Headlines news about e-cigarettes causing bladder cancer based on non-specific biomarkers

By Dr Farsalinos

It is all over the news today that e-cigarette use is associated with bladder cancer. This is an impressive statement that would certainly raise concerns if any such association was really shown in any study. First, this is based just on a conference abstract, not a published study. Second, the abstract did not measure any association between e-cigarette use and bladder cancer. It evaluated chemicals linked with bladder cancer in the urine of 13 e-cigarette users compared 10 non-users as controls. No smokers were recruited for comparison. The authors of the abstract found higher levels of o-toluidine and 2-naphthylamine in e-cigarette users compared to controls.

The problems with this abstract are:

  1. Very low sample size
  2. Non-verified smoking cessation in e-cigarette users (history taking only, no verification with exhaled carbon monoxide)
  3. No inclusion of smoking controls for comparison
  4. It is unknown if and how these compounds are formed in the e-cigarette aerosol
  5. The biomarkers measured are not established biomarkers of smoking exposure

For the latter, I will quote Stephen S Hecht, a well-known expert of biomarkers of smoking exposure, who wrote a review on human urinary carcinogen biomarkers in 2002. He mentions: “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).

So, for both chemicals, there is significant exposure from the environment and studies have shown similar levels excreted from smokers and non-smokers. That is why these biomarkers are non-specific of smoking exposure and are not routinely used as a measure of toxicant exposure from tobacco cigarette smoking. However, we need to verify the presence or absence of these chemicals in e-cigarettes by analyzing the aerosol.



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