Abstract  This concise, well illustrated monograph on respiratory deposition and retention of inhaled aerosols is of special interest to the industrial hygenist or physician, and to specialists in radiation health, infectious diseases and pollution. Starting with initial intake-anatomical and physiological characteristics of the respiratory system- and the physical factors in the deposition of aerosols, the book includes: Experimental studies on the deposition of inhaled aerosols; Pulmonary clearance; Experimental studies on pulmonary clearance; Disease risk from inhaled aerosols; and, concludes with the measurement of resparable aerosol exposure. There are 237 references, author and subject indexes

Abstract  As the field of colloidal science continues to expand, tools for rapid and accurate physiochemical characterization of colloidal particles will become increasingly important. Here, we present Particle Scattering Diffusometry (PSD), a method that utilizes dark field microscopy and the principles of particle image velocimetry to measure the diffusivity of particles undergoing Brownian motion. PSD measures the diffusion coefficient of particles as small as 30 nm in diameter and is used to characterize changes in particle size and distribution as a function of small, label-free, surface modifications of particles. We demonstrate the rapid sizing of particles using three orders-of-magnitude less sample volume than current standard techniques and use PSD to quantify particle uniformity. Furthermore, PSD is sensitive enough to detect biomolecular surface modifications of nanometer thickness. With these capabilities, PSD can reliably aid in a wide variety of applications, including colloid sizing, particle corona characterization, protein footprinting, and quantifying biomolecule activity.

Abstract  The biological effects of inhaled aerosols are often related to their site(s) of deposition within the respiratory tract. However, deposition patterns may differ between humans and those experimental animals commonly used in inhalation toxicology studies, making cross-species risk extrapolations difficult. This paper reviews the factors that control deposition and synthesizes much of the available data on comparative regional deposition.

Abstract  This document describes the U .S . Environmental Protection Agency (EPA) methodology for estimation of inhalation reference concentrations (RfCs) (earlier terminology was inhalation reference dose or RfDi) as benchmark estimates of the quantitative doseresponse assessment of chronic noncancer toxicity for individual inhaled chemicals. Noncancer toxicity refers to adverse health effects other than cancer and gene mutations. This overview chapter discusses general principles of dose-response assessment for noncancer toxicity, the development of the RfC methodology, and its role within the context of the risk assessment process. Subsequent chapters of the document discuss criteria and information to be considered in selecting key studies for RfC derivation, provide an overview of the respiratory system and its intra- and interspecies variables, and discuss areas of uncertainty and data gaps in relation to the proposed methodology.

Abstract  The outputs and mass median droplet diameters of useful aerosols and the effect of solvent evaporation on the concentration of nebulizer solutions have been measured for four nebulizers of designs which have been employed for inhalation studies. Outputs ranging from 2.3 to 30.4 microliters of solution per liter of jet air were observed, with corresponding mass median droplet diameters of 1.4 to 5.4 microns. For jet pressure drops of 2.5 to 30 psi, from 7 to 10 microliters of solvent (water), in excess of that associated with the aerosol, was carried away per liter of jet air. The effects of baffling and of augmenting the jet air with additional flow through a vent were also determined.

Abstract  The use of the log-normal function in particle size analysis is reviewed and a maximum likelihood method for fitting and testing the fit of a log-normal function to grouped particle size data is described. Since particle size data are usually grouped into size intervals, it is commonly assumed for mathematical purposes that all the particles in a group are equal in size to some mid-size in the interval. This assumption may lead to errors in fitting a function to data. This assumption is avoided by using the grouped data maximum likelihood method. The method is applicable even if the numbers of particles observed in the size groups are small or nil. Also discussed are the statistical tests which may be applied to the fitted parameters of the log-normal function in order to provide estimates of their statistical reliability. A chi-square test is used to justify or discredit the assumption that the data can be considered as a sample from a parent population which is log-normally distributed.

Abstract  In 1964, ICRP Committee II created a special Task Group for the purpose of reviewing the so-called lung model, (1) a scheme for computing dust deposition in and clearance from the human respiratory tract thereby providing a basis for lung dosimetry and the setting of exposure limits. The principal working assumption adopted by the Task Group at the outset was that the present lung model used by Committee II is arbitrary in some respects and inadequate in others: its principal virtue is simplicity. We attempted, therefore, to improve the model in the first two regards and to maintain the third quality as desirable.

Abstract  Nanoparticles are defined as elementary particles with a size between 1 and 100 nm for at least 50% (in number). They can be made from natural materials, or manufactured. Due to their small sizes, novel toxicological issues are raised and thus determining the accurate size of these nanoparticles is a major challenge. In this study, we performed an intercomparison experiment with the goal to measure sizes of several nanoparticles, in a first step, calibrated beads and monodispersed SiO₂ Ludox®, and, in a second step, nanoparticles (NPs) of toxicological interest, such as Silver NM-300 K and PVP-coated Ag NPs, Titanium dioxide A12, P25(Degussa), and E171(A), using commonly available laboratory techniques such as transmission electron microscopy, scanning electron microscopy, small-angle X-ray scattering, dynamic light scattering, wet scanning transmission electron microscopy (and its dry state, STEM) and atomic force microscopy. With monomodal distributed NPs (polystyrene beads and SiO₂ Ludox®), all tested techniques provide a global size value amplitude within 25% from each other, whereas on multimodal distributed NPs (Ag and TiO₂) the inter-technique variation in size values reaches 300%. Our results highlight several pitfalls of NP size measurements such as operational aspects, which are unexpected consequences in the choice of experimental protocols. It reinforces the idea that averaging the NP size from different biophysical techniques (and experimental protocols) is more robust than focusing on repetitions of a single technique. Besides, when characterizing a heterogeneous NP in size, a size distribution is more informative than a simple average value. This work emphasizes the need for nanotoxicologists (and regulatory agencies) to test a large panel of different techniques before making a choice for the most appropriate technique(s)/protocol(s) to characterize a peculiar NP.