Introduction
Iodine deficiency is one of the factors affecting growth factor and the main cause of human growth decline. Iodine deficiency is also the most common preventable cause of brain damage worldwide 1 .
More than 2 billion people (38%) of the world's population in 130 countries are at risk due to iodine deficiency. Iodine deficiency diminishes the production of thyroid hormone, that is, iodine is an essential component for the thyroid hormone secretion, and iodine deficiency is known as one of the main causes of goiter development 2 , but now studies have shown that the effects on the growing brain (in children and infants) are much more deadly and threaten the social and economic development of many countries 3 . Iodine deficiency disorders, which are known to be one of the health priorities in any country, have created many problems for more than 400 million people in Asia 4 , with 50% of the world's population receiving less-than -required amounts of iodine 5 .
Given the fact that iodine is a small amount and vital mineral to human life 6 , and soils in many areas do not contain sufficient amount of this essential microelements, then agricultural and livestock products are deficient in iodine 7 , the best way to compensate for iodine deficiency is use of iodized salt 8 . In addition, in areas where this strategy cannot be implemented quickly, temporary use of iodine supplements is recommended. In 1989, assessing the prevalence of goiter in all provinces of Iran showed that goiter was hyper endemic due to iodine deficiency 9 . In 1994, the Joint Committee of the World Health Organization (WHO) and UNICEF proposed a global food iodization plan as a safe and cost-effective strategy to supply the required amounts of iodine for all individuals. Iodizing edible salt has been one of the most effective interventions worldwide to eliminate iodine deficiency disorders 10 . Various studies have shown that human daily need 100 micrograms of iodine that reach the body by nutrients. According to reports, the most important source of iodine in Iran is iodized salt and the standard iodine value for these salts is set at 40 ± 10 ppm
11
. Complications due to iodine deficiency are various depending on different life stages and have various complications such as abortion, congenital malformations, increased mortality at birth, cretinism, neurological disorders, increased neonatal mortality, infant goiter, hypothyroidism, mental impairment, and physical developmental delays 12 . According to statistics, the prevalence of goiter in Iran declined to 8.9% in 2013, reflecting that there is still a risk of iodine deficiency among people in the community 6 . In Iran, some measures have been taken in this regard since 1989 which significantly increased the level of urinary iodine and reduced the prevalence of goiter in most regions of the country 13 . In the third national monitoring of the program in 2001, the results were very satisfactory and Iran was recognized as an iodine deficiency-free zone 9, 14 . But the results of the fourth national monitoring in 2006 showed the fact that the iodine intake in the regions of the country significantly decreased, leading to the concern that the level of iodine-induced abnormalities would increase again in the event of insufficient attention and supervision 10 .The results of this monitoring in Yazd province showed that the percentage of goiter was desirable, and the median urinary iodine in the province was higher than 100 μg/l, which represents the success of the country's program and the accuracy monitoring of the iodization program 15 . A study in 2014 on the assessment of impairments of height, weight and head circumference in the five years old childs with congenital hypothyroidism in Yazd in showed that, iodine deficiency in pregnant mothers could lead to permanent mental retardation and physical development impairment 16 . Some studies have also shown that iodine intake in households in Yazd is lower than the Iran standard 15 . Therefore, the aim of this study was to evaluate iodine levels in iodized salts distributed in Abarkouh city during 2017-2018.
Materials and Methods
This cross-sectional study was conducted to evaluate the iodine concentration of iodized salt brands distributed in Abarkouh city in 2017-2018. Random sampling was done by census on all 30 distributed brands in Abarkouh city in different stages in stores across the city. Sixty samples (30 samples after one month from the production and 30 samples after 6 months from the production the salts) were collected and transferred to the laboratory. Each sample was tested twice. To measure iodine levels in iodized salts, the British Pharmacopoeia recommended method 17 . Data analysis was performed by the SPSS version 20 and using independent sample t-test and one-sample t-test and P ≤ 0.05 was considered significance level. Results A total of 120 experiments were carried out on salts as 60 distributed salt brands across the city (30 samples after one month from the production and 30 samples after 6 months from the production the salts). were tested twice, in 34% of the tested samples produced one month before, the iodine concentration was compatible with the standard iodine salt in Iran (50-50 ppm), in 50%, the iodine concentration was lower than the standard, and in 16%, the iodine concentration was higher than the standard. In salt samples produced six months before, in 37% of samples, iodine concentration was compatible with Iran standard, in 57% of them was lower, and in 6%, was higher than Iran's standard (Table 1) . The average iodine concentration in salts decreased one month after production date by 29.8 ppm and in salts six months after production date by 24.26 ppm. Independent t-test showed that iodine reduction was not statistically significant six months after production date (P = 0.242). The maximum iodine concentrations in salts at one and six after production date were 69 ppm and 52 ppm, respectively. And the minimum iodine content was zero (according to the fact that the two brands of iodine were iodine-free (Table 2 ). From the total salt brands tested one month after production, iodine concentration in 50% of the samples was below the minimum standard, 34% in compliance with the standard, and 16% higher than the standard (30-50 ppm) (Figure 1 ). In addition, one-sample t-test to compare iodine concentration in the produced salts and Iran's standard showed that the difference between iodine concentration in the salt samples and the set standard concentration was significant (P ≤ 0.001), meaning that the shortage of iodine concentration in both dates after production is not in line with the standards set by the Iran's Standard Organization, and in most of the distributed brands across the city, the iodine concentration is less than standard.
Discussion
In this study, the average iodine concentration in 50% of the supplied salts was lower than the Iran's standard (30-50 ppm), and the concentration of iodine decreased six months after production date. A study by Pasdar and et al in 2013-2014 showed that iodine in salts delivered in Kermanshah was less than Iran's standards in over 50% of the samples, and after the date of production of salts, their iodine content decreased significantly over time 17 . The findings of this study also confirm that, over time, iodine levels are reduced by the influence of physical factors such as exposure to light, humidity and ambient temperature; more clearly, the exposure of salt to light relative to darkness, humidity relative to the dry environment, and the high temperatures relative to lower temperatures, can cause more iodine loss in iodized salt at a faster rate 18, 19 .
Other studies have also found that excessive humidity destroys the iodine in iodized salts and significantly reduces iodine levels 17 . In addition, the results of a study in Karaj showed that 40% of the studied salt samples were good, 39% were acceptable, and 21% were unacceptable 8 . The results also showed that 79% of the samples were from in view of iodine, 61% of samples are acceptable for purity and 60% for insoluble matter 8 . The present study also confirms that iodine content of salt in the market is unacceptable according to Iran's standards. A study was conducted in 2009 in order to evaluate the adequacy of iodine, goiter prevalence and urinary iodine concentration at 17 years after iodization and iodized salt consumption in Yazd province, showed that a high percentage of households in Yazd province used refined and iodized salt as well as the method of salt storage was acceptable in 48% of households. Five percent of household salts also had less than 15 gamma iodine, which controlled some of the diseases associated with iodine deficiency, including hypothyroidism due to iodine deficiency 20 , but the households' iodine was still below the Iran's standard, which is consistent with the findings of this study 15 . The findings of the study of Mahdinia showed that none of the iodized salts distributed in Semnan province during the study complied with the standard, and 31.2 % of distributed iodized salts we're outside the acceptable range of 30-50 ppm 21 , which is consistent with the findings of the present study. A direct correlation between the amount of iodine in salt and urine iodine level in southern Tehran in 2011 showed that, due to inadequate iodine amount in salt, the amount of iodine intake decreases and, in some cases, the amount of iodine in the salts used by households in Tehran was less than the standard set by the Iranian Bureau of Standards 22 , which is consistent with the findings of this study. Nourooz-zadeh and et al, reported iodine deficiency in 87% of cases, and the rate of using iodized salt in cooking and dinner table salt was 92% and 96%, respectively. In 49% of cases, iodized salt was kept under favorable conditions, and 16% of households added salt in the final stages of cooking, which results in loss of iodine in salt due to heat during cooking 5 . According to the study of Arab conducted in Shirvan in 2010, 11% of households used untreated salt for daily consumption, and 27% did not know favorable conditions of maintaining iodized salts and 15% the correct way to use iodized salt in cooking 6 . During the years 1955 to 1970, the problems of iodine deficiency in the Soviet Union were largely eliminated due to the significant production of iodine salts and the accurate monitoring and control of iodine deficiency. In 1969, the prevalence of goiter was less than 5%, but during the 1970s and 1980s, iodine deficiency gradually recurred 15 due to discontinuation of monitoring and controlling prevention programs. The reduction of iodized salt consumption by people and the use of iodized salts by a few foodproducing factories in Australia is another example of the recurrence of iodine deficiency in this country 23 . Finally, due to the lack of continuous monitoring of intake and consumption of edible iodine and the lack of systematic and periodic implementation of anti-iodine deficiency programs are the most important reasons for failure to control iodine deficiency in some population 24 . Despite the desirable iodine amounts in some salt brands, it is necessary to educate the housewives to keep salt under favorable conditions and then consume it, and only monitoring the amount of iodine in the household salts is not enough.
Conclusion
The results of this study indicate that the amount of iodine in the salts distributed across Abarkouh city is often less than the WHO standard. Therefore, it is suggested that, in order to reduce the risks of iodine deficiency for people's health, iodine amount of distributed salts across the Abarkouh city should be monitored continuously and accurately.

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