Characterization of Airborne Particulates and Worker Exposures in Electro-static Powder Coating Operations.

This study was to examine the airborne particulates/dusts and worker exposures in electro-static powder coating operations. Temporal variation and size distribution of dusts were assessed using direct-reading instrument, while the worker task-specific dust exposures (n = 41) were measured in three factories using conventional filter method. Additionally, toxic metal levels in the coating powder (n = 27) were analyzed to assess hazard potentials. Continuous monitoring of airborne respirable dust levels indicated large temporal variation across a normal working day. The particulate levels outside spraying booths were generally low (below 0.10 mg m-3) during normal spraying operation, but short-term level may reach as high as 21.8 mg m-3 (averaged at 4-5 mg m-3) when specific task such as cleaning the pipelines and spraying booth, was performed. Exploratory assessment on particle size distribution at four major working zones, administration, uploading, spraying, and baking, indicated no major difference among the zones, and between factories. The particle count median aerodynamic diameter was 0.88-1.69 µm, while the mean number concentrations were 10.97, 15.17, 18.49, and 27.03 (# cm-3) for zones administration, uploading, spraying, and baking, respectively. The worker task-specific dust exposures were found low during normal spraying, with the mean short-term total and respirable dust concentrations being 0.88 and 0.41 mg m-3, respectively. Both levels increased to 3.48 and 5.19 mg m-3, respectively (P < 0.05), if powder changing and system cleaning were done. Short-term total and respirable dust concentrations were 94.2 and 56.1 mg m-3, respectively, when complete cleaning process was performed inside spraying booth. Both levels exceeded the short-term exposure limits. The mean concentration of metals in the powder samples were 6.78, 9.52, 10 717, 2805, 1020, and 1361 µg g-1 for Pb, Cr (total), Al, Fe, Cu, and Sr, respectively. This study demonstrated that cleaning of spraying booth resulted in high dust exposures well exceeding the exposure limit. Toxic metals, particularly Pb, Cd, and Cr (total), levels measured in the powder samples were found low, and the resulting exposures were below the exposure limits, indicating relative low risks associated with the exposure at current dust levels.

Water-Based Automobile Paints Potentially Reduce the Exposure of Refinish Painters to Toxic Metals.

Exposure to lead-containing dusts is a global public health concern. This work addresses an important issue of whether eco-friendly water-based paints reduce the exposure potential of auto-repainting workers to metals. With this aim, metal levels in automobile paints and worker metal exposure were measured using both solvent- and water-based paints. The levels of metals, and particularly Pb, Cr (total), Fe, and Cu, in solvent-based paints varied greatly among colors and brands. Lead concentrations ranged from below the detection limit (~0.25 μg/g) to 107,928 μg/g (dry film) across all samples. In water-based paints, the concentrations of Pb and Cr (total) were generally two to three orders of magnitude lower, but the concentrations of Al and Cu exceeded those in some solvent-based paints. The personal short-term exposure of workers who applied water-based paints of popular colors, such as black and white, were generally low, with Pb levels of less than <4 µg/m³ and Cr (total) levels of less than 1 µg/m³. Conversely, mean short-term exposure to Pb during the painting of a yellow cab using solvent-based paints were 2028 µg/m³, which was ~14 times the Taiwan short-term permissible exposure limit, while the mean level of exposure to Cr (total) was 290 µg/m³, which was well below the exposure limit. This study demonstrates that water-based paints reduce the exposure potential to lead, and highlights the importance of source control in limiting the toxic metals in paints.

Inhibition of lung cancer cells A549 and H460 by curcuminoid extracts and nanoemulsions prepared from Curcuma longa Linnaeus.

The objectives of this study were to explore the inhibition mechanism of lung cancer cells A549 and H460 by curcuminoid extracts and nanoemulsions prepared from Curcuma longa Linnaeus. In addition, human bronchus epithelial cell line BEAS-2B (normal cell) was selected for comparison. A high-performance liquid chromatography (HPLC) method was developed to separate and quantify the various curcuminoids in C. longa extract, including curcumin (1,714.5 µg/mL), demethoxycurcumin (1,147.4 µg/mL), and bisdemethoxycurcumin (190.2 µg/mL). A high-stability nanoemulsion composed of Tween 80, water, and curcuminoid extract was prepared, with mean particle size being 12.6 nm. The cell cycle was retarded at G2/M for both the curcuminoid extract and nanoemulsion treatments; however, the inhibition pathway may be different. H460 cells were more susceptible to apoptosis than A549 cells for both curcuminoid extract and nanoemulsion treatments. Growth of BEAS-2B remained unaffected for both the curcuminoid extract and nanoemulsion treatments, with a concentration range from 1 to 4 µg/mL. Also, the activities of caspase-3, caspase-8, and caspase-9 followed a dose-dependent increase for both A549 and H460 cells for both the treatments, accompanied by a dose-dependent increase in cytochrome C expression and a dose-dependent decrease in CDK1 expression. Interestingly, a dose-dependent increase in cyclin B expression was shown for A549 cells for both the treatments, while a reversed trend was found for H460 cells. Both mitochondria and death receptor pathways may be responsible for apoptosis of both A549 and H460 cells.