Chapter 21: Cognitive Effects of Manganese in Children and Adults

The interest in cognitive effects associated with manganese (Mn) exposure has constantly grown in the last 20 years. Mn is an essential element for humans, but concentrations even slightly exceeding the homeostatic range can affect cognition, especially in sensitive early life exposure windows. Exposure to Mn may impact adults and children differently, as based on different mechanisms. This chapter summarizes the main findings about the effect of manganese on specific cognitive domains, both in children and in adults, occupationally or environmentally exposed. A reduction of the intelligent quotient as a general cognitive deficit, and impairment of executive functions, memory, academic achievement, and mental development have been shown as a result of early life exposure to Mn. These outcomes are mainly related to high Mn content in drinking water but also to Mn airborne emission from ferroalloy and mining operations. New data on Mn exposure of pregnant mothers are also available as a result of the application of Mn-based fungicides. Adult studies have shown Mn-related effects on attention, memory, perceptual and motor speed, and visuospatial scanning abilities. The exposure route for adults is inhalation, from direct occupational exposure such as welding or caused by living in the vicinity of industrial emissions.