A field trial study on urinary iodine change of the target population with different iodine contents in drinking water after non-iodized salt intervention

Abstract

Objective To evaluate urinary iodine change of the target population with different iodine contents in drinking water after non-iodized salt intervention so as to provide evidence for making strategies of scientific supply of iodized salt. Methods Three counties were chosen as investigation site by adopting purposive sampling method. The school children aged 8 - 13 years old and women aged of 18 - 49 years old in each selected family were used as investigation subjects. The families with different iodine contents in drinking water were chosen to substitute non-iodized salt for their current iodized salt for the 2 months through field trail study. Iodine content in the drinking water of each selected family was determined, and urine samples of the target population were collected for determination of iodine change respectively before and 1, 2 months after the intervention. Linear regression was used to analyze the factors that affected the urinary iodine concentration. Results The median of iodine in drinking water of families in the investigation site was 99.4 μg/L, and the scope was 5.0-867.6 μg/L. Before intervention, the medians of urinary iodine of school children and women were > 300 μg/L except the groups of iodine content in the drinking water less than 30 μg/L and 30 μg/L groups. Two months after the intervention, the scope of the median urinary iodine of school children was 188.5-308.3 μg/L, which was reduced obviously than that before intervention(287.9-514.2 μg/L) ; in women, it was also reduced obviously(181.1-301.7 μg/L) than that before intervention(299.9-632.2 μg/L), in the 140 μg/L groups of iodine content in the drinking water. Two months after the intervention in the group of iodine content in the drinking water above 150 μg/L, the medians of urinary iodine of school children and women were > 400 μg/L. The difference of average urine iodine level before and after was no statistical significance(X~2 = 2.684, 1.742, all P > 0.05). The urine iodine level of target population increased gradually with the elevation of water iodine level 2 months after the intervention (P < 0.05). Linear regression equation was obtained(r=0.950,0.938, all P < 0.01). When the median urinary iodine was 200 μg/L, the median iodine in drinking water was 103.4 μg/L. Conclusions The iodine nutrition level of school children and women are not deficient after stopping iodized salt supplement. Measures should be taken to stop the supply of iodized salt areas where the iodine content is more than 103.4 μg/L and less than or equal 150 μg/L in drinking water. It is necessary to take measures to improve water quality and to decrease iodine content in addition to stopping supply of iodized salt in areas where iodine content is more than 150 μg/L in dringking water. Key words: Iodine; Salts; Intervention studies