Comparison of size and geography of airborne tungsten particles in Fallon, Nevada, and Sweet Home, Oregon, with implications for public health

Tungsten in Washington State surface waters

At high concentrations, tungsten can be toxic to humans, animals, and the environment, though little is known about natural, aqueous tungsten in surface waters. To improve understanding and develop a model predicting tungsten concentrations, we collected water and sediment from 77 water bodies in 20 watersheds in Washington State, USA. We found aqueous tungsten concentrations spanning two orders of magnitude (10.3 ng L^-1 - 2.05 μg L^-1) with average tungsten concentrations in both water and sediments more than two-fold higher in watersheds with tungsten-bearing underlying rock types (average: 0.217 μg L^-1, 0.669 mg kg^-1; range: 0.010-2.05 μg L^-1, 0.0713-4.691 mg kg^-1 for surface waters and sediments, respectively) than in watersheds without such underlying geology (average: 0.068 μg L^-1, 0.352 mg kg^-1; range: 0.010-0.211 μg L^-1, 0.0349-2.399 mg kg^-1 for surface waters and sediments, respectively). Aqueous concentrations of tungsten significantly correlated with beryllium (Be) and copper (Cu) (R² = 0.31, 0.41, respectively) and a multiple linear regression model using Be and Cu explained 65% of the variance in measured aqueous tungsten concentrations. Applying this model to existing Be and Cu data from 19 sites across the Pacific Northwest resulted in predicted tungsten concentrations ranging from 0.116 to 0.458 μg L^-1. These predicted concentrations along with our measured concentrations indicate none of these sites were close to the drinking water standard for tungsten set by the former Soviet Union-the only country so far to set limits for tungsten in drinking water (50 μg L^-1).

Structural Evidence of Programmed Cell Death Induction by Tungsten in Root Tip Cells of Pisum sativum

Previous studies have shown that excess tungsten (W), a rare heavy metal, is toxic to plant cells and may induce a kind of programmed cell death (PCD). In the present study we used transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) to investigate the subcellular malformations caused by W, supplied as 200 mg/L sodium tungstate (Na₂WO₄) for 12 or 24 h, in root tip cells of Pisum sativum (pea), The objective was to provide additional evidence in support of the notion of PCD induction and the presumed involvement of reactive oxygen species (ROS). It is shown ultrastructurally that W inhibited seedling growth, deranged root tip morphology, induced the collapse and deformation of vacuoles, degraded Golgi bodies, increased the incidence of multivesicular and multilamellar bodies, and caused the detachment of the plasma membrane from the cell walls. Plastids and mitochondria were also affected. By TEM, the endoplasmic reticulum appeared in aggregations of straight, curved or concentric cisternae, frequently enclosing cytoplasmic organelles, while by CLSM it appeared in bright ring-like aggregations and was severely disrupted in mitotic cells. However, no evidence of ROS increase was obtained. Overall, these findings support the view of a W-induced vacuolar destructive PCD without ROS enhancement.

Tungsten Toxicity in Plants

Tungsten (W) is a rare heavy metal, widely used in a range of industrial, military and household applications due to its unique physical properties. These activities inevitably have accounted for local W accumulation at high concentrations, raising concerns about its effects for living organisms. In plants, W has primarily been used as an inhibitor of the molybdoenzymes, since it antagonizes molybdenum (Mo) for the Mo-cofactor (MoCo) of these enzymes. However, recent advances indicate that, beyond Mo-enzyme inhibition, W has toxic attributes similar with those of other heavy metals. These include hindering of seedling growth, reduction of root and shoot biomass, ultrastructural malformations of cell components, aberration of cell cycle, disruption of the cytoskeleton and deregulation of gene expression related with programmed cell death (PCD). In this article, the recent available information on W toxicity in plants and plant cells is reviewed, and the knowledge gaps and the most pertinent research directions are outlined.