Document 2J0eaRGJqpDQng3pbwXzQ70Da

ON THE RETENTION OF AIR-BORNE PARTICULATES IN THE HUMAN LUNG: II H. D. LANDAHL T. N. TRACEWELL AND W. H. LASSEN CHICAGO EXPERIMENTS have been carried out on human subjects to measure the amounts of inhaled homogeneous droplets, which appear in various fractions of the expired air. Theoretical considerations *1 enable one to calculate the various values. The present experiments were carried out in order to check these calcula tions and thus further evaluate the importance of the various factors which may influence the results. GENERAL PROCEDURE A homogeneous cloud of approximately equal size particles of triphenyl phosphate was produced and breathed. A sample, equal to that inspired, was collected and quantitatively analyzed for triphenyl phosphate. The air expired was collected in four equal serial fractions, and each was quantitatively analyzed for triphenyl phosphate. The amount retained in each of the four sections of the respiratory tract represented by the four serial fractions of the expired air was then calculated and expressed in terms of per cent of the total retained. The process was repeated with various subjects, with different patterns of respiration and with particles of various sizes. METHODS Particle Generation and Size Determination.--Triphenyl phosphate was chosen because it is not very toxic, it can be measured in small quantities, and it can be produced as a smoke composed of droplets which are approximately equal to each other in diameter. Particles of various sizes were generated by a homogeneous particles generator which had the outlet tube from the mixing flask extending in a downward direction.2 These particles were diluted with filtered air up to a flow rate of 36 l./min. and then passed through a long tube to a Y tube as described previously.3 When the aerosol was not in use, this tube was closed and an outlet tube to a hood ventilator opened. From the University of Chicago Toxicity Laboratory. The work described in this paper was conducted at the University of Chicago Toxicity Laboratory under a research contract supported by the Atomic Energy Commission -and administered through the Medical Division, Chemical Corps, United States Army. Under the terms of the contract neither the Atomic Energy Commission nor the Army Chemical Corps is responsible for the opinions or. conclusions of the authors. 1. (a) Findeisen, W.: Ueber das Absetzen kleiner, in der Luft suspendierter Teilchen in der menschlichen Lunge bei der Atmung, Arch. f. d. ges. Physiol. 236:367, 1935. (6) Landahl, H. D.: On the Removal of Air-Borne Droplets by the Human Respiratory Tract: I. The Lung, Bull. Math. Biophys. 12:43, 1950. 2. Sinclair, D.Formation of Aerosols, chap. 6; Optical Properties of Aerosols, chap. 7, in Handbook of Aerosols,. Washington, D. G, Atomic Energy Commission, 1950, pages 77-96. 3. Landahl, H. D., and Herrmann, R. G.: On the Retention of Air-Borne Particulates in the Human Lung, J. Indust. Hyg. & Toxicol. 30:181, 1948. 359