This degree of adaptability is evident in the staggering diversity of mod vape hardware. There are dozensif not much, much moreof choices for a rig body and atomizer. Different brands come out with different lines, each with many different models and builds.

There are, for example, atomizers that come with prebuilt heating coils that vapers just need to replace once burnt out. Others yield even more control to the user, allowing them to assemble their own coil-and-wick setup.

In turn, this opens up layers upon layers of customization possibilities. Some coils are more resistive, have more turns, and are longer than others; some look like typical coils, while other come in mesh form. Wicks come in different materials. Some atomizers come with a tank, while others dont. Mouthpiece barrels have different allowances for airflow.

The one indispensable thing that all box modsand all vapes in generalshare is the need for e-juice. What good is a decked-out rig for if theres nothing to aerosolize?

But juices themselves are very diverse. Fundamentally, e-juices will contain some ratio of organic solvents that liquefy nicotine and carry it in the aerosols. Many different solvents can fill this role, but the most popular ones are propylene glycol and vegetable glycerin.

To add yet another layer to this variety, juices also come in many different flavors: tobacco; menthol; fruity, like mango and strawberry; and dessert, like cheesecake and cinnamon. Already,over 15,000 flavors had been documented as early as 2014, and the playing field was expanding by some 200 new flavors per month.

In a lot of ways, the market of mod vapes resembles the landscape of smartphones. The sheer number of options is daunting and overwhelming, but can also become intoxicating.

People have different needs, Jess says. For people who are just after high nicotine content, the small pods would be their best bet. The big mods and atomizers, usually those are for cloud chasers.

The dizzying variety of mod vapes shouldnt distract from the often-underplayed risks they come with, though.

Theyve been associated with explosions and poisoning, says Dr Riz Gonzalez, MD, Chairwoman of the Tobacco Control Advocacy Group of the Philippine Pediatric Society, referring to mod vapes.

Mods need regular maintenance and cleaning, particularly in its internal workings, she continues. Neglecting to do so might cause a short circuit and lead to an explosion. This may also be the case when the vape, particularly the battery, is exposed to moisture or extreme temperatures, or when improperly charged. (It is worth noting, though, that explosions have become increasingly rare, especially with the newer mods that have built-in safety features).

The coils themselves are cause for concern. During heating, they leach metallic nanoparticles into the juice, Dr Gonzalez said, and these are irritants. Several studies, indeed, have found considerable levels of metals such as aluminum, nickel, lead, copper, iron, tin, and zinc in the e-juice. And they dont just stay there. When the juice evaporates, it carries these tiny nanoparticles in the aerosols.

The microparticles float in the aerosols, and when you inhale, they go into the lungs, and lungs are only meant to inhale clean air, Dr Gonzalez explains. Anything beyond what is needed by the body, the body reacts to through inflammatory processes.

In the same way that the body tries to clot up a wound, it floods the lungs with platelets, fibrin, thrombin, and other coagulants in response to these metallic invaders. This blocks the airways. Its the same thing that happens with EVALI, she adds, referring to the e-cigarette-related lung injury epidemic that took the US by storm late last year.

This goes for e-juices, too. In fact, more particularly so. There continues to be a lot of debate about the safety of the solvents, particularly around propylene glycol and vegetable glycerin. Both have been designated by the US FDA as GRAS, or substances that are generally recognized as safe.

But Dr Gonzalez points out that these are GRAS for ingestion, not for inhalation. The cells that line the airway, after all, are different from the cells that line the stomach. It follows, too, that they respond to chemicals in different ways.

Several studies have shown, for example, that the aerosols from e-cigarettes mess with our respiratory tract even on a very basic, cellular level. Lab studies have shown that in response to these aerosols the cells that line the airway show signs of stress. Ultimately, such an exposure led to lower cell viability and an excess in the rate of cell death.

E-cigarette aerosols also assault the lungs. When exposed, in culture, to the aerosols, cells that line the tiny air sacs likewise show signs of stress and release indicators of cellular destruction. Aerosols might also make the lungs more susceptible to infection.

A 2016 study found that e-cigarette aerosols weaken the immune cells of the lungs. Mice who had inhaled these vapors showed altered inflammatory activity in their airways. To make things worse, the same type of exposure empowered Staphylococcus aureus, a common respiratory pathogen in humans. The bacteria grew more resistant to immune defenses, and became more potentsticking to the hosts cells better and entering them with greater ease.

The outbreak of EVALI late last year in the US demonstrates that what happens in the lab isnt just a test-tube artefact. Short for e-cigarette or vaping product use-associated lung injury, EVALI describes lung injuries and infections that were inexplicable except when seen in connection to the use of these devices.

Patients would present with unspecific symptoms: coughs, shortness of breath, and fevers. But in the most unfortunate cases, the disease would escalate and kill an otherwise healthy person.

Majority of cases were linked to vitamin E acetate, a common additive in juices that contained tetrahydrocannabinol, but a sizeable minority had no such connection. According to Dr Gonzalez, the culprit chemical (or chemicals) is still at large.

Though still such a very young phenomenon, there is already a substantial body of literature suggesting harms associated with vaping. It is true, however, that theres a shortage of conclusive, unassailable, clinical evidence that vaping does more harm than good. All there is, still, is smoke, not a smoking gun.

The same can be said, though, of safety. There likewise hasnt been irrefutable proof that these chemicals, and vaping in general, are completely devoid of serious health risks.

This is especially true in the face of all the flavorings. Many sweet flavors, like butter, caramel, and strawberry, owe their appeal to diacetyl, acetylpropionyl, and acetoin. Diacetyl is also GRAS for the stomach, but definitely not for the lungs. Used traditionally as the main butter flavoring in popcorn, diacetyl has since become notorious as the culprit behind bronchiolitis obliteransmore commonly known as popcorn lung.

Flavorings are also chiefly responsible for the aldehydes produced during vaping. Under heat, flavoring compounds break down into their aldehyde building blockslike formaldehyde, benzaldehyde, and acroleinin levels that exceed occupational safety thresholds.

Theres little doubt in her head that vapes will emerge more harmful than beneficial. But as of the moment, Dr Gonzalez concedes, theres no way for us know, with a comfortable degree of statistical certainty, how harmful it truly is. Its just still too early.

Maybe in a few years, she says, though even now, were starting to see some cases of COPD. Before, it [used to take] about 20 to 30 years. Vaping, in comparison, has been around 17 years, and only in the most recent handful years did it hit its stride. Its going to take time for all the chronic side effects to arise, and even more time to study and peer-review any future findings.

Unfortunately, this high bar of scientific rigor is more of a convenience than a
requirement for marketing. In the face of these sparsely substantiated claims, all health advocates like Dr Gonzalez can do is call for caution and wait.

[Vapes] still do contain unidentified harmful chemicals and still-unidentified carcinogens because of the process of heating, she says. They say its for harm-reduction, but in the long run, its still really not safe.MF

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The anatomy and physiology of vapes: Mods - FlipScience