Pulmonary effects induced by ultrafine PTFE particles

PTFE (polytetrafluoroethylene) fumes consisting of large numbers of ultrafi ne (uf) particles and low concentrations of gas-phase compounds can cause s evere acute lung injury. Our studies were designed to test three hypotheses : (i) uf PTFE fume particles are causally involved in the induction of acut e lung injury, (ii) uf PTFE elicit greater pulmonary effects than larger si zed PTFE accumulation mode particles, and (iii) preexposure to the uf PTFE fume particles will induce tolerance. We used uf Teflon (PTFE) fumes (count median particle size similar to 16 nm) generated by heating PTFE in a tube furnace to 486 degreesC to evaluate principles of ultrafine particle toxic ity. Teflon fumes at ultrafine particle concentrations of 50 mug/m(3) were extremely toxic to rats when inhaled for only 15 min. We found that when ge nerated in argon, the ultrafine Teflon particles alone are not toxic at the se exposure conditions; neither were Teflon fume gas-phase constituents whe n generated in air. Only the combination of both phases when generated in a ir caused high toxicity, suggesting either the existence of radicals on the surface or a carrier mechanism of the ultrafine particles for adsorbed gas compounds. Aging of the fresh Teflon fumes for 3.5 min led to a predicted coagulation to >100 nm particles which no longer caused toxicity in exposed animals. This result is consistent with a greater toxicity of ultrafine pa rticles compared to accumulation mode particles, although changes in partic le surface chemistry during the aging process may have contributed to the d iminished toxicity. Furthermore, the pulmonary toxicity of the ultrafine Te flon fumes could be prevented by adapting the animals with short 5-min expo sures on 3 days prior to a 15-min exposure. Messages encoding antioxidants and chemokines were increased substantially in nonadapted animals, yet were unaltered in adapted animals. This study shows the importance of preexposu re history for the susceptibility to acute ultrafine particle effects, (C) 2000 Academic Press.