Vaping and lung damage: the truth about popcorn lung, EVALI, and serious respiratory injuries

In recent years, vaping has become a particularly visible phenomenon among adolescents and young adults.

Many people believe that inhaling the aerosol from an electronic cigarette is practically equivalent to breathing water vapour.

Others believe that anyone who vapes will eventually develop an irreversible lung disease.

Neither of these two statements accurately describes the scientific evidence.

Electronic cigarettes do not simply produce water vapour. They generate an aerosol that can contain nicotine, ultrafine particles, carbonyl compounds, metals and flavouring substances.

But neither can we attribute the same substances, concentrations or clinical consequences to all devices.

One of the greatest sources of confusion lies in using three terms interchangeably:

• Popcorn lung, or bronchiolitis obliterans.

• EVALI, e-cigarette or vaping product use-associated lung injury.

• Acute respiratory distress syndrome (ARDS).

These are distinct entities, although certain inhalation exposures may be associated with more than one form of lung injury.

In this article we will analyse their mechanisms, the research that led to their identification, radiological findings, diagnosis, treatment and what remains unknown.

1. What really enters our lungs when we vape?

An electronic cigarette uses a heating element to heat a liquid and generate an inhalable aerosol.

Depending on the product, that liquid may contain:

• Propylene glycol.

• Vegetable glycerin.

• Nicotine.

• Nicotine salts.

• Flavorings.

• Other additives.

• In certain devices, cannabinoids such as THC.

Heating can generate new substances from the original components.

The composition of the aerosol depends on factors such as temperature, device power, materials, liquid formulation, and manner of use.

Therefore, two products marketed as electronic cigarettes can generate very different chemical exposures.

Is it just water vapor?

No.

The term "vapor" is commonly used, but from a physical and toxicological standpoint it is more accurate to speak of an aerosol.

An aerosol contains particles and droplets suspended in a gas.

These can deposit in different regions of the respiratory tract.

The absence of tobacco combustion does not mean the absence of potentially harmful substances.

2. Which pulmonary structures can be affected?

To understand vaping-related diseases, we must distinguish three structures.

• Bronchi: tubes that carry air into the lungs.

• Bronchioles: small airways located in deeper regions.

• Alveoli: microscopic structures where the exchange of oxygen and carbon dioxide takes place.

An injury that predominantly affects the bronchioles can cause persistent airflow obstruction.

An inflammatory alveolar injury can seriously impair oxygenation.

This difference explains why obliterative bronchiolitis and ARDS are not synonymous.

Part One: the real “popcorn lung”

3. What is obliterative bronchiolitis?

Obliterative bronchiolitis, particularly its constrictive form, is a disease characterized by injury and fibrosis of the small airways.

Inflammation and subsequent scarring can progressively narrow the bronchioles.

As a result, air has difficulty moving through them.

The disease can produce persistent obstruction that is often poorly reversible.

Its causes include certain toxic inhalation exposures, transplant complications, autoimmune diseases, and other conditions.

It is not a disease exclusive to vaping.

4. Why is it called “popcorn lung”?

The popular name comes from research carried out on workers at facilities where microwave popcorn was manufactured.

Cases of severe obstructive pulmonary disease associated with occupational inhalation of flavoring mixtures were identified, particularly compounds related to butter flavoring.

Among these, diacetyl — also known as 2,3-butanedione — stood out.

Investigations by the National Institute for Occupational Safety and Health (NIOSH) helped identify the respiratory risks of these exposures.

The name does not come from a radiological image shaped like popcorn.

It is a historical reference to the occupational setting where an important series of cases was investigated.

5. What is diacetyl?

Diacetyl is a substance used to provide certain aromas and flavors.

Its presence in food does not mean that inhaling it is harmless.

This distinction is fundamental in toxicology.

A substance that can be safely ingested is not necessarily one that can be safely inhaled.

The route of exposure changes the tissues affected, local concentrations, and the mechanisms of toxicity.

NIOSH has linked occupational inhalation exposure to diacetyl and flavoring mixtures with serious bronchiolar disease.

It has also studied other compounds, such as 2,3-pentanedione.

6. Has diacetyl been found in vaping liquids?

Yes, certain studies have identified diacetyl and other flavoring compounds of toxicological concern in some vaping products.

However, the composition varies depending on the manufacturer, the product, and the period of commercialization.

Detecting a potentially toxic substance does not automatically prove that all exposed individuals will develop the same disease.

To establish clinical causality, we need to assess concentration, duration, inhaled dose, aerosol characteristics, and epidemiological findings.

7. Is it proven that vaping causes “popcorn lung”?

We must differentiate three levels of evidence.

First: it is proven that certain occupational inhalatory exposures to flavoring agents such as diacetyl can cause serious bronchiolar damage.

Second: potentially harmful flavoring substances have been identified in certain vaping products.

Third: there is no sufficiently robust epidemiological evidence to assert that conventional vaping frequently or inevitably causes obliterative bronchiolitis.

There are clinical reports of small airway injuries in e-cigarette users, but isolated cases do not allow us to calculate an incidence rate or attribute all presentations to a single component.

The correct medical conclusion is that there is a well-founded toxicological concern, but we must not present a universal relationship as though it were proven.

8. Symptoms of Bronchiolitis Obliterans

It can cause:

• Persistent cough.

• Progressive dyspnea.

• Wheezing.

• Exercise intolerance.

• Sensation of shortness of breath.

• Persistent respiratory obstruction.

Spirometry may show an obstructive pattern.

High-resolution computed tomography can identify air trapping, a mosaic pattern, and other findings of small airway disease.

In certain cases, specialized pulmonology evaluation is required.

9. Is bronchiolitis obliterans reversible?

Established fibrosis of the bronchioles may be irreversible.

Treatment depends on the cause and may include removal of the responsible exposure, symptom management, and treatment of associated conditions.

In advanced cases, significant respiratory limitations may be present.

However, this does not mean that every vaping-related lung injury necessarily leads to such fibrosis.

Part Two: EVALI, vaping-associated lung injury

10. What does EVALI mean?

EVALI stands for E-cigarette or Vaping Product Use-Associated Lung Injury.

It is a term used to describe acute lung injury associated with the use of e-cigarette or vaping products, after other possible causes have been ruled out.

It gained particular relevance during the 2019 United States epidemic.

Patients could present with respiratory, gastrointestinal, and systemic symptoms.

Some developed severe respiratory failure and required intensive care.

11. How many cases and deaths were recorded?

According to the report published by the Centers for Disease Control and Prevention (CDC), as of February 18, 2020, the following had been reported in the United States:

• 2,807 hospitalized cases of EVALI or reported deaths.

• 68 confirmed deaths.

These figures correspond to that epidemic and to that surveillance period.

They do not represent the cumulative worldwide total of all vaping-related injuries.

Nor do they allow for a direct calculation of the individual risk of any current e-cigarette user.

12. What caused the EVALI epidemic?

Epidemiological and laboratory investigations identified a particularly important association with vaping products containing THC, especially those obtained through informal sources.

One of the main compounds implicated was vitamin E acetate.

This substance had been used as an additive or diluent in certain formulations.

The accumulated evidence strongly linked it to the epidemic.

However, researchers noted that they could not completely rule out other causative agents in certain cases.

13. The scientific study that changed the course of research

A study published in The New England Journal of Medicine analyzed bronchoalveolar lavage samples from 51 patients with EVALI.

Vitamin E acetate was detected in 48 of the 51 patients, approximately 94%.

The substance was not identified in the samples from the healthy comparison group.

These results provided important evidence of pulmonary exposure and reinforced its role in the epidemic.

However, identifying a substance in a sample does not mean that every molecular mechanism is fully explained.

14. What is the difference between vitamin E and inhaled vitamin E acetate?

Vitamin E is an essential nutrient.

But vitamin E acetate used as an additive in certain inhaled formulations represents a different toxicological situation.

We must not confuse the ingestion of a nutrient with the inhalation of a heated and aerosolized substance.

Safety depends on the route of exposure.

This principle also applies to certain oils, flavorings, and other additives.

15. What happens inside the lungs during EVALI?

EVALI does not present a single histological pattern.

Different forms of acute lung injury have been described, including:

• Organizing pneumonia.

• Diffuse alveolar damage.

• Acute pneumonitis.

• Bronchiolar injury.

• Accumulation of macrophages with lipid content, a non-specific finding.

The mechanism may involve direct toxicity, epithelial injury, inflammation, and impairment of gas exchange.

In severe cases, alveolar damage can trigger respiratory failure.

16. What symptoms does EVALI cause?

Symptoms can develop over days or weeks.

Respiratory symptoms include:

• Cough.

• Dyspnea.

• Chest pain.

• Sensation of tightness.

• Progressive respiratory distress.

General symptoms may also appear:

• Fever.

• Chills.

• Fatigue.

• Malaise.

And digestive symptoms:

• Nausea.

• Vomiting.

• Abdominal pain.

• Diarrhea.

The combination of respiratory and digestive symptoms in a person who uses vaping products should raise consideration of this possibility, without excluding infections or other causes.

17. What appears on an X-ray or CT scan?

Bilateral pulmonary opacities have been observed in many patients with EVALI.

On CT imaging, areas known as ground-glass opacities may appear.

These reflect an increase in lung density that does not completely obscure the vascular structures.

They are not specific to EVALI.

They may also be seen in infections, inflammatory diseases, and other conditions.

There is no characteristic popcorn-pattern image that allows for a diagnosis of EVALI.

18. How is EVALI diagnosed?

The evaluation begins with a careful clinical history.

It is important to ask:

• Whether the patient uses e-cigarettes.

• Which products they use.

• Whether they contain nicotine, THC, or other substances.

• When use began.

• When symptoms appeared.

• Whether they have used cartridges from informal sources.

• Whether there is a history of respiratory conditions.

The evaluation may include pulse oximetry, X-ray, CT scan, and tests to rule out infectious causes.

EVALI is a diagnosis of exclusion: there is no single test that definitively confirms it.

The suspicion must be assessed alongside other causes of acute lung injury.

19. What is the treatment?

The first step is to stop exposure to the suspected product.

Treatment depends on severity and may include:

• Oxygen therapy.

• Hospital monitoring.

• Respiratory support.

• Treatment of infections when present or when they cannot be ruled out.

• Systemic corticosteroids in selected patients, based on specialist assessment.

• Mechanical ventilation in severe cases.

The evidence on corticosteroids comes primarily from case series and observational experience, not from large randomized trials specifically designed for EVALI.

For this reason, they should not be administered indiscriminately without considering alternative diagnoses, particularly infections.

20. Do all patients with EVALI end up with irreversible damage?

No.

Many patients improved clinically following treatment and cessation of exposure.

However, some presented with severe illness, required intensive care, or died.

Persistent symptoms and functional impairment following the acute episode have also been reported.

Prognosis depends on initial severity, complications, and individual patient characteristics.

It is not accurate to state that all EVALI is irreversible, nor that all patients make a full recovery.

Part Three: acute respiratory distress syndrome

21. What is ARDS?

Acute respiratory distress syndrome is a form of respiratory failure characterized by acute inflammatory lung injury, impaired oxygenation, and compatible pulmonary opacities.

It can be triggered by various causes.

Among them:

• Severe pneumonia.

• Sepsis.

• Aspiration.

• Trauma.

• Certain toxic inhalation injuries.

• Some severe forms of vaping-associated lung injury.

Therefore, ARDS is a clinical syndrome, not a disease exclusive to electronic cigarettes.

22. What happens in the alveoli?

The inflammatory injury can increase the permeability of the alveolar-capillary barrier.

As a result, protein-rich fluid accumulates in the alveolar space and gas exchange is impaired.

Changes in surfactant and pulmonary mechanics may also occur.

The result is hypoxemia, which can be severe.

23. Why might mechanical ventilation be needed?

In the most severe cases, the patient is unable to maintain adequate oxygenation.

It may require advanced respiratory support.

Mechanical ventilation is used following lung-protective strategies to reduce ventilator-associated injury.

In selected situations, other measures may be used, including prone positioning and, exceptionally, extracorporeal support.

These interventions fall within the scope of specialized hospital units.

24. Is ARDS irreversible?

Not necessarily.

Some patients recover considerable lung function.

Others may develop functional, muscular, or pulmonary sequelae.

The progression depends on the cause, severity, and complications.

That is why it is incorrect to state that ARDS related to EVALI is always irreversible.

Part Four: comparison of the three conditions

25. Comparative Table

Part Five: other respiratory risks of vaping

26. Irritation and Inflammation of the Airways

Inhaled aerosol can come into contact with the respiratory epithelium and activate inflammatory responses.

The magnitude of the effect depends on the composition and the exposure.

Some users experience coughing, throat irritation, or a sensation of chest tightness.

These symptoms alone are not sufficient to diagnose a specific pulmonary disease.

27. Oxidative Stress

Aerosols may contain compounds capable of promoting oxidative stress.

Oxidative stress occurs when the production of reactive species exceeds the body's antioxidant defense capacity.

In experimental studies, inflammatory cellular responses and alterations in protective mechanisms have been observed.

The translation of these findings to chronic human diseases depends on dose, duration, and other variables.

28. Impairment of Mucociliary Clearance

The airways have a defense system based on mucus and ciliary movement.

Its function is to facilitate the removal of particles and microorganisms.

Certain inhalatory exposures can disrupt this mechanism.

The long-term clinical significance of vaping on these defenses remains a subject of ongoing research.

29. Effects on Macrophages and the Immune Response

Alveolar macrophages play a role in the elimination of particles and in the response against microorganisms.

Experimental studies have investigated changes in their function following exposure to e-cigarette aerosols.

These findings support the need to study possible effects on pulmonary defenses.

However, an experimental result should not automatically be interpreted as a proven clinical disease.

30. Asthma and bronchitis

Observational studies have found associations between e-cigarette use and symptoms such as cough, wheezing, and bronchitis.

Interpretation is complex because many users have also smoked conventional cigarettes.

Furthermore, there may be important differences between exclusive users, former smokers, and dual users.

The evidence is more consistent for certain respiratory symptoms than for establishing causality of specific chronic diseases.

31. Can it cause chronic obstructive pulmonary disease?

Chronic obstructive pulmonary disease, or COPD, is strongly associated with conventional smoking and other exposures.

Observational studies and meta-analyses have been published linking e-cigarette use to diagnoses or symptoms of COPD.

However, causal interpretation requires carefully controlling for smoking history, dual exposure, and other factors.

Long-term cohorts of exclusive users who have never smoked are still needed.

32. Can it cause lung cancer?

Aerosols may contain compounds with carcinogenic potential, depending on the product and conditions of use.

However, cancer typically develops after prolonged periods of exposure.

For this reason, the epidemiological data currently available do not yet allow us to precisely quantify the risk of lung cancer attributable exclusively to long-term vaping.

The absence of a definitive estimate is not equivalent to proving harmlessness.

Nor does it justify claiming that the risk is identical to that of combustible tobacco.

Part Six: conventional cigarettes versus electronic cigarettes

33. Are they equally harmful?

They are not identical exposures.

The combustion of tobacco generates a complex mixture of toxic substances, including carbon monoxide and numerous carcinogenic compounds.

Electronic cigarettes do not burn tobacco in the same way.

For this reason, exposure to certain toxic substances may be lower when a person who smokes completely replaces combustible tobacco with a regulated electronic product.

But lower exposure to some toxic substances does not mean that the product is harmless.

34. What about dual use?

Some people use conventional cigarettes and e-cigarettes simultaneously.

This situation can maintain significant exposure to combustion products.

It should not be assumed that adding vaping to habitual smoking automatically provides a relevant reduction in risk.

35. What if a person has never smoked?

In a person who has never consumed tobacco, starting to vape introduces an inhalatory exposure that did not previously exist.

It can also produce nicotine dependence.

From a medical prevention standpoint, there is no health-based reason to recommend that a non-smoker take up vaping.

36. Can it help with quitting smoking?

Some research has found that nicotine-containing electronic cigarettes can help certain adult smokers quit combustible tobacco, especially when used as part of a structured cessation programme.

But the clinical goal remains to quit tobacco use and, where possible, nicotine dependence.

The choice of treatment should be individualised and take into account current health recommendations.

Part Seven: young people, dependence and prevention

37. Why is vaping among adolescents a particular concern?

Many devices offer appealing flavours, ease of use and discreet formats.

Some contain high concentrations of nicotine.

Nicotine can cause dependence, and exposure to it during adolescence raises concerns related to brain development.

It may also encourage continued use.

38. Is a nicotine-free vape safe?

Not necessarily.

The absence of nicotine removes an important source of pharmacological dependence, but does not guarantee that the aerosol is harmless.

Exposure to solvents, heating by-products, particles and flavouring agents may still occur.

The composition and the risk depend on the product.

39. Are sweet flavors harmless?

We must not confuse pleasant taste with pulmonary safety.

A substance used as a food flavoring may have a different toxicological profile when inhaled.

Diacetyl is an important example of why the route of exposure must be studied specifically.

Part Eight: warning symptoms and medical evaluation

40. When should a person who vapes seek medical attention?

Medical evaluation is recommended if any of the following appear:

• Persistent cough.

• New onset of breathing difficulty.

• Recurrent wheezing.

• Chest pain.

• Exercise intolerance.

• Fever associated with respiratory symptoms.

• Digestive symptoms accompanied by breathing difficulty.

The consultation should include a complete exposure history.

41. When should you go to the emergency room?

Urgent medical attention should be sought in the presence of:

• Significant respiratory distress.

• Severe chest pain.

• Bluish discoloration of the lips.

• Confusion.

• Fainting.

• Abnormally low oxygen saturation.

• Rapid respiratory deterioration.

42. What tests can the doctor order?

Depending on the clinical situation:

None of these tests, on its own, proves that vaping is the cause of a lesion.

Interpretation requires integrating symptoms, exposure, physical examination, and alternative diagnoses.

Part Nine: what we know and what we are still investigating

43. Findings supported by solid evidence

We can state that:

• Occupational inhalation of certain flavoring mixtures, including diacetyl, has been linked to bronchiolitis obliterans.

• The American EVALI epidemic resulted in thousands of hospitalizations and dozens of deaths.

• Vitamin E acetate was strongly implicated in that epidemic.

• Some forms of EVALI can cause severe respiratory failure.

• Electronic cigarette aerosols may contain potentially toxic substances.

44. Questions that still require research

Among the main outstanding questions we find:

• The exact risk of chronic lung disease after decades of exclusive vaping.

• The contribution of different formulations and devices.

• The magnitude of cancer risk over the very long term.

• The true incidence of constrictive bronchiolitis attributable to vaping.

• The effects of repeated exposures to certain flavoring agents.

• The respiratory outcomes of users who never smoked combustible tobacco.

Acknowledging these uncertainties does not mean minimizing the risk.

It means practicing evidence-based medicine.

Frequently asked questions

45. Does popcorn lung look like popcorn on an X-ray?

No.

The name comes from research carried out on workers exposed to flavorings used in the food industry.

46. Does every vaper develop bronchiolitis obliterans?

No.

There is no evidence to support that claim.

47. Are EVALI and bronchiolitis obliterans the same disease?

No.

EVALI describes a lung injury associated with the use of vaping products and can present different pathological patterns.

Bronchiolitis obliterans is a small airway disease characterized by narrowing and fibrosis.

48. Does EVALI affect only former smokers?

No.

During the epidemic, cases were identified in people with different consumption histories.

Exposure to certain vaping products was the central epidemiological element.

49. Is vitamin E dangerous for the lungs?

The problem studied in EVALI was particularly linked to the inhalation of vitamin E acetate used as an additive in certain products.

This does not mean that consuming foods containing vitamin E causes EVALI.

50. Can a CT scan confirm EVALI?

Not on its own.

Radiological findings can point in that direction, but other causes must be ruled out first.

51. Can a person make a full recovery?

Yes, some patients recover significantly.

Others may experience lasting complications or serious sequelae.

The course of the illness is not the same in every case.

52. Is vaping better than smoking?

For an adult who already smokes, completely replacing combustible tobacco with vaping may reduce exposure to certain toxic substances.

However, vaping is not harmless, and maintaining both habits does not guarantee a sufficient reduction in harm.

For someone who has never smoked, the preventive recommendation is not to start.

53. What should someone who vapes do if they develop a cough or shortness of breath?

Stop the exposure and seek a medical evaluation, especially if the symptoms are persistent or progressive.

If there is significant respiratory difficulty, they should go to the emergency room.

Conclusion: the real danger is confusing scientific information with alarmist messages

Vaping should not be presented as a harmless activity.

But neither should we explain its risks by using different diseases as though they were one and the same.

"Popcorn lung" refers to a bronchiolar disease historically associated with occupational inhalation exposure to certain flavoring agents.

EVALI is an acute lung injury associated with vaping products, particularly significant during the American epidemic linked to THC products and vitamin E acetate.

Acute respiratory distress syndrome is a form of respiratory failure that can arise as a complication of multiple diseases, including severe EVALI.

These are three distinct concepts. Understanding them allows us to communicate more accurately and to prevent harm without exaggerating.

Medical prevention must be grounded in verifiable facts, acknowledge uncertainties, and explain risks in a way that is easy to understand.

The fact that a product does not produce combustion does not mean it is safe to inhale.

And the fact that a substance can be ingested does not mean our lungs are equipped to receive it.

This article is intended for educational purposes and does not replace individual medical evaluation. In the event of significant breathing difficulty, severe chest pain, or rapid clinical deterioration, urgent medical attention should be sought.