In order to see if exposure to cold temperature affects the development of 
bleomycin lung toxicity in mammals, 14 rats received endotracheal injections of 
bleomycin, while another 14 rats received saline. Half of the saline-treated 
animals were then exposed to room temperature for 7 days (SRT), and half were 
exposed to 4 degrees C for 7 days (SC). The bleomycin-treated animals similarly 
yielded groups kept at room temperature (BRT) and in the cold (BC). After 1 wk 
the rats were killed and the lungs were sectioned for assessment of histologic 
changes. All the bleomycin-treated animals had evidence of lung toxicity but 
this was much less marked in group BC than in group BRT. The lungs in group SC 
remained normal. These results were confirmed by morphometric methods, which 
showed significantly increased volume proportions of alveolar walls in groups 
BRT and BC compared with that in groups SRT and SC (p less than 0.001), with BRT 
being greater than BC (p less than 0.001). It is concluded that exposure of 
bleomycin-treated rats to low ambient temperature significantly reduces lung 
toxicity.