A quarter of the 75 brands of US vaping products studied by Harvard researchers showed traces of bacteria – and four out of five had fungal contamination. The study included sealed and refillable products.
The researchers looked for chemical markers that can trigger lung conditions such as asthma, including bacterial endotoxins produced by the E coli bug, and β-D-glucan, part of the cell wall of invasive fungi.
These bacteria and fungi by-products have been shown to cause “acute and chronic respiratory effects”, said senior author and environmental geneticist Professor David Christiani.
He added: “Finding these toxins in e-cigarette products adds to the growing concerns about the potential for adverse respiratory effects in users.”
The findings, published in the journal Environmental Health Perspectives, come as academics warned that UK health authorities are ignoring the potential risks of vaping being used as a quitting aid for smokers.
Professor Martin McKee this week warned they have not existed for long enough to fully understand their impact.
There have been several studies with animals and humans which suggest that additives and flavourings used to help form vapour may have long-term negative effects.
One University of Birmingham study found that condensed vapour can interfere with the immune system’s ability to clean up the lungs.
If vapours are also introducing potentially harmful invaders this could have major effects, particularly with rising levels of resistance to antibiotic and antifungal treatments.
The Harvard study found 17 of 75 products (23 per cent) showed traces of endotoxins and 61 of 75 included glucans.
Bacterial contaminants were more common in tobacco and menthol flavourings, while glucans were more common in fruit flavourings and cartridge refills, suggesting differences in manufacturing were to blame.
The authors said these findings should be considered when drawing up regulatory policies, however independent experts said the findings needed to be tested in real world settings.
Dr Penny Woods, chief executive of the British Lung Foundation, said the results were “interesting” but preliminary, adding that the UK has ”different, tighter e-cigarette regulations” than the American market.
“We do need to keep adding to our knowledge on the long-term effects of e-cigarettes, however we know that vaping is 20 times less harmful than smoking,” she added.
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