Environmental health hazards of e-cigarettes and their components: Oxidants and copper in e-cigarette aerosols

Abstract

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.

Keywords: Copper; ENDS; EPR; Electronic cigarettes; Oxidants; ROS.

Fig. 1. Activation of the pump initiates pressure changes within the e-cigarette which automatically activates the battery

A current is subsequently delivered to the heating element within the cartomizer and the liquid housed within is vaporized. Air and vapor flow into the glass bubbler (impinger) containing the DCFH solution through tubing that is coupled to the cartomizer. The air and vapor finally passes through the DCFH solution, through the pump, and exits the apparatus via additional tubing.

Fig. 2. Oxidants/ROS associated with e-cigarette components

Immersion of e-cigarette components in DCFH solution (see Materials and Methods). Y axis - measurement of DCF fluorescence, (A) Components removed from cartomizer casing and placed in DCFH solution (n=12), Control; DCFH solution alone (n=3) (B) Non-functional lithium-ion battery of e-cigarette placed in DCFH solution (n=4) Control; DCFH solution alone (n=3). Data are shown as mean ± SD. **P< 0.01. Significant compared to control based on unpaired 2-tail t-test.

Fig. 3. Oxidants/ROS levels in conventional cigarette filters

(A,B) Filters removed from cigarettes following consumption and immersed in DCFH solution (n=3). Unused cigarette filters immersed in DCFH solution (n=3) serve as reference control. Data are shown as the mean ± SD. ***P<0.001.

Fig. 4. Detection of ROS in vapor produced from e-cigarettes

E-cigarette vapor or conventional cigarette smoke bubbled into DCFH solution and DCF fluorescence measured as described in Materials and Methods. (A) E-cigarette (E-Cig) aerosols (10 minute exposure period) produced from a single Classic Tobacco flavor cartomizer with nicotine (n=3), compared to ambient air control (n=4) (B) Conventional cigarette smoke (5 minute exposure period) from brand name or research grade cigarettes (n= 3), compared to air sham control (n=3). Data are shown as means ± SD.*P<0.05; **P<0.01; ***P<0.001 vs. Air group.

Fig. 5. Electron paramagnetic resonance detection of radicals in ENDS aerosols

EPR Spectra of aerosols produced from (A) Air (control), and the experimental groups: (B) eGO Vision refillable ENDS (filled with ECTO tobacco e-liquid 18 mg nicotine), and (C) Blu e-cigarette (Classic tobacco, 16 mg nicotine). Spectra were obtained on an a Bruker 200ER X-Band EPR spectrometer using the following instrument parameters: Modulation: 100 kHz, Microwave Freq.: 9.587 GHz, Power: 2 mW, Modulation Amplitude: 4.0 G, Scan range: 100 G, Time constant: 40.96 msec, Sweep Time: 167.77 seconds, Receiver gain: 3.56 x 104. The thin lines above each spectrum represent the first integral of the data (the calculated absorbance spectrum). The Y-axis represents the first derivative of the EPR signal from the static magnetic field. The X-axis represents the range of increasing magnetic field strength in which the EPR signal is detected.

Fig. 6. Detection of copper nanoparticles in vapors produced by e-cigarettes

Amount of copper measured in Blu e-cigarette (E-cig) aerosols per 4 second puff (n=4), Control; amount of copper measured on nitrocellulose filter not exposed to aerosols (n=4). Data are shown as mean ± SD, *P<0.05 significant compared to control.