Effects of prenatal exposure and co-exposure to metallic or metalloid elements on early infant neurodevelopmental outcomes in areas with small-scale gold mining activities in Northern Tanzania

•Infants in mining communities in Tanzania are exposed prenatally to Pb, Hg, Cd and As.•31% of infants in these mining communities displayed neurodevelopmental impairment.•Higher levels of prenatal exposure to Hg increased the risk of neurodevelopmental impairment.•Co-exposure to As and Pb potentiated the adverse effects of prenatal Hg exposure. 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). 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. 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. Prenatal T-Hg concentration was associated with global neurodevelopment status (aPR 1.03, CI:1.01–1.04; p