title: A Device-Independent Evaluation of Carbonyl Emissions from Heated Electronic Cigarette Solvents.
abstract: OBJECTIVE
  To investigate how the two main electronic (e-) cigarette solvents-propylene glycol (PG) and glycerol (GL)-modulate the formation of toxic volatile carbonyl compounds under precisely controlled temperatures in the absence of nicotine and flavor additives.
  
  
  METHODS
  PG, GL, PG:GL = 1:1 (wt/wt) mixture, and two commercial e-cigarette liquids were vaporized in a stainless steel, tubular reactor in flowing air ranging up to 318°C to simulate e-cigarette vaping. Aerosols were collected and analyzed to quantify the amount of volatile carbonyls produced with each of the five e-liquids.
  
  
  RESULTS
  Significant amounts of formaldehyde and acetaldehyde were detected at reactor temperatures ≥215°C for both PG and GL. Acrolein was observed only in e-liquids containing GL when reactor temperatures exceeded 270°C. At 318°C, 2.03±0.80 μg of formaldehyde, 2.35±0.87 μg of acetaldehyde, and a trace amount of acetone were generated per milligram of PG; at the same temperature, 21.1±3.80 μg of formaldehyde, 2.40±0.99 μg of acetaldehyde, and 0.80±0.50 μg of acrolein were detected per milligram of GL.
  
  
  CONCLUSIONS
  We developed a device-independent test method to investigate carbonyl emissions from different e-cigarette liquids under precisely controlled temperatures. PG and GL were identified to be the main sources of toxic carbonyl compounds from e-cigarette use. GL produced much more formaldehyde than PG. Besides formaldehyde and acetaldehyde, measurable amounts of acrolein were also detected at ≥270°C but only when GL was present in the e-liquid. At 215°C, the estimated daily exposure to formaldehyde from e-cigarettes, exceeded United States Environmental Protection Agency (USEPA) and California Office of Environmental Health Hazard Assessment (OEHHA) acceptable limits, which emphasized the need to further examine the potential cancer and non-cancer health risks associated with e-cigarette use.
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Ping
authors.identifier: http://orcid.org/0000-0002-4149-5308
authors.initials: P
authors.lastname: Wang
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Chen
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.|Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, California, United States of America.
authors.forename: Jiawen
authors.initials: J
authors.lastname: Liao
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.|Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Matsuo
authors.affiliation: Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka, Japan.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Ito
authors.affiliation: Exposure Assessment Section, Environmental Health Investigation Branch, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Jeff
authors.initials: J
authors.lastname: Fowles
authors.affiliation: Division of Occupational and Environmental Medicine, School of Medicine, University of California, San Francisco, California, United States of America.
authors.forename: Dennis
authors.initials: D
authors.lastname: Shusterman
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Mark
authors.initials: M
authors.lastname: Mendell
authors.affiliation: Indoor Air Quality Program, Environmental Health Laboratory, California Department of Public Health, Richmond, California, United States of America.
authors.forename: Kazukiyo
authors.initials: K
authors.lastname: Kumagai
mesh_terms: D000079:Acetaldehyde / Q000032:analysis*; D000171:Acrolein / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D066300:Electronic Nicotine Delivery Systems / Q000009:adverse effects*; D005557:Formaldehyde / Q000032:analysis*; D005990:Glycerol / Q000737:chemistry; D019946:Propylene Glycol / Q000737:chemistry; D013696:Temperature
chemical_list: D005557:Formaldehyde; D019946:Propylene Glycol; D000171:Acrolein; D000079:Acetaldehyde; D005990:Glycerol