Health Risk Assessment of Iodine Status in Chinese Residents

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1 Asian Journal of Ecotoxicology Vol No # * USI 8 ~ ~ 10 5% benchmark dose BMD μg L % 150 μg L mg kg μg L - 1 USI R18 A Health Risk Assessment of Iodine Status in Chinese Residents Hu Xindi Gao Fei # Hu Jianying * Key Laboratory for Earth Surface Processes of Ministry of Education College of Urban and Environmental Sciences Peking University Beijing China Received 11 October 2011 accepted 27 December 2011 Abstract Due to great variation in the natural background levels of iodine found across China the universal salt iodization USI policy which lacks sufficient consideration on this regional variation is not the most proper strategy for preventing and controlling iodine deficiency disease and even may increase potential health risk caused by excessive iodine intake. Recently the Ministry of Health MOH of China has amended the USI policy. However it is still in urgent needs to evaluate and analyze this policy from a perspective of health risk assessment. In this paper the iodine status of Chinese residents was assessed and potential morbidity of subclinical hypothyroidism caused by excessive iodine intake in China was determined by integrating the distribution of urinary iodine concentrations of Chinese 8-10 year-old children dose-response curves and threshold levels. Then the region-specific recommended iodine upper limits in edible salt were calculated based on the 5 % benchmark dose combined with the results of national dietary survey. Results showed that urinary iodine concentrations of national 8-10 year-old children varied greatly in different regions. The geo ZX @ pku. edu. cn # rita-gaofei@ 163. com * Corresponding author hujy@ urban. pku. edu. cn

2 286 7 metric mean value and geometric standard deviation were and μg L - 1 respectively. The morbidity of subclinical hypothyroidism induced by excessive iodine intake reached 4. 00%. Recommended iodine upper limit in edible salt for regions with water iodine concentrations below 150 μg L - 1 was mg kg - 1. However for regions with water iodine concentrations above 150 μg L - 1 adequate iodine status has been achieved through intake pathways other than iodized salt and thus there is no need to consume iodized salt for residents in those regions. These conclusions stay in support of the current salt iodization policy that region-specific iodine content in edible salt should be established according to iodine status of local residents. Keywords universal salt iodization policy urinary iodine levels subclinical hypothyroidism health risk assessment regional salt iodization 0 ~ Szabolcs ~ % USI % 8 ~ 10 12% 6 USI 10 1 Materials and methods TDI ~ TDI 6 16 World Health Organization WHO 100 ~ 199 μg L ~ μg L ~ 199 μg L Fig. 1 Framework for calculation of recommended iodine contents added in edible salt

3 ~ ~ WHO 8 ~ TDI ~ 10 TDI - = = BMD 95% BMDL dichotomous logistic μg L - 1 5% 95% 30. 0% ~ BMDS V % ~ 300 μg L % ~ 52. 5% 150 μg L - 1 Risk Risk = 0 f x G x dx % ~ 86. 1% 3 f x G x ~ 4 4 ~ 7 7 ~ ~ 14 Crystal Ball TDI TDI = BMDL V 92% 2 V 0 ~ 2 2 ~ 4 4 ~ 7 7 ~ L 14 Excel ~ g Institute of Medicine % TDI 2 Results μg L - 1 BMDL ~ μg L

4 ~ d % 1 / % μg L / % 7 / μg L ~ 10 p m x Table 1 Distribution of urinary iodine x μg L - 1 concentrations of 8-10 year-old children in China P m x = 1 / 1 + e x 5 / / μg L - 1 / μg L χ 2 = d. f. = 1 P = % 95% BMDL μg L BMDL ~ ~ 10 Fig. 2 Probability distribution of urinary iodine concentrations ATSDR of 8-10 year-old children in China and dose-response 2 Szabolcs 9 curve between urinary iodine concentration and 1997 subclinical hypothyroidism risk μg L ~ mg kg - 1 2

5 Table 2 Health risk evaluation of excessive iodine intake of residents in China 90% % % TDI TDI 2 TDI BMDL μg L ~ 10 TDI 0 ~ % ~ 2 ~ 4 4 ~ 7 7 ~ ~ ~ % 4. 00% 9 18 TDI % μg d % TDI / / μg d - 1 Table 3 3 Age specific recommended iodine upper limits in edible salt for regions with different water iodine concentrations / μg d - 1 / μg d - 1 / mg kg - 1 / μg d - 1 / μg d - 1 / mg kg - 1 / μg d - 1 / μg d - 1 / mg kg ~ N /A N /A 4 ~ N /A N /A 7 ~ N /A 11 ~ N /A 14 ~ N /A N /A TDI N /A TDI

6 μg L P mg kg ~ 300 μg L μg L - 1 benchmark response BMR 5% μg 19 logistic L - 1 logistic BMDL 3 Discussion TDI μg d mg kg - 1 d kg mg kg - 1 d Scientific Committee on Food SCF 600 μg d ~ 10 WHO 99 μg L ~ 199 μg L ~ 299 μg L μg L mg kg ~ 30 mg kg μg L WHO 150 μg L - 1 WHO μg L % 3. 2 TDI TDI UF USI 1965 BMD logistic probit Weibull Wheeler Bailer World Health Organization. Assessment of the Iodine Deficiency Disorders and Monitoring Their Elimination R. BMD Geneva World Health Organization Agency for Toxic Substances and Disease Registry ATS-

7 3 291 DR. Toxicological Profile for Iodine R. Atlanta U. S. Department of Health and Human Services Public Health Service ATSDR Vanadium and Zinc M. Washington DC National A- R. cademy Press M J Bleichrodt N Born M P. A Meta-Analysis of Research on Iodine and Its Relationship to Cognitive Development M / /Stanbury J B. The Damaged Brain of Iodine Deficiency. New York Cognizant Communication J. Lancet Li Y Liu X. Iodine and human health J. Guangdong Trace Elements Science in Chinese 8 Andersson M Takkouche B Egli I et al. Current global iodine status and progress over the last decade towards the elimination of iodine deficiency J. Bulletin of the World Health Organization Szabolcs I Podoba J Feldkamp J et al. Comparative screening for thyroid disorders in old age in areas of iodine deficiency long-term iodine prophylaxis and abundant iodine intake J. Clinical Endocrinology Crump K S. A new method for determining allowable daily intakes J. Fundamental and Applied Toxicology J EB /OL http / /www. moh. gov. cn /publicfiles / / /business /cmsre- 12. sources / mohwsjdj / cmsrsdocument / doc9331. doc M Institute of Medicine. Dietary Reference Intakes for Vitamin A Vitamin K Arsenic Boron Chromium Copper Iodine Iron Manganese Molybdenum Nickel Silicon M Boyages S C Bloot A M Maberly G F et al. Thyroid autoimmunity in endemic goitre caused by excessive iodine intake J. Clinical Endocrinology R. 17 Li M Qu C Y Qian Q D et al. Endemic goitre in central China caused by excessive iodine intake J. The 18 Wheeler M W Bailer A J. Properties of model-averaged BMDLs A study of model averaging in dichotomous response risk estimation J. Risk Analysis Agency for Toxic Substances and Disease Registry ATS- DR. ATSDR Minimal Risk Levels and Worksheets R / OL http / /www. atsdr. cdc. gov / ToxProfiles / tp150-a. pdf 20 European Commission. Opinion of the Scientific Committee on Food on the Tolerable Upper Intake Level of Iodine. SCF /CS /NUT /UPPLEV /26 Final. R. Brussels European Commission S /OL http / / www. moh. gov. cn /publicfiles / / /business /cmsresources / mohwsjdj / cmsrsdocument / doc9330. doc

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