Even our table salt isn't pure!

The Morton Salt site says:

Why is iodine added to salt? Why is dextrose added to salt?
In 1924 Morton became the first company to produce iodized salt for the table in order to reduce the incidence of simple goiter. Dextrose is added to stabilize the iodide. Iodine is vital to the proper functioning of the thyroid gland and the prevention of goiter. Actually, the amount of dextrose in salt is so small that it is dietetically insignificant. Morton® Iodized Table Salt contains 0.04 percent dextrose or 40 milligrams per 100 grams of salt. Morton® Plain Table Salt contains neither iodine nor dextrose. All Morton Salt products containing potassium iodide are labeled as such.