Abstract
Despite the rigorous emission control measures in the ferroalloy industry, there are still emissions of dust during the production of various alloys. Dust particles were collected from laboratory scale processes where oxide particulate matter was formed from liquid silicon (metallurgical grade). The dust was produced in a dry air atmosphere to mimic industrial conditions. To investigate possible effects of ultrafine dust on the central nervous system, a human astrocytic cell line was employed to investigate inflammatory effects of particles as astrocytes play a number of active and neuron supporting roles in the brain. Toxicity on the astrocytes by amorphous silica generated in laboratory scale was compared to crystalline macro-sized silica using several doses to determine toxicological dose response curves. The cell viability experiments indicated that low particle doses of amorphous silica induced a small nonsignificant reduction in cell viability compared to crystalline silica which led to increased levels of toxicity. The gene expression of amyloid precursor protein (APP), a biomarker of neurodegenerative disease, was affected by particle exposure. Furthermore, particle exposure, in a dose-and time-dependent manner, affected the ability of the cells to communicate through gap junction channels. In conclusion, in vitro studies using low doses of particles are important to understand mechanisms of toxicity of occupational exposure to silica particles. However, these studies cannot be extrapolated to real exposure scenarios at work place, therefore, controlling and keeping the particle exposure levels low at the work place, would prevent potential negative health effects.
Highlights
Occupational exposure both to fine and ultrafine silica (SiO2) particles present in the dust in the silicon alloy-producing industry has become an area of concern
A number of cellular endpoints were studied and the findings indicate that cellular responses to SiO2 depend on the physicochemical properties of the dust, in addition to the dose and duration of exposure
To investigate if the observations for amyloid precursor protein (APP) mRNA correlated with protein levels, western blot analysis was performed using doses that significantly reduced mRNA expression (Figure 4B)
Summary
Occupational exposure both to fine and ultrafine silica (SiO2) particles present in the dust in the silicon alloy-producing industry has become an area of concern. The majority of the airborne particulate matter (PM) in this industry consists of amorphous silica fume This silica fume is formed in hot processes where liquid silicon is in contact with air. The field of cancer immunotherapy increasingly looks into the use of amorphous silica as immunoadjuvant to treat cancer in humans [12,13,14] Despite their common and increased use, cytotoxic effects have been reported [15,16]. In this study the cells were exposed to both amorphous (collected in the laboratory process), and crystalline SiO2, using a range of low, moderate, and relatively high doses to avoid overload toxicity. A number of cellular endpoints were studied and the findings indicate that cellular responses to SiO2 depend on the physicochemical properties of the dust, in addition to the dose and duration of exposure
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