In Vitro Dermal Absorption of Nicotine from Electronic Cigarette Mixtures

摘要

Nicotine plus flavorings in a propylene glycol (PG) vehicle are the components of electronic cigarette mixtures (e-cigarette "juices"), which are vaporized and inhaled by the user. Dermal exposure to nicotine occurs in the mixing and filling of e-cigarettes in the manufacturing process. The nicotine solutions are mixed in the factory and dispensed into individual electronic cigarette cartridges. Workers may be supplied with inappropriate or inadequate PPE: contamination of the fingertips has been reported. In order to investigate the potential for nicotine uptake from skin exposures, in vitro human epidermal permeation of nicotine was undertaken from surrogate and commercial e-cigarette juices and from neat nicotine donor formulations. Steady-state fluxes (J_(SS), μg/cm~2/h) and lag times (t, h) were measured from 3 skin samples taken from each of 3 human donors (n = 9) for each formulation. Nicotine in PG at 24 mg/mL produced an average J_(SS) of 4.0 and an average t of 10.1. Some flavoring components substantially enhanced nicotine permeation. A commercial e-juice containing menthol and 25 mg/mL nicotine produced an average J_(SS) of 10.2 with an average t of 8.3. A commercial e-juice containing limonene and 25 mg/mL nicotine produced an average J_(SS) of 23.7 with an average t of 5.0. Neat nicotine J_(SS) was 175 and t was 1.9.These data were applied to a dermal risk assessment paradigm, assuming an 8 h exposure to volar surfaces of all fingers followed by washing, to estimate total systemic nicotine uptake (mg) over a work shift. The estimates are: for nicotine in PG, 8.2; for menthol e-juice, 18.3; for limonene e-juice, 31.1; for neat nicotine, 151. These data demonstrate the potential for substantial nicotine absorption through the skin from contact with e-cigarette refill solutions and the neat nicotine used to mix those solutions. The data reinforce the need for adequate personal protective equipment for workers when mixing and dispensing nicotine solutions.