E-cigarettes an evidence update A report commissioned by Public Health England

E-cigarettes: an evidence updateThese findings have an important implication. Above the necessary minimum level ofnicotine, nicotine concentrations in e-liquid and even the concentrations in vapour, ifmeasured by standard puffing schedules, are of limited relevance. For light smokers,18mg/ml ‘mild’ e-liquid may be sufficient, but they may also prefer a stronger liquid andtake shorter and less frequent puffs. A heavy smoker who would be expected to prefer a28mg/ml ‘strong’ liquid may in fact chose a ‘moderate’ strength if they favour long andfrequent puffs.In real-life use, vapers have no way of knowing in advance what liquid strength andproduct characteristics they will prefer. As with other consumer products of this type,such as cigarettes, coffee and soft drinks, vapers have to try several EC models anddifferent e-liquids before settling on a preferred product that matches their preferences.For practical purposes, general labelling of the strength of e-liquid, along the lines usedfor indicating coffee strength, may provide sufficient information for consumers. Thecurrent vapers’ preferences suggest as a rough rule of thumb that ‘mild’ equates to 16–20mg/ml, ‘medium’ to 21–26mg/ml and ‘strong’ to 27–36mg/ml.Translating these findings into regulatory recommendations, it would seem thatregulation to enforce standard nicotine delivery may not be needed because nicotinedelivery is influenced by a host of factors, including user puffing preferences, andbecause consumer preferences differ. EC products will hopefully continue to evolveguided by differential market success, with the result that more smokers find EC helpfuland switch to them.SummaryAcross the middle range of nicotine levels, nicotine delivery to vapour is determinedprimarily by mechanical and electrical characteristics of EC products and by theduration and frequency of puffs. General labelling of the strength of e-liquids, along thelines used for indicating coffee strength (eg mild, medium and strong), is likely toprovide sufficient information for consumers.Nicotine delivery to e-cigarette usersTo assess nicotine intake from EC, a number of studies took blood samples fromsmokers during and after vaping. Table 8 summarises data from 17 studies thatinvestigated nicotine delivery from EC in humans. The narrative description of thestudies and additional details concerning their findings are presented in Appendix C.The two key questions in this field are:a) How much nicotine EC deliver compared to cigarettes, andb) How fast EC deliver nicotine compared to cigarettes.70