The blast furnace granulated slag when treated with a solution of silver nitrate indicates a shiny deposition of metallic silver showing its capacity to cause electrochemical reduction. The major and minor components of the slag have been determined. The capacity of the slag to cause chemical reduction has been attributed to the presence of certain reactive metals in their elemental states. Alkyllead, in gasoline or aqueous system, when treated with the blast furnace granulated slag is found to be substantially or completely removed depending on the conditions of the treatment. The method has been found simple, economical and useful for the treatment of alkyllead-contaminated aqueous systems.