According to The Salt Institute, the majority of table salt is made by solution mining of salt beds, then processing the salt and adding anti-clumping additives and iodine. Solution mining is accomplished by creating wells over salt beds and injecting fresh water so that the salt is dissolved. The resulting solution is extracted and moved to an evaporation and processing plant.
Salt can be produced in several other ways, such as deep-shaft mining or solar evaporation. Deep-shaft mining is similar to other mineral mining and extracts salt from old underground sea beds. Salt extracted via deep-shaft mining is mostly used as rock salt. Solar evaporation consists of evaporating shallow pools of salt water, leaving only the salt behind. This can be done in areas with abundant sun coverage and low rainfall. As of 2011, the leading salt producers in the world are China, U.S., Germany, India and Australia.
Iodine is an essential nutrient to the human body, and major health problems arise without it. Iodine has been added to salt since 1924. The Salt Institute states that this has increased the IQ of U.S. citizens by preventing iodine deficiency, the leading cause of avertable mental retardation globally. Table salt usually contains 97 to 99 percent sodium chloride, the rest being additives and iodine. The World Health Organization recommends that people limit salt consumption to 0.17 ounces per day.