Open Access Open Badges Research article

Improved salt iodation methods for small-scale salt producers in low-resource settings in Tanzania

Vincent D Assey123*, Thorkild Tylleskär2, Philip B Momburi4, Michael Maganga1, Nicholaus V Mlingi1, Marie Reilly5, Ted Greiner6 and Stefan Peterson378

Author Affiliations

1 Food Science and Nutrition Department, Tanzania Food and Nutrition Centre (TFNC), 22 Ocean Road, PO Box 977 Dar-Es-Salaam, Tanzania

2 Centre for International Health (CIH), University of Bergen, Årstadveien 21, N-5009 Bergen, Norway

3 Department of Women's and Children's Health, Unit of International Maternal and Child Health (IMCH), Akademiska Sjukhuset, Uppsala University, SE -75185 Uppsala, Sweden

4 Geological Survey of Tanzania, Ministry of Energy and Minerals, PO Box 903 Dodoma, Tanzania

5 Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden

6 Food and Nutrition Department, Hanyang University, 17 Haengdang-dong, Seongdong-gu Seoul 133-790, South Korea

7 Department of Public Health Sciences, Division of International Health (IHCAR), Nobel v 9, Karolinska Institutet, S-17177, Stockholm, Sweden

8 Makerere University School of Public Health, Kampala, Uganda

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BMC Public Health 2009, 9:187  doi:10.1186/1471-2458-9-187

Published: 17 June 2009



Universal salt iodation will prevent iodine deficiency disorders (IDD). Globally, salt-iodation technologies mostly target large and medium-scale salt-producers. Since most producers in low-income countries are small-scale, we examined and improved the performance of hand and knapsack-sprayers used locally in Tanzania.


We studied three salt facilities on the Bagamoyo coast, investigating procedures for preparing potassium-iodate solution, salt spraying and mixing. Different concentrations of solution were prepared and tested using different iodation methods, with the aim of attaining correct and homogeneous iodine levels under real-life conditions. Levels achieved by manual mixing were compared to those achieved by machine mixing.


The overall median iodation level in samples of salt iodated using previously existing methods was 10.6 ppm (range 1.1 – 110.0 ppm), with much higher levels in the top than the bottom layers of the salt bags, p < 0.0001. Experimentation using knapsack-sprayers and manual mixing led to the reliable achievement of levels (60.9 ppm ± 7.4) that fell within the recommended range of 40 – 80 ppm. The improved methods yielded homogenous iodine concentrations in all layers of salt-bags (p = 0.58) with 96% of the samples (n = 45) falling within 40 – 80 ppm compared to only 9% (n = 45) before the experiment and training (p < 0.0001). For knapsack-spraying, a machine mixer improved the iodine levels and homogeneity slightly compared to manual mixing (p = 0.05).


Supervised, standardized salt iodation procedures adapted to local circumstances can yield homogeneous iodine levels within the required range, overcoming a major obstacle to universal salt iodation.