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Mercury as a global pollutant: sources, pathways, and effects.

ABSTRACT: Mercury (Hg) is a global pollutant that affects human and ecosystem health. We synthesize understanding of sources, atmosphere-land-ocean Hg dynamics and health effects, and consider the implications of Hg-control policies. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments. Transfers of Hg emissions to largely unavailable reservoirs occur over the time scale of centuries, and are primarily mediated through atmospheric exchanges of wet/dry deposition and evasion from vegetation, soil organic matter and ocean surfaces. A key link between inorganic Hg inputs and exposure of humans and wildlife is the net production of methylmercury, which occurs mainly in reducing zones in freshwater, terrestrial, and coastal environments, and the subsurface ocean. Elevated human exposure to methylmercury primarily results from consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin but health effects of highly exposed populations and wildlife are also a concern. Integration of Hg science with national and international policy efforts is needed to target efforts and evaluate efficacy.

SUBMITTER: Driscoll CT

PROVIDER: S-EPMC3701261 | biostudies-other | 2013 May

REPOSITORIES: biostudies-other

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Project description:The delta smelt (Hypomesus transpacificus) is a pelagic fish species endemic to the Sacramento-San Joaquin Estuary in Northern California, listed as endangered under both the USA Federal and Californian State Endangered Species Acts and acts as an indicator of ecosystem health in its habitat range. Interrogative tools are required to successfully monitor effects of contaminants upon the delta smelt, and to research potential causes of population decline in this species. We used microarray technology to investigate genome-wide effects in 47-day old larvae after a 7-day exposure to ambient water samples from the Sacramento River at a monitoring field station (Hood) situated 8 miles downstream of the Sacramento regional Wastewater Treatment Plant. Genomic assessments were carried out on surviving organisms and contrasted to laboratory controls. Microarray assessments were conducted on larvae exposed for 7-days to Sacramento River water collected at Hood and pooled laboratory controls. Assessments were carried out in quadruplicate, using 3 fish per treatment. RNA was extracted from frozen whole, individual organisms, using Trizol Reagent (Invitrogen) as per manufacturer's guidelines. Total RNA from 5 fish was pooled per treatment and cDNA was synthesized from a total of 2ug total RNA, amplified using a SuperScripttm Indirect RNA Amplification System (Invitrogen). Resulting aRNA was labeled with Alexa fluor dyes (Invitrogen) as per manufacturerM-bM-^@M-^Ys instructions. Two color microarray assessments were carried out on quadruplicate treatments, using 5M-BM-5g of aRNA for pooled controls vs exposed sample, (total 4 samples). Microarray hybridizations were performed manually, and incubated in a waterbath at 42C for 16 hours. Slides were scanned using a GenePix 4000B scanner (Axon Instruments). Data was analyzed using LIMMA GUI (Linear model for microarray analysis graphical user interface) (Smyth, 2005), written in the R-programming language available through Bioconductor http://www.Bioconductor.org. Data was normalized within using print-tip Lowess and between arrays applying average intensity quantile (Aquantile) normalization methods with background correction (Smyth, 2005). A linear model fit was computed using the duplicates on the arrays and the least-squares method, with Benjamin Hochberg false discovery rate adjustment.

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Mercury as a global pollutant: sources, pathways, and effects.

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