Risa J. Robinson

Vapors Produced by Electronic Cigarettes and E-Juices with Flavorings Induce Toxicity, Oxidative Stress, and Inflammatory Response in Lung Epithelial Cells and in Mouse Lung

Oxidative stress and inflammatory response are the key events in the pathogenesis of chronic airway diseases. The consumption of electronic cigarettes (e-cigs) with a variety of e-liquids/e-juices is alarmingly increasing without the unrealized potential harmful health effects. We hypothesized that electronic nicotine delivery systems (ENDS)/e-cigs pose health concerns due to oxidative toxicity and inflammatory response in lung cells exposed to their aerosols. The aerosols produced by vaporizing ENDS e-liquids exhibit oxidant reactivity suggesting oxidants or reactive oxygen species (OX/ROS) may be inhaled directly into the lung during a “vaping” session. These OX/ROS are generated through activation of the heating element which is affected by heating element status (new versus used), and occurs during the process of e-liquid vaporization. Unvaporized e-liquids were oxidative in a manner dependent on flavor additives, while flavors containing sweet or fruit flavors were stronger oxidizers than tobacco flavors. In light of OX/ROS generated in ENDS e-liquids and aerosols, the effects of ENDS aerosols on tissues and cells of the lung were measured. Exposure of human airway epithelial cells (H292) in an air-liquid interface to ENDS aerosols from a popular device resulted in increased secretion of inflammatory cytokines, such as IL-6 and IL-8. Furthermore, human lung fibroblasts exhibited stress and morphological change in response to treatment with ENDS/e-liquids. These cells also secrete increased IL-8 in response to a cinnamon flavored e-liquid and are susceptible to loss of cell viability by ENDS e-liquids. Finally, exposure of wild type C57BL/6J mice to aerosols produced from a popular e-cig increase pro-inflammatory cytokines and diminished lung glutathione levels which are critical in maintaining cellular redox balance. Thus, exposure to e-cig aerosols/juices incurs measurable oxidative and inflammatory responses in lung cells and tissues that could lead to unrealized health consequences.

Deposition of Cigarette Smoke Particles in the Human Respiratory Tract

Understanding tobacco related cancer etiology requires the knowledge of cigarette smoke particle (CSP) deposition. Measurements of CSP deposition are inconsistent with typical deposition data. A deposition model that accounts for hygroscopic growth, coagulation, particle charge, and cloud behavior of CSP has not yet been presented. Nor have smoking patterns been accounted for in either deposition measurements or computer models. The dosimetry of Benzo[a]pyrene (BaP), which would add critical information to the relationship between anatomic site preferences of tumors and their histology, is currently unknown. The deposition model presented in this study is the first to accurately account for the dynamic behavior of CSP. Using the model results, the effects of each dynamic behavior on deposition is examined along with the effect of smoking patterns. The dosimetry of BaP is also calculated. The results indicate that coagulation, hygroscopicity, and particle charge increase the total deposition by 16% over the stable charge-neutral case, which predicts 46%. Cloud behavior increases total deposition efficiency by 36% over the simple case. Increasing exhalation time increases the deposition fraction by 3.9%/s. BaP concentrations are found to be as large as 1.8E-4ng/cm2 for the cloud model and 2.4E-5 ng/cm2 for single particle behavior. Mass deposition occurs preferentially in the pulmonary region for all cases. However, significant increases in the tracheo-bronchial region are found if cloud behavior is considered. The model results indicate that cloud behavior,and not particle charge, coagulation, and hygroscopic growth, has a predominant effect on deposition. More data is required on cloud behavior in the airways to improve the accuracy of the model.

Environmental Health Hazards of e-Cigarettes and their Components: Oxidants and Copper in e-cigarette aerosols

To narrow the gap in our understanding of potential oxidative properties associated with Electronic Nicotine Delivery Systems (ENDS) i.e. e-cigarettes, we employed semi-quantitative methods to detect oxidant reactivity in disposable components of ENDS/e-cigarettes (batteries and cartomizers) using a fluorescein indicator. These components exhibit oxidants/reactive oxygen species reactivity similar to used conventional cigarette filters. Oxidants/reactive oxygen species reactivity in e-cigarette aerosols was also similar to oxidant reactivity in cigarette smoke. A cascade particle impactor allowed sieving of a range of particle size distributions between 0.450 and 2.02 μm in aerosols from an e-cigarette. Copper, being among these particles, is 6.1 times higher per puff than reported previously for conventional cigarette smoke. The detection of a potentially cytotoxic metal as well as oxidants from e-cigarette and its components raises concern regarding the safety of e-cigarettes use and the disposal of e-cigarette waste products into the environment.

Electronic Cigarette Topography in the Natural Environment.

This paper presents the results of a clinical, observational, descriptive study to quantify the use patterns of electronic cigarette users in their natural environment. Previously published work regarding puff topography has been widely indirect in nature, and qualitative rather than quantitative, with the exception of three studies conducted in a laboratory environment for limited amounts of time. The current study quantifies the variation in puffing behaviors among users as well as the variation for a given user throughout the course of a day. Puff topography characteristics computed for each puffing session by each subject include the number of subject puffs per puffing session, the mean puff duration per session, the mean puff flow rate per session, the mean puff volume per session, and the cumulative puff volume per session. The same puff topography characteristics are computed across all puffing sessions by each single subject and across all subjects in the study cohort. Results indicate significant inter-subject variability with regard to puffing topography, suggesting that a range of representative puffing topography patterns should be used to drive machine-puffed electronic cigarette aerosol evaluation systems.

Theoretical Analysis of Hygroscopic Growth Rate of Mainstream and Sidestream Cigarette Smoke Particles in the Human Respiratory Tract

ABSTRACT The deposition of cigarette smoke particles (CSP) in the human respiratory tract is difficult to predict theoretically due to the uncertainties in the characterization of these particles. Measured deposition efficiencies for CSP do not agree with those for typical particles of similar size. One explanation of this discrepancy is the hygroscopic growth of CSP once inside the respiratory tract. However, a minimum of experimental data exists and no theoretical study was done to explain the hygroscopic nature of CSP. In this paper, hygroscopic growth of mainstream and sidestream CSP is determined theoretically for conditions simulating the human respiratory tract. Good agreement is found between calculated growth and experimental growth reported in Li [Ph.D. Thesis, Department of Chemistry, Clarkson University, NY, (1993)] and Kousaka et al. [J. Chem. Eng. Jpn. 15: 75–76, (1982)]. Growth ratios ranging from 0 to 1.52 were found for mainstream CSP with initial sizes ranging from 0.03 to 0.6 μm. Growth...

Application of Cloud Dynamics to Dosimetry of Cigarette Smoke Particles in the Lungs

Clinical data suggest a relationship between in vivo deposition patterns of cigarette smoke particles and the occurrence of tumors in the lung. Traditional dosimetry models fail to predict the preferential proximal deposition of cigarette smoke in the human airways, which resembles deposition of aerosol with a larger mass median aerodynamic diameter (MMAD) than that representative of cigarette smoke. Previous work has shown that accounting for the so-called cloud effect leads to enhanced proximal deposition and to better agreement with clinical and experimental data. This work presents an improved model of transport and deposition of cigarette smoke in the airways of smokers, accounting for possible particle-particle interactions (cloud effect) and their effect on the mobility of individual particles and on the deposition profile. Brinkmans effective medium approach is used for modeling the flow through and around the cloud, with the clouds permeability changing according to the clouds solid volume fraction. Although the weakest of all interparticle hydrodynamic interactions is considered, it significantly alters the deposition pattern along the respiratory tract, both alone and simultaneously with other synergistic processes (coagulation, hygroscopic growth) that dynamically modify the particle size distribution. Model results compare favorably with clinical data available on CSP deposition in the lungs and indicate that a combination of cloud behavior, hygroscopic growth, and coagulation may explain the preferential proximal deposition of smoke particles in the tracheobronchial region.

Flow field analysis in a compliant acinus replica model using particle image velocimetry (PIV).

Inhaled particles reaching the alveolar walls have the potential to cross the blood-gas barrier and enter the blood stream. Experimental evidence of pulmonary dosimetry, however, cannot be explained by current whole lung dosimetry models. Numerical and experimental studies shed some light on the mechanisms of particle transport, but realistic geometries have not been investigated. In this study, a three dimensional expanding model including two generations of respiratory bronchioles and five terminal alveolar sacs was created from a replica human lung cast. Flow visualization techniques were employed to quantify the fluid flow while utilizing streamlines to evaluate recirculation. Pathlines were plotted to track the fluid motion and estimate penetration depth of inhaled air. This study provides evidence that the two generations immediately proximal to the terminal alveolar sacs do not have recirculating eddies, even for intense breathing. Results of Peclet number calculations indicate that substantial convective motion is present in vivo for the case of deep breathing, which significantly increases particle penetration into the alveoli. However, particle diffusion remains the dominant mechanism of particle transport over convection, even for intense breathing because inhaled particles do not reach the alveolar wall in a single breath by convection alone. Examination of the velocity fields revealed significant uneven ventilation of the alveoli during a single breath, likely due to variations in size and location. This flow field data, obtained from replica model geometry with realistic breathing conditions, provides information to better understand fluid and particle behavior in the acinus region of the lung.

Determination of Nicotine Content and Delivery in Disposable Electronic Cigarettes Available in the United States by Gas Chromatography-Mass Spectrometry

INTRODUCTION Electronic cigarettes (E-Cigs) are popular alternatives to conventional tobacco cigarettes. Disposable E-Cigs are single-use devices that emit aerosols from a nicotine-containing solution (e-liquid) by activating a heating coil during puffing. However, due to lack of regulations and standards, it is unclear how product claims are aligning with actual content and performance. Some analytical methods for characterizing E-Cigs are still in an exploratory phase. METHODS Five products of disposable E-Cigs (purchased March-April, 2014 from a local smoke shop and an on-line US distributor) were studied for nicotine content, number of puffs obtained before depletion, portion of nicotine delivered via aerosolization, and e-liquid pH. Protocols were developed to consistently extract e-liquid from puffed and unpuffed E-Cigs. An in-house mechanical puffing machine was used to consistently puff E-Cig aerosols onto filter pads. A gas chromatography-mass spectrometry method was developed that produced sensitive and repeatable nicotine determinations. RESULTS Under our experimental parameters, results showed a disparity between nicotine content and number of puffs achieved relative to what was claimed on product packaging. The portion of nicotine delivered to filter pads was often less than half that which was available, indicating much of the nicotine may be left in the E-Cig upon depletion. CONCLUSIONS Analyses of unpuffed E-Cigs by gas chromatography-mass spectrometry indicate the nicotine content of these products can be considerably different from manufactures labeling. Furthermore, a large portion of the nicotine in E-Cigs may not be transferred to the user, and that which is transferred, may often be in the less bioavailable form.

Predicted tracheobronchial and pulmonary deposition in a murine asthma model.

Particulate matter dosimetry provides the critical link between exposures and initial doses reaching various sites in the respiratory tract. To extrapolate findings from animal models to humans, quantitative respiratory‐tract anatomical data dosimetry in these animal models is required. The goal of this study was to provide anatomical information for the tracheobronchial and pulmonary region so predictions of particle deposition could be performed for a widely used model of asthma; the sensitized Balb/c mouse. Tracheobronchial airway morphometry of sensitized male Balb/c mice was generated from three in situ prepared lung casts. Distribution of the number of generations to terminal bronchiole for each lung lobe was determined by assigning a unique binary number to each airway. This strategy enabled the median path length to terminal bronchiole to be determined. A total of 25 median length paths to terminal bronchiole were measured (airway length, diameter, and branch angle) in each lung cast. These 25 paths were proportionately distributed among the six lobes based upon the number of median length pathways in each cast. Airway length, diameter, and branch angle were measured for each airway in the 25 median length pathways. Measurements of airway length, diameter, and branch angle for each generation were averaged to create a typical path tracheobronchial anatomy model. A pulmonary airway model was also developed so that particle deposition predictions could be performed for particle diameters of 0.2–10 micrometers. Particle deposition efficiency predictions were consistent with in vivo measured deposition. Anat Rec, 290:1309–1314, 2007.

Performance of a portable whole-body mouse exposure system

A mobile whole-body exposure system was developed for exposing mice to concentrated ambient particulate matter smaller than 2.5 μm in mass median aerodynamic diameter (MMAD). Each 20-L exposure cage was designed to hold 9 mice within individual compartments. This allowed for transport and subsequent exposure. Airflow mixing and the potential for stagnant areas within the compartments were modeled using computational fluid dynamic modeling (CFD). CFD analysis showed no stagnant areas and good mixing throughout the exposure cage. The actual performance of the exposure system was determined for 0.5 to 2.0 μm diameter aerosols by measuring (1) uniformity of aerosol distribution and (2) particle deposition in the tracheobronchial and pulmonary regions of mice exposed in the system. A 0.6-μm MMAD (GSD = 2.0) cigarette smoke aerosol was used to experimentally measure the uniformity of aerosol distribution to the nine individual compartments. The average data from three runs showed no statistically significant difference among individual compartments. Particle deposition efficiency in adult male BALB/c mice was measured after exposure (30 min) in the system using monodisperse fluorescent polystyrene latex particles (0.5, 1, and 2 μm aerodynamic diameter). The measured deposition efficiency in this mobile exposure system for the combined tracheobronchial and pulmonary regions of the adult male BALBc mice was 21% for 0.5 μm, 11% for 1.0 μm, and 6.5% for 2.0 μm particles. These deposition efficiencies are similar to those reported for mice exposed in a nose-only exposure system, which indicates that particle losses to animal fur and exposure system surfaces were acceptable.