Human Exposure to Mercury during the Last Half-Century: Worldwide Trends in Human Blood and Breast Milk Levels and Their Implications on Health

Abstract

Mercury is a pollutant of global concern. It has been found in various biological media including human blood and breast milk, globally. This study assesses global and regional trends of mercury levels in human blood and breast milk in the last half-century. This study also provides an overview of epidemiological literature showing evidence of associations between mercury exposure and various human health conditions.We searched electronic databases to identify articles published prior to June 14, 2017. Our search finalized a pool of 562 studies reporting total mercury levels in whole blood, cord blood, or breast milk and associations with human health conditions. Temporal trends of mercury levels in target media were estimated using a linear fit of the log-transformed data. Choropleth maps were created to provide an overview of worldwide mercury levels in human blood and breast milk. Furthermore, a summary of significant and relevant associations between mercury exposure and human health conditions in children and adults was prepared.We found significant declines in mercury levels in whole blood, cord blood, and breast milk between 1966–2015. A regional overview of mercury exposure suggests highest levels in South America, followed by Africa and Asia. Populations from North America and Europe were found with the lowest mercury exposure levels. We observed conclusive consistent associations of mercury exposure with only selected health conditions, especially neurodevelopment and neurotoxicity in children and adults. For several other health conditions, reported findings do not support conclusive associations.Our study establishes a baseline for the evaluation of mercury levels and health risks that will be measured under the Minamata Convention in the future and highlights the demand for well-designed epidemiological investigations to fully understand the health implications of mercury exposure.