(See: Rehan VK, Sakurai R, Torday JS. Thirdhand smoke: a new dimension to the effects of cigarette smoke on the developing lung. Am J Physiol Lung Cell Mol Physiol 301:L1-L8, 2011.)
According to one of the study authors quoted in a KABC-TV article about the study, the results of the study showed that: "exposure to thirdhand smoke is as damaging, and in some cases, more damaging than secondhand or firsthand smoke." This was not an aberrant quotation, as a press release issued by the research institute where the authors work made the same claim.
The study itself 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, all over the world: a problem of global proportions!"
The Rest of the Story
What is the actual scientific evidence uncovered in this study of thirdhand smoke that demonstrates it is a problem of global proportions, threatening hotel workers throughout the world?
The evidence is as follows: "Fetal rat lung explants were exposed to nicotine, 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA), or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the two main tobacco-specific N-nitrosamine constituents of THS, for 24 h. We then determined key markers for alveolar paracrine signaling [epithelial differentiation markers surfactant phospholipid and protein synthesis; mesenchymal differentiation markers peroxisome proliferator-activated receptor (PPAR- ), fibronectin and calponin], the BCL-2-to-Bax ratio (BCL-2/Bax), a marker of apoptosis and the involvement of nicotinic acetylcholine receptors (nAChR)- 3 and - 7 in mediating NNA’s and NNK’s effects on the developing lung. Similar to the effects of nicotine, exposure of the developing lung to either NNK or NNA resulted in disrupted homeostatic signaling, indicated by the downregulation of PPAR- , upregulation of fibronectin and calponin protein levels, decreased BCL-2/Bax, and the accompanying compensatory stimulation of surfactant phospholipid and protein synthesis. Furthermore, nAChR- 3 and - 7 had differential complex roles in mediating these effects. NNK and NNA exposure resulted in breakdown of alveolar epithelial-mesenchymal cross-talk, reflecting lipofibroblast-to-myofibroblast transdifferentiation, suggesting THS constituents as possible novel contributors to in utero smoke exposure-induced pulmonary damage."
To translate this into plain English:
"We chopped up fetal rat lungs into cubes and marinated the cubes in a solution containing nicotine, NNK, or NNA [which are tobacco-specific nitrosamines present in tobacco smoke that have been demonstrated to cause lung cancer and lung damage]. We found that exposure to these chemicals caused damage to the fetal rat lung tissue."
That's interesting, but how do you get from that to the conclusion that touching a bed sheet in a room where someone smoked is a problem of global proportions and may be even more hazardous than active smoking?
This is about as fallacious an extrapolation as I've ever seen in a scientific paper.
In fact, the paper did not study thirdhand smoke exposure and it did not study the effects of this exposure on humans under conditions of realistic exposure. It does suggest that if you splatter tobacco-specific carcinogens and toxins directly onto the lungs of children, you will cause damage, but it provides no evidence whatsoever regarding the actual effects of exposure to the residue left on surfaces after active smoking has concluded. And it certainly doesn't provide evidence that thirdhand smoke exposure is as harmful as or more harmful than active smoking.
The authors themselves acknowledge that: "We must state that a comprehensive assessment of the risks of THS on the developing lung, the molecular pathways, the specific cell-types involved, and the levels of different THS constituents required in mediating these risks requires further extensive characterization of levels of THS constituents in the environment, and the realistic exposure of the developing fetus and growing child to these constituents."
In other words, the authors acknowledge in the paper that in order to draw a conclusion about the actual risks associated with thirdhand smoke, one would need to examine and identify the "levels of different THS constituents required" to cause lung damage. But this study made no attempt to measure the levels of exposure to THS constituents under realistic conditions (or even under unrealistic conditions - it simply did not measure exposure to thirdhand smoke).
Unfortunately, this limitation did not stop the authors from concluding that thirdhand smoke is a health threat of global proportions that is as dangerous as, or perhaps even more dangerous than active smoking.
If readers were not convinced of the deterioration of the science within the anti-smoking movement last week when I revealed the poor quality and blatant bias of two recent studies purporting to show that smoking bans cause an immediate and dramatic reduction in heart attacks, they should hopefully be convinced by the rest of this story.
This is yet another example of a study conclusion that has no relation to the actual scientific investigation. The authors could have made the same conclusion without presenting any data. In fact, it has the appearance of investigators who had a pre-determined conclusion that they wanted to disseminate this conclusion and simply needed to have some data on hand to give them an excuse to spread their conclusion across the world.
It actually fits into the unscientific framework set up by the California research program which funded this work, as that program itself drew pre-determined conclusions about the effects of thirdhand smoke.
(Thanks to Michael McFadden for the tip.)