As the debate on second hand smoke rages on the anti tobacco lobby have moved onto third hand smoke (THS). Whereby the residue of chemicals exhaled onto surfaces and the smoker’s clothes constitutes a health hazard. Here is an article published in the British Medical Journal (BMJ) in January 2011 where he concludes “The omission of this information in such reports risks harming the credibility of tobacco control.”
“Many constituents of third hand smoke can be found in all homes and cars, regardless of smoking
- Simon Chapman, Professor of Public Health
University of Sydney
Matt et al’s demonstration that nicotine can be detected in house dust, on surfaces and on fingers in homes formerly occupied by smokers is used as a springboard to promote concern about third hand smoke(THS). Given the rudimentary nature of most domestic cleaning and the common experience of the distinctive smell of stale tobacco smoke, few will find it surprising that traces of nicotine can be found in smokers’ homes long after they have vacated them.
While Schick notes several times that the health consequences of this level of exposure are unknown, the title of her editorial says that THS is “here to stay”, presumably an intended pun suggesting that concerns about the health implications of THS are now established. Schick notes that nicotine “and all the other things that go along with it” can pollute houses. But the soup of gases, fine and ultra-fine particles in tobacco smoke that include irritants, toxins and carcinogens has much in common with smoke emitted as pyrolisis products from the combustion of other organic matter: when you breath wood smoke, cooking smoke or petroleum smoke, you are exposed to many of the very same irritants and carcinogens that are also in tobacco smoke.
So why did Matt et al consider only nicotine? There is not a house anywhere that is not finely carpeted with many of the very same pyrolysis compounds “that go along with” nicotine but which originate from everyday activities like heating, cooking, candles, electrical appliances, and leaving windows and doors open to allow household exposure to motor transport fumes. Had they done so, equally “alarming” information about all our houses would have emerged to give their findings some important perspective.
The evidence base that has supported indoor smoking restrictions is concentrated around fine particle (PM2.5) concentrations emitted in unhealthy abundance by smoking and on the evidence of harm from particularly chronic exposure to those particles and what they contain. While nicotine is often used as a marker for secondhand smoke exposure and not benign, nicotine is far from being the chief health concern.
Ott and Seigmann and Wallace and Ott provide data on fine and ultra-fine particle emissions from different sources: “Controlled experiments with 10 cigarettes averaged 0.15 ng mm-2 … ambient wood smoke averaged 0.29 ng mm-2 or about twice those of cigarettes and cigars … In-vehicle exposures measured on 43 and 50 min drives on a California arterial highway gave PC/DC ratios of 0.42 and 0.58 ng mm-2 … Interstate highways had PC/DC ratios of approximately 0.5 ng mm-2 with ratios above 1 ng mm-2 when driving behind diesel trucks. These PC/DC ratios were higher than the ”signature” value of the cigarette (0.11-0.19 ngmm-2)measured in a large Indian gaming casino with smoking.” 
Tobacco smoke also contains ultra-fine particles. Other sources of ultra-fine particles (UFPs) include “laser printers, fax machines, photocopiers, the peeling of citrus fruits, cooking, penetration of contaminated outdoor air, chimney cracks and vacuum cleaners.” Wallace and Ott’s data on concentrations of UFPs in restaurants and cars found “cooking on gas or electric stoves and electric toaster ovens was a major source of UFP, with peak personal exposures often exceeding 100,000 particles/cm3 …. Other common sources of high UFP exposures [in restaurants] were cigarettes, a vented gas clothes dryer, an air popcorn popper, candles, an electric mixer, a toaster, a hair dryer, a curling iron, and a steam iron.”
It is important that research documents residuals from tobacco smoke. But it is equally important that consumers and policy makers are not led to believe that the chemical compounds thus located are somehow unique to tobacco smoke. Unless in the extremely unlikely event that residents burn copious quantities of solanaceous vegetables (aubergine, tomato) which contain small amounts of nicotine, tobacco is going to be the only source of nicotine in homes. But it will not by any means be the only source of many of the ingredients of “third hand smoke” that the unwitting or the fumophobic may believe are attributable only to smoking. The omission of this information in such reports risks harming the credibility of tobacco control.
1. Matt, G.E., et al., When smokers move out and non-smokers move in: residential thirdhand smoke pollution and exposure. Tob Control, 2011. 20(1): p. e1.
2. Schick, S., Thirdhand smoke: here to stay. Tob Control, 2011. 20(1): p. 1-3.
3. Naeher, L.P., et al., Woodsmoke health effects: a review. Inhal Toxicol, 2007. 19(1): p. 67-106.
4. Lijinsky, W., The formation and occurrence of polynuclear aromatic hydrocarbons associated with food. Mutat Res, 1991. 259(3-4): p. 251-61.
5. Mehlman, M.A., Dangerous properties of petroleum-refining products: carcinogenicity of motor fuels (gasoline). Teratog Carcinog Mutagen, 1990. 10(5): p. 399-408.
6. Hyland, A., et al., A 32-country comparison of tobacco smoke derived particle levels in indoor public places. Tobacco Control, 2008. 17(3): p. 159-65.
7. Sleiman, M., et al., Formation of carcinogens indoors by surface- mediated reactions of nicotine with nitrous acid, leading to potential thirdhand smoke hazards. Proc Natl Acad Sci U S A, 2010. 107(15): p. 6576- 81.
8. Ott, W. and M. Siegmann, Using multiple continuous fine particle monitors to characterize tobacco, incense, candle, cooking, wood burning, and vehicular sources in indoor, outdoor, and in-transit settings. Atmospheric Environment, 2006. 40: p. 821-843.
9. Wallace, L. and W. Ott, Personal exposure to ultrafine particles. Journal of Exposure Science and Environmental Epidemiology 0, 2011. 21: p. 20-30.
Conflict of Interest: