ACUTE AND SUBCHRONIC INHALATION TOXICITY OF TETRAETHOXYSILANE (TEOS) IN MICE

To clarify the acute and subchronic inhalation toxicity of tetraethoxy silane [TEOS, Si(OC2H5)(4)], groups of ten male ICR mice (SPF grade) w ere exposed to 1000 ppm TEOS for 1, 2, 4 or 8 h (acute inhalation stud y), or to 200 ppm of TEOS for 6 h/day, 5 days/week, for 2 or 4 weeks ( subchronic inhalation study). The numbers of mice that died during 2 w eeks of observation were 0, 1, 1 and 6 in the 1-, 2-, 4- and 8-h inhal ation experiments and zero in the subchronic inhalation study. In the acute inhalation study, body weight decreased after TEOS exposure and did not reach the level of control mice during 2 weeks of observation except in the 1-h inhalation study. In the subchronic exposure study, weight gain was suppressed during the exposure period. Body weight in mice exposed for 2 weeks reached the level of non-exposed mice during the 2-week observation period, but did not do so in mice exposed for 4 weeks. Acute tubular necrosis (ATN) and acute splenic atrophy (ASA) w ere observed in all dead mice in the acute inhalation study, and tubul ointerstitial nephritis (TIN) was frequently found in the surviving mi ce in both the acute and subchronic studies. However, blood biochemica l examinations revealed no evidence of renal dysfunction. The olfactor y epithelium was necrotic in all dead mice. In the subchronic inhalati on study, infiltration of polymorphonuclear neutrophils in the nasal m ucosa was observed in all mice killed 1 day after exposure. These resu lts indicate that the LCL(0) for 1-h exposure to TEOS and LC(50) for 4 -h exposure are greater than 1000 ppm, and that the kidney and nasal m ucosa are the target organs for TEOS inhalation.