Ever since e-cigarettes came onto the market in 2004, researchers have wondered and debated whether these devices might contain chemicals that lead to lung diseases or cancer.
This week, new research from the Harvard School of Public Health suggests that the flavorings in some types of e-cigarettes contain chemicals that have been linked to a rare disease called "popcorn lung."
There are a lot of questions about what the health risks actually are — and what this means for e-cigarettes more broadly. Here's what we know (and don't know).
What is "popcorn lung," and how was it discovered?
In 2001, newspaper reporters broke a story about a mysterious illness that was plaguing workers in factories that produced microwave popcorn.
Employees at the plants were turning up at their doctors' offices with trouble breathing. On examination, the doctors realized their patients' wheezing and shortness of breath was caused by permanent lung damage. Some people needed full lung transplants. Federal health officials looked into the cases and discovered these irreversible lung problems were exclusive to the plant employees who had worked closely with — and inhaled — the fragrant whiff of artificial butter.
Simply breathing in diacetyl, the chemical that adds that buttery flavor and smell to popcorn, could increase the risk of a rare and life-threatening condition called bronchiolitis obliterans, known as "popcorn lung." The disease scars the tissue of the lungs, causing the small airways to become compressed and narrowed. In less severe cases, the exposure to diacetyl was also linked to asthma and bronchitis.
How is popcorn lung linked to e-cigarette use?
Diacetyl, the chemical that causes popcorn lung, is present in some e-cigarette products, used to produce flavors like popcorn, caramel, strawberry, and butterscotch.
The people who study the health effects of e-cigarettes have long worried about whether long-term e-cigarette use might also cause popcorn lung.
This week, researchers at the Harvard School of Public Health announced that they'd found evidence suggesting people who regularly use flavored e-cigarettes were at risk of developing popcorn lung.
In their study, published in the journal Environmental Health Perspectives, the researchers tested 51 types of flavored e-cigarettes for the presence of several chemicals. They found diacetyl in more than 75 percent of the products they examined. The researchers also noted that inhaling these chemicals produced exposure similar to that faced by workers in microwave popcorn plants.
So do e-cigarettes cause popcorn lung?
We don't know that yet, in part because there have been no published long-term studies on e-cigarette users.
E-cigarettes are currently not regulated by the FDA, and there's a lot we still don't understand about the health effects of regular use. Most researchers believe that vaping is probably better for you than smoking conventional cigarettes. But that still leaves a lot of questions — like what the risk of popcorn lung might be.
One reason this is so tough to study is that there's such a large variation in products available on the market. At last count, there were about 500 e-cigarette brands and more than 7,000 flavors available, and they work in different ways, delivering varying amounts of nicotine, toxins, and carcinogens. This means it’s often hard to generalize from individual studies.
Still, the concerns about "popcorn lung" add to a growing body of literature about chemicals in these devices and worries that chronic use may lead to other diseases like cancer.
As the researchers on the new study put it, "Due to the associations between diacetyl, bronchiolitis obliterans and other severe respiratory diseases among workers inhaling heated vapors containing diacetyl, urgent action is recommended to further evaluate the extent of this new exposure to diacetyl and related flavoring compounds in e-cigarettes."
You can read all about the science of e-cigarettes here.