The Acute Toxicity of Tris(Dimethylamino) Silane

Abstract

The acute handling hazards of tris(dimethylamino)silane [TDMAS] were investigated. The acute male rat peroral LD₅₀ (with 95% confidence limits) was 0.71 (0.51-0.97) ml/kg, and the acute male rabbit percutaneous LD ₅₀ was 0.57 (0.35-0.92) ml/ kg. The liquid was severely irritating to the rabbit eye and skin, and the vapor severely irritating to the rat eye. The dynamically generated saturated vapor Lt₅₀ in female rats was 12 (9.7-15) min. The effect of varying the atmospheric concentration of vapor from TDMAS on acute inhalation toxicity was investigated by passing ordinary moist air countercurrent to liquid TDMAS metered into a slightly heated glass tube. Based on nominal concentrations, the 4 hr-LC₅₀ for vapor from TDMAS was 734 (603-893) ppm in female rats by this procedure. Stoichiometrically, this accords with toxicity due to liberation of dimethylamine (DMA)from TDMAS. In a subsequent study designed to assess the influence of relative humidity on vapor toxicity, nitrogen was passed over heated liquid TDMAS and the resultant atmosphere was introduced into the air intake duct of the inhalation exposure chamber. Gas chromatographically measured TDMAS concentrations (± SD) were 395 ± 111, 127 ± 25, 62 ± 8 and 23 ± 21 ppm; the corresponding DMA vapor concentrations were 112 ± 171, 31 ± 43, 10 ± 6 and 26 ± 44 ppm. The 4-hr LC₅₀ (males and females) was 38 (34-43) ppm TDMAS vapor. Thus, TDMAS is of moderate acute peroral and percutaneous toxicity, a severe primary skin and eye irritant, an aspiration hazard, and of high intrinsic acute inhalation toxicity, but in moist air conditions lethal toxicity may be reduced and in such circumstances DMA may be a significant factor in toxicity.