Toxic effects of acute inhalation exposure to 1,2,4-trimethylbenzene (pseudocumene) in experimental animals.

Neurotoxic and sensory respiratory irritation effects of 1,2,4-trimethylbenzene (pseudocumene) in male rats and male Balb/C mice were investigated in condition of acute inhalation exposure. Rotarod performance and pain sensitivity behaviour were tested in rats exposed to pseudocumene at concentrations of 1230-9840 mg/m3 (250-2000 ppm) immediately after termination of a four-hour exposure. The respiratory rate was measured in mice by the whole body plethysmographic method in 6 min duration exposure to various concentrations of pseudocumene. Exposure to pseudocumene resulted in concentration-dependent disturbances in rotarod performance, decrease in pain sensitivity in rats and depression of respiratory rate in mice. The EC50 value for rotarod performance behaviour disturbances was 4693 mg/m3 (954 ppm) and for decrease pain sensitivity EC50 was 5682 mg/m3 (1155 ppm). The concentration depressing the respiratory rate to 50% (RD50) was 2843 mg/m3 (578 ppm). As based on RD50 value the MAC values for pseudocumene 85 mg/m3 (17.0 ppm) is suggested.