Based on data collected by Lee et al. (57) from the years 2006–2010, the total FGD gypsum production in the United States, EU, China, Korea, and Japan equaled to 46 Mt annually. CárdenasEscudero et al. (26) studied a method to stabilize phosphogypsum waste ( Table ) containing, for example, chromium, nickel, vanadium, cadmium and lead, using NaOH to raise solution pH levels.