Inorganic and organic mercury levels in the United States National Health and Nutrition Examination Survey (NHANES) 2005-2010

Abstract

OBJECTIVES: Mercury is an environmental hazard. Therefore, we studied recent trends in the blood level of organic and inorganic mercury in the United States. METHODS: We analysed newly available data on blood inorganic mercury levels in the United States National Health and Nutrition Examination Survey (NHANES) 2005-2010. Organic mercury level was calculated by subtracting inorganic mercury level from the total mercury level. As complex sampling was used in NHANES, appropriate weights were used to adjust for oversampling of minorities and sampling from the same location. RESULTS: There were 8364, 8161, and 8727 participants in NHANES 2005-6, 2007-8, and 2009-10, respectively. Inorganic mercury levels (geometric mean [95% confidence interval]) were 0.31 [0.30-0.32], 0.30 [0.30-0.31], 0.28 [0.27-0.28] µg/L and organic mercury levels were 0.24 [0.19-0.30], 0.19 [0.14-0.25], 0.27 [0.22-0.33] µg/L in 2005-6, in 2007-8, and in 2009-10, respectively. Inorganic mercury levels showed a significant decreasing trend (P < 0.05). The adjusted proportion (mean ± standard error) of participants with a total mercury level of ≥5.8 µg/L was 3.0 ± 0.2%, 3.5 ± 0.6%, and 4.0 ± 0.4% (P < 0.05) in NHANES 2005-6, 2007-8, and 2009-10, respectively. CONCLUSIONS: Inorganic mercury level has been decreasing during the study period. Organic mercury level was lower in 2007-2008 but increased in 2009-10. The significant increase in organic mercury level in the US general population in 2009-10 is of concern, suggesting that continual monitoring of mercury levels is needed.