Risk assessment of farmers handling pelleted seeds containing crystalline silica and attapulgite.

OBJECTIVES: This study aimed to assess the risk to farmers from handling pelleted seeds that include crystalline silica and attapulgite. METHODS: We measured personal exposure levels to respirable crystalline silica and attapulgite in the experimenter representing a farmer in a simulated workplace. From these values, the annual occupational exposure levels were estimated and compared with the established occupational exposure limits. To assess the toxicity of respirable crystalline silica and attapulgite, digital chest images of workers in a factory producing pelleted seeds were examined. RESULTS: The personal exposure measurement results showed that the concentrations of total dust, respirable dust, and respirable crystalline silica generated during work handling of pelleted seeds were 0.27, 0.06, and 0.00043 mg/m3 , respectively. The estimated annual occupational exposure level to total dust, respirable dust, and respirable crystalline silica in farmers was 103 to 104 times lower than established occupational exposure limits. Attapulgite was not detected by analysis of the pelleted seeds themselves or dust collected during the personal exposure measurements. No pulmonary parenchymal or pleural lesions were detected in the digital chest images of the factory workers. CONCLUSION: We found that farmers handling pelleted seeds would not be exposed to levels of total dust, respirable dust, respirable crystalline silica, and attapulgite derived from pelleted seeds exceeding occupational exposure limits. These results suggest that the risk to farmers of handling pelleted seeds is negligible.

Toxicity assessment of SiC nanofibers and nanorods against bacteria.

In the present study, evidence of the antibacterial effects of silicon carbide (SiC) nanofibers (NFSiC) and nanorods (NRSiC) obtained by combustion synthesis has been presented. It has been shown that the examined bacteria, Pseudomonas putida, could bind to the surface of the investigated SiC nanostructures. The results of respiration measurements, dehydrogenase activity measurements, and evaluation of viable bacteria after incubation with NFSiC and NRSiC demonstrated that the nanostructures of SiC affect the growth and activity of the bacteria examined. The direct count of bacteria stained with propidium iodide after incubation with SiC nanostructures revealed that the loss of cell membrane integrity could be one of the main effects leading to the death of the bacteria.

Assessment of cytotoxicity and DNA damage exhibited by siloranes and oxiranes in cultured mammalian cells.

The potential reactivity and structural properties of oxiranes (epoxides) are advantageous when considering polymers for medical devices. However, epoxy compounds are widely known to have genotoxic properties. The objective of the study was to evaluate the cytotoxicity and primary DNA damage effects induced by oxiranes and siloranes, silicon containing oxiranes. The siloranes, Ph-Sil, Tet-Sil, and Sil-Mix and the oxiranes Cyracure UVR-6105 and 1,3-bis[2-(2-oxiranylmethyl) phenoxy]pentane (OMP-5) were dissolved in organic solvents and dilutions containing less than 0.5% solvent were used in biological assays. The concentration that reduced the viability of 50% (TC(50)) of L929 cells was measured using the MTT assay and guided the selection of subtoxic doses for evaluation of DNA damage. Ph-Sil was more cytotoxic than OMP-5, Cyracure UVR-6105 and Sil-Mix. However, the TC(50) value of Tet-Sil could not be determined due to its poor solubility. DNA damage was evaluated in the sister chromatid exchange (SCE) assay with CHO cells, and the alkaline comet assay with L929 cells. In contrast to the siloranes, the oxiranes exhibited significant increases (p>0.05) in SCE frequencies and DNA migration relative to their solvent controls. Our findings support previous reports that siloranes have low genotoxic potential and can be suitable components for development of biomaterials.