与许多早先将电子烟与吸烟直接比较的研究不同，本次综述评估的是电子烟本身是否致癌。研究者指出，电子烟在全球被广泛使用仅约20年，因此依赖流行病学数十年证据进行最终证明并不现实，因此采用了生物标志物和实验数据：吸电子烟的人可检测到尼古丁相关化合物、重金属等化学物，且与DNA损伤和炎症相关，这是癌症发展标志。Stewart 表示，口腔和肺部的细胞与组织会因电子烟吸入而发生改变。动物研究表明，暴露于电子烟气溶胶的小鼠出现远高于对照组的肺肿瘤率，并出现与癌症相关的膀胱改变，尽管该综述未给出绝对癌症风险的数值估计。
该报告也指出监管难题在于“dual use”（双重使用）：许多用户并未完全从香烟转向电子烟，而是同时使用两者。研究者称，超过一半使用者无法戒掉任何一种。UNSW 共同作者 Freddy Sitas 引用美国最近的流行病学证据，称同时吸烟和吸电子烟者的肺癌风险还增加四倍。鉴于吸烟史表明证明危害可能经历数十年，作者认为随着年轻人迅速采用，监管者不应重复这一延误，强调“我们不应再等80年”。专家进一步说明，这并不意味着吸烟者应回归香烟，因为香烟的危害远高于电子烟，但电子烟也可能并不安全。
A review in Carcinogenesis concludes nicotine-based e-cigarettes are likely carcinogenic to humans, especially likely to cause lung and oral cancers, even though definitive long-term population studies are still missing. Bernard Stewart, a UNSW cancer researcher who led the study, said clinical monitoring, animal studies, and mechanistic evidence all support that conclusion. The finding sharpens scrutiny of the global e-cigarette market, estimated at US$30 billion to US$46 billion, including major tobacco groups investing heavily in vaping such as Altria Group, British American Tobacco, and Imperial Brands, and raises questions for public health frameworks that have treated vaping as a lower-harm alternative.
Unlike many earlier studies that compared e-cigarettes directly with cigarettes, this review assessed whether e-cigarettes are carcinogenic in their own right. The authors noted widespread use is only about 20 years old, so waiting for decades of epidemiological certainty is impractical, and they relied instead on biomarkers and experimental evidence: users absorb nicotine-related compounds, heavy metals, and other chemicals linked to DNA damage and inflammation, both hallmarks of cancer. Stewart said e-cigarette inhalation alters cells and tissues in the mouth and lungs. In animal studies, mice exposed to vape aerosols showed far higher lung tumor rates than controls and bladder changes linked to cancer, though the review did not give a numerical estimate of absolute cancer risk.
The report also highlights a regulatory challenge from dual use: many users do not fully switch and instead use both cigarettes and e-cigarettes. The researchers found that more than half are unable to quit either product. Co-author Freddy Sitas cited U.S. epidemiological evidence that dual users have an additional four-fold increased risk of lung cancer. Given smoking’s history, where proving harm took decades, the authors argue regulators should not repeat that delay as youth uptake rises, cautioning, “we should not wait another 80 years.” Experts added this does not mean smokers should return to cigarettes, since cigarettes remain far more harmful, but that e-cigarettes may not be as safe as once assumed.