Morphology of tracheal and bronchial epithelium and type II cells of the peripheral lung of the guinea pig after inhalation of toluene diisocyanate vapors.

Toluene diisocyanate (TDI), a polymerizing agent used in production of plastics, can cause airways disease in some exposed individuals. Using guinea pigs as a model, the response of the airways and the type II cells of the peripheral lung was monitored morphologically and morphometrically after exposure to TDI vapors at 30 ppb, 260 ppb, and 3100 ppb. The two low doses of TDI caused little change in airways epithelium. There was no gross inflammatory cell infiltrate, however, surface infoldings and intracellular ciliated cysts increased in numbers. Animals exposed to 3100 ppb TDI 4 h/day for 5 days, sustained considerable damage to the epithelium, and stratified nonkeratinizing cells lined the airways until one week after exposure. Polymorphonuclear leukocytes were present in the early period after exposure. Increased numbers of eosinophils were present between one and two weeks following exposure. Mitoses in the epithelium were common during recovery. In the peripheral lung, though a modest subjective increase in the number of type II cells was seen after 3100 ppb TDI, the volume density of type II cells, and organellar components (lamellar bodies, mitochondria, cisternal bodies) did not change significantly after any exposure level of TDI.