Reviewed by Cecile S. Rose,

Bronchiolitis obliterans is an inflammatory obstruction of the lung's tiniest airways, called bronchioles. The bronchioles become damaged and inflamed by chemical particles or respiratory infections, particularly after organ transplants, leading to extensive scarring that blocks the airways. The disease is sometimes referred to as constrictive bronchiolitis, a similar condition in which the small airways become constricted in diameter because of inflammation and scarring.



The disease can be caused by breathing in irritant fumes, such as chlorine, ammonia, oxides of nitrogen or sulfur dioxide. Diacetyl, a chemical used to provide butter flavor in many foods and commonly used in e-cigarette flavoring, has been shown to cause bronchiolitis obliterans in workers who manufacture it or mix it into foods, such as butter-flavored popcorn.

In addition to diacetyl, here are other common and dangerous chemicals to avoid:


Acetaldehyde is in cannabis and e-cigarette smoke. It irritates the skin, eyes, mucous membranes, throat and respiratory tract. It can also cause nausea, vomiting, headache, drowsiness, delirium and hallucinations in high concentrations. Other effects of acetaldehyde can include damage the mucous lining of the mouth, throat, stomach; skin irritation; kidney and liver damage; and cancer. Acetaldehyde is also known as acetic aldehyde, ethanal, ethyl aldehyde.



This chemical is used to add flavorings to electronic cigarettes, some microwave popcorns and other foods and liquids. Inhaling diacetyl, especially the heated chemical, has been linked to serious respiratory diseases including bronchiolitis obliterans which is irreversible. When inhaled, diacetyl can cause a persistent dry cough, shortness of breath, wheezing, phlegm production, fatigue, drowsiness, headache, fever, aches and nausea. However, exposed workers have developed lung disease in the absence of these warning symptoms. Diacetyl vapors irritate the eyes, skin, nose and throat and may lead to fixed airway restriction or obstruction. Diacetyl is also known as butanedione, 2,3-butandedione and food flavorings containing diacetyl (FFCD).



This colorless, flammable gas is used in building materials, household products, pressed-wood products, glues and adhesives, some fabrics, insulation materials, paper coatings, fungicides, germicides, disinfectants, and medical and scientific preservatives. Formaldehyde is a carcinogen. It has a strong odor and can irritate the eyes, nose, skin and throat, and causes coughing, wheezing and nausea. Formaldehyde is also known as methanal.



This chemical compound is a stimulant drug that is found in the nightshade family of plants including nicotiana rusticacultivated tobacco and asclepias syriaca.

Nicotine is highly addictive and is associated with cardiovascular disease, birth defects, lung infections. Inhaling nicotine stimulates production of saliva and phlegm, increases heart rate and blood pressure, elevates serum cholesterol levels, promotes blood clot formation, and aids in plaque formation in the cardiovascular system. 

Bronchiolitis obliterans also can result from respiratory infections, a connective tissue disorder such as rheumatoid arthritis, a medication reaction, and after a bone marrow, lung or heart-lung transplant. Also, the disease may be idiopathic (without a known cause).

Another similarly named disease, bronchiolitis obliterans organizing pneumonia, is a completely different disease.

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