Imports In 2014, Tonga imported $384 in Non-Iron and Steel Slag, Ash and Residues, becoming the 0th largest importer of Non-Iron and Steel Slag, Ash and Residues in the world. At the same year, Non-Iron and Steel Slag, Ash and Residues was the 0th most imported product in Tonga. Tonga imports Non-Iron and Steel Slag, Ash and Residues primarily from: N/A.