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Last Monday on the 15th of May, at a joint press conference at the Boston Convention and Exhibition Center, the AUA released data showing links between the use of e-cigarettes, and an increased risk of bladder cancer. However, points out Dr. Farsalinos, this alarming claim was not presented in a published study, but only in a conference abstract.

This abstract did not measure the correlation between vaping and bladder cancer in a direct manner, but noted the presence of substances linked with bladder cancer in the urine of 13 e-cigarette users, as compared with the urine samples of a control group made of 10 non-vapers. The abstract authors found higher levels of o-toluidine and 2-naphthylamine in e-cigarette users as compared to the controls.

Why is this data flawed?

However, the reasons and methodology that led the study authors to their conclusions are problematic. “No smokers were recruited for comparison.” pointed out Dr. Farsalinos, whilst presenting a list of reasons as to why these findings may be flawed:

  • Very low sample size
  • Non-verified smoking cessation in e-cigarette users (history taking only, no verification with exhaled carbon monoxide)
  • No inclusion of smoking controls for comparison
  • It is unknown if and how these compounds are formed in the e-cigarette aerosol
  • The biomarkers measured are not established biomarkers of smoking exposure
These biomarkers are not normally correlated to smoking exposure and are not usually used as a measure of toxicant exposure from tobacco cigarette smoking.
In order to explain this argument, Farsalinos quoted renowned expert of biomarkers of smoking exposure, Stephen S Hecht, who in 2002 wrote a review on human urinary carcinogen.

In one study, smokers excreted 6.3 ± 3.7 μg/ 24 h of 2-toluidine while levels in non-smokers were 4.1 ± 3.2 μg/24 h, not significantly different from smokers (93). Another investigation reported higher levels of 2-toluidine in smokers than in non-smokers (94). There appear to be significant sources of human uptake of 2-toluidine in addition to cigarette smoke. Smokers excreted similar amounts of 4-aminobiphenyl (78.6 ± 85.2 ng/24 h) as non-smokers (68.1 ± 91.5 ng/24 h), and similar amounts of 2-naphthylamine (84.5 ± 102.7 ng/24 h) as non-smokers (120.8 ± 279.2) (95).

Toxic substances present via environment exposure

Farsalinos concluded by explaining that both o-toluidine and 2-naphthylamine, are present via environment exposure, with studies showing similar levels in smokers and non-smokers. He pointed out that these biomarkers are not normally correlated to smoking exposure and are not usually used as a measure of toxicant exposure from tobacco cigarette smoking. Hence, the presence or absence of these chemicals in e-cigarettes needs to be verified by analyzing the aerosol.

Dr Farsalinos makes a review of the year 2016