Saltcake contains contaminants like oxides, carbides and sulphides as well as metallic aluminium which is entrapped in the salt and traces of pollutants polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD and PCDF). In contact with water it emits flammable gases such as acetylene (which in turn can cause explosions), and is liable to give off toxic gases, such as ammonia, in dangerous quantities. Sources: Australian Government – Department of the Environment and Water Resources Characterizing the Physical and Chemical Properties of Aluminum Dross – Article by O. Manfred, W. Huth, and I.