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

Abstract

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).

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Acknowledgements

The team would like to thank the BGS Global, BGS ODA and BGS Centre for Environmental Geochemistry for financial support. We would like to thank the many people who assisted in the collection of samples, including the Public Health Officers from each county and in particular the field and laboratory staff from the University of Eldoret (UoE), Moi University (Moi) and BGS: David Samoie, Doreen Meso, Charles Owano (UoE), Esilaba Anabwani Amimo Anabwani (Moi), Nicholas Porter, Sophia Dowell (BGS). Thanks also to David Gardner at the University of Nottingham the School of Veterinary Sciences for creatinine and osmolality measurements. This manuscript is published with the permission of the Executive Director of the British Geological Survey.

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Watts, M.J., Middleton, D.R.S., Marriott, A. et al. Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations. Environ Geochem Health 42, 1141–1151 (2020). https://doi.org/10.1007/s10653-019-00352-0

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Keywords

  • Urinary iodine concentrations
  • Iodine excess
  • Hydration status corrections