The purpose of this study was to assess chronic mercury exposure within the US population. Time trends were analyzed for blood inorganic mercury (I-Hg) levels in 6,174 women, ages 18–49, in the NHANES, 1999–2006 data sets. Multivariate logistic regression distinguished a significant, direct correlation within the US population between I-Hg detection and years since the start of the survey (OR = 1.49, P < 0.001). Within this population, I-Hg detection rose sharply from 2% in 1999–2000 to 30% in 2005–2006. In addition, the population averaged mean I-Hg concentration rose significantly over that same period from 0.33 to 0.39 μ/L (Anova, P < 0.001). In a separate analysis, multivariate logistic regression indicated that I-Hg detection was significantly associated with age (OR = 1.02, P < 0.001). Furthermore, multivariate logistic regression revealed significant associations of both I-Hg detection and mean concentration with biomarkers for the main targets of mercury deposition and effect: the liver, immune system, and pituitary. This study provides compelling evidence that I-Hg deposition within the human body is a cumulative process, increasing with age and in the population over time, since 1999, as a result of chronic mercury exposure. Furthermore, our results indicate that I-Hg deposition is associated with the significant biological markers for main targets of exposure, deposition, and effect. Accumulation of focal I-Hg deposits within the human body due to chronic mercury exposure provides a mechanism which suggests a time dependent rise in the population risks for associated disease.
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This study began as an analysis of the 1999–2002 NHANES data sets for my M.S. thesis at U.C. Berkeley, Department of Environmental Health Sciences. It has since been expanded to include 1999–2006 survey populations as data became available. I would like to thank my thesis advisors, Dr. Katharine Hammond, Dr. Michael Bates, and Dr. Alan Hubbard for their patient guidance and thorough reviews of the methods and analysis of preliminary data for this study.
Conflict of interest statement
The authors declare that there are no conflicts of interest.
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