A recent study by researchers at the Harvard T. H. Chan School of Public Health found electronic cigarettes are 
contaminated with bacterial and fungal toxins.
A study of 75 e-cigarette products, including both single use cartridges and refillable e-liquids, found 27% had traces of “endotoxin,” a microbial agent found on gram-negative bacteria.
Additionally, 81% had traces of “glucan” a highly noxious substance found in the cell walls of most fungi. Both elements are known to be associated with a host of health issues including asthma, reduced lung function and inflammation.
The fast rise of e-cig usage by high school students has spawned a growing concern from health care officials. In 2011 approximately 220,000 high school students used these cigarette substitutes. By 2018 that number rose to over 3 million.
There is substantial research showing the dangerous health effects of these airborne biological contaminants, but almost no studies have been done regarding the presence of these substances in electronic cigarettes.
According to Dr. Mi-Sun Lee, a research fellow and lead author of the paper, “In addition to inhaling harmful chemicals, e-cig users could also be exposed to biological contaminants like endotoxins and glucan”
For more information click link: //www.hsph.harvard.edu/news/press-releases/microbial-contaminants-found-in-popular-e-cigarettes/