The contention that e-cigarettes represent a safe form of nicotine consumption has taken a blow with a study finding that their use may trigger unique immune responses – as well as producing the same potentially lung-damaging outcomes associated with conventional cigarettes.
The small study – which the authors concede has significant limitations – is published in the American Journal of Respiratory and Critical Care Medicine.
Researchers led by pathologist Mehmet Kesimer of the University of North Carolina Chapel Hill in the US took sputum samples from 15 e-cigarette users, 14 smokers and 15 non-smokers.
The e-cigarette and standard cigarette user cohorts both showed increased levels of at least two biomarkers – thioredoxin (TXN), and matrix metalloproteinase-9 (MMP9) – associated with oxidative stress and defence mechanisms linked to lung disease.
Both groups also returned significant measures of a mucus secretion called mucin 5AC, high levels of which are associated with conditions such as asthma and bronchitis.
The e-cigarette users, however, also showed high levels of two additional proteins, from a class called neutrophils. These play a role in fighting pathogens but when produced in excess are linked to lung diseases such as cystic fibrosis.
One of these proteins – called a neutrophil-extracellular-trap-related protein – was also found outside e-smokers’ lungs. In these locations they are associated with damage to tissues surrounding blood vessels and organs, and may be implicated in the development of conditions such as vasculitis and psoriasis.
“There is confusion about whether e-cigarettes are ‘safer’ than cigarettes because the potential adverse effects of e-cigarettes are only beginning to be studied,” says Kesimer.
“Our results suggest that e-cigarettes might be just as bad as cigarettes.”
More research, however, is clearly needed. Kesimer’s team write that the value of the findings is limited, because 12 members of the e-cigarette cohort said they had smoked traditional cigarettes in the past.
Nevertheless, the study results are sufficient to both raise the alarm and point towards new targets for investigation.
“Comparing the harm of e-cigarettes with cigarettes is a little like comparing apples to oranges,” says Kesimer.
“Our data shows that e-cigarettes have a signature of harm in the lung that is both similar and unique, which challenges the concept that switching from cigarettes to e-cigarettes is a healthier alternative.”
The need for vigorous research is arguably urgent. E-cigarette uptake is surging, largely driven by the assumption that it is safe. In 2016 the US Surgeon General reported that in the previous five years e-cigarette usage had increased by 900% — just in high school students.