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Background:This report presents urinary iodine (UI) concentrations for the general U.S. population during 2005–2006 and 2007–2008. These findings are the fourth and fifth assessments of the population since National Health and Nutrition Examination Survey (NHANES) III (1988–1994), when the median UI concentration for the population decreased from NHANES I (1971–1974).Methods:During 2005–2006 and 2007–2008, ∼5000 participants per year were selected to participate in NHANES. The participants were interviewed and examined. UI concentration was measured on a random one third subsample of 2649 participants, aged 6 years and older in 2005–2006, and in all participants in 2007–2008. These urine iodine concentrations are representative of the general U.S. population by age, sex, and race/ethnicity.Results:(i) The median UI concentrations for the general U.S. population in 2005–2006 and 2007–2008 were 164 μg/L (95% confidence interval [CI] 154–174) and 164 μg/L (95% CI 154–173), respectively. Also, the proportions of the population with a UI concentration of <50 μg/L during these survey periods were 9.8% ± 1.3% and 8.8% ± 0.4%, respectively. The median UI concentration and prevalence of ≥200 μg/L appeared to be higher in children and persons ≥70 years than in other age groups. (ii) In both surveys, children aged 6–11 years had median UI concentrations of ≥200 μg/L, and about 5% of them had a UI concentration of <50 μg/L. (iii) All pregnant women (sample size 184) surveyed during 2005–2008 had a median UI concentration of 125 μg/L (95% CI 86–198), and 56.9% ± 7.9% of this group had a UI concentration of <150 μg/L. UI concentrations were lower among non–Hispanic black survey participants than non–Hispanic white and Mexican-American participants.Conclusions:These findings affirm the stabilization of UI concentration and adequate iodine nutrition in the general U.S. population since 2000. However, certain groups likely do not achieve a sufficient dietary iodine intake according to the World Health Organization. The needs of these vulnerable groups and the inadequacy of their dietary iodine intake should be addressed in future efforts. [ABSTRACT FROM AUTHOR]

Background: Conventional wisdom regarding exposures to persistent organic chemicals via breastfeeding assumes that concentrations decline over the course of lactation and that the mother's body burden reflects her cumulative lifetime exposure. Two important implications stemming from these lines of thought are, first, that assessments of early childhood exposures should incorporate decreasing breast milk concentrations over lactation; and, second, that there is little a breast-feeding mother can do to reduce her infant's exposures via breast-feeding because of the cumulative nature of these chemicals. Objectives: We examined rates of elimination and milk/serum partition coefficients for several groups of persistent organic chemicals. Methods: We collected simultaneous milk and blood samples of 10 women at two times postpartum and additional milk samples without matching blood samples. Results: Contrary to earlier research, we found that lipid-adjusted concentrations of polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and furans, and organochlorine pesticides in serum and milk do not consistently decrease during lactation and can increase for some women. Published research has also suggested an approximate 1:1 milk/serum relationship (lipid adjusted) on a population basis for 2,3,7,8-tetrachlorodibenzo-p-dioxin; however, our results suggest a more complex relationship for persistent, lipophilic chemicals with the milk/serum relationship dependent on chemical class. Conclusions: Decreases in concentration of lipophilic chemicals on a lipid-adjusted basis during lactation should no longer be assumed. Thus, the concept of pumping and discarding early milk as means of reducing infant exposure is not supported. The hypothesis that persistent lipophilic chemicals, on a lipid-adjusted basis, have consistent concentrations across matrices is likely too simplistic. [ABSTRACT FROM AUTHOR]

Background:Since 1971, the general U.S. population has been monitored for dietary iodine sufficiency by urinary iodine (UI) measurements through the National Health and Nutrition Examination Survey (NHANES). This report presents the UI levels for the population participating in NHANES 2003–2004. It is the third assessment of the U.S. population since NHANES III (1988–1994), when the median UI level was observed to decrease from NHANES I (1971–1974).Methods:In 2003–2004, a stratified, multistage, probability sample of approximately 5000 participants per year were selected to participate in NHANES Household interviews, and specimen collection were performed. UI level was measured by inductively coupled plasma mass spectrometry on a random subsample of 2526 participants aged 6 years and older.Results:The median UI level for the general U.S. population in 2003–2004 was 160 μg/L (95% confidence interval [CI] 146–172), and 11.3 ± 1.8% of the population had a UI level below 50 μg/L. Children had a higher UI level than adolescents and adults. Among all (pregnant and nonpregnant) women of reproductive age, the median UI level was 139 μg/L (95% CI 117–156), 15.1 ± 3.2% women had a UI level <50 μg/L, and Non-Hispanic blacks in this group had a lower UI level than other racial/ethnic groups.Conclusions:These findings affirm the stabilization of the UI level and the adequate iodine nutrition in the general U.S. population since 2000. Future surveys designed to achieve UI levels representative of pregnant women can improve the estimate of iodine sufficiency in this population subgroup. Continued monitoring of the population for iodine sufficiency is warranted because of groups at risk for iodine deficiency disorders. [ABSTRACT FROM AUTHOR]