New Study Concludes that Thirdhand Smoke Causes Lung Damage to the Fetus; Declares Changing Bedsheets a Problem of Global Proportions

An article published online ahead of print in the American Journal of Physiology has concluded that changing bedsheets is a problem of global proportions, given evidence it reports that direct application of tobacco-specific nitrosamines to fetal lung extracts induces lung damage (see: Rehan VK, Sakurai R, Torday JS. Thirdhand smoke: A new dimension to the effects of cigarette smoke on the developing lung. American Journal of Physiology: Lung Cellular and Molecular Physiology 2011; doi: 10.​1152/​ajplung.​00393.​201).

In the study, researchers applied tobacco-specific nitrosamines directly to fetal lung extracts and detected physiologic changes that signaled impairment of lung development. Specifically, the study found that: "exposure of the developing lung to either NNK or NNA resulted in disrupted homeostatic signaling, indicated by the downregulation of PPARγ, up-regulation of fibronectin and calponin protein levels, decreased BCL-2/Bax ratio, and the accompanying compensatory stimulation of surfactant phospholipid and protein synthesis."

From this, the authors conclude that "thirdhand smoke can have as serious or an even more negative impact on an infants' lung development as postnatal or childhood exposure to smoke."

They also conclude that "exposure to the constituents of thirdhand smoke is as damaging and, in some cases, more damaging than secondhand smoke or firsthand smoke."

Furthermore, they conclude that "prenatal disruption of lung development [by thirdhand smoke] can lead to asthma and other respiratory ailments that can last a lifetime."

Finally, the study concludes that "THS [thirdhand smoke] is a hidden toxin present in the households of smokers where pregnant women and small children live without realizing that they are being exposed to such dangerous toxicants. The same risk exists for adult workers who clean and change bed sheets in hotel rooms where cigarette smoking is allowed the world over, especially in China and other countries in Africa, Asia, South America and North America – a problem of global proportions!"

Based on the press release, international news headlines warned that "'Thirdhand' smoke hurts infant lungs" and "Thirdhand smoke dangerous to unborn babies' lungs."

The Rest of the Story

The conclusions of this study are grossly exaggerated and have almost no relationship to the actual findings of the study.

The study did not actually examine the effects of thirdhand smoke exposure at all. It merely examined, in a laboratory setting, the effects of directly treating fetal lung extracts with tobacco-specific nitrosamines.

To jump from "downregulation of PPARγ" to changing bedsheets as a "problem of global proportions" has to win the award for most extreme (and scientifically unsupported) extrapolation in the research literature.

The study cannot draw any conclusions about the effects of thirdhand smoke exposure because it did not examine thirdhand smoke exposure. It did not document that pregnant women are exposed to any carcinogens from thirdhand smoke. Thus, how can it possibly conclude that thirdhand smoke exposure causes lung damage to the developing fetus?

What the study can conclude is that significant exposure to tobacco-specific nitrosamines can impair fetal lung development. But it does not demonstrate that thirdhand smoke results in significant exposure to tobacco-specific nitrosamines.

The conclusion that thirdhand smoke exposure among pregnant women can lead to asthma in their children is completely unsupported by any evidence. This is a scientifically unjustifiable extrapolation from the evidence presented in this study.

Another unsupportable conclusion of this study is that thirdhand smoke exposure is "more damaging" than secondhand smoke or firsthand smoke. The study merely examined the effects of tobacco-specific nitrosamine exposure. It did not compare the levels of such exposure among active smokers, secondhand smokers, and thirdhand smokers. How it could therefore draw the conclusion that thirdhand smoke effects are worse than that of firsthand smoke effects is completely beyond my comprehension.

Finally, the conclusion that changing bedsheets is a public health problem of global proportions strains credulity.

How do you get from this:

directly applying tobacco-specific nitrosamines to fetal lung extracts causes downregulation of PPARγ, up-regulation of fibronectin and calponin protein levels, decreased BCL-2/Bax ratio, and the accompanying compensatory stimulation of surfactant phospholipid and protein synthesis

to this:

changing bedsheets is a problem of global proportions.

Especially when you don't even measure exposure to thirdhand smoke.

There is really only one apparent explanation for this, which is that the authors had a pre-determined conclusion that thirdhand smoke is extremely hazardous and that they were determined to draw such a conclusion, regardless of the actual findings of the research.

Not only does this threaten to undermine the credibility of the tobacco control movement, but it also undermines the public's understanding of the hazards of active smoking (and secondhand smoke exposure). If the public believes these researchers, and accepts that active smoking is only as bad as thirdhand smoke exposure, then the public will perceive that active smoking is not nearly as bad as it actually is. Thus, these wild exaggerations do damage in two ways.

The rest of the story is that this is yet another example of the deterioration of the scientific integrity in the tobacco control movement. That you can go from a finding that directly applying tobacco-specific nitrosamines to fetal lung extracts impairs lung development to a conclusion that changing bedsheets is an international public health problem of global proportions - without actually documenting that changing bedsheets leads to significant tobacco-specific nitrosamine exposure - is a sign that the scientific credibility of the movement is shot.


NOTE: You can read Christopher Snowdon's take on this research here at his blog: Velvet Glove, Iron Fist.