Long-term lung clearance in humans studied with Teflon particles labeled with chromium-51.
Six healthy nonsmoking males inhaled 4-micron diameter Teflon particles labeled with chromium-51. Lung retention was measured for approximately 300 days. Three subjects inhaled "high-leaching" particles and three "low-leaching" particles. The high-leaching leaching particles leached 0.26%/day in water at 37 degrees C for the first 100 days and the low-leaching particles 0.065%/day. On an average, urine sampled for 24 h contained 0.13% of the lung burden for the high-leaching particles and 0.02% for the low-leaching particles. Thirty percent of the long-term clearance occurred with a fast phase, with half-times ranging from 4.5-45 days, and 70% with a slow phase, with half-times ranging from 200-2500 days. The fast phase was similar for the high-leaching and low-leaching groups. The slow phase varied widely among the subjects. There was no clear-cut relationship between half-time and type of particle. However, it seems probable that the slow phase was dependent on the degree of leaching, i.e., the half-times for elimination of intact particles from the lung are even slower. The large differences in long-term clearance among subjects indicate that long-term exposure to highly insoluble particles will result in large differences in lung burden. Subjects with a low capacity to eliminate alveolarly deposited particles are thus expected to be more susceptible to diseases in the alveolar part of the lung, i.e., diseases caused by certain insoluble particles.
D000328:Adult; D000368:Aged; D000818:Animals; D002860:Chromium Radioisotopes / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011138:Polytetrafluoroethylene / Q000378:metabolism*; D011817:Rabbits
D002860:Chromium Radioisotopes; D011138:Polytetrafluoroethylene