No abstract

Elemental mercury (Hg 0 ) contamination in artisanal and small-scale gold mining (ASGM) communities is widespread, and Hg 0 -contaminated tailings are often reprocessed with cyanide ( − CN) to extract residual gold remaining after amalgamation. Hg 0 reacts with − CN under aerobic conditions to produce Hg(CN) 4 2− and other Hg(CN) n n−2 complexes. The production of solvated Hg(CN) n n−2 complexes increases upon agitation in the presence of synthetic and authentic Hg 0 -contaminated tailings that aid in dispersing the Hg 0 , increasing its reactive surface area. Adult rats were exposed to various concentrations of Hg(CN) 2 , and accumulation in organs and tissues was quantified using direct mercury analysis. The primary site of Hg(CN) 2 accumulation was the kidney, although accumulation was also detected in the liver, spleen, and blood. Little accumulation was observed in the brain, suggesting that Hg(CN) 2 complexes do not cross the blood−brain barrier. Renal tissue was particularly sensitive to the effects of Hg(CN) 2 , with pathological changes observed at low concentrations. Hg(CN) 2 complexes are handled by mammalian systems in a manner similar to other inorganic species of Hg, yet appear to be more toxic to organ systems. The findings from this study are the first to show that Hg(CN) 2 complexes are highly stable complexes that can lead to cellular injury and death in mammalian organ systems.

Humans throughout the world are exposed regularly to mixtures of environmental toxicants. Four of the most common heavy metal toxicants in the environment are mercury (Hg), cadmium (Cdd), lead (Pb), and arsenic (As). Numerous previous studies assessed the effects and disposition of individual metals in organ systems; however, humans are usually exposed to mixtures of toxicants or metals rather than to a single toxicant. Therefore, the purpose of the current study was to test the hypothesis that exposure to a mixture of toxic heavy metals alters the disposition of single metals in target organs. Wistar rats (Rattus norvegicus) were exposed to Hg, Cd, Pb, or As as a single metal or as a mixture of metals. Rats were injected intravenously for three days, following which kidneys, liver, brain, and blood were harvested. Samples were analyzed for content of Hg, Cd, Pb, and As via inductively coupled plasma mass spectrometry. In general, exposure to a mixture of metals reduced accumulation of single metals in target organs. Interestingly, exposure to mixtures of metals with Pb and/or As increased the concentration of these metals specifically in the liver. The findings from this study indicate that exposure to mixtures of toxic heavy metals may alter significantly the distribution and accumulation of these metals in target organs and tissues.

No abstract