Use of repeated CO2 challenges to evaluate the pulmonary performance of guinea pigs exposed to toluene diisocyanate.

Guinea pigs were exposed to 1.4 ppm toluene diisocyanate (TDI) for 3 h/d on 5 consecutive days to produce chemical bronchitis. Following these exposures, the ventilatory response of the animals to challenge with 10% CO2 was greatly diminished. Response recovered during the next 40 d. In contrast, animals exposed to 0.02 ppm TDI daily for 70 d showed no change in ventilatory response to challenge with 10% CO2, nor did control animals which were not exposed to TDI. These results indicated both the absence of pulmonary toxicity following exposure to low TDI concentrations for an extended time and the effectiveness of the methodology utilizing the ventilatory response to CO2 to monitor recovery from acute pulmonary toxicity.