Elias C Nyanza1, Francois P Bernier2, Jonathan W Martin3, Mange Manyama4, Jennifer Hatfield5, Deborah Dewey6. 1. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada; Department of Environmental, Occupational Health and GIS, School of Public Health, Catholic University of Health and Allied Sciences, P.O. Box 1464, Bugando, Mwanza, Tanzania. 2. Department of Paediatrics, University of Calgary, Alberta Children's Hospital, 28 Oki Drive NW, Calgary, AB T3B 6A8, Canada; Department of Medical Genetics, Cumming School of Medicine, 3330 Hospital Drive NW University of Calgary, Canada; Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Room 294, Heritage Medical Research Building, 3330 Hospital Drive, NW Calgary, AB T2N 4N1, Canada. 3. Science for Life Laboratory, Department of Environmental Science, Stockholm University, 106 91 Stockholm, Sweden; Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2R3, Canada. 4. Division of Medical Education, Weill-Cornell Medicine-Qatar, Doha, Qatar. 5. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada. 6. Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada; Department of Paediatrics, University of Calgary, Alberta Children's Hospital, 28 Oki Drive NW, Calgary, AB T3B 6A8, Canada; Department of Medical Genetics, Cumming School of Medicine, 3330 Hospital Drive NW University of Calgary, Canada; Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Room 294, Heritage Medical Research Building, 3330 Hospital Drive, NW Calgary, AB T2N 4N1, Canada; Owerko Centre, #397 Child Development Centre, University of Calgary, 2500 University Dr. NW Calgary, AB T2N 1N4, Canada. Electronic address: dmdewey@ucalgary.ca.
Abstract
BACKGROUND: Artisanal and small-scale gold mining (ASGM) is associated with release of neurotoxic metallic or metalloid chemical elements including lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As). OBJECTIVE: To examine associations between prenatal exposure and co-exposure to total lead (T-Pb), total mercury (T-Hg), total cadmium (T-Cd) and total arsenic (T-As) and infant neurodevelopment at 6 to 12 months of age in areas with ASGM activities in Tanzania. METHODS: Women in their second trimester of pregnancy who resided in ASGM areas were enrolled from 2015 to 2017 (n = 883). At 6 to 12 months of age, children were assessed with the Malawi Developmental Assessment Tool (MDAT) (n = 439). We measured T-Pb, T-Hg, and T-Cd in maternal dried blood spots and T-As in maternal urines. Poisson regression was used to examine associations between prenatal concentrations of these elements and neurodevelopmental outcomes. RESULTS: Prenatal T-Hg concentration was associated with global neurodevelopment status (aPR 1.03, CI:1.01-1.04; p < 0.001) and language impairment (aPR 1.05, CI:1.03-1.07; p < 0.001) on the MDAT. When prenatal T-Hg and T-As values were at or above the human biomonitoring reference values (≥95%) of the German Environmental Survey for Human Biomonitoring, that is 0.80 µg/L and 15 µg/L, respectively, the prevalence ratio of global neurodevelopmental impairment was two times higher (aPR 2.1, CI:1.0-4.3; p = 0.034). There was a 40% increase in the prevalence ratio of global neurodevelopmental impairment (aPR 1.4, CI:0.90-2.10, p = 0.027), when prenatal T-Hg was at or above the reference value of 0.80 µg/L and T-Pb was at or above the reference value of 35 µg/L. When prenatal T-Hg was at or above the reference value of 0.80 µg/L and T-As was at or above the reference value of 15 µg/L, the prevalence ratio of global neurodevelopmental impairment was two times higher (aPR 2.1, CI:1.0-4.3; p < 0.034). DISCUSSION: Infants born to women in areas with ASGM activities are at significant risk for neurodevelopmental impairment and this is associated with exposure to higher concentrations of Hg prenatally. Co-exposure to high concentrations of Hg and Pb, or Hg and As appeared to have negative potentiated effects on infants' neurodevelopment.
BACKGROUND: Artisanal and small-scale gold mining (ASGM) is associated with release of neurotoxic metallic or metalloid chemical elements including lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As). OBJECTIVE: To examine associations between prenatal exposure and co-exposure to total lead (T-Pb), total mercury (T-Hg), total cadmium (T-Cd) and total arsenic (T-As) and infant neurodevelopment at 6 to 12 months of age in areas with ASGM activities in Tanzania. METHODS:Women in their second trimester of pregnancy who resided in ASGM areas were enrolled from 2015 to 2017 (n = 883). At 6 to 12 months of age, children were assessed with the Malawi Developmental Assessment Tool (MDAT) (n = 439). We measured T-Pb, T-Hg, and T-Cd in maternal dried blood spots and T-As in maternal urines. Poisson regression was used to examine associations between prenatal concentrations of these elements and neurodevelopmental outcomes. RESULTS: Prenatal T-Hg concentration was associated with global neurodevelopment status (aPR 1.03, CI:1.01-1.04; p < 0.001) and language impairment (aPR 1.05, CI:1.03-1.07; p < 0.001) on the MDAT. When prenatal T-Hg and T-As values were at or above the human biomonitoring reference values (≥95%) of the German Environmental Survey for Human Biomonitoring, that is 0.80 µg/L and 15 µg/L, respectively, the prevalence ratio of global neurodevelopmental impairment was two times higher (aPR 2.1, CI:1.0-4.3; p = 0.034). There was a 40% increase in the prevalence ratio of global neurodevelopmental impairment (aPR 1.4, CI:0.90-2.10, p = 0.027), when prenatal T-Hg was at or above the reference value of 0.80 µg/L and T-Pb was at or above the reference value of 35 µg/L. When prenatal T-Hg was at or above the reference value of 0.80 µg/L and T-As was at or above the reference value of 15 µg/L, the prevalence ratio of global neurodevelopmental impairment was two times higher (aPR 2.1, CI:1.0-4.3; p < 0.034). DISCUSSION: Infants born to women in areas with ASGM activities are at significant risk for neurodevelopmental impairment and this is associated with exposure to higher concentrations of Hg prenatally. Co-exposure to high concentrations of Hg and Pb, or Hg and As appeared to have negative potentiated effects on infants' neurodevelopment.
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