Daniel sent us this one — and it's the kind of question that sounds simple until you actually sit with it. He's asking about vaping, specifically the risks that have nothing to do with nicotine or THC. What happens when you heat propylene glycol and vegetable glycerin to two hundred degrees and inhale the result? How is vaporization different from combustion at the chemical level? And here's the provocative part — are there scenarios where vaping actually does more damage than a cigarette? Not safer, not "reduced harm," but worse.
The answer to that last one is yes, under specific conditions, which I think surprises most people. Not because smoking is good — smoking is catastrophic — but because vaping introduces its own injury pathways that combustion simply doesn't.
The vape pen doesn't burn anything. That's the whole pitch. No tar, no carbon monoxide, none of the polycyclic aromatic hydrocarbons that make tobacco smoke carcinogenic. So why are pulmonologists seeing lung injuries they've never seen from cigarettes?
Because "not burning" is not the same as "not chemically transforming." And that's where I want to start — with what actually happens inside that little metal chamber. You press the button, current flows through a resistive coil, and the coil heats up. Combustion requires temperatures around six hundred to nine hundred degrees Celsius, an open flame, and it produces smoke — solid carbon particles, tar, carbon monoxide, thousands of compounds from thermal decomposition of plant matter. A vape coil operates at maybe one-fifty to two-fifty degrees. It doesn't burn the liquid — it aerosolizes it. Tiny droplets suspended in air. No smoke, just what the industry likes to call vapor.
Which sounds almost gentle. Like a facial mist.
Except facial mists aren't heated on a nickel-chromium wire and inhaled directly into alveolar sacs. And that word — vapor — is doing a lot of heavy lifting. People hear "vapor" and think steam. But it's not water. The base liquids in nearly every e-liquid are propylene glycol and vegetable glycerin. PG and VG. Both are generally recognized as safe for ingestion — you'll find them in food, cosmetics, pharmaceuticals. But your stomach is not your lungs, and heating something to two hundred degrees is not the same as swallowing it at room temperature.
The safety profile for eating PG doesn't transfer to inhaling heated PG aerosol.
Not even slightly. And that's where the first big risk category comes in — thermal decomposition. PG and VG are stable at room temperature, but when you push them past roughly two hundred degrees Celsius, they start to break down through pyrolysis. The molecular bonds crack. And what forms are reactive carbonyl compounds — formaldehyde, acetaldehyde, acrolein, glyoxal. These are potent respiratory irritants and known carcinogens.
Formaldehyde is embalming fluid.
Among other things, yes. And the quantities are not trivial. There was a landmark study by Pankow and colleagues in twenty eighteen — they found that under high-wattage conditions, the formaldehyde hemiacetal levels in e-cigarette aerosol reached about three hundred eighty micrograms per ten puffs. A cigarette delivers roughly four hundred micrograms per ten puffs. So we're in the same ballpark. In some cases, the vape aerosol exceeded the cigarette.
The device that's marketed as the healthier alternative can, depending on how you use it, produce carcinogen levels comparable to a cigarette.
Comparable, and in some configurations higher. And here's the mechanism that makes this so variable — it's called the dry puff phenomenon. The coil is wrapped around a wick, usually cotton, that draws liquid from a reservoir. When the wick is fully saturated, the liquid itself acts as a coolant — it absorbs heat from the coil through vaporization, keeping the temperature stable at around one-eighty to two-twenty degrees. But if you chain-vape, or if the liquid viscosity is too high for the wicking rate, or if the tank is running low, the wick starts to dry out. The liquid isn't there to absorb the heat. The coil temperature spikes to three hundred, four hundred degrees Celsius.
At four hundred degrees, PG and VG don't just aerosolize — they cook.
They pyrolyze aggressively. Formaldehyde production goes through the roof. Acrolein — which is the compound that makes burning fat smell acrid and is a severe respiratory irritant — spikes dramatically. The user often notices this as a burnt, harsh hit. That's the dry puff. But even before it becomes noticeable, the chemistry has already shifted.
The user experience tracks the toxicity — when it tastes burnt, it is burnt. But the damage may start before the taste does.
And this is where wattage becomes a critical variable. A low-power pod device running at seven to fifteen watts with high-nicotine salt liquid operates at relatively low temperatures. The carbonyl output is measurable but modest. But the sub-ohm devices — the ones that produce massive clouds, the cloud-chasing rigs — they run at eighty, a hundred, sometimes a hundred twenty watts. At those power levels, the coil temperature is consistently at the upper end of the range, and every puff is edging into thermal decomposition territory.
Cloud chasing is the vaping equivalent of hot-rodding — you're pushing the hardware past its sweet spot for the sake of performance. And the performance metric here is aerosol volume.
More vapor means more liquid aerosolized per puff, which means more carrier solvent inhaled, which means more thermal decomposition products, even if the temperature is exactly the same. It's a dose-response issue on top of a temperature issue. A cloud chaser might inhale five to ten times the aerosol volume per puff compared to a low-power pod user. So even at equivalent temperatures, the total carbonyl exposure per session is much higher.
That's just the carrier liquids breaking down. We haven't even talked about the coil itself.
The coil is a metal alloy — typically kanthal, which is iron-chromium-aluminum, or nichrome, nickel-chromium. Sometimes stainless steel. When you repeatedly heat and cool a metal wire in the presence of an oxidizing liquid, you get thermal stress and electrochemical corrosion.
The coil is slowly degrading.
Releasing metal nanoparticles into the aerosol. A twenty twenty study from Johns Hopkins — Olmedo and colleagues — measured the metal content in e-cigarette aerosol and compared it to cigarette smoke. The findings were striking. Lead levels in vape aerosol averaged zero point seven micrograms per ten puffs. Cigarette smoke averaged zero point zero three micrograms. That's a twenty-five-fold difference.
Wait — twenty-five times more lead in vape aerosol than cigarette smoke?
And it wasn't just lead. Chromium, nickel, manganese — all elevated. Nickel was particularly high, which makes sense given that nichrome coils are roughly eighty percent nickel. These metals are not in the e-liquid before it's heated. They're coming directly from the coil. The heating process is leaching them.
The lungs are not great at clearing heavy metal nanoparticles. Alveolar macrophages can handle some particulate burden, but chronic exposure to these metals is associated with interstitial lung disease, fibrosis, oxidative stress.
The particle size makes this worse. Vape aerosol has a mass median aerodynamic diameter of roughly zero point five to one micrometer. Cigarette smoke particles are larger — one point five to two point five micrometers. The smaller the particle, the deeper it penetrates into the respiratory tree. Vape aerosol reaches the terminal bronchioles and alveoli more efficiently than cigarette smoke. And once it's there, clearance is slower. The mucociliary escalator doesn't extend that deep — you're relying on macrophages, and macrophages struggle with ultrafine particles.
You've got a triple problem. Smaller particles deposit deeper. They carry reactive carbonyls that damage epithelial tissue directly. And they're studded with heavy metals that trigger inflammatory cascades. It's a delivery system optimized for deep-lung injury.
That brings us to EVALI. The e-cigarette or vaping product use-associated lung injury outbreak in twenty nineteen and twenty twenty. The CDC ultimately identified vitamin E acetate as the primary culprit — it was being used as a cutting agent in black-market THC vape cartridges. Vitamin E acetate is an oil — it's fine on the skin, it's fine in supplements, but when inhaled, it doesn't get absorbed. It sits in the alveoli, disrupts the surfactant layer, and causes lipoid pneumonia. The lungs essentially fill with lipid-laden macrophages.
That's the mechanism — it's not chemical toxicity in the traditional sense. It's a physical incompatibility between an oil-based substance and the aqueous environment of the lung.
And here's the thing — EVALI was driven by vitamin E acetate specifically, but the underlying vulnerability is inherent to the vaping delivery mechanism. Any lipophilic additive, any oil-soluble flavoring, any cutting agent that isn't fully water-miscible could theoretically do the same thing. The lung is designed to handle gases and water-soluble compounds. It is not designed to handle oil microdroplets.
EVALI was a specific outbreak with a specific cause, but it exposed a general principle — the lung doesn't care if the oil came from a licensed dispensary or a street dealer. If it's an oil, it's a problem.
Which leads naturally to flavoring compounds. This is a whole second front of risk that has nothing to do with the base liquid or the coil.
The thing that makes vaping appealing to a lot of people, especially younger users — the crème brûlée, the mango, the cinnamon roll.
Some of these flavoring agents are independently toxic when inhaled. The most famous example is diacetyl. It's the compound that gives butter its buttery flavor. It was used extensively in microwave popcorn factories, and workers who inhaled it chronically developed bronchiolitis obliterans — scarring and narrowing of the smallest airways. It's irreversible. The condition is called popcorn lung.
Which sounds almost cute, except it's a progressive, debilitating respiratory disease.
Diacetyl was detected in a large fraction of commercial e-liquids. A twenty fifteen study by Farsalinos and colleagues tested fifty-one e-liquid flavors from major brands and found diacetyl in thirty-nine of them. That's over seventy-five percent. Some of the concentrations were comparable to what popcorn factory workers were exposed to.
A vaper isn't standing in a factory — they're drawing this directly into their lungs, puff after puff.
A heavy vaper might take four to six hundred puffs a day. Each puff delivers a bolus of whatever is in that liquid directly to the airway epithelium. For context, a pack-a-day smoker takes roughly two hundred puffs. So the vaper is getting two to three times as many exposure events, each delivering a cocktail of compounds that haven't been safety-tested for inhalation.
Diacetyl is just the one we know about. What about cinnamaldehyde?
Cinnamaldehyde — the compound that gives cinnamon its flavor — is cytotoxic to bronchial epithelial cells at concentrations found in commercial e-liquids. There's a body of in vitro work showing it disrupts cell membranes, triggers oxidative stress, impairs ciliary function. The cilia are the tiny hair-like structures that sweep mucus and debris out of the airways. If you paralyze them, you lose a primary defense mechanism.
The cinnamon vape doesn't just taste like cinnamon — it's actively damaging the cells that keep your lungs clean.
The flavor industry is largely self-regulated in this space. The Flavor and Extract Manufacturers Association has a safety program, but it's designed for ingestion, not inhalation. They've explicitly stated that their GRAS determinations — generally recognized as safe — do not apply to inhalation. Yet that's exactly how these compounds are being used. There's a regulatory gap.
We've been talking about what the vaper inhales. What about what everyone else inhales?
Secondhand exposure is different with vaping than with smoking, and not necessarily better. With cigarettes, most of the smoke is sidestream — it comes off the burning tip between puffs. That's what fills a room. With vaping, there is no sidestream — the aerosol is only produced when the user exhales. So the total mass of secondhand emissions is lower. But what is emitted is not benign.
It's not water vapor.
It's fine particulate matter — PM two point five — composed of PG and VG droplets, nicotine, and flavoring compounds. A twenty twenty-one study measured PM two point five levels in vape shops and found averages of one hundred twenty micrograms per cubic meter. The EPA twenty-four-hour air quality standard is thirty-five micrograms per cubic meter. So vape shop air was more than three times the federal limit, and that's an occupational environment where people are working eight-hour shifts.
PM two point five is the stuff that gets past your upper airways and into the deep lung, into the bloodstream. It's associated with cardiovascular disease, asthma exacerbation, low birth weight. It's one of the most well-studied environmental health hazards we have.
The particles persist. Unlike cigarette smoke, which dissipates relatively quickly, vape aerosol is a dense fog of hygroscopic droplets — PG and VG are humectants, they absorb water from the air. They can hang suspended for extended periods, especially in poorly ventilated spaces. So the exposure window is longer.
The person who's vaping in their living room while watching a movie, windows closed, is creating a persistent PM two point five exposure for anyone else in the home.
Including children, including people with asthma, including anyone with pre-existing cardiovascular disease. And this is one of the areas where the "safer than smoking" framing can become genuinely misleading, because it implies a binary — either you're safe or you're not. The reality is that vaping and smoking have different harm profiles. There's overlap, and there are areas of non-overlap where vaping may actually be worse.
That's the part of Daniel's question that I think makes people uncomfortable — are there cases where vaping is more harmful than smoking? Not just "not harmless," but worse.
The answer is yes, and we need to be specific about when and how. The clearest case is high-wattage sub-ohm vaping. At eighty to a hundred watts, the formaldehyde yield can be five to fifteen times higher than a cigarette, per puff. If you're taking six hundred puffs a day at those levels, your total carbonyl exposure could substantially exceed that of a pack-a-day smoker.
Nobody is counting puffs the way a smoker counts cigarettes. There's no natural endpoint — a cigarette burns down and you're done. A vape just keeps going.
That's a critical behavioral difference. Cigarettes have a built-in stop signal. You finish it, you stub it out, you have to make a conscious decision to light another one. A vape has no such signal. You can puff continuously for an hour, put it down, pick it up five minutes later. The usage pattern tends toward more frequent, more prolonged exposure.
The friction to the next dose is zero. It's the infinite scroll of nicotine delivery.
Then there's dual use. A significant fraction of vapers also still smoke — they're using both. For a dual user, the carbonyl exposure from vaping is additive to the exposure from cigarettes. They're not subtracting one for the other — they're stacking risks. And because vaping doesn't produce the immediate sensory irritation that smoking does — no coughing fit, no burning throat — the dual user may not perceive how much total exposure they're getting.
The person who switches from a pack a day to half a pack plus vaping might think they've cut their risk in half, when in reality their total carbonyl burden could be unchanged or even higher.
Depending on the device and the use pattern, absolutely. And there's another dimension to this — the nicotine pharmacokinetics. Nicotine salt formulations, which use benzoic acid to lower the pH, produce a much faster rise in arterial nicotine levels. Peak plasma concentration in about thirty seconds, compared to roughly five minutes for a cigarette.
Why does the speed matter?
Because the rate of rise is a major determinant of addictive potential. A faster spike means a bigger dopamine hit, which means stronger reinforcement. It also means greater cardiovascular strain — that rapid nicotinic surge causes vasoconstriction, increased heart rate, increased blood pressure, all compressed into a shorter time window. For someone with underlying cardiovascular disease, that's not trivial.
The nicotine salt formulation, which was designed to make high-nicotine liquids tolerable to inhale, also makes them more addictive and potentially more stressful on the cardiovascular system.
That's the benzoic acid piece. Benzoic acid isn't just a pH adjuster — when you aerosolize it, it becomes a respiratory irritant in its own right. At high concentrations, it can cause airway inflammation. So you're adding a chemical specifically to make the product more palatable, but that same chemical has its own toxicity profile when inhaled.
It's almost elegant in a dark way. The industry solved the throat-hit problem by adding an acid, which enabled higher nicotine concentrations, which increased addictiveness, which drove more frequent use, which increased exposure to everything else. Each innovation solved a consumer complaint and deepened the harm.
The consumer base has expanded dramatically among people who never smoked. That's the population where the risk-benefit calculus completely flips. For a current smoker switching entirely to vaping, there's evidence of reduced harm — not zero harm, but reduced — for some biomarkers. But for a never-smoker who starts vaping, there is no benefit, only risk. And the absolute risk for that population is not zero. It's not even close to zero.
That's the population that's being targeted, whether intentionally or not, by the flavor portfolio. Nobody who's smoked Marlboro Reds for thirty years is asking for unicorn milk or blue raspberry lemonade.
The flavor landscape is a youth onboarding mechanism. It reduces the barrier to initiation. And once you're initiated on a nicotine salt device, the addiction takes over, and then you're a long-term user. The twenty twenty-four National Youth Tobacco Survey showed that over two million middle and high school students reported current e-cigarette use. Of those, nearly ninety percent used flavored products.
Two million kids. And that's just the US.
Here's the thing about adolescent lungs — they're still developing. The alveoli continue to multiply and mature into the early twenties. Exposing developing lung tissue to acrolein, formaldehyde, heavy metal nanoparticles, and diacetyl is not the same as exposing a fifty-year-old smoker's lungs. The injury is happening during a critical developmental window.
The risk profile is different not just by device and use pattern, but by age. A sixteen-year-old vaping mango pods is in a fundamentally different risk category than a forty-five-year-old who switched from cigarettes to a low-power device.
The long-term data doesn't exist yet. Vaping has only been widespread for about fifteen years. Cigarette-induced lung cancer typically takes twenty to thirty years of exposure to manifest. We're just now entering the window where we might start to see the long-term consequences of chronic vaping in the earliest adopters. The absence of evidence for long-term harm is not evidence of absence — it's evidence that we haven't been looking long enough.
To circle back to the core question — how does vaporization differ from combustion in terms of what's released? Combustion gives you tar, carbon monoxide, and a suite of polycyclic aromatic hydrocarbons from burning plant matter. Vaporization eliminates those — and then introduces its own set of compounds from thermal decomposition of carrier solvents, metal leaching from the heating element, and whatever toxicology comes with the flavoring agents. Different process, different toxins, different injury patterns.
The injury patterns are clinically distinct. Cigarette smoking is primarily associated with COPD, emphysema, chronic bronchitis, and lung cancer — diseases of long-term cumulative exposure. Vaping has produced acute lung injuries — EVALI, hypersensitivity pneumonitis, acute eosinophilic pneumonia — that can develop over weeks to months, not decades. The pathology is different because the insult is different.
That's a point that doesn't get enough attention. The timeline of harm is compressed for certain vaping-related injuries. You don't need thirty years to develop lipoid pneumonia or bronchiolitis obliterans. Those can happen in a season.
The coil degradation issue means that the risk actually increases over the life of a coil. A fresh coil leaches less metal. A coil that's been used for two weeks, with repeated heating and cooling cycles, with e-liquid residues baked onto the surface, with micro-cracks forming in the metal — that coil can leach three times more chromium than when it was new.
The frugal behavior — stretching a coil as long as possible — is actively increasing metal exposure.
Most users don't change their coil until the taste becomes unbearable. By that point, they've been inhaling elevated metal levels for days or weeks.
Which brings us to the practical question. Given all of this, if someone is going to vape — whether as a smoking cessation tool or because they're already a vaper and not planning to quit — what actually reduces the risk?
Use the lowest wattage that gives you a satisfactory experience. Every ten-watt increase above roughly forty watts approximately doubles carbonyl output. The cloud-chasing devices running at eighty to a hundred watts are in a completely different risk category than a low-power pod system. If harm reduction is actually the goal, wattage is the single biggest lever you can pull.
The big mod with the digital display and the adjustable everything — that's not a feature, it's a liability if you crank it up.
Second, flavor selection. Unflavored e-liquid or flavors with simpler, better-studied profiles — menthol, tobacco — are likely lower risk than the complex dessert and fruit flavors that contain diacetyl, cinnamaldehyde, and other compounds with known inhalation toxicity. The flavor industry has not safety-tested these for inhalation, and in the cases where independent researchers have tested them, the results are not reassuring.
If the liquid tastes like a cinnamon roll, something in it is doing that. And that something was designed for your tongue, not your alveoli.
Third, coil maintenance. Replace coils regularly. A coil used for more than two weeks is a metal-leaching liability. If it tastes burnt, you're already deep into the thermal decomposition zone. The coil should be changed before that point, not after.
Treat it like an oil change — scheduled, not reactive.
Fourth, and this is the one that people don't want to hear, but it's the most important — if you're using vaping to quit smoking, have an exit plan. Vaping is harm reduction, not harm elimination. The goal should be to taper down and eventually stop, not to trade one permanent habit for another. A planned reduction in nicotine concentration over six to twelve months, with a target quit date, is a fundamentally different approach than indefinite maintenance.
That's where the clinical guidance and the marketing diverge sharply. The marketing says "switch" — permanent migration from one product to another. The evidence says "step down" — temporary use as a bridge to cessation.
The evidence for vaping as a smoking cessation tool is mixed. Some randomized controlled trials — notably the Hajek trial in twenty nineteen — showed that e-cigarettes were more effective than nicotine replacement therapy for smoking cessation when both were accompanied by behavioral support. But the absolute quit rates were still modest, and a significant fraction of the e-cigarette group was still vaping at one year. So they quit smoking but didn't quit nicotine.
Which is better than continuing to smoke — don't get me wrong — but it's not the same as being nicotine-free and aerosol-free.
And the long-term health implications of indefinite vaping are unknown. We're making a probabilistic bet that it's safer than smoking. The evidence supports that bet for complete switching at low wattage with simple flavors. It does not support the bet for high-wattage dual use with complex flavor profiles.
If we zoom out, the picture is this. Combustion burns plant matter at high temperature and produces a well-characterized set of carcinogens and respiratory toxins. Vaporization heats carrier liquids at lower temperature and produces a different, less well-characterized set of toxins through thermal decomposition, metal leaching, and flavor compound inhalation. The absence of tar and carbon monoxide is a real advantage. But the presence of ultrafine particles, reactive carbonyls sometimes exceeding cigarette levels, heavy metals at twenty-five times cigarette levels, and flavoring agents never tested for inhalation — that's a real disadvantage. The net risk depends on how the device is used, what's in it, and who's using it.
The regulatory framework is struggling to keep up. The FDA has been reviewing premarket tobacco product applications — PMTAs — and has authorized a limited number of e-cigarette products, primarily tobacco-flavored. But the authorization process has focused heavily on liquid composition and marketing practices. It has not adequately addressed device-specific variables like coil materials, wattage ranges, and the interaction between power settings and aerosol chemistry.
Because regulating the liquid is straightforward — here's what can and can't be in it. Regulating the device means regulating how hot it gets, what the coil is made of, what the maximum wattage is. That's a much more intrusive regulatory framework.
The next generation of products complicates this further. Heat-not-burn devices like IQOS and glo operate at intermediate temperatures — around three hundred fifty degrees Celsius. They heat solid tobacco without burning it. So they're not combustion, but they're also not liquid vaporization. They're pyrolysis of solid plant material. The aerosol chemistry is different again — lower in some combustion byproducts than cigarettes, but higher in others compared to e-cigarettes. And they introduce their own unknowns.
We're looking at a spectrum. Cigarettes at one end — full combustion, maximum known harm. E-cigarettes at various wattages in the middle — no combustion, but variable thermal decomposition. Heat-not-burn somewhere in between. And nothing on this spectrum is zero risk.
The absence of smoke doesn't mean the absence of harm. It means a different harm profile. And "different" is not necessarily "better" in every dimension. For some endpoints — acute lung injury from specific additives, heavy metal exposure — vaping may be worse. For others — lung cancer risk, COPD — the evidence points toward reduced risk for complete switchers. But we won't have definitive answers for another decade or two.
Which is a deeply unsatisfying place to be if you're trying to make a personal health decision right now.
That's why the precautionary principle matters. If you don't currently use nicotine, don't start vaping. The risk is not zero, and the addiction is real. If you currently smoke, switching completely to a low-wattage, unflavored or simply flavored e-liquid is likely to reduce your harm — but only if you actually switch completely and don't end up as a dual user. And if you currently vape, treat it as a temporary state, not a permanent identity.
That's about as clean a summary as the evidence allows.
Now: Hilbert's daily fun fact.
Hilbert: During Japan's Edo period, sumptuary laws restricted commoners from wearing bright colors, leading to the development of subtle, sophisticated dyeing techniques using iron mordants and plant-based pigments — a practice known as "iki" that celebrated understated elegance through muted browns, grays, and indigos.
A legally mandated aesthetic of restraint produced an entire color theory of muted elegance. That's somehow the most Japanese thing I've ever heard.
Iki as a design philosophy coming out of sumptuary law feels like the kind of thing that should be studied by every startup founder who thinks "disruption" means making things louder.
Looking ahead, the FDA's twenty twenty-seven PMTA deadline is going to force some hard conversations about whether our regulatory framework is built for the actual risks — the wattage, the coil chemistry, the thermal dynamics — or just for the liquid in the bottle. If we're still regulating ingredients lists while ignoring device engineering, we're missing most of the picture.
The heat-not-burn products are coming fast. Different temperature range, different substrate, different chemistry. We're going to have to do this whole analysis again for a new category.
The question isn't whether vaping is safer than smoking. It's whether we're paying attention to the right risks. Right now, mostly, we're not.
This has been My Weird Prompts. Thanks to our producer Hilbert Flumingtop. You can find us at myweirdprompts dot com, on Spotify, or wherever you get your podcasts.
We'll be back. Until then — maybe don't inhale metal nanoparticles if you can avoid it.
