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BACKGROUND: Cigarette smoke contains microbes and microbial toxins, such as endotoxin and (1 -> 3)-beta-D-glucan, that may have adverse respiratory effects. To our knowledge, the potential for contamination of electronic cigarette (EC) products sold in the United States has not been investigated.

OBJECTIVES: We aimed to determine whether popular cartridge and e-liquid EC products were contaminated with endotoxin or glucan and to examine differences according to the type and flavor of products.

METHODS: We selected 37 cartridges and 38 e-liquid products with the highest nicotine content from the ten top-selling U.S. brands. Flavors were classified into four groups: tobacco, menthol, fruit, and other. Endotoxin and glucan were measured using an endotoxin-specific kinetic turoidimetric assay and a Glucatell (R) Kinetic Assay (Associates of Cape Cod, Inc.), respectively.

RESULTS: Endotoxin concentrations were over the limit of detection (LOD) in 17 of 75 products tested (23%), and glucan concentrations were greater than LOD in 61 of 75 products (81%). After adjusting for brand and flavor, the mean glucan concentration was 3.2 times higher [95% confidence interval (CI): -0.1, 18.4] in cartridge vs. c-liquid samples. After adjusting for brand and type of product, glucan concentrations in tobacco- and menthol-flavored ECs were 10.4 (95% CI: 1.8, 44.9) and 3.5 (95% CI: 0.1, 17.3) times higher than concentrations found in fruit-flavored products.

CONCLUSIONS: EC products may be contaminated with microbial toxins. Further studies with large representative samples of products are needed to confirm our findings, identify sources and routes of contamination, and evaluate health effects associated with the use of contaminated products.