Key points from article :
Study examined 75 popular e-cigarette products, 27 % of which contained traces of endotoxin.
Cartridge samples had 3.2 times higher concentrations of glucan than the e-liquid samples.
Glucan concentrations were higher in tobacco- and menthol-flavoured products.
Endotoxin concentrations were higher in fruit-flavoured products.
More than 3 million high school students used e-cigarettes in 2018.
Study was published online in Environmental Health Perspectives.