| Temporal Patterns in Perchlorate, Thiocyanate, and Iodide Excretion in Human Milk Andrea B. Kirk,1 Jason V. Dyke,1 Clyde F. Martin,2 and Purnendu K. Dasgupta1 1Department of Chemistry and Biochemistry, and 2Department of Mathematics and Statistics, Texas Tech University, Lubbock, Texas, USA Abstract
Background: Perchlorate and thiocyanate interfere with iodide uptake at the sodium–iodide symporter and are potential disruptors of thyroid hormone synthesis. Perchlorate is a common contaminant of water, food, and human milk. Although it is known that iodide undergoes significant diurnal variations in serum and urinary excretion, less is known about diurnal variations of milk iodide levels. Objectives: Variability in perchlorate and thiocyanate excretion in human milk has not been examined. Our objective was to determine variability of perchlorate, thiocyanate, and iodide in serially collected samples of human milk. Methods: Ten lactating women were asked to collect six milk samples on each of 3 days. As an alternative, subjects were asked to collect as many milk samples as comfortably possible over 3 days. Samples were analyzed for perchlorate, iodide, and thiocyanate by ion chromatography coupled with mass spectrometry. Results: Individual perchlorate, iodide, and thiocyanate levels varied significantly over time ; there was also considerable variation among individuals. The iodide range, mean ± SD, and median for all samples (n = 108) were 3.1–334 µg/L, 87.9 ± 80.9 µg/L, and 55.2 µg/L, respectively. The range, mean ± SD, and median of perchlorate in all samples (n = 147) were 0.5–39.5 µg/L, 5.8 ± 6.2 µg/L, and 4.0 µg/L. The range, mean ± SD, and median of thiocyanate in all samples (n = 117) were 0.4 –228.3 µg/L, 35.6 ± 57.9 µg/L, and 5.6 µg/L. The data are not symmetrically distributed ; the mean is higher than the median in all cases. Conclusions: Iodine intake may be inadequate in a significant fraction of this study population. Perchlorate and thiocyanate appear to be common in human milk. The role of these chemicals in reducing breast milk iodide is in need of further investigation. Key words: breast-feeding, human milk iodide, milk, perchlorate, thiocyanate. Environ Health Perspect 115: 182–186 (2007) . doi:10.1289/ehp.9558 available via http://dx.doi.org/ [Online 20 November 2006]
Address correspondence to P.K. Dasgupta, Department of Chemistry, University of Texas at Arlington, Arlington, TX 76009-0065 USA. Telephone: (817) 272-3171. Fax: (817) 272-3808. E-mail: Dasgupta@uta.edu The contributions of our donors and their infants are sincerely appreciated and gratefully acknowledged. This study was primarily supported by Paul Whitfield Horn Professorship funds to P.K.D. and C.F.M. Overlapping perchlorate epidemiologic research at Texas Tech University is also supported by the State of Texas Advanced Research Program (3644-0007-2006) and by the Gerber Foundation. The authors declare they have no competing financial interests. Received 27 July 2006 ; accepted 20 November 2006.
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