposure to lead and ETS.
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    • "It is postulated that mercury binds to haemoglobin and glutathione in red blood cells, and since foetuses have higher haemoglobin levels than their mothers, they are more likely to have higher mercury levels (Sakamoto et al., 2007; Vahter et al., 2000). Although overall concentrations of mercury in this study were found to be lower when compared with those reported from other countries, there is cause for concern, due to the irreversible neurological damage mercury may cause to the foetus at very low cord blood concentration (0.80 μg/l) (Jedrychowski et al., 2006). "
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