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1.
Environ Res ; 200: 111744, 2021 09.
Article in English | MEDLINE | ID: mdl-34310966

ABSTRACT

BACKGROUND: Although several epidemiological studies have suggested mercury (Hg) might be associated with cardiotoxicity, the impact of Hg exposure on cardiac autonomic activity and blood pressure in children has not been investigated at Hg exposure levels equivalent to the Environmental Protection Agency (EPA) reference dose. OBJECTIVE: To investigate the association between low dose prenatal and recent methylmercury (MeHg) exposures and cardiac autonomic function and blood pressure with adjustment for factors such as fish consumption among children from a high fish consumption coastal city. METHODS: Children aged 7-8 years were recruited from the birth cohort of our previous study. Heart rate variability (HRV), resting heart rate (RHR) and blood pressure were measured as surrogate markers of cardiac autonomic function. Cord blood and current whole blood Hg concentration were used as biomarkers of prenatal and recent MeHg exposure, respectively. Recent fish consumption information was estimated with a food frequency questionnaire. RESULTS: Among 604 children, median cord blood and whole blood Hg concentrations were 45.9 nmol/L (IQR: 32.8-65.03 nmol/L) and 13.57 nmol/L (IQR: 9.29-19.72 nmol/L), respectively. Our results demonstrated that prenatal MeHg exposure was associated with decreased HRV (i.e. low CVRR, SDRR, and RMSSD), reflecting reduced parasympathetic activity (i.e. low CCVHF and HF), and a sympathovagal balance shift toward sympathetic predominance (i.e. high %LF and LF/HF ratio). Adjustment of recent fish consumption further increased the significance and magnitude of the adverse associations of MeHg. CONCLUSION: The results of this study suggest that prenatal MeHg exposure is associated with decreased parasympathetic modulation of cardiac autonomic function in children.


Subject(s)
Mercury , Methylmercury Compounds , Animals , Blood Pressure , Child , Female , Fishes , Heart Rate , Humans , Methylmercury Compounds/toxicity , Pregnancy
2.
Environ Res ; 144(Pt A): 66-72, 2016 Jan.
Article in English | MEDLINE | ID: mdl-26562044

ABSTRACT

BACKGROUND: Mercury exposure have been shown to affect immune status in animals as reflected by cytokine expression. It is unclear whether low levels of exposure during fetal and/or childhood periods could impact on immune status in humans. OBJECTIVES: To test the hypothesis that fetal and childhood mercury exposure is associated with childhood cytokine profiles and to investigate whether childhood selenium levels interact with any of the associations found. METHODS: Children were recruited from a previously established birth cohort between the ages of 6-9 years for assessment and measurement of blood mercury, selenium and cytokine profile (interleukin (IL)-4, IL-6, IL-8, IL-10, IL-13 and TNF-alpha). Multivariable linear regression models were used to assess the adjusted association of cord blood mercury concentration and current mercury concentrations with levels of the cytokine levels. We tested whether the association with current mercury level varied by current selenium level and cord blood mercury level. RESULTS: IL-10 was negatively associated with current blood mercury concentration. The effect was greatest in cases with low cord blood mercury and low current selenium concentrations. None of the other cytokine levels were associated with either cord blood or current blood mercury concentrations, except that cord blood mercury was negatively associated with IL-6. CONCLUSIONS: Childhood mercury exposure was negatively associated with childhood IL-10 levels. It is postulated that while selenium is protective, low levels of fetal mercury exposure may increase the degree of this negative association during childhood. Further studies into the clinical significance of these findings are required.


Subject(s)
Cytokines/blood , Environmental Pollutants/blood , Mercury/blood , Child , Environmental Exposure , Female , Fetal Blood/chemistry , Fetus , Humans , Male , Pregnancy , Selenium/blood
3.
Environ Int ; 54: 59-64, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23416249

ABSTRACT

BACKGROUND: International studies suggest that low dose prenatal methylmercury exposure (>29 nmol/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. OBJECTIVE: To study whether there are any associations between low-dose prenatal methylmercury exposure and neurocognitive outcomes in Hong Kong children. MATERIALS AND METHODS: 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. RESULTS: 608 subjects were recruited (median age 8.2 years, 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. CONCLUSIONS: 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.


Subject(s)
Cognition Disorders/epidemiology , Environmental Exposure/statistics & numerical data , Environmental Pollutants/metabolism , Methylmercury Compounds/metabolism , Prenatal Exposure Delayed Effects/epidemiology , Adolescent , Behavior , Child , Child, Preschool , Diet/statistics & numerical data , Environmental Pollutants/blood , Female , Fetal Blood/metabolism , Hong Kong/epidemiology , Humans , Intelligence Tests , Learning , Male , Maternal Exposure/statistics & numerical data , Memory/drug effects , Mercury/blood , Mercury/toxicity , Methylmercury Compounds/blood , Methylmercury Compounds/toxicity , Pregnancy , Seafood/statistics & numerical data , Wechsler Scales
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