Effect of altered G levels on deposition of particulates in the human respiratory tract.

The primary mode of depositon of particles in the respiratory tract in the size range 0.5-10 mum diam (unit density) is sedimentation. The rate of sedimentation is directly proportional to the velocity of settling of the particle. Therefore, the total deposition of particles in the respiratory tract as well as the region of deposition is affected by changes in gravity. Human subjects were exposed to aerosols of 2.02-mum-diam polyvinyltoluene particles at 0, 0.5, 1.0, and 2.0 G. Total deposition was measured at each G level. Results indicate an almost linear increase in total deposition with increasing G levels over the range studied. The deposition measured at 1 G was less than reported in earlier experiments and the deposition at levels less than 1 G was less than had been calculated by Muir and Beeckmans. These data show that although sedimentation plays the major role in depostion of 2.02 mum particles, it is less than previously described.