A study at Harvard University found that electronic cigarette products made by Juul Labs had a microbial toxin that can cause long-term lung damage.
The researchers from Harvard T.H. Chan School of Public Health found that 46 percent of the 54 Juul pods they analyzed contained detectable levels of glucan, a component of fungal cell walls.
"Chronic exposure to glucan can cause inflammation in the airway and lead to long-term lung damage," David Christiani, a co-author of the study, said in a news release.
The study, published online in the American Journal of Respiratory and Critical Care Medicine, found that pods with menthol and tobacco flavors had the highest levels of glucan: 1,353 and 307 times higher, respectively, than in the company's other flavored products.
Those are the two flavors exempted from the U.S. Food and Drug Administration 's ban on the sale of flavored e-cigarettes.
The ban is for cartridge-based systems, like pods produced by Juul, the leading manufacturer. It does not include flavors in tank systems sold in vape shops. Juul, which leads the e-cigarette market, had already stopped selling its fruit-flavored products, including mint, prior to the ban. It continues to sell products with tobacco and menthol flavors.
The Harvard study follows another study at the school, published in April, that found bacterial and fungal toxins in many popular e-cigarette products. That study was conducted on 37 cartridges and 38 e-liquid products with the highest nicotine content from the 10 top-selling U.S. brands in 2013, which before Juul joined the market in 2015.
The April study found that 17 of the 75 e-cigarette products, or 23%, were contaminated with endotoxin, a microbial agent and a component of the exterior cell wall of certain types of bacteria. It also found that 61, or 81% of the 75 products, were contaminated with glucan. Like the latest study, glucan concentrations were higher in the tobacco- and menthol-flavored e-cigarettes.
Christiani, co-author of the latest study, said the glucan found in Juul pods is not related to the current vaping-related illness in the U.S., which the Centers for Disease Control and Prevention reports has hospitalized over 2,500 patients and killed 55 as of Dec. 27.
In Kentucky, 43 cases are under investigation, with six of them confirmed and 12 of them probable. In 10 of the suspected cases, e-cigarettes have been ruled out as a cause.
The CDC says vitamin E acetate, an additive in some e-cigarette products with THC (the psychoactive ingredient in marijuana), is closely associated with the vaping-related illness, which is called EVALI, for "E-cigarette or Vaping product use Associated Lung Injury."
Christiani said he's not sure why Juul's tobacco- and menthol-flavored pods have such high levels of glucan. He said it could be related to the raw materials used in the products or could be occurring during the production process.
Abby Haglage reports for Yahoo Lifestyle that most of the research so far on the health effects of glucan comes from working environments, and adds that traditional cigarettes have also been shown to contain glucan, "likely at far higher levels than e-cigarettes," she writes.
Greg Conley, president of the American Vaping Association, took issue with the report.
"Microbial contamination is a reality with everything in life, including e-liquids and traditional tobacco products," Conley told Haglage. "These authors have identified no actual risk, just that some microorganisms were detected, and they are promoting their findings knowing that many will falsely interpret the paper to mean that vaping could be equally or more hazardous than smoking cigarettes."
The study said its main limitation was that it did not evaluate contamination of aerosols inhaled by users. It called for further research to be conducted with larger representative samples of products. (Despite the term "vaping," many devices do not produce a vapor, which has liquid particles suspended in the air. They produce an aerosol, which has liquid and/or solid particles suspended in a gaseous medium.)