Salt fortification involves adding micronutrients like iodine and iron to common salt to prevent deficiencies. Iodized salt contains added iodine to prevent goiter, with production levels at 30 ppm and consumer levels at 15 ppm. Double fortified salt contains both iodine and iron to prevent goiter and iron deficiency anemia. It provides 40 mcg of iodine and 1 mg of iron per gram of salt. While salt fortification helps prevent deficiencies, iodization can potentially cause issues like thyrotoxicosis and Hashimoto's disease.