3. Health Aspects

3.2 Acute Toxicity

It can be concluded from animal experiments that the acute oral toxicity of styrene is low; the oral LD50 is reported to be well above 2,000 mg/kg body weight. As the oral toxicity is low, any small amounts accidentally ingested are unlikely to cause injury. Ingestion of large amounts of styrene may cause irritation of the mouth, throat and gastro-intestinal tract. Aspiration into the lungs may cause chemical pneumonitis, which can be fatal. Inhalation studies in rats and mice indicate that styrene generally has a moderate acute toxicity (4 hour LC50 >280 -2,800 ppm (2-20 mg/L)), thereby some strains of mice are particularly sensitive i.e. deaths occurred in mice exposed for 6 hours at a concentration of 500 ppm styrene.

Humans exposed at 100 ppm for up to 7 hours have described slight irritation to the eyes and the throat with the effects becoming more severe with increasing dose. Higher styrene exposures (i.e. > 100 ppm), but still well below the lethal dose in the rat, produce immediate eye and nose irritation accompanied by depressant effects on the central nervous system (e.g. narcosis, fatigue, dizziness). As the smell (odour threshold = 0.1 ppm) and the irritant properties of styrene preclude exposures at such high and harmful concentrations, it is virtually impossible under normal working conditions to be exposed to a lethal dose of styrene.

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