Salt is present in large quantities in seawater, with about 35g/L of seawater. Salt is essential to life, and is one of the oldest food seasonings. Iodized salt is a good source of iodine.
Salting is an important method of preserving food, used in many cultures around the world. Salt is produced by evaporating sea water and mineral-rich spring water in shallow pools. Industrial byproducts include caustic soda and chlorine, and is used to manufactur many products like plastics and paper pulp. Two hundred million tonnes of salt are use for human consumption per year.