Potential Inflammatory and Health Effects of Flavorings in ENDS. Pamela Dalton, PhD, MPH Monell Chemical Senses Center Philadelphia, PA 19104

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1 Potential Inflammatory and Health Effects of Flavorings in ENDS Pamela Dalton, PhD, MPH Monell Chemical Senses Center Philadelphia, PA 19104

2 Family Smoking Prevention & Control Act (September, 2009) a cigarette or any of its component parts (including the tobacco, filter, or paper) shall not contain, as a constituent (including a smoke constituent) or additive, an artificial or natural flavor (other than tobacco or menthol) or an herb or spice, including strawberry, grape, orange, clove, cinnamon, pineapple, vanilla, coconut, licorice, cocoa, chocolate, cherry, or coffee, that is a characterizing flavor of the tobacco product or tobacco smoke

3 Monell Research Areas: Flavors in ENDS Sensory appeal of added flavors, especially to youth and beginning users Respiratory health implications of inhaled flavors

4 What do we know about the inhalation toxicity of flavor compounds used in ENDS? There are thousands of e-cigarette flavors currently marketed. Flavor chemicals gained notoriety in the early 2000s when inhalation exposure of the buttery flavor chemical diacetyl was found to be associated with a disease that became known as "popcorn lung." Despite this, there has been limited research on flavoring chemicals in e-cigarettes.

5 Airway/Oral Sensory Properties of Nicotine Trigeminal system in airways and oral cavity responds to multiple irritant compounds Nicotine is a potent airway irritant, triggering prickling, burning, stinging & coughing Nicotine is also a bitter agonist Sensory properties of nicotine can be sufficiently aversive to discourage initiation or maintenance of e- cigarette use Flavor compounds may ameliorate aversive sensations from nicotine

6 Respiratory Health Issues from Flavors in E-cigarettes Respiratory toxicity from inhaled flavors TRP-channel and SCC activation Disruption of innate immunity from stimulation of airway taste receptors

7 Are Flavor Compounds GRAS in the Airways? Since 1959, Flavor & Extract Manufacturers Association has evaluated safety of flavor ingredients for GRAS* certification Flavoring agents subjected to safety assessment by expert panel Determination of GRAS status considers the conditions of intended use (e.g. food flavor) Panel does not evaluate flavorings for use in products other than human food.or products involving routes of exposure other than ingestion *generally recognized as safe

8 Amounts of aldehydes produced per gram of e-liquid. Error bars represent one standard deviation of triplicate measurements (N = 3). V designates vapor (aerosol), and L designates liquid. Reprinted with permission from: Andrey Khlystov; Vera Samburova; Environ. Sci. Technol. 2016, 50, DOI: /acs.est.6b05145 Copyright 2016 American Chemical Society

9 Amounts of formaldehyde, acetaldehyde, acrolein, and propionaldehyde as a function of flavored e-liquid volume fraction after dilution with unflavored e-liquid. Also shown are TLV ceiling levels for formaldehyde and acrolein, assuming each puff is diluted in 500 ml of air (a typical lung tidal volume). Error bars represent one standard deviation of triplicate measurements (N = 3). Reprinted with permission from: Andrey Khlystov; Vera Samburova; Environ. Sci. Technol. 2016, 50, DOI: /acs.est.6b05145 Copyright 2016 American Chemical Society

10 Caramel 43 Chocolate 56 Vanilla 58 Buttery 51 Citrus 124 Apple 118 Banana 65 Berry/cherry 135 Coconut 41 Minty 74

11 One commercial flavor blend html 11

12 Cation channels of the transient receptor potential (TRP) class mediate chemosensory responses to irritant ligands Example Ligands Capsaicin, Camphor, Formaldehyde Menthol, Citral, Linalool Formaldehyde, Acrolein, Nicotine Reprinted with permission from: Félix Viana; ACS Chem. Neurosci. 2011, 2, DOI: /cn100102c Copyright 2010 American Chemical Society

13 Involvement of SCCs (blue) in neurogenic inflammation, immune response, and airway protection reflexes Published in: Tizzano, M. & Finger, T. Physiology (Bethesda) Jan; 28(1): doi: /physiol Copyright 2013 Int. Union Physiol. Sci./Am. Physiol. Soc.

14 Tobacco Flavored E-liquid induces IL-6 production in primary human airway epithelial cells. Wu Q, Jiang D, Minor M, Chu HW (2014) Electronic Cigarette Liquid Increases Inflammation and Virus Infection in Primary Human Airway Epithelial Cells. PLOS ONE 9(9): e doi: /journal.pone

15 Flavorings decreased metabolic activity, cell viability and increased inflammatory response in HBE cells Leigh, NJ, Lawton, RI, Hershberger, PA et al. Tob Control 2016;25, ii81-ii87.

16 Is Propylene Glycol a Respiratory Irritant? 20 participants, 10 males, 10 females, aged All were healthy, non-asthmatic individuals with no recent respiratory infections 4 sessions Visit 1: Screening for normal pulmonary function & health status Visit 2: 4 hour exposure to either 20 mg/ 3 or 100 mg/m 3 propylene glycol aerosol Visit 3: 4 hour exposure to either 100 mg/m 3 or 20 mg/ 3, depending on visit 2 condition Visit 4: 30 minute exposure to 200 mg/m 3 PG aerosol Participants rode an exercise bicycle for 10 minutes in each 30 minutes of exposure

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18 20 mg/m 3 PG

19 100 mg/m 3 PG

20 200 mg/m 3 PG

21 Results: Pulmonary Function * * Spirometry was performed at baseline, at the midpoint break and postexposure for the 20 & 100 mg/m 3 exposures *Spirometry was only performed twice for the 200 mg/m 3 exposure Dalton PH, Soreth, B, Maute, C et al, in preparation

22 PG aerosol does not appear to directly elicit airway irritation or decrease pulmonary function Objective measures of pulmonary function did not reveal any exposure-related changes FEV 1 and FEV 1 /FVC did not decrease from pre- to postexposure Slight exposure-related change in subjective symptom reporting Hygroscopic nature of PG suggests that drying of the mucosa may predispose epithelium to greater impact of other ENDS consituents, including flavor compounds

23 Extraoral Taste Receptors and Innate Immunity Bitter receptors (T2Rs) are expressed on airway epithelial cells (solitary chemosensory cells) which respond potently to chemical irritants. Bitter receptors in the nose appear to protect against bacterial infection T2Rs are found in mouse & human noses and in human airway smooth muscle Reprinted with permission from: Tizzanno, M. et al., (2010) Proc Natl Acad Sci USA, 107: doi: /pnas

24 Extraoral Taste Receptors and Innate Immunity Bitter receptors (T2Rs) are expressed in the respiratory tract within ciliated epithelial cells and solitary chemosensory cells (SCCs) They detect bacteria & their activation increases ciliary beat frequency and mucociliary clearance T2R38, expressed in respiratory ciliated cells, is stimulated by gram-negative bacteria to produce bactericidal concentrations of nitric oxide Sweet receptors are also co-located within SCCs although their function is less well known

25 Sweet receptor activation inhibits T2Ractivated calcium signaling Reprinted with permission from: Lee, RJ & Cohen, NA (2014) Bitter and sweet taste receptors in the respiratory epithelium in health and disease, J Clin Invest 124(3), doi: /s Copyright: American Society of Clinical Investigation

26 Research concerns and priorities Chemical analysis of flavor agents, including effects of thermal decomposition Identify/develop biomarker(s) of exposure Vaping behaviors vary substantially even in controlled laboratory sessions, requiring better measures of airway exposure Evaluate disruption of airway immune response following exposure to sweet e-liquids