Observations on the lung retention of inhaled, relatively insoluble, environmentally-related particles.

M any particles found in the environment, such as those from diesel engine exhaust, fly ash from coal-burning power plants, fallout from nuclear weapons testing and natural dusts may be relatively insoluble in body fluids. A toxic material may be associated primarily with the surface of these particles or may be homogeneously or heterogeneously distributed throughout the mass of the particles. When inhaled, the deposition and subsequent disposition of these particles and their constituents determines the organs and tissues that may be at risk for production of short-or long-term biologic effects.1 Particle characteristics such as size, density and solubility, as well as anatomic and physiologic characteristics of the host all can influence the doses received by individual tissues and organs.' Many experiments have been conducted in our institute to study the long-term disposition and resulting doses received from materials inhaled in a relatively insoluble form. Important results from these studies will be given to illustrate basic principles of pulmonary clearance and translocation mechanisms. MATERIALS AND METHODS The general approach used in these studies was to expose laboratory-raised, purebred Beagle dogs to a single, brief (< 30 mm), nose-only, inhalation exposure to a well characterized aerosol. Aerosols studied to date include PuO, and fused alummnosilicate particles labeled with gamma emitters such as 144Ce, " 4Cs or 377 7 3 The particle size distributions of these aerosols had activity median aerodynamic diameters in the range of 0.75 to 3.0 and geometric standard deviations of 1.1 to 2.0.. The retention of the initially deposited material was quantitated by whole-body counting and analysis of urine and feces for the radionuclide being studied. In some studies, lung lavage with physiologic saline solution was used to determine the availability for removal of particles from the lung at different intervals after exposure.' Serial sacrifices of dogs at times ranging from two hr to seven yr after the inhalatiOn exposure were performed to determine the temporal and spatial patterns of radionuclide distribution among organs. After necropsy, these organs were analyzed for their total radionuelide content and autoradiography was used to study localized distribution patterns within individual tissue regions when appropriate. Kinetic models, aFrom the Lovelace Inhalation Toxicology Research Institute , Albuquerque. U.S. Department of Energy Contract Number DE-ACO4-76EV01013 in animal facilities fully accredited by the American Association of Laboratory Animal Care. 87115 constructed from the data, provided a means to extrapolate the results to inhalation exposures involving aerosols …