Monitoring the effect of introducing mandatory iodisation at an elevated iodine concentration on the iodine content of retailer salt after 1, 3 and 5 years in South Africa.

In this study we monitored the short-term, medium-term and long-term effects of introducing mandatory iodisation at an elevated iodine concentration on the iodine content of retailer salt. In 1995 retailer salt samples were purchased in 48 sentinel towns, situated in three of the nine provinces of South Africa, shortly before the introduction of mandatory iodisation at an elevated iodine concentration of 40-60 ppm, and again 1, 3 and 5 years later. The iodine concentrations in these salt samples were determined by means of the iodometric titration method. Within 1 year the mean iodine concentration more than doubled from 14 to 33 ppm, and further increased to 42 ppm over the next 2 years. However, after another 2 years, the mean iodine concentration relapsed to a lower concentration of 33 ppm. The distribution of iodine values followed the same trend and exhibited a sharp increase in the percentage of under-iodised salt samples at 5 years of follow-up. This study showed the favourable short-term and medium-term impact of introducing mandatory iodisation at an elevated iodine concentration on the iodine content of retailer salt, as well as the reality of a relapse in the long term, emphasising the need for regularly monitoring the iodine content of retailer salt.