Background: Menthol, through its cooling sensory effects, facilitates smoking and tobacco product initiation, which is reflected by the high popularity of mint/menthol-flavored E cigarettes. More recently, E cigarette vendors started marketing synthetic cooling agents as additives that impart a cooling effect but lack a characteristic minty odor. Knowledge about content of synthetic coolants in US-marketed E cigarette products and associated health risks is limited. Methods: E-liquid vendor sites were searched with the terms koolada, kool / cool, ice or WS 3 / WS 23, denoting individual cooling agents. Ice flavor varieties of Puffbar, the popular disposable E cigarette brand, were compared with non-Ice varieties. GC/MS and GC/FID were used for detection of synthetic coolants. Margin of exposure (MOE), a risk assessment parameter, was calculated to assess the risk associated with synthetic coolant exposure from E cigarette use. Results: WS 3 was widely present in refill E liquids. Almost all liquids in Puffbar-branded disposable E cigarettes contained WS 23 (13/14 varieties), and some WS 3 (5/14), in both Ice- and non-Ice varieties. Modeling consumption of WS 3 from vaped E liquids resulted in MOEs below the safe margin of 100 for most daily use scenarios (3-mL:14/25 E liquids; 5-mL:18/25; 10-mL:20/25 ). MOEs for WS 23 from 11/13 Puffbar products were ≤100 in all use scenarios. Conclusions: Manufacturers add synthetic cooling agents (WS 3, WS 23) to US-marketed E cigarettes, at levels that may result in consumer exposures exceeding safety thresholds set by regulatory agencies. Synthetic cooling agents are not only found in mint-or menthol-flavored products, but also in fruit- and candy-flavored products, including popular disposable E cigarette products such as Puffbar.