In 2014, AIHA’s Indoor Environmental Quality and Risk Committees delivered a groundbreaking white paper on electronic cigarettes, which revealed the potential hazards associated with the use of such products in the indoor environment. Since the original white paper was published, a significant amount of scientific research has been performed, identifying additional hazards from flavorings, potential health effects not previously described, and concerns related to surface deposition and thirdhand exposure. As a result, the IEQ and Risk Committees recently updated the white paper, which can be found on AIHA's website (PDF). 

With more information now available about the potential hazards posed by e-cigarettes, the general public is becoming more aware of these hazards. The continued growth of the industry, however, is unprecedented, and young people (middle and high school students) are picking up the habit every day. A report from CDC published in the Nov. 15, 2018, issue of Morbidity and Mortality Weekly Report noted that, since 2017, the use of e-cigarettes by high school students had jumped 78 percent; usage by middle school students increased by 48 percent. So how should we, as industrial hygienists and safety and health professionals, address the occupational and public health concerns associated with e-cigarettes?
RESOURCES American Industrial Hygiene Conference and Exposition: “When Cloud Chasing Spills Over: A Different Kind of ‘Vapor Intrusion’” (presentation, June 2017). American Journal of Industrial Medicine: “Effects of Theatrical Smokes and Fogs on Respiratory Health in the Entertainment Industry” (May 2005). American Journal of Public Health: “Sales of Nicotine-Containing Electronic Cigarette Products: United States, 2015” (May 2017). American National Standards Institute/American Society for Heating Refrigeration and Air-Conditioning Engineers: “ANSI/ASHRAE Addenda a, c, j, k, q, r, and s to ANSI/ASHRAE Standard 62.1–2013: Ventilation for Acceptable Indoor Air Quality” (PDF, 2015).  CDC: “Current Intelligence Bulletin 67: Promoting Health And Preventing Disease and Injury Through Workplace Tobacco Policies” (PDF).   CDC: Morbidity and Mortality Weekly Report, “Notes from the Field: Use of Electronic Cigarettes and Any Tobacco Product Among Middle and High School Students—United States, 2011–2018” (November 2018).  Current Neuropharmacology: “Effects of Nicotine During Pregnancy: Human and Experimental Evidence” (September 2007). Environmental Health Perspectives: “Metal Concentrations in E-Cigarette Liquid and Aerosol Samples: The Contribution of Metallic Coils” (February 2018).  Journal of Medical Internet Research: “Evolution of Electronic Cigarette Brands from 2013–2014 and 2016–2017: Analysis of Brand Websites” (March 2018). Journal of Occupational and Environmental Hygiene: “E-cigarette Nicotine Deposition and Persistence on Glass and Cotton Surfaces” (March 2019).  National Institute on Drug Abuse: “Tobacco/Nicotine and E-Cigs.” NIOSH: “Nicotine: Systemic Agent.” PLoS ONE: “Exposure to Electronic Cigarettes Impairs Pulmonary Anti-Bacterial and Anti-Viral Defenses in a Mouse Model” (February 2015). PLoS ONE: “Metal and Silicate Particles Including Nanoparticles Are Present in Electronic Cigarette Cartomizer Fluid and Aerosol” (March 2013). Proceedings of the National Academy of Sciences of the United States of America: “Formation of Carcinogens Indoors by Surface-Mediated Reactions of Nicotine with Nitrous Acid, Leading to Potential Thirdhand Smoke Hazards” (April 2010). Tobacco Control: “Levels of Selected Carcinogens and Toxicants in Vapour from Electronic Cigarettes” (March 2014). Tobacco Control: “Nicotine Arms Race: JUUL and the High-Nicotine Product Market,” (February 2019).
E-CIGARETTE COMPONENTS AND HAZARDS While the design of e-cigarettes can vary, the primary components consist of a rechargeable lithium battery, a vaporization chamber, a wicking system, a cartridge containing the “e-liquid,” and an atomizer or heating coil. When the user inhales, the atomizer is activated, and the heating coil begins to vaporize the liquid. The liquid, in turn, wicks more liquid from the cartridge to the atomizer. The vaporized liquid cools and condenses into a fine aerosol (called the “vapor”), which the user inhales. The e-liquid typically contains one or more flavorings, nicotine, and diluents (vehicles for the delivery of nicotine and flavorings). Propylene glycol, a chemical commonly found in theatrical smoke, and vegetable glycerin are both used as diluents in e-liquid. Components of the “vapor” that is emitted can include nicotine; metals from the heating coil, solder, and other parts; diluent; and flavorings. The vapor can also include pyrolysis byproducts from the heating of the e-liquid by the coil.  In 2015, 99 percent of e-cigarettes or e-liquids sold in the United States contained nicotine. Studies have shown that advertising and product labels regarding nicotine content in the liquids are often inaccurate. In some instances, the amount of nicotine present has been found to be two to five times greater than the amount indicated by the manufacturers. Recently, some e-cigarette manufacturers have dramatically increased the amount of nicotine in their liquids. Many refill liquids sold in the U.S. now contain 5 to 7 percent nicotine, versus 1 to 3 percent just a few years ago. Nicotine is addictive and teratogenic, and exposure can contribute to learning and attention deficits.  Aerosols from popular disposable e-cigarettes have been shown to contain at least 35 different elements  including metals. Several of these elements have not been reported in regular cigarette smoke, including tin, silver, iron, sodium, magnesium, and potassium, and nanoparticles of tin, chromium, and nickel. Resistive wire filaments (nickel-chromium or other metals) are used to heat the wick and evaporate the e-liquid. Often these resistive wires are coupled to non-resistive extensions of copper wire (sometimes coated with silver), and tin solder joints connect the wires to each other. One study found lead and chromium concentrations in e-cigarette aerosols that were similar to those found in the smoke from conventional cigarettes. While the use of lead in solder has been banned in most countries—including China, where most e-cigarette components and liquids are manufactured—the ban is not strictly enforced in many countries. Users cannot assume that e-cigarettes and related products are lead-free. Exposure to propylene glycol in theatrical smoke has been connected to both acute and chronic health issues, such as asthma, wheezing, chest tightness, decreased lung function, respiratory irritation, and airway obstruction. Of greater concern, though, are the pyrolysis byproducts formed from heating vegetable glycerin in the coil. Formaldehyde, a recognized human carcinogen, is a degradation product of propylene glycol and glycerol and has been found in the emissions of e-cigarettes. In general, the higher the voltage to the e-cigarette’s heating coil, the higher the formaldehyde concentration. Acrolein and acetaldehyde, both irritants, are also byproducts of glycerin pyrolysis in e-cigarettes. Of additional concern is the impact of formaldehyde, acrolein, and acetaldehyde on the mucociliary clearance function of the lung. E-cigarette exposure has also been shown to reduce bacterial and viral clearance.
One of the biggest, and most uncertain, concerns with e-cigarettes is the wide variety of flavorings used in the liquids. A 2018 paper reported that over 15,500 distinct e-cigarette flavors were on the market and available to consumers. These flavorings are, in most cases, considered GRAS—generally recognized as safe—for ingestion. But little, if any, research exists on the potential health hazards from inhaling those flavoring chemicals. An example of this potential problem is the use of diacetyl as a butter flavoring in the food industry. While diacetyl is considered safe to ingest, inhalation of diacetyl has been associated with bronchiolitis obliterans, a rare and serious disease of the lungs. Acetyl propionyl (aka 2,3-pentandione) is another flavoring agent that is considered GRAS for ingestion but whose risks associated with inhalation may be as high as those of diacetyl, based on inhalation studies with rats. Both diacetyl and acetyl propionyl have been found in many e-cigarette flavorings. It is unknown what, if any, health effects are associated with the inhalation of other flavors that are currently affirmed as GRAS by the FDA. In addition, current literature reveals little about the potential synergistic effects of the main chemical components, the numerous flavoring additives, and potential pyrolysis byproducts. Given the wide variety of e-cigarette devices and users’ vaping styles, which can range from “stealth vaping” (where nearly all emissions are intentionally limited) to “cloud chasing” (where the intent is to generate as large and long of a “cloud” of vapor as possible), it is difficult to predict secondhand exposures to bystanders. However, research has shown that users do not absorb all of the nicotine and other chemicals they inhale. Therefore, secondhand exposures are clearly possible. The amount of scientific literature on potential surface deposition of nicotine from e-cigarette use (potentially resulting in thirdhand exposure) has been increasing over the past few years. Some recent research has shown that e- cigarette aerosols can spread through ventilation systems to adjacent parts of a building, where they can then be deposited onto surfaces, and that nicotine deposition can be retained on surfaces for up to three days or more. Such surface deposition can potentially contribute to thirdhand exposure to nicotine and other potentially hazardous contaminants. According to work published in the Proceedings of the National Academy of Sciences, surface deposition of nicotine from three days of exposure to traditional cigarette smoke followed by only three hours of exposure to nitrous acid or nitrogen oxides (which are naturally present in ambient air) was sufficient to form potentially carcinogenic tobacco-specific nitrosamines.  E-CIGARETTES AND INDOOR AIR QUALITY It is important for industrial hygienists and safety and health professionals to understand these issues in order to limit the impact of e-cigarettes on the indoor environment. In its 2015 document, “Current Intelligence Bulletin 67: Promoting Health and Preventing Disease and Injury Through Workplace Tobacco Policies,” NIOSH recommended that employers “establish and maintain smoke-free workplaces that protect those in workplaces from involuntary, secondhand exposures to tobacco smoke and airborne emissions from e-cigarettes and other electronic nicotine delivery systems.” The American Society of Heating, Refrigerating, and Air-Conditioning Engineers' (ASHRAE) Standard 62.1: Ventilation for Acceptable Air Quality contains requirements for ventilation of spaces that are free of environmental tobacco smoke, and provides requirements for separation of ETS-free areas from any areas containing ETS. Addendum C to the standard clarifies that ETS “includes smoke produced from the combustion of cannabis and controlled substances and the emissions produced by electronic smoking devices” and states that “provision of acceptable indoor air quality is incompatible with the presence of ETS, including cannabis smoke and e-cigarette emissions” (emphasis added). Because the magnitude of health and safety hazards that vaping may present to nonusers remains unclear, it is important to manage and control vaping in indoor locations where smoking is currently restricted. To better understand, and protect the public from, potential health and safety risks associated with vaping, the AIHA white paper offers four recommendations. First, e-cigarettes should be considered a source of aerosols, volatile organic compounds, and particulates in the indoor environment that have not been thoroughly characterized or evaluated for health risk or safety. Second, additional research should be conducted on the health effects from inhaling e-cigarette flavorings and other ingredients; the effects of secondhand emissions, thirdhand exposures, e-cigarettes, and nicotine addiction; and the lifecycle and end-of-use issues associated with e-cigarette manufacturing, use, and disposal. Third, the health risks and economic consequences of accidental exposure by children, adults, and pets should be addressed, including requirements for proper labeling and child-resistant packaging. Finally, as e-cigarettes are a potential source of pollutants, it is prudent to manage and control vaping in indoor environments consistent with current smoking policies until and unless research demonstrates that these devices will not significantly increase the risk of adverse health effects to occupants.   CHERYL L. (CHERI) MARCHAM, PhD, CSP, CIH, CHMM, FAIHA, is an assistant professor and program chair for the Master of Science in Occupational Safety Management degree program at Embry-Riddle Aeronautical University. She is a past member of the AIHA Board, a current director on the ABIH Board, and the 2018 recipient of AIHA’s Henry F. Smyth, Jr. Award. JOHN (JACK) SPRINGSTON, CIH, CSP, FAIHA, is the Industrial Hygiene Services manager for ATC Group Services’ New York operations. Send feedback to The Synergist.

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In general, the higher the voltage to the e-cigarette’s heating coil, the higher the formaldehyde concentration. 
Updated White Paper Covers Latest Research

Electronic Cigarettes and the IH
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Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers