Response of the rat lung to respirable fractions of composite fiber-epoxy dusts.

It is unknown whether respirable dusts derived from the machining of composite fiber-epoxy materials pose a health risk. To evaluate the potential pulmonary toxicity of these materials, we studied the effects of six samples of dusts previously well characterized physically, chemically, and morphologically in the lungs of specific pathogen-free rats. A single intratracheal bolus of 5 mg of each sample was injected into separate groups of five rats each. For comparison, free crystalline silica (quartz) and aluminum oxide were used as positive and negative controls in additional animals. One month later, the lungs were fixed and sectioned for light microscopy. Histopathology scores for the six composite-epoxy samples showed a continuum of lung injury that was between the negative and positive controls. None of the composite dusts had effects that paralleled those of quartz; however, four of the composite dusts produced reactions that were more severe than that seen with aluminum oxide. Therefore, respirable fractions of some types of composite materials can induce pathological changes in lungs of experimental animals. The features responsible for the variation in host response between samples are, as yet, unclear.