Pulmonary Response of Rats Exposed to Polytetrafluoroethylene and Tetrafluoroethylene Hexafluoropropylene Copolymer Fume and Isolated Particles

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Abstract
Rats were exposed to thermal degradation products of polytetrafluoroethylene (PTFE) and tetrafluoroethylene/hexafluoropropylene copolymer (FEP). The approximate lethal concentration (ALC) of fume evolved over 4 h from PTFE at 425°C was 0.1 mg/m3 in a glass battery jar. The ALC of particulate generated in National Bureau of Standards (NBS) exposure chamber was 0.3 mg/m3 of FEP pyrolysis products evolved for 30 min at 560°C. Numerous particles were evolved from PTFE and FEP pyrolysis, but fresh small particles (0.02–0.15 μm) appeared to be a toxic agent. Exposed rats died due to respiratory difficulty with pulmonary congestion and edema. When these particles were aged, they were agglomerated. lntratracheal instillation in rats with 0.05 mg of aged PTFE particulate agglomerates did not produce the generalized pulmonary edema as produced by the inhalation exposure. Respiratory epithelial damage in nasal cavity or airways was minimal in rats exposed to PTFE or FEP fume by inhalation. Pulmonary lesions were characterized by alveolar and interstitial edema and intraalveolar hemorrhage. The pulmonary edema and hemorrhage were related to extensive damage on Type I pneumocytes by toxic fume. Alveolar capillary endothelium was much less damaged than Type I pneumocytes. Alveolar capillary neutrophilia was associated with these pulmonary lesions. Small numbers of inhaled PTFE and FEP particle aggregates were found in the edematous alveoli, but it was extremely difficult to identify small individual particles.

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