Geographic and dietary differences of urinary uranium levels in the Strong Heart Family Study

Abstract

BACKGROUND AND AIM: Chronic low-dose exposure to uranium (U) through diet is not well characterized in the US. American Indian (AI) participants in the Strong Heart Family Study (SHFS) have higher urinary uranium concentrations compared to the general US population. This disproportionate exposure might be explained by groundwater contamination in rural and sub-urban regions, or through dietary exposures. The objective of this study was to evaluate differences in urinary uranium concentrations by diet and geography among American Indians from the Northern Plains, the Southern Plains, and the Southwest. METHODS: We evaluated food frequency questionnaires to determine the major dietary sources of urinary uranium concentrations for 2,170 AI participants in the SHFS, collected during phase IV (2001-2003). We assessed adjusted geometric mean ratios (GMRs) of urinary uranium for an interquartile (IQR) increase in self-reported food group consumption using generalized estimating equations. Exploratory analyses were stratified by gender and study center. RESULTS:In fully adjusted models, the percent increase (95% confidence interval) of urinary uranium per increase in reported food consumption corresponding to the IQR was 29% (14%, 47%) for organ meat, 9% (1%, 19%) for legumes, and 17% (5%, 32%) for alcohol. In analyses stratified by study center, the associations with organ meat and legumes were only observed for North/South Dakota participants. Consumption of fries and chips [percent increase -16% (-23%, -9%)] and any shellfish [-21% (-0.35%, -4%)] were inversely associated with urinary uranium. Overall, we estimated that self-reported dietary exposures explain 16.8% of variability in urine uranium concentrations. CONCLUSIONS:Organ meat, legumes, and alcohol contribute to higher uranium exposure in the SHFS population. After stratification, organ meat remained significantly associated with uranium for North and South Dakota participants. These findings warrant further investigation into the relative contribution of diet and drinking water to total uranium exposure in American Indian communities. KEYWORDS: Heavy metals, food/nutrition, environmental epidemiology, environmental disparities