Computation of ammonium bisulfate aerosol deposition in conducting airways

Evaluation of PM2.5 air pollution sources and cardiovascular health

Long-term air pollution exposure, notably fine particulate matter, is a global contributor to morbidity and mortality and a known risk factor for coronary artery disease (CAD) and myocardial infarctions (MI). Knowledge of impacts related to source-apportioned PM2.5 is limited. New modeling methods allow researchers to estimate source-specific long-term impacts on the prevalence of CAD and MI. The Catheterization Genetics (CATHGEN) cohort consists of patients who underwent a cardiac catheterization at Duke University Medical Center between 2002 and 2010. Severity of coronary blockage was determined by coronary angiography and converted into a binary indicator of clinical CAD. History of MI was extracted from medical records. Annual averages of source specific PM2.5 were estimated using an improved gas-constrained source apportionment model for North Carolina from 2002 to 2010. We tested six sources of PM2.5 mass for associations with CAD and MI using mixed effects multivariable logistic regression with a random intercept for county and multiple adjustments. PM2.5 fractions of ammonium bisulfate and ammonium nitrate were associated with increased prevalence of CAD (odds ratio [OR] 1.20; 95% CI = 1.11, 1.22 and OR 1.18; 95% CI = 1.05, 1.32, respectively). PM2.5 from ammonium bisulfate and ammonium nitrate were also associated with increased prevalence of MI (OR 1.20; 95% CI = 1.10, 1.29 and OR 1.35; 95% CI = 1.20, 1.53, respectively). Greater PM2.5 concentrations of ammonium bisulfate and ammonium nitrate are associated with greater MI and CAD prevalence. The association with bisulfate suggests aerosol acidity may play a role. Our findings suggest analyses of source specific PM2.5 mass can reveal novel associations.

Behavior of hygroscopic pharmaceutical aerosols and the influence of hydrophobic additives

The high temperature and relative humidity in the lung can result in the hygroscopic growth of susceptible aerosol particles or droplets. The term hygroscopic growth describes the increase in particle diameter which occurs as the result of association with water vapor. The influence of hygroscopicity upon lung deposition of aerosols has been a productive area of research in industrial hygiene, environmental sciences, and inhalation toxicology. Many pharmaceutical inhalation aerosols display hygroscopic behavior in their passage through the airways; however, the effect has been neglected. Controlling the phenomenon of hygroscopic growth and, thus, the related lung deposition of aerosols might result in the therapeutic advantage of targeting the site of action. Such an approach might also allow identification of the location of pharmacologic receptor sites in the lung. This Review discusses an approach to achieving control of hygroscopic growth of aerosol particles. Theoretical and experimental studies have indicated that inhaled particle diameters increased significantly for drugs commonly administered to the lung. The presence of certain additives, notably glycerol, cetyl alcohol, and lauric and capric acids, has been demonstrated to reduce the growth of particles under conditions approaching those in the lung. Very few quantitative studies of the nature discussed herein have appeared in the literature. It is conceivable that an aerosol particle could be fabricated of known initial size and density, and by implication, deposition characteristic, and this might be induced to follow specific growth kinetics to enhance deposition in a particular region of the lung. Thus, physical targeting of regions within the lung might be achieved.

Effect of hydrophobic coating on the behavior of a hygroscopic aerosol powder in an environment of controlled temperature and relative humidity

Powders of uncoated disodium fluorescein (DF) and DF coated with various amounts of lauric or capric acids were generated as aerosols in an environment of controlled temperature and relative humidity. The particle size and distribution of these powders were characterized using a cascade impactor and a computerized data inversion method of analysis. Disodium fluorescein exhibited a hygroscopic growth ratio of 1.5 at a relative humidity of 97%. This growth was reduced to 1.3 by coating with 0.15 g of lauric acid or 0.8 g of capric acid per gram of DF, and was eliminated with 0.2 g of lauric acid or 0.18 g of capric acid per gram of DF. The reduction in hygroscopic growth probably reflects an inhibition of the growth rate. In the time following generation and prior to deposition in the collection device, approximately 40 s, the coated aerosol powders do not seem to reach their equilibrium droplet diameter. These studies indicate that these combinations of DF and fatty acid would result in larger equilibrium droplet diameters than that of the dye alone.

Deposition of inhaled particulate matter in the upper respiratory tract, larynx, and bronchial airways: a mathematical description

A mathematical description of inhaled particle behavior suitable for analysis of factors affecting deposition in the human upper respiratory tract (nasopharyngeal and oropharyngeal compartments), larynx, and ciliated airways is presented. When upper respiratory tract and larynx filtering efficiencies are incorporated in the model, theoretical calculations of aerosol deposition agree with tracheobronchial (TB) data reported in the open literature. The model predicts the sigmoidal shape of TB deposition patterns measured in human subjects, the slopes of the quasilinear segments of these curves, and the positions of their two asymptotes. The model could therefore be used to evaluate the health effects of toxic airborne particles.