Erratum Igor Burstyn, Drexel University 12 June 2015 I am thankful to Dr. Zvi Herzig for noticing an error in units in one result reported in the paper (Burstyn, 2014). The sentence “Assuming extreme consumption of the liquid per day via vaping (5 to 25 ml/day and 50-95% propylene glycol in the liquid), levels of propylene glycol in inhaled air can reach 1–6 mg/m3” should read “… levels of propylene glycol in inhaled air can reach 1–6 g/m3”. This strengthens the stated conclusion that “… estimated levels of exposure to propylene glycol … warrant concern.” The corrected calculation was one of several that were used to draw this conclusion. It was a worse-than-worst-realistic-case scenario and would have to be reconciled with measurements of emissions, and thus should not be considered a realistic quantification unless further measurements change our assessment of what constitutes a realistic scenario. The corrected estimate suggests greater caution is warranted than the original estimate, but is still not cause for alarm. It implies that we should be doing more active research to understand the effects of inhalation exposure to propylene glycol at levels higher than those that have been studied in the past, if the predicted exposures are indeed verified by measurements. I sincerely apologize to my readers for the error and am thankful for such attentive readership. Reference: Burstyn I: Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks. BMC Public Health 2014, 14: 18. Competing interests The author is a currently a member of the Board of Directors of the Consumer Advocates for Smoke-free Alternatives Association(CASAA; http://casaa.org/), particiapted in FDA workshops on electronc cigaretters, and gave numerous interviews about his research on electronic cigaretters. However, he does not view any of these as a source of actual conflict of interest in correcting an error in arithmetic. The authors firmly beleives that suitability of methods, accuracy of calculations and analysis are the only important contribution of a scientific paper, not the conclusions stated by the authors. The authors is also a proponent of harm reduction and an opponent of the "precautionary principle".The author declares no other potential conflicts of interest.