Smoking and health
Tobacco smoking, as we all are aware, is detrimental to overall health and is associated with ocular surface disease. A 2016 meta-analysis suggests that smoking may associate with the risk of dry eye in general population.5 Furthermore, a separate study concluded that smoking might decrease tear secretion, goblet cell density, and tear MUC5AC concentration.6 These studies corroborate a 2008 study by Matsumoto.7
Also, consider secondhand smoke. Secondhand smoke (also called environmental tobacco smoke, involuntary smoke, and passive smoke) is the smoke given off by a burning tobacco product and the smoke exhaled by a smoker.
The National Cancer’s Institute’s Fact Sheet on Secondhand Smoke notes that there is no safe level of exposure, with even low levels of secondhand smoke being harmful.8
The Johnson & Johnson Ocular Surface and Visual Optics Department at Keio University of Medicine in Japan investigated the effects of acute passive cigarette smoke exposure on the ocular surface and the tear film in healthy non-smokers. Researchers found that even after brief exposure, adverse effects on ocular surface health was evidenced by an increase of tear inflammatory cytokines, tear instability, and damage to the ocular surface epithelia.9
Similarly, Ward et al showed that passive exposure to cigarette smoke is associated with an increase in tear instability and damage to the ocular surface epithelia in soft contact lens wearers and non-contact lens wearers.10
Of added concern, passive smoking represents a significant risk factor of dry eye in children.11
To parallel, let us consider secondhand vape. Logue et al computed the integrated health damage from passive vaping. This was derived by computing disability-adjusted life years (DALYs) lost due to exposure of toxic compounds in secondhand vapor. Acrolein and other compounds including formaldehyde were the contributors to aggregate harm.12,13
DALYs for the various vape device and voltage combinations were lower than or comparable to those estimated for exposures to secondhand and thirdhand tobacco smoke. Thirdhand smoke is residual nicotine and other chemicals left on indoor surfaces by tobacco smoke. This residue is thought to react with common indoor pollutants to create a toxic mix, including cancer-causing compounds, posing a potential health hazard to nonsmokers, especially children.12,13
Aldehydes are emitted by electronic cigarettes due to thermal decomposition of liquid components. Overheating produces an unpleasant taste—called a dry puff—and elevated levels of aldehydes, which vapers learn to avoid.14
The vaping market
Why have electronic cigarettes become popular? They do not contain tobacco, although they do use nicotine from tobacco plants. They do not generate cigarette smoke but rather an aerosol. An aerosol is a suspension of fine particles of liquid, solid, or both in a gas: both the particulate and gas phases are mixtures of chemical substances in e-cigarette aerosols15) that is frequently but inaccurately referred to as vapor (a vapor is a substance in the gas phase).
Related: It’s all about the ocular surface!
E-cigarettes sales reached $2.76B U.S. in 2014 and are expected to grow to $10B U.S. this year.16 They are readily available for purchase in convenience stores, smoke shops, mall kiosks, supermarkets, or even online, while traditional cigarettes shipments are regulated.
Adult e-cigarette use is increasing globally, and early studies have suggested that similar trends may be observed among the adolescent population. A 2014 literature review suggests that adolescents are nearing complete awareness of e-cigarettes;17 however, relatively low observed number of patients with ENDS use documented in electronic health records (EHR) suggests vast under documentation.18
Alarmingly, one in four U.S. high school teens who has used e-cigarettes has also tried a potentially dangerous new vaping method called “dripping”—dropping e-cigarette liquid directly onto the hot coils of the device to produce thicker, more flavorful vapor.19
Similarly, adolescent users of e-cigarettes and other electronic vaping products (EVPs) report performing “vape tricks” (exhaling aerosol to make shapes). Vape tricks pose a potential threat to adolescent health because they may encourage nonusers to initiate or current EVP users to use more frequently or switch to advanced devices that produce more harmful chemical emissions.20 “Vape-bending (tricks)” tutorials are readily available on an Internet search.