**2.4 Food and plants**

372 Macro to Nano Spectroscopy

air, soil and food constitute the most common group of analyzed samples derived from our

In water iodine is predominantly found in the iodide (I-) or iodate (IO3-) form (Gilfedder et al., 2007; Schwehr & Santschi, 2003). Other forms of iodine species in water include: IO4-

iodide), C3H7I (propyl iodide), C 4H9I (butyl iodide), and CH2 BrI (methyl iodide bromide) (Hou, 1999, Hou et al., 2009). Organic iodine concentrations may be especially high in fresh

Generally, the air contains iodine in particulate form, as inorganic gaseous iodine (I2, HIO) and as some forms of organic gaseous iodine (CH3l, CH2l2). High iodine concentrations are found in urban areas due to the combustion of oil and coal. Coastal areas also have high iodine concentration due to the emission of gaseous I2 from algae, seawater and sea spray, which varies with location, season and climate (Hou, 2009; Yoshida & Muramatsu, 1995). There are numerous pathways that may be responsible for transferring I2 from the sea to air.

laboratory (Miyake & Tsunogai, 1963). Another means of obtaining elemental I2 is through the

Strong evidence suggests that atmospheric transport from the oceans is responsible for the deposition of iodine in soil. Iodine exists in various forms in soil and varies largely with

acidic soils whilst IO3- (less mobile) will occur in alkaline soils. In low pH oxidizers, e.g. Fe3+ and Mn4+ convert I - into molecular I2. The activity of reducing bacteria impacts the form of iodine in the soil as well. CH2I2 and other volatile organic complexes of iodine are generated by microbial activity (Johnson, C.C. 2003). Generally, organic bound iodine is more abundant in soil samples. The secondary environment (soil) has high iodine content compared to the primary environment (parent rocks) from which it is derived as a result of weathering. Weathered rocks and soils are richer in iodine than the unweathered bedrocks (Fuge & Johnson, 1986). On average, the igneous rocks contain an average of 0.25 mg/kg of iodine, the sedimentary rocks have 2.3 mg /kg iodine and the metamorphic rocks have 0.81 mg/kg of iodine. Organic matter is the major concentrator of iodine in sedimentary basins (Mani et al., 2007). The highest values were found in soil samples from areas close to the coast, where there is high rainfall, and from areas with high soil organic matter. In one study, the iodine concentration in Japanese soils was found to range from 0.2 mg/kg to 150

 into organic CH3I, which has a residence time between 1.1-8 days (Cicerone, 1981). Lovelock et al. (Lovelock et al., 1973) measured the mean atmospheric CH3I concentration above the Atlantic as 1.2 ppt (6.8 ng/m3). Rasmussen et al. (Rasmussen et al., 1982) found the background level of CH3I to vary between 1 and 3 ppt (5.7-17 ng/m3) with measurements near

thought to be from microbial activity within the oceans, through the transformation of I-

oceans with high biomass productivity to be around 7-22 ppt (40-125 ng/m3).

with ozone (O3)(Garland & Curtis, 1981). The greatest source of atmospheric I2 is

(hypoiodite), CH3I (methyl iodide), CH2I2 (methyl diiodide), C2H5I (ethyl

from seawater to elemental iodine has been recreated in the

(more mobile form) is believed to be the dominant species in

and

external environment.

water (from rivers, lakes and rain).

Photochemical oxidation of I-

respect to its concentration. I-

**2.1 Water** 

**2.2 Air** 

reaction of I-

IO3 -

**2.3 Soil** 

(periodate), IO-

Geographic differences in topsoil iodine content and irrigation procedures determine food iodine levels. In most diets the mainstay sources of iodine are fish, shellfish, milk and iodinated salt. Food supplements constitute an alternative means of obtaining dietary iodine. Fish contain iodine in similar forms to those found in humans. Perhaps the widest assortment of forms is encountered in different species of seaweed. Brown seaweeds contain mostly I- , however green seaweeds play host to a wide array of organic molecules to which iodine is bound, including numerous proteins and polyphenols. Dietary iodine is obtained from a variety of sources and individual dietary habits contribute to the wide disparity in iodine intake among populations. In 1993, the World Health Organization [WHO] published the first version of the WHO Global Database on Iodine Deficiency with global estimates on the prevalence of iodine deficiency based on total goitre prevalence (TGP), using data from 121 countries. Since the international community and the authorities in most countries where IDD was identified as a public health problem have taken measures to control iodine deficiency, in particular through salt iodization programmes – the WHO recommended strategy to prevent and control IDD (World Health Organization [WHO], 2004). Salt iodization programmes are carried out in more than seventy countries, including the United States of America and Canada. There is a wide variation in the scope of iodine supplement; almost 90% of households in North and South America utilize iodized salt while in Europe and the East Mediterranean regions this figure is less than 50%, with a worldwide figure about 70% (WHO, 2007). WHO, ICCIDD (International Council for the Control of Iodine Deficiency Disorders) and UNICEF (United Nations International Children's Emergency Fund) recommend that the term "iodized" be used to designate the addition of iodine to any substance, regardless of the form. Iodine is commonly added as the I or IO3 - of potassium, calcium or sodium. 70% of salt sold for household use in the U.S.A. is iodized with 100 ppm KI (400 µg iodine per teaspoon) (U.S. Salt Institute, 2007). In Canada all salt must be iodized with 77 ppm KI. Mexico requires 20 ppm levels of iodization. Recommendations for the maximum and minimum levels of iodization of salt are calculated as iodine and determined by local national health authorities in accordance with regional variations in iodine deficiency. In Poland iodine deficiency prophylaxis was first started in 1935. Near the end of the 1940's and 80's, the practice of iodizing table salt was abandoned. A nonobligatory recommendation of iodizing salt took place in 1989. In 1991 the Polish Council for Control of Iodine Deficiency Disorders (PCCIDD) was established and an epidemiological survey performed in 1992-1993, defined Poland as an area with moderated – the seaside region as light – severity of iodine deficiency. In 1996 the production of table salt without the addition of KI was made illegal. An obligatory law was passed, mandating the addition of 30(+/-10) mg of KI per kilogram of salt (Szybiński, 2009). Iodization of salt in Turkey has been mandatory since 1998 and the recommended iodine concentration is 50-70 mg KI/kg or 25- 40 mg KIO3/kg (Gurkan et al., 2004). In Switzerland, iodization of salt was altered three times. Iodization was first introduced in 1922 at 3.75 mg/kg. In 1962 the concentration was doubled and in 1980 it was doubled again giving a present level of 15 mg/kg. Although it's use is voluntary, by 1988, 92% of retail salt and 76% of all salt for human consumption

A Review of Spectrophotometric and Chromatographic Methods

(Okerlund, 1997).

control group.

iodine concentration (-0.32, P < 0.01).

and Sample Preparation Procedures for Determination of Iodine in Miscellaneous Matrices 375

According to Hou (Hou et al. 1997), the contents of iodine expressed as ng/g wet weight tissue±1SD) in five tissues, plus hair, averaged over 9–11 individuals were: the heart (46.6±14.9), liver (170±34), spleen (26±8.6), lung (33.3±10.6), muscle (23.5±14.3), and hair (927±528). In the U.S. population, Okerlund found a mean value of 10 mg iodine per thyroid, with a range of 4-19 mg. In 56 patients suffering from autoimmune thyroiditis but with normal thyroid function, a mean value of 4.8 mg/thyroid was reported. In 13 patients with autoimmune thyroiditis and hypothyroidism, the mean value was 2.3 mg/thyroid

Zaichick and Zaichick (Zaichick & Zaichick, 1997) used instrumental neutron activation and X-ray fluorescent analyses to determine the concentration and total iodine content of iodine within thyroids. They obtained 90 samples (at autopsy) from subjects of a broad age spectrum, from 2 to 87 years old and calculated correlations between iodine concentration and age. All their thyroid samples were weighed, lyophilised and homogenised. Iodine was analyzed in approximately 50-mg samples. The mean intrathyroidal iodine concentration (mean +/- S.E.) of a normal subject aged 26-65 averaged 345 +/- 21 μg/g dry tissue in nonendemic goitre region with no obligatory salt iodination. Maximum iodine concentration was found to be 494 +/- 65 μg/g (P < 0.05) for the age of 16-25. For the elderly aged over 65 an increase in iodine of 668 +/- 60 μg/g was shown (P < 0.001). When comparing the right and left lobes, the authors found no variation in weight, iodine concentration or the total content. An inverse correlation was found between the thyroid weight and intrathyroidal

Tadros et al. (Tadros et al., 1981) determined iodine in 48 normal thyroids obtained at autopsy. According to the authors' findings, the iodine concentration ranged from 0.02 to 3.12 mg/g of tissue with a mean value of 1.03 +/- 0.67 mg/g. In 91 surgical thyroid specimens with a variety of abnormalities they found that iodine concentration was much lower. The samples of thyroids with cancer had the lowest values. Sixteen (76%) of 21 analyzed malignant thyroid specimens had undetectable iodine (less than 0.02 mg/g), whereas 22 (96%) of 23 benign nodules had measurable iodine concentrations. Błażewicz et al. (Błażewicz et al., 2011) examined correlations between the content of iodides in 66 nodular goitres and 100 healthy human thyroid tissues. The authors presented an accurate assessment of the iodine content in the thyroids of patients with a nodular goitre (mean concentration was 77. 1 +/- 14.02 μg/g) and in the thyroids obtained at autopsy - considered as a control group (mean concentration 622.62 +/- 187.11 μg/g -for frozen samples and 601.49 +/- 192.11 μg/g- for formalin fixed samples). Statistical analysis showed approx. 8 fold reduction of iodine concentration in the pathological tissues in comparison with the

Interesting research into iodine content in human thyroids was also conducted by Zabala et al. (Zabala et al., 2009). Their study focuses on the determination of iodine content in healthy thyroid samples on male population from Caracas in Venezuela. The authors aimed at establishing a baseline of iodine content in thyroid glands and hence to compare the iodine thyroid concentration of the Venezuelan population with other countries. Male post-mortem individual samples were analyzed using a spectrophotometric flow injection method, based on the Sandell-Kolthoff reaction. The median intrathyroidal iodine concentration was 1443+/-677 µg/g (wet weight), ranging from 419 to 3430 µg/g, which corresponds to a median of total iodine content of 15+/-8 mg (ranging from 4 to 37). These results were

(including food industry) was iodized. Most other countries add from 10 to 40 μg iodine per gram of salt (10-40 ppm) (Bürgi et al., 1990).

Bread (0.14 mg/kg), milk (0.32 mg/kg), eggs (0.48 mg/kg), meat (0.13 mg/kg), and poultry (0.1 mg/kg) constitute other important sources of iodine (figures in parentheses represent the average iodine content per fresh weight) (Food Standards Agency [FSA], 2000). In certain individuals, medications may contribute to the ingested daily iodine. Examples include amiodarone, an antiarrythmic agent (Fang et al, 2004), iodized intravenous radiographic contrast agents and certain topical antiseptics (Aiba et al., 1999).

When considering multivitamins and mineral supplements as a source of iodine, one can find that the majority of iodine they contain is in the KI or NaI forms. According to Zimmerman's research, iodine concentrations in plant matter can range from as little as 10 µg/kg to 1 mg/kg dry weight (Zimmermann, 2009). This variability is relevant because plant matter affects the iodine content of meat and animal products (Pennington et al., 1995). Iodine content of different seaweed species varies greatly (Teas et al., 2004). Japanese iodine intake from edible seaweeds is relatively high compared to the rest of the world. Having taken into consideration many factors, such as information from dietary records, food surveys, urinalysis and seaweed iodine content, Zava and Zava estimated that the daily iodine intake in Japan averages approximately 1,000 to 3,000 μg/day (Zava & Zava, 2011). In certain diets, seafood is a large source of iodine, containing 2 to 10 times more iodine than meat (Hemken, 1979). Saltwater seafood usually contains significantly more iodine than freshwater food, some edible seaweeds may contain up to 2500 µg iodine per gram (Teas et al., 2004).

Simon et al. (Simon et al., 2002) presented an example of the value of the determination of iodine compounds in fish. The authors analyzed whole-body homogenates of zebrafish (Danio rerio) and tadpoles of the African clawed frog (Xenopus laevis). They detected five previously unknown iodinated compounds and measured the concentrations of I–, MIT, DIT, T4, T3 and rT3 in these species.
