Long term neurocognitive impact of low dose prenatal methylmercury exposure in Hong Kong

• Published in: Environment international Vol. 54; pp. 59 - 64
• Main Authors: Lam, Hugh Simon, Kwok, Ka Ming, Chan, Peggy Hiu Ying, So, Hung Kwan, Li, Albert Martin, Ng, Pak Cheung, Fok, Tai Fai
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2013; Elsevier
• Subjects: Adolescent; Behavior; Biological and medical sciences; blood; boys; Chemical and industrial products toxicology. Toxic occupational diseases; Child; Child, Preschool; Childhood; children; China; chronic exposure; cognition; Cognition Disorders - epidemiology; Diet - statistics & numerical data; Environment. Living conditions; Environmental Exposure - statistics & numerical data; Environmental Pollutants - blood; Environmental Pollutants - metabolism; Environmental pollutants toxicology; Female; Fetal Blood - metabolism; fish consumption; Hong Kong - epidemiology; Humans; Intelligence Tests; Learning; Low dose prenatal mercury exposure; Male; Maternal Exposure - statistics & numerical data; Medical sciences; memory; Memory - drug effects; mercury; Mercury - blood; Mercury - toxicity; Metals and various inorganic compounds; Methylmercury; methylmercury compounds; Methylmercury Compounds - blood; Methylmercury Compounds - metabolism; Methylmercury Compounds - toxicity; mothers; multivariate analysis; Neurocognitive outcomes; Pregnancy; Prenatal Exposure Delayed Effects - epidemiology; Public health. Hygiene; Public health. Hygiene-occupational medicine; Seafood - statistics & numerical data; Toxicology; Verbal memory; Wechsler Scales; Hong Kong; Asia; China; Verbal memory; HK-WISC; TEACH; Childhood; Methylmercury; HKLLT; Low dose prenatal mercury exposure; Neurocognitive outcomes; Human; Prognosis; Toxicity; Low dose; Memory; Exposure; Long term; Heavy metal; Prenatal; Mercury Organic compounds; Child
• ISSN: 0160-4120; 1873-6750; 1873-6750
• DOI: 10.1016/j.envint.2013.01.005

International studies suggest that low dose prenatal methylmercury exposure (>29nmol/L) has long-term adverse neurocognitive effects. There is evidence that the majority of children in Hong Kong exceed this level as a result of high fish consumption of mothers during pregnancy. To study whether there are any associations between low-dose prenatal methylmercury exposure and neurocognitive outcomes in Hong Kong children. All 1057 children from the original birth cohort were eligible for entry into the study, except children with conditions that would affect neurocognitive development, but were unrelated to methylmercury exposure. Subjects were assessed by a wide panel of tests covering a broad range of neurocognitive functions: Hong Kong Wechsler Intelligence Scale for Children (HK-WISC), Hong Kong List Learning Test (HKLLT), Tests of Everyday Attention for Children (TEACH), Boston Naming Test, and Grooved Pegboard Test. 608 subjects were recruited (median age 8.2years, IQR 7.3, 8.8; 53.9% boys). After correction by confounders including child age and sex, multivariate analysis showed that cord blood mercury concentration was significantly associated with three subtests: Picture Arrangement of HK-WISC (coefficient −0.944, P=0.049) and Short and Long Delay Recall Difference of the HKLLT (coefficient −1.087, P=0.007 and coefficient −1.161, P=0.005, respectively), i.e., performance worsened with increasing prenatal methylmercury exposure in these subtests. Small, but statistically significant adverse associations between prenatal methylmercury exposure and long-term neurocognitive effects (a visual sequencing task and retention ability of verbal memory) were found in our study. These effects are compatible with findings of studies with higher prenatal methylmercury exposure levels and suggest that safe strategies to further reduce exposure levels in Hong Kong are desirable. ► The majority of Hong Kong children are exposed to >29nmol/L mercury in cord blood. ► Prenatal mercury exposure was adversely associated with a visual sequencing task and verbal memory subtests. ► Adverse effects of prenatal mercury exposure at lower doses than previously shown.