The Iodine Status of Queensland Preschool Children After the Introduction of Mandatory Iodine Fortification in Bread: An Exploratory Study Using a Convenience Sample.

Introduction Appropriate dietary iodine is essential for thyroid hormone synthesis, especially in young children. Following an iodine fortification in bread initiative, approximately 6 % of Australian preschool children were expected to have an excessive iodine status. The aim of this study was to document the current iodine status of preschool children using urinary iodine concentration (UIC) as a biomarker of iodine intake. Methods A convenience sample of fifty-one preschool children, aged 2-3 years, were recruited from south east Queensland. UIC was ascertained from spot morning and afternoon urine samples collected on two consecutive days and food frequency questionnaires were completed for each participant. Dietary iodine intake was extrapolated from UIC assuming 90 % of dietary iodine is excreted in urine and a urine volume of 0.5 L/day. Results A median UIC of 223.3 µg/L was found. The calculated median dietary iodine intake was 124.8 µg/day (SD 47.0) with 9.8 % of samples above the upper level of 200 µg for dietary iodine for children within this age group. No foods were associated with UIC. Discussion Limited by sample size and recruitment strategies, no association was found between usual food intake and UIC. Extrapolated dietary iodine intake indicated that children within this cohort consumed adequate amounts of dietary iodine, although the number of children consuming above the upper limit of 300 µg/day was almost double of expected. The development of a UIC criteria to assess appropriate parameters for varying degrees of iodine status is required for the monitoring of iodine nutrition in this vulnerable age group.

Advantages of collecting multiple urinary iodine concentrations when assessing iodine status of a population.

AIM: To evaluate the effect of collecting multiple (four) urine samples on the extensive variance often observed within a cohort when determining iodine status via urinary iodine concentration (UIC). METHODS: Fifty-one children aged two to three years and thirty children aged 8-10 years participated in the study in South East Queensland, Australia. Each child's four urine samples were analysed using ammonium persulphate digestion before a Sandell-Kolthoff reaction method. Analysis of variance techniques were used to assess the effect of using multiple urine samples. RESULTS: The median UICs were 223.3 and 141 µg/L for two- to three-year-olds and eight- to 10-year-olds, respectively. The coefficient of variance (CV) of UIC for children aged two to three years was reduced by 35.6%, 36.5% and 39.7% when two, three and four samples were included in the adjustment, respectively. Similarly, the CV of UIC for children aged 8-10 years was reduced by 24.7%, 30.7% and 34.7%, respectively. CONCLUSION: Although the practicality and cost of collecting multiple UICs need to be considered, collecting multiple UIC samples from each participant provides a more accurate reflection of a cohort iodine status.

Short term variability in urinary bisphenol A in Australian children.

Used frequently in food contact materials, bisphenol A (BPA) has been studied extensively in recent years, and ubiquitous exposure in the general population has been demonstrated worldwide. Characterizing within- and between-individual variability of BPA concentrations is important for characterizing exposure in biomonitoring studies, and this has been investigated previously in adults, but not in children. The aim of this study was to characterize the short-term variability of BPA in spot urine samples in young children. Children aged ≥2-<4 years (n=25) were recruited from an existing cohort in Queensland, Australia, and donated four spot urine samples each over a two day period. Samples were analysed for total BPA using isotope dilution online solid phase extraction-liquid chromatography-tandem mass spectrometry, and concentrations ranged from 0.53 to 74.5 ng/ml, with geometric mean and standard deviation of 2.70 ng/ml and 2.94 ng/ml, respectively. Sex and time of sample collection were not significant predictors of BPA concentration. The between-individual variability was approximately equal to the within-individual variability (ICC=0.51), and this ICC is somewhat higher than previously reported literature values. This may be the result of physiological or behavioural differences between children and adults or of the relatively short exposure window assessed. Using a bootstrapping methodology, a single sample resulted in correct tertile classification approximately 70% of the time. This study suggests that single spot samples obtained from young children provide a reliable characterization of absolute and relative exposure over the short time window studied, but this may not hold true over longer timeframes.