title: Benzene formation in electronic cigarettes.
abstract: OBJECTIVE
  The heating of the fluids used in electronic cigarettes ("e-cigarettes") used to create "vaping" aerosols is capable of causing a wide range of degradation reaction products. We investigated formation of benzene (an important human carcinogen) from e-cigarette fluids containing propylene glycol (PG), glycerol (GL), benzoic acid, the flavor chemical benzaldehyde, and nicotine.
  
  
  RESULTS
  Three e-cigarette devices were used: the JUULTM "pod" system (provides no user accessible settings other than flavor cartridge choice), and two refill tank systems that allowed a range of user accessible power settings. Benzene in the e-cigarette aerosols was determined by gas chromatography/mass spectrometry. Benzene formation was ND (not detected) in the JUUL system. In the two tank systems benzene was found to form from propylene glycol (PG) and glycerol (GL), and from the additives benzoic acid and benzaldehyde, especially at high power settings. With 50:50 PG+GL, for tank device 1 at 6W and 13W, the formed benzene concentrations were 1.9 and 750 μg/m3. For tank device 2, at 6W and 25W, the formed concentrations were ND and 1.8 μg/m3. With benzoic acid and benzaldehyde at ~10 mg/mL, for tank device 1, values at 13W were as high as 5000 μg/m3. For tank device 2 at 25W, all values were ≤~100 μg/m3. These values may be compared with what can be expected in a conventional (tobacco) cigarette, namely 200,000 μg/m3. Thus, the risks from benzene will be lower from e-cigarettes than from conventional cigarettes. However, ambient benzene air concentrations in the U.S. have typically been 1 μg/m3, so that benzene has been named the largest single known cancer-risk air toxic in the U.S. For non-smokers, chronically repeated exposure to benzene from e-cigarettes at levels such as 100 or higher μg/m3 will not be of negligible risk.
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.|Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon, United States of America.
authors.forename: James F
authors.initials: JF
authors.lastname: Pankow
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.
authors.forename: Kilsun
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon, United States of America.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: McWhirter
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.|Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon, United States of America.
authors.forename: Wentai
authors.initials: W
authors.lastname: Luo
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.
authors.forename: Jorge O
authors.initials: JO
authors.lastname: Escobedo
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Strongin
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.
authors.forename: Anna K
authors.initials: AK
authors.lastname: Duell
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, United States of America.
authors.forename: David H
authors.initials: DH
authors.lastname: Peyton
mesh_terms: D001554:Benzene / Q000737:chemistry*; D003500:Cyclization; D003653:Decarboxylation; D003681:Dehydration; D066300:Electronic Nicotine Delivery Systems; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D009538:Nicotine / Q000032:analysis; D010084:Oxidation-Reduction
chemical_list: D009538:Nicotine; D001554:Benzene