Huh, why do they use that in the EU over silicates? (That was why I referenced sand btw). Also, not sure what the relevance to iodine is? Incidentally, iodine

Huh, why do they use that in the EU over silicates? (That was why I referenced sand btw). Also, not sure what the relevance to iodine is? Incidentally, iodine isn't easily sourced in some countries, due to soils that contain very little of it. My country (NZ) used to have a very real goitre problem until the introduction of iodised salt in the 1920s.