Iodine source apportionment in the Malawian diet

Influence of tree species on selenium and iodine partitioning in an experimental forest ecosystem

Storage of selenium and iodine can greatly vary between forest ecosystems, but the influence of tree species on partitioning and recycling of those elements remains elusive. In this study, contents of Se and I were measured in tree compartments, litterfall, humus, and soil horizons in monospecific stands of Douglas fir, pine, spruce, beech, and oak under identical climatic and edaphic conditions. The cycle of each element was characterized in terms of stocks and fluxes. Lowest concentrations were in wood (Se: 8-13 μg kg^-1; I: <16.5 μg kg^-1). Senescing organs had higher Se and I content, than the living parts of trees due to direct exposure to atmospheric deposition, with some variation between coniferous and deciduous trees. For all stands, low amounts of Se and I were involved in biological cycle as reflected by low root uptake. In humus, the enrichment of elements greatly increased with the stage of organic matter (OM) degradation with average factors of 10 and 20 for Se and I. OM degradation and element persistence in humus was influenced by tree species. Deciduous trees, with low biomass, and fast degradation of OM stored less Se and I in humus compared to fir and spruce with high humus biomass. Interestingly, tree species did not affect soil reserves of Se and I. Concentration ranges were 331-690 μg Se kg^-1 and 4.3-14.5 mg I kg^-1. However, the divergent vertical profiles of the elements in the soil column indicated greater mobility of I. Selenium concentrations regularly decreased with depth in correlation with OM and Fe oxides content. For iodine, the maximum iodine concentration at a soil depth of 15 to 35 cm was caused by a parallel precipitation/sorption behavior of aluminium and organic iodine dissolved in the topsoil.

Multiple geochemical factors may cause iodine and selenium deficiency in Gilgit-Baltistan, Pakistan

Deficiencies of the micronutrients iodine and selenium are particularly prevalent where populations consume local agricultural produce grown on soils with low iodine and selenium availability. This study focussed on such an area, Gilgit-Baltistan in Pakistan, through a geochemical survey of iodine and selenium fractionation and speciation in irrigation water and arable soil. Iodine and selenium concentrations in water ranged from 0.01-1.79 µg L^-1 to 0.016-2.09 µg L^-1, respectively, which are smaller than levels reported in similar mountainous areas in other parts of the world. Iodate and selenate were the dominant inorganic species in all water samples. Average concentrations of iodine and selenium in soil were 685 µg kg^-1 and 209 µg kg^-1, respectively, much lower than global averages of 2600 and 400 µg kg^-1, respectively. The 'reactive' fractions ('soluble' and 'adsorbed') of iodine and selenium accounted for < 7% and < 5% of their total concentrations in soil. More than 90% of reactive iodine was organic; iodide was the main inorganic species. By contrast, 66.9 and 39.7% of 'soluble' and 'adsorbed' selenium, respectively, were present as organic species; inorganic selenium was mainly selenite. Very low distribution coefficients (kd = adsorbed/soluble; L kg^-1) for iodine (1.07) and selenium (1.27) suggested minimal buffering of available iodine and selenium against leaching losses and plant uptake. These geochemical characteristics suggest low availability of iodine and selenium in Gilgit-Baltistan, which may be reflected in locally grown crops. However, further investigation is required to ascertain the status of iodine and selenium in the Gilgit-Baltistan food supply and population.

Environmental and human iodine and selenium status: lessons from Gilgit-Baltistan, North-East Pakistan

Iodine and selenium deficiencies are common worldwide. We assessed the iodine and selenium status of Gilgit-Baltistan, Pakistan. We determined the elemental composition (ICP-MS) of locally grown crops (n = 281), drinking water (n = 82), urine (n = 451) and salt (n = 76), correcting urinary analytes for hydration (creatinine, specific gravity). We estimated dietary iodine, selenium and salt intake. Median iodine and selenium concentrations were 11.5 (IQR 6.01, 23.2) and 8.81 (IQR 4.03, 27.6) µg/kg in crops and 0.24 (IQR 0.12, 0.72) and 0.27 (IQR 0.11, 0.46) µg/L in water, respectively. Median iodised salt iodine was 4.16 (IQR 2.99, 10.8) mg/kg. Population mean salt intake was 13.0 g/day. Population median urinary iodine (uncorrected 78 µg/L, specific gravity-corrected 83 µg/L) was below WHO guidelines; creatinine-corrected median was 114 µg/L but was unreliable. Daily selenium intake (from urinary selenium concentration) was below the EAR in the majority (46-90%) of individuals. Iodine and selenium concentrations in all crops were low, but no health-related environmental standards exist. Iodine concentration in iodised salt was below WHO-recommended minimum. Estimated population average salt intake was above WHO-recommended daily intake. Locally available food and drinking water together provide an estimated 49% and 72% of EAR for iodine (95 µg/day) and selenium (45 µg/day), respectively. Low environmental and dietary iodine and selenium place Gilgit-Baltistan residents at risk of iodine deficiency disorders despite using iodised salt. Specific gravity correction of urine analysis for hydration is more consistent than using creatinine. Health-relevant environmental standards for iodine and selenium are needed.

Human urinary biomonitoring in Western Kenya for micronutrients and potentially harmful elements

Spot urinary elemental concentrations are presented for 357 adults from Western Kenya collected between 2016 and 2019 as part of a wider environmental geochemical survey. The aim of this study was to establish population level urinary elemental concentrations in Western Kenya for micronutrients and potentially harmful elements for inference of health status against established thresholds. For elements where thresholds inferring health status were not established in the literature using urine as a non-invasive matrix, this study generated reference values with a 95% confidence interval (RV95s) to contextualise urinary elemental data for this population group. Data are presented with outliers removed based upon creatinine measurements leaving 322 individuals, for sub-categories (e.g. age, gender) and by county public health administrative area. For Western Kenya, reference values with a 95% confidence interval (RV95s) were calculated as follows (μg/L): 717 (I), 89 (Se), 1753 (Zn), 336 (Mo), 24 (Cu), 15.6 (Ni), 22.1 (As), 0.34 (Cd), 0.47 (Sn), 0.46 (Sb), 7.0 (Cs), 13.4 (Ba and 1.9 (Pb). Urinary concentrations at the 25th/75th percentiles were as follows (μg/L): 149/368 (I), 15/42 (Se), 281/845 (Zn), 30/128 (Mo), 6/13 (Cu), 1.7/6.1 (Ni), 2.0/8.2 (As). 0.1/0.3 (Cd), 0.05/0.22 (Sn), 0.04/0.18 (Sb), 1.2/3.6 (Cs), 0.8/4.0 (Ba) and 0.2/0.9 (Pb). Urinary concentrations at a population level inferred excess intake of micronutrients I, Se, Zn and Mo in 38, 6, 57 and 14% of individuals, respectively, versus a bioequivalent (BE) upper threshold limit, whilst rates of deficiency were relatively low at 15, 15, 9 and 18%, respectively. Each of the administrative counties showed a broadly similar range of urinary elemental concentrations, with some exceptions for counties bordering Lake Victoria where food consumption habits may differ significantly to other counties e.g. I, Se, Zn. Corrections for urinary dilution using creatinine, specific gravity and osmolality provided a general reduction in RV95s for I, Mo, Se, As and Sn compared to uncorrected data, with consistency between the three correction methods.

Consumption of multiple micronutrients or small-quantity lipid-based nutrient supplements containing iodine at the recommended dose during pregnancy, compared with iron and folic acid, does not affect women's urinary iodine concentration in rural Malawi: a secondary outcome analysis of the iLiNS DYAD trial

OBJECTIVES

Inadequate iodine intake during pregnancy increases the risk of neonatal morbidity and mortality. We aimed to evaluate whether prenatal supplements containing iodine affect urinary iodine concentrations (UIC) of pregnant women in Malawi.

DESIGN

A randomised controlled trial. Pregnant women (n 1391) were assigned to consume 60 mg/d Fe and 400 µg/d folic acid (IFA) or 18 vitamins and minerals including 250 µg/d iodine (MMN) or 20 g/d small-quantity lipid-based nutrient supplements (SQ-LNS) with similar nutrient contents as MMN group, plus macronutrients (LNS) until childbirth. In a sub-study (n 317), we evaluated group geometric mean urinary iodine concentration (UIC) (µg/L) at 36 weeks of gestation controlling for baseline UIC and compared median (baseline) and geometric mean (36 weeks) UIC with WHO cut-offs: UIC < 150, 150-249, 250-499 and ≥500 reflecting insufficient, adequate, above requirements and excessive iodine intakes, respectively.

SETTING

Mangochi District, Malawi.

PARTICIPANTS

Women ≤20 weeks pregnant.

RESULTS

Groups had comparable background characteristics. At baseline, overall median (Q1, Q3) UIC (319 (167, 559)) suggested iodine intakes above requirements. At 36 weeks, the geometric mean (95 % CI) UIC of the IFA (197 (171, 226)), MMN (212 (185, 243)) and LNS (220 (192, 253)) groups did not differ (P = 0·53) and reflected adequate intakes.

CONCLUSIONS

In this setting, provision of supplements containing iodine at the recommended dose to pregnant women with relatively high iodine intakes at baseline, presumably from iodised salt, has no impact on the women's UIC. Regular monitoring of the iodine status of pregnant women in such settings is advisable. Clinicaltrials.gov identifier: NCT01239693.

Agronomic iodine biofortification of leafy vegetables grown in Vertisols, Oxisols and Alfisols

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha^-1 I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Agronomic iodine biofortification of leafy vegetables grown in Vertisols, Oxisols and Alfisols

Iodine deficiency disorders (IDD) in sub-Saharan African countries are related to low dietary I intake and generally combatted through salt iodisation. Agronomic biofortification of food crops may be an alternative approach. This study assessed the effectiveness of I biofortification of green vegetables (Brassica napus L and Amaranthus retroflexus L.) grown in tropical soils with contrasting chemistry and fertility. Application rates of 0, 5 and 10 kg ha^-1 I applied to foliage or soil were assessed. Leaves were harvested fortnightly for ~ 2 months after I application before a second crop was grown to assess the availability of residual soil I. A separate experiment was used to investigate storage of I within the plants. Iodine concentration and uptake in sequential harvests showed a sharp drop within 28 days of I application in all soil types for all I application levels and methods. This rapid decline likely reflects I fixation in the soil. Iodine biofortification increased I uptake and concentration in the vegetables to a level useful for increasing dietary I intake and could be a feasible way to reduce IDD in tropical regions. However, biofortification of green vegetables which are subject to multiple harvests requires repeated I applications.

Assessing the impact of drinking water iodine concentrations on the iodine intake of Chinese pregnant women living in areas with restricted iodized salt supply

PURPOSE

The supply of non-iodized salt and the water improvement project have been conducted to reduce the iodine concentration in drinking water in areas with elevated water iodine. We aimed to assess the impact of water iodine concentration (WIC) on the iodine intake of pregnant women in areas with restricted iodized salt supply, and determine the cutoff values of WIC in areas with non-iodized salt supply.

METHODS

Overall, 534 pregnant women who attended routine antenatal outpatient visits in Zibo Maternal and Child Health Hospital in Gaoqing County were recruited. The 24-h urine iodine excretion (UIE) in 534 samples and the iodine concentration in 534 drinking water samples were estimated. Urinary iodine excretion, daily iodine intake, and daily iodine intake from drinking water (WII) were calculated. The relationship between WIC and daily iodine take was analyzed.

RESULTS

The median WIC, spot urine iodine concentration (UIC), and 24-h UIE were 17 (6, 226) μg/L, 145 (88, 267) μg/L, and 190 (110, 390) μg/day, respectively. A significant positive correlation was found between WIC and UIE (R² = 0.265, p < 0.001) and UIC (R² = 0.261, p < 0.001). The contribution rate of WII to total iodine intake increased from 3.0% in the group with WIC of < 10 μg/L to 45.7% in the group with WIC of 50-99 μg/L.

CONCLUSION

The iodine content in drinking water is the major iodine source in pregnant women living in high-water iodine areas where iodized salt supply is restricted. The contribution rate of daily iodine intake from drinking water increases with the increase in water iodine concentration.

Elemental composition of aquaculture fish from West Bengal, India: nutrition versus food safety

Aquaculture production continues to grow in West Bengal, where on average people consume 8.2 kg capita^-1 of fish each year, and an extensive mosaic of aquaculture ponds has developed along the River Hugli as clay pits are repurposed. The adjacent brickworks and industry (especially tanneries) are a source of environmental pollution, with potential for bioaccumulation of potentially harmful elements (PHEs) in fish farmed in these ponds. Fish from aquaculture present an opportunity to meet food sufficiency in West Bengal; however, an investigation to assess their effectiveness for micronutrient supply balanced against food safety is required. Five ponds close to industrial brick manufacture (urban) and three from rural areas were assessed for the degree of pollution within their pond sediments and waters. Fish were also sampled from each location including a subset from the market in Kolkata to determine the concentrations of PHEs in their fish muscle tissue. Dietary intake and PHE loading were calculated for four fish species to evaluate their nutrient content with respect to recommended daily intakes for adults, e.g. calcium (Ca), potassium (K), magnesium (Mg), iron (Fe), zinc (Zn) and selenium (Se), and to establish whether the provisional maximum tolerable intakes (PMTIs) are exceeded for PHEs, e.g. aluminium (Al), arsenic (As), mercury (Hg), chromium (Cr), tin (Sn), copper (Cu) and lead (Pb). Preliminary results suggest that aquaculture is making an important contribution to nutrition, with fish being a good source of Se. However, in contrast to small wild-caught fish, aquaculture fish in the present study were poor sources of Fe, Ca and Zn. The fish also made substantial contributions (> 10%) to the PMTI of Hg and As. Therefore, there is an urgent need for ongoing monitoring and an expanded sampling programme, as well as research into approaches which might improve the nutritional quality of the farmed fish.

Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations

Spot urinary iodine concentrations (UIC) are presented for 248 individuals from western Kenya with paired drinking water collected between 2016 and 2018. The median UIC was 271 µg L-1, ranging from 9 to 3146 µg L-1, unadjusted for hydration status/dilution. From these data, 12% were potentially iodine deficient (< 100 µg L-1), whilst 44% were considered to have an excess iodine intake (> 300 µg L-1). The application of hydration status/urinary dilution correction methods was evaluated for UICs, using creatinine, osmolality and specific gravity. The use of specific gravity correction for spot urine samples to account for hydration status/urinary dilution presents a practical approach for studies with limited budgets, rather than relying on unadjusted UICs, 24 h sampling, use of significantly large sample size in a cross-sectional study and other reported measures to smooth out the urinary dilution effect. Urinary corrections did influence boundary assessment for deficiency-sufficiency-excess for this group of participants, ranging from 31 to 44% having excess iodine intake, albeit for a study of this size. However, comparison of the correction methods did highlight that 22% of the variation in UICs was due to urinary dilution, highlighting the need for such correction, although creatinine performed poorly, yet specific gravity as a low-cost method was comparable to osmolality corrections as the often stated 'gold standard' metric for urinary concentration. Paired drinking water samples contained a median iodine concentration of 3.2 µg L-1 (0.2-304.1 µg L-1). A weak correlation was observed between UIC and water-I concentrations (R = 0.11).

Environmental geochemistry and cancer: a pertinent global health problem requiring interdisciplinary collaboration

Primary prevention is a key strategy to reducing the global burden of cancer, a disease responsible for ~ 9.6 million deaths per year and predicted to top 13 million by 2030. The role of environmental geochemistry in the aetiology of many cancers-as well as other non-communicable diseases-should not be understated, particularly in low- and middle-income countries where 70% of global cancer deaths occur and reliance on local geochemistry for drinking water and subsistence crops is still widespread. This article is an expansion of a series of presentations and discussions held at the 34th International Conference of the Society for Environmental Geochemistry and Health in Livingstone, Zambia, on the value of effective collaborations between environmental geochemists and cancer epidemiologists. Key technical aspects of each field are presented, in addition to a case study of the extraordinarily high incidence rates of oesophageal cancer in the East African Rift Valley, which may have a geochemical contribution. The potential merit of veterinary studies for investigating common geochemical risk factors between human and animal disease is also highlighted.

Short-Term Iodine Dynamics in Soil Solution

Assessing the reactions of iodine (I) in soil is critical to evaluate radioiodine exposure and understand soil-to-crop transfer rates. Our mechanistic understanding has been constrained by method limitations in assessing the dynamic interactions of iodine between soil solution and soil solid phase over short periods (hours). We use microdialysis to passively extract soil solution spiked with radioiodine (¹²⁹I^- and ¹²⁹IO₃^-) to monitor short-term (≤40 h) in situ fixation and speciation changes. We observed greater instantaneous adsorption of ¹²⁹IO₃^- compared to ¹²⁹I^- in all soils and the complete reduction of ¹²⁹IO₃^- to ¹²⁹I^- within 5 h of addition. Loss of ¹²⁹I from solution was extremely rapid; the average half-lives of ¹²⁹I^- and ¹²⁹IO₃^- in soil solution were 4.06 and 10.03 h, respectively. We detected the presence of soluble organically bound iodine (org-¹²⁹I) with a low molecular weight (MW) range (0.5-5 kDa) in all soils and a slower (20-40 h) time-dependent formation of larger MW org-I compounds (12-18 kDa) in some samples. This study highlights the very short window of immediate availability in which I from rainfall or irrigation remains in soil solution and available to crops, thus presenting significant challenges to phytofortification strategies in soil-based production systems.

Source apportionment of micronutrients in the diets of Kilimanjaro,Tanzania and Counties of Western Kenya

Soil, water and food supply composition data have been combined to primarily estimate micronutrient intakes and subsequent risk of deficiencies in each of the regions studied by generating new data to supplement and update existing food balance sheets. These data capture environmental influences, such as soil chemistry and the drinking water sources to provide spatially resolved crop and drinking water composition data, where combined information is currently limited, to better inform intervention strategies to target micronutrient deficiencies. Approximately 1500 crop samples were analysed, representing 86 food items across 50 sites in Tanzania in 2013 and >230 sites in Western Kenya between 2014 and 2018. Samples were analysed by ICP-MS for 58 elements, with this paper focussing on calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), selenium (Se), iodine (I), zinc (Zn) and molybdenum (Mo). In general, micronutrient supply from food groups was higher from Kilimanjaro,Tanzania than Counties in Western Kenya, albeit from a smaller sample. For both countries leafy vegetable and vegetable food groups consistently contained higher median micronutrient concentrations compared to other plant based food groups. Overall, calculated deficiency rates were <1% for Cu and Mo and close to or >90% for Ca, Zn and I in both countries. For Mg, a slightly lower risk of deficiency was calculated for Tanzania at 0 to 1% across simplified soil classifications and for female/males, compared to 3 to 20% for Kenya. A significant difference was observed for Se, where a 3 to 28% risk of deficiency was calculated for Tanzania compared to 93 to 100% in Kenya. Overall, 11 soil predictor variables, including pH and organic matter accounted for a small proportion of the variance in the elemental concentration of food. Tanzanian drinking water presented several opportunities for delivering greater than 10% of the estimated average requirement (EAR) for micronutrients. For example, 1 to 56% of the EAR for I and up to 10% for Se or 37% for Zn could be contributed via drinking water.

Iodine uptake, storage and translocation mechanisms in spinach (Spinacia oleracea L.)

Iodine is an essential micronutrient for human health; phytofortification is a means of improving humans' nutritional iodine status. However, knowledge of iodine uptake and translocation in plants remains limited. In this paper, plant uptake mechanisms were assessed in short-term experiments (24 h) using labelled radioisotopes; the speciation of iodine present in apoplastic and symplastic root solutions was determined by (HPLC)-ICP-QQQ-MS. Iodine storage was investigated in spinach (Spinacia oleracea L.) treated with I^- and IO₃^-. Finally, translocation through the phloem to younger leaves was also investigated using a radioiodine (¹²⁹I^-) label. During uptake, spinach roots demonstrated the ability to reduce IO₃^- to I^-. Once absorbed, iodine was present as org-I or I^- with significantly greater concentrations in the apoplast than the symplast. Plants were shown to absorb similar concentrations of iodine applied as I^- or IO₃^-, via the roots, grown in an inert growth substrate. We found that whilst leaves were capable of absorbing radioactively labelled iodine applied to a single leaf, less than 2% was transferred through the phloem to younger leaves. In this paper, we show that iodine uptake is predominantly passive (approximately two-thirds of total uptake); however, I^- can be absorbed actively through the symplast. Spinach leaves can absorb iodine via foliar fertilisation, but translocation is severely limited. As such, foliar application is unlikely to significantly increase the iodine content, via phloem translocation, of fruits, grains or tubers.

Investigating the use of microdialysis and SEC-UV-ICP-MS to assess iodine interactions in soil solution

Element cycling in the terrestrial environment is heavily reliant upon processes that occur in soil solution. Here we present the first application of microdialysis to sample iodine from soil solution. In comparison to conventional soil solution extraction methods such as Rhizon™ samplers, centrifugation, and high-pressure squeezing, microdialysis can passively sample dissolved compounds from soil solution without altering the in-situ speciation of trace elements at realistic soil moisture conditions. In order to assess the suitability of microdialysis for sampling iodine, the permeability factors and effect of perfusion flowrate on I^- and IO₃^- recovery was examined in stirred solutions. Furthermore, microdialysis was used to sample native soluble iodine at a range of water contents and iodine-enriched soils to investigate iodine soil dynamics. Total iodine concentrations were measured using ICP-MS. Inorganic species and the molecular weight distribution of organically bound iodine were determined by anion exchange and size exclusion chromatography (SEC) coupled to an ICP-MS, respectively. The most effective recovery rates in stirred solution were observed with the slowest perfusion flowrate yielding 66.2 ± 7.1 and 70.5 ± 7.1% for I^- and IO₃^-, respectively. Microdialysis was proven to be capable of sampling dissolved iodine from the soil solution, which accounted for <2.5% of the total soil iodine and speciation followed the sequence: organic-I > I^- > IO₃^-. The use of SEC coupled to (i) UV and (ii) ICP-MS analysis provided detail regarding the molecular weight distribution of dissolved org-I compounds. Dissolved org-I was detected with approximate molecular weights between 0.1 and 4.5 kDa. The results in this study show that microdialysis is a suitable technique for sampling dissolved iodine species from soils maintained at realistic moisture contents. In addition, inorganic iodine added to soils was predominately bound with relatively low molecular weight (<4.5 kDa) soluble organic matter.

African savanna elephants (Loxodonta africana) as an example of a herbivore making movement choices based on nutritional needs

Background

The increasing human population and global intensification of agriculture have had a major impact on the world’s natural ecosystems and caused devastating effects on populations of mega-herbivores such as the African savanna elephants, through habitat reduction and fragmentation and increased human–animal conflict. Animals with vast home ranges are forced into increasingly smaller geographical areas, often restricted by fencing or encroaching anthropogenic activities, resulting in huge pressures on these areas to meet the animals’ resource needs. This can present a nutritional challenge and cause animals to adapt their movement patterns to meet their dietary needs for specific minerals, potentially causing human–animal conflict. The aim of this review is to consolidate understanding of nutritional drivers for animal movement, especially that of African savanna elephants and focus the direction of future research. Peer reviewed literature available was generally geographically specific and studies conducted on isolated populations of individual species. African savanna elephants have the capacity to extensively alter the landscape and have been more greatly studied than other herbivores, making them a good example species to use for this review. Alongside this, their movement choices, potentially linked with nutritional drivers could be applicable to a range of other species. Relevant case study examples of other herbivores moving based on nutritional needs are discussed.

Methods

Three databases were searched in this review: Scopus, Web of Science and Google Scholar, using identified search terms. Inclusion and exclusion criteria were determined and applied as required. Additional grey literature was reviewed as appropriate.

Results

Initial searches yielded 1,870 records prior to application of inclusion and exclusion criteria. A less detailed review of grey literature, and additional peer-reviewed literature which did not meet the inclusion criteria but was deemed relevant by the authors was also conducted to ensure thorough coverage of the subject.

Discussion

A review of peer reviewed literature was undertaken to examine nutritional drivers for African elephant movement, exploring documented examples from free-ranging African savanna elephants and, where relevant, other herbivore species. This could help inform prediction or mitigation of human–elephant conflict, potentially when animals move according to nutritional needs, and related drivers for this movement. In addition, appropriate grey literature was included to capture current research.

Effect of Excess Iodine Intake from Iodized Salt and/or Groundwater Iodine on Thyroid Function in Nonpregnant and Pregnant Women, Infants, and Children: A Multicenter Study in East Africa

BACKGROUND

Acute excess iodine intake can damage the thyroid, but the effects of chronic excess iodine intake are uncertain. Few data exist for pregnant and lactating women and infants exposed to excessive iodine intake.

METHODS

This was a multicenter cross-sectional study. At study sites in rural Kenya and urban Tanzania previously reporting iodine excess in children, urinary iodine concentration (UIC), thyrotropin, total thyroxine, and thyroglobulin (Tg) were measured in school-age children (SAC), women of reproductive age, pregnant (PW) and lactating women, and breast-feeding and weaning infants. In a national study in Djibouti, UIC was measured in SAC and PW. At all sites, daily iodine intake was estimated based on UIC, and iodine concentration was measured in household salt and drinking water.

RESULTS

The total sample size was 4636: 1390, 2048, and 1198 subjects from Kenya, Tanzania, and Djibouti, respectively. In Kenya and Tanzania: (i) median UIC was well above thresholds for adequate iodine nutrition in all groups and exceeded the threshold for excess iodine intake in SAC; (ii) iodine concentrations >40 mg of iodine/kg were found in approximately 55% of household salt samples; (iii) iodine concentrations ≥10 μg/L were detected in 9% of drinking water samples; (iv) Tg was elevated in all population groups, but the prevalence of thyroid disorders was negligible, except that 5-12% of women of reproductive age had subclinical hyperthyroidism and 10-15% of PW were hypothyroxinemic. In Djibouti: (i) the median UIC was 335 μg/L (interquartile range [IQR] = 216-493 μg/L) in SAC and 265 μg/L (IQR = 168-449 μg/L) in PW; (ii) only 1.6% of Djibouti salt samples (n = 1200) were adequately iodized (>15 mg/kg); (iii) the median iodine concentration in drinking water was 92 μg/L (IQR = 37-158 μg/L; n = 77). In all countries, UIC was not significantly correlated with salt or water iodine concentrations.

CONCLUSIONS

Although iodine intake was excessive and Tg concentrations were elevated, there was little impact on thyroid function. Chronic excess iodine intake thus appears to be well tolerated by women, infants, and children. However, such high iodine intake is unnecessary and should be avoided. Careful evaluation of contributions from both iodized salt and groundwater iodine is recommended before any review of iodization policy is considered.

Iodine soil dynamics and methods of measurement: a review

Iodine is an essential micronutrient for human health: insufficient intake can have multiple effects on development and growth, affecting approximately 1.9 billion people worldwide. Previous reviews have focussed on iodine analysis in environmental and biological samples, however, no such review exists for the determination of iodine fractionation and speciation in soils. This article reviews the geodynamics of both stable ¹²⁷I and the long-lived isotope ¹²⁹I (t_1/2 = 15.7 million years), alongside the analytical methods for determining iodine concentrations in soils, including consideration of sample preparation. The ability to measure total iodine concentration in soils has developed significantly from rudimentary spectrophotometric analysis methods to inductively coupled plasma mass spectrometry (ICP-MS). Analysis with ICP-MS has been reported as the best method for determining iodine concentrations in a range of environmental samples and soils due to developments in extraction procedures and sensitivity, with extremely good detection limits typically <μg L^-1. The ability of ICP-MS to measure iodine and its capabilities to couple on-line separation tools has the significance to develop the understanding of iodine geodynamics. In addition, nuclear-related analysis and recent synchrotron light source analysis are discussed.

Has iodized salt reduced iodine-deficiency disorders among school-aged children in north-west Iran? A 9-year prospective study

OBJECTIVE

Low iodine intakes are associated with goitre and other iodine-deficiency disorders (IDD) that have affected billions of people worldwide. We aimed to assess total goitre rate (TGR) and urinary iodine concentration (UIC) in schoolchildren between 2007 and 2015, percentage of iodized salt consumption by households, and salt iodine content at production, distribution and household levels in north-west Iran. Design/Setting/Subjects UIC assessed among schoolchildren in nine consecutive years; 240 schoolchildren aged 8-10 years selected by systematic random sampling each year in the West Azerbaijan Province.

RESULTS

Median UIC was >100 μg/l in all years. More than 50 % of children had iodine deficiency (UIC≤99 μg/l) in 2010 and 2011, while this rate was approximately 15-35 % in other years. Proportion with UIC below 50 μg/l was <20 % in all years except 2010 and 2011. Excessive UIC (≥300 μg/l) rate was between 5·4 and 27·5 %. TGR decreased from 44 % in 1996 to 7·6 % and 0·4 % in 2001 and 2007, respectively. Regular surveys from 2002 to 2015 showed that 98 % or more of households consumed iodized salt. Iodine level ≥20 ppm was observed in 87·5, 83 and 73 % of salt at production, distribution and household level, respectively (data from national study in 2007). The last national study in 2014 showed that median iodine level in household salt was 27 ppm.

CONCLUSIONS

Our focused data suggest that the universal salt iodization programme is improving the iodine status of schoolchildren in the West Azerbaijan Province of Iran. Reduction of TGR to less than 5 % in schoolchildren indicates successful elimination of IDD as a major public health problem.

Elemental composition of Malawian rice

Widespread potential dietary deficiencies of calcium (Ca), iron (Fe), iodine (I), selenium (Se) and zinc (Zn) have been identified in Malawi. Several deficiencies are likely to be compounded by high phytic acid (PA) consumption. Rice (Oryza sativa) is commonly consumed in some Malawian populations, and its mineral micronutrient content is important for food security. The considerable irrigation requirements and flooded conditions of paddy soils can also introduce or mobilise potentially toxic elements including arsenic (As), cadmium (Cd) and lead (Pb). The aim of this study was to determine the mineral composition of rice sampled from farmers' fields and markets in Malawi. Rice was sampled from 18 extension planning areas across Malawi with 21 white (i.e. polished) and 33 brown samples collected. Elemental composition was determined by inductively coupled plasma-mass spectrometry (ICP-MS). Arsenic speciation was performed using high-performance liquid chromatography (HPLC)-ICP-MS. Concentration of PA was determined using a PA-total phosphorus assay. Median total concentrations (mg kg^-1, dry weight) of elements important for human nutrition in brown and white rice, respectively, were: Ca = 66.5 and 37.8; Cu = 3.65 and 2.49; Fe = 22.1 and 7.2; I = 0.006 and <0.005; Mg = 1130 and 265; Mn = 18.2 and 9.6; Se = 0.025 and 0.028; and Zn = 17.0 and 14.4. In brown and white rice samples, respectively, median PA concentrations were 5438 and 1906 mg kg^-1, and median PA:Zn molar ratios were 29 and 13. Concentrations of potentially toxic elements (mg kg^-1, dry weight) in brown and white rice samples, respectively, were: As = 0.030 and 0.006; Cd  ≤ 0.002 and 0.006; Pb = 0.008 and 0.008. Approximately 95 % of As was found to be inorganic As, where this could be quantified. Malawian rice, like the more widely consumed staple grain maize, contains inadequate Ca, I, Se or Zn to meet dietary requirements. Biofortification strategies could significantly increase Se and Zn concentrations and require further investigation. Concentrations of Fe in rice grain varied greatly, and this was likely due to contamination of rice samples with soil. Risk of As, Cd or Pb toxicity due to rice consumption in Malawi appears to be minimal.

Health risk assessment of potentially harmful elements and dietary minerals from vegetables irrigated with untreated wastewater, Pakistan

In the developing world, vegetables are commonly grown in suburban areas irrigated with untreated wastewater containing potentially harmful elements (PHEs). In Pakistan, there is no published work on the bioaccessibility aspect of PHEs and dietary minerals (DMs) in sewage-irrigated soil or the vegetables grown on such soils in Pakistan. Several industrial districts of Pakistan were selected for assessment of the risk associated with the ingestion of vegetables grown over sewage-irrigated soils. Both the total and bioaccessible fraction of PHEs (Cd, Co, Cr, Ni, and Pb) and DMs (Fe, Cu, Mn, Zn, Ca, Mg, and I) in soils and vegetable samples were measured. The concentrations of these PHEs and DMs in sewage-irrigated and control soils were below published upper threshold limits. However, compared to control soils, sewage irrigation over the years decreased soil pH (7.7 vs 8.1) and enhanced dissolved organic carbon (1.8 vs 0.8 %), which could enhance the phyto-availability of PHEs and DMs to crops. Of the PHEs and DMs, the highest transfer factor (soil to plant) was noted for Cd and Ca, respectively. Concentrations of PHEs in most of the sewage-irrigated vegetables were below the published upper threshold limits, except for Cd in the fruiting portion of eggplant and bell pepper (0.06-0.08 mg/kg Cd, dry weight) at three locations in Gujarat and Kasur districts. The bioaccessible fraction of PHEs can reduce the context of dietary intake measurements compared to total concentrations, but differences between both measurements were not significant for Cd. Since the soils of the sampled districts are not overly contaminated compared to control sites, vegetables grown over sewage-irrigated soils would provide an opportunity to harvest mineral-rich vegetables potentially providing consumers 62, 60, 12, 104, and 63 % higher dietary intake of Cu, Mn, Zn, Ca, and Mg, respectively. Based on Fe and vanadium correlations in vegetables, it is inferred that a significant proportion of total dietary Fe intake could be contributed by soil particles adhered to the consumable portion of vegetables. Faecal sterol ratios were used to identify and distinguish the source of faecal contamination in soils from Gujranwala, Gujarat, and Lahore districts, confirming the presence of human-derived sewage biomarkers at different stages of environmental alteration. A strong correlation of some metals with soil organic matter concentration was observed, but none with sewage biomarkers.

Assessing urinary flow rate, creatinine, osmolality and other hydration adjustment methods for urinary biomonitoring using NHANES arsenic, iodine, lead and cadmium data

BACKGROUND

There are numerous methods for adjusting measured concentrations of urinary biomarkers for hydration variation. Few studies use objective criteria to quantify the relative performance of these methods. Our aim was to compare the performance of existing methods for adjusting urinary biomarkers for hydration variation.

METHODS

Creatinine, osmolality, excretion rate (ER), bodyweight adjusted ER (ERBW) and empirical analyte-specific urinary flow rate (UFR) adjustment methods on spot urinary concentrations of lead (Pb), cadmium (Cd), non-arsenobetaine arsenic (As(IMM)) and iodine (I) from the US National Health and Nutrition Examination Survey (NHANES) (2009-2010 and 2011-2012) were evaluated. The data were divided into a training dataset (n = 1,723) from which empirical adjustment coefficients were derived and a testing dataset (n = 428) on which quantification of the performance of the adjustment methods was done by calculating, primarily, the correlation of the adjusted parameter with UFR, with lower correlations indicating better performance and, secondarily, the correlation of the adjusted parameters with blood analyte concentrations (Pb and Cd), with higher correlations indicating better performance.

RESULTS

Overall performance across analytes was better for Osmolality and UFR based methods. Excretion rate and ERBW consistently performed worse, often no better than unadjusted concentrations.

CONCLUSIONS

Osmolality adjustment of urinary biomonitoring data provides for more robust adjustment than either creatinine based or ER or ERBW methods, the latter two of which tend to overcompensate for UFR. Modified UFR methods perform significantly better than all but osmolality in removing hydration variation, but depend on the accuracy of UFR calculations. Hydration adjustment performance is analyte-specific and further research is needed to establish a robust and consistent framework.