Silica, respiratory toxicity

In acute exposures, respiratory disease may be limited to interstitial inflammation of the alveolar epithelium, leading eventually to emphysema or pulmonary fibrosis (Cooper et al. 1982 Dungworth 1989 Stokinger 1981 Wedeen 1992). In studies of the pulmonary effects of airborne uranium dust in uranium miners and in animals, the respiratory diseases reported are probably aggravated by the inhalable dust particles (the form in which uranium is inhaled) toxicity because most of the respiratory diseases reported in these studies are consistent with the effects of inhaled dust (Dockery et al. 1993). In some of these instances, additional data from the studies show that the workers were exposed to even more potent respiratory tract irritants, such as silica and vanadium pentaoxide (Waxweiler et al. 1983). 

Health concerns regarding VA have focused primarily on respiratory effects in heavily exposed populations such as short-term respiratory irritation and longer-term development of pneumoconiosis. The potential toxicity of crystalline silica in the ash has been of particular concern (Baxter et al, 1999 Wilson et al, 2000 CDC, 1986 Vallyathan et al, 1983a,b Baxter et al, 1983). These studies indicate that the potential toxicity of VA can vary between different ash eruptions from a given volcano and between different volcanoes. The variability is probably due to difference in the crystalline silica content and in the proportion of respirable particles. 

Saponite is a natural clay mineral that is not acutely toxic therefore, no toxicity values have been established. However, it may contain small amounts of crystalline silica in the form of quartz. Chronic exposure to crystalline silica can have adverse effects on the respiratory system. EU labeling states the material is not classified as dangerous. 

Toxicology ACGIH TLV/TWA 10 mg/m (total dust) when toxic impurities are not present nuisance particulate inh. may cause mild respiratory and eye irritation fibers may cause changes in lungs similar to those caused by silica questionable carcinogen experimental neoplastigen TSCA listed... 

Pulmonary exposure is the most popular route for in vivo investigations of nanomaterials-induced toxidty. In order to better understand the toxic effect of amorphous silica nanomaterials, the nanomaterials were instilled into the respiratory tract [38, 44—46, 100] and, after a period of treatmenf the acute and subacute pulmonary toxic effects were monitored. However, this phenomenon was an induced transient toxicity, and pulmonary function was fully recovered after several days post-exposure. Compared to the persistent pulmonary inflammation caused by crystalline silica nanomaterials, the negative effect of amorphous silica nanomaterials was considered insignificant. 

Toxicology May cause burning, redness, and tearing of eyes on direct contact may cause skin irritation, dermatitis overexposure to hot vapors may cause nausea, respiratory tract irritation, pneumonitis, pulmonary edema mod. toxic by ing. may cause Gl upset TSCA listed Precaution Avoid contact with open flame or sparks Hazardous Decomp. Prods. Hydrocarbon decomp, prods., silica HMIS Health 1, Flammability 1, ReactivityO... 

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