Probability of intellectual disability is associated with soil concentrations of arsenic and lead

► We used a retrospective cohort design with 3988 mother child pairs. ► We identified maternal addresses during pregnancy and soil concentrations of metals. ► We associated soil metal concentrations with intellectual disability (ID) in the children. ► We identified an interaction between soil lead and arsenic. ► The combination of soil lead and arsenic was associated with ID in the child.