Abstract
The food supply of more than 1.6 billion people is lacking in adequate iodine, resulting in the widespread prevalence of a spectrum of iodine-deficiency disorders. The virtual elimination of iodine-deficiency disorders in the world through universal iodization of salt by the year 2000 has been set as a goal at several international forums. The stability of iodine in salt and the levels of iodization are questions of crucial importance to national planners and salt producers, as they have implications for programme effectiveness, safety, and cost. The purpose of this study was to assess the effect of humidity and packaging materials on the stability of iodine in typical salt samples from countries with tropical and subtropical climates, under controlled climatic conditions typical of these countries. High humidity resulted in rapid loss of iodine from iodized salt, ranging from 30% to 98% of the original iodine content. Solid low-density polyethylene packaging protected the iodine to a great extent. The highest losses occurred from woven high-density polyethylene bags, whereas losses from open containers were intermediate. By using packaging with a good moisture barrier, such as low-density polyethylene bags, iodine losses can be significantly reduced, and in most cases salt can be produced that has relatively stable iodine content for at least six months. The findings of this study indicate that to ensure the effectiveness of local salt iodization programmes, countries should determine iodine losses from local iodized salt under local conditions of production, climate, packaging, and storage.