This study investigates the impact of environmental chemicals on oligodendrocyte development, a critical process for nervous system function. Using a high-throughput developmental screen in cultured cells, the authors identified two classes of chemicals that disrupt oligodendrocyte development: quaternary compounds and organophosphate flame retardants. Quaternary compounds, commonly found in disinfectants and personal care products, were found to be cytotoxic to developing oligodendrocytes, while organophosphate flame retardants arrested oligodendrocyte maturation. These chemicals impaired oligodendrocyte development in both mice and a human 3D organoid model. Epidemiological data showed that childhood exposure to organophosphate flame retardants was associated with adverse neurodevelopmental outcomes. The study highlights the need for further research to understand the full impact of these chemicals on human health.This study investigates the impact of environmental chemicals on oligodendrocyte development, a critical process for nervous system function. Using a high-throughput developmental screen in cultured cells, the authors identified two classes of chemicals that disrupt oligodendrocyte development: quaternary compounds and organophosphate flame retardants. Quaternary compounds, commonly found in disinfectants and personal care products, were found to be cytotoxic to developing oligodendrocytes, while organophosphate flame retardants arrested oligodendrocyte maturation. These chemicals impaired oligodendrocyte development in both mice and a human 3D organoid model. Epidemiological data showed that childhood exposure to organophosphate flame retardants was associated with adverse neurodevelopmental outcomes. The study highlights the need for further research to understand the full impact of these chemicals on human health.