Inhalation Toxicology of Trimethylamine

Abstract

Trimethylamine (TMA) is a pungent gas that occurs in nature and has many industrial applications, including use as an intermediate in the manufacture of many chemicals. The lowest lethal concentration following a single 4-h inhalation exposure was determined to be 3500 ppm. Croups of 70 male rats each were then exposed by nose-only inhalation 6 h/d, 5 d/wk for 2 wk to either 0 (control), 75, 250, or 750 ppm TMA. Rats were sacrificed either immediately following exposure or following a 14-d recovery period. Parameters investigated included in-life observations and body weights, clinical pathology, and histopathology with organ weights. Exposure to 750 ppm produced a decreased rate of weight gain in rats. Evidence of mild, reversible, polycytnemia was also seen in these rats. Effects of TMA were present in the nose, trachea, and lungs. Degenerative changes in the nose were reversible at 75 ppm, but not at 250 or 750 ppm. Mild emphysematous alveoli were seen in lungs of rats exposed to 750 ppm immediately following the exposures, but not after a recovery period. A no-observed-effect level for TMA under these test conditions was not determined, although the nasal effects seen at 75 ppm were minimal.