Severe long-term consequences of THS (thirdhand smoke) exposure.
A new study published in the journal Environment International, has estimated for the first time the potential cancer risk by age group through non-dietary ingestion and dermal exposure to third hand smoke. The results indicate potentially severe long-term consequences, particularly to children.
The research was carried out by York’s Wolfson Atmospheric Chemistry Laboratories, the National Centre for Atmospheric Science, and the Chromatography and Environmental Applications research group at the Universitat Rovira i Virgili, Spain.
The study, which was supported by the UK Natural Environment Research Council (NERC) and the General Research Directorate of the Government of Catalonia, also demonstrates for the first time the widespread presence of tobacco related carcinogens in house dust, even in ‘smoke-free’ environments.
Scientists collected dust samples from private homes occupied by both smokers and non-smokers. Using observations of house dust composition, they estimated the cancer risk by applying the most recent official toxicology information.
They found that for children aged one to six years old, the cancer risks exceeded the limit recommended by the US Environmental Protection Agency (EPA) in three quarters of smokers’ homes and two thirds of non-smokers’ homes. The maximum risk predicted from the third hand smoke levels in a smoker occupied home equated to one extra cancer case per one thousand population exposed.
Dr Jacqueline Hamilton, from York’s Wolfson Atmospheric Chemistry Laboratories, said: “The risks of tobacco exposure do not end when a cigarette is extinguished. Non-smokers, especially children, are also at risk through contact with surfaces and dust contaminated with residual smoke gases and particles, the so-called third hand smoke. This risk should not be overlooked and its impact should be included in future educational programs and tobacco-related public health policies.”
Each year 600,000 people die worldwide through passive inhalation of environmental tobacco smoke, also known as second hand smoke. As numerous countries have introduced smoking bans in public places, the home has become the main source of passive smoking exposure.
Professor Alastair Lewis, from York’s Wolfson Atmospheric Chemistry Laboratories and the National Centre for Atmospheric Science, said: “Over 40 per cent of children have at least one smoking parent and whereas there is a general public awareness about the harms of second hand smoke, there is little knowledge about the dangers of third hand smoke.
Carcinogenic materials can be passed from smokers to non-smokers during shared contact, for example between clothes and surfaces and also enter homes via airborne transport of cigarette smoke.”
The researchers examined exposure to carcinogen N-nitrosamines and tobacco specific nitrosamines (TSNAs) in the dust samples. These are produced when nicotine deposits on indoor surfaces and then is released again to the gas phase or reacts with ozone, nitrous acid and other atmospheric oxidants. They are classified as carcinogenic for humans.
Measurements were made using a comprehensive two-dimensional gas chromatography system, which was originally funded by NERC to study particulate matter in the atmosphere.
“This highly selective and sensitive instrument has allowed the small amounts of TSNAs stuck to the surface of house dust to be measured for the first time.” Professor Rosa Maria Marcé, from the Universitat Rovira i Virgili, Tarragona, said:
Dr Noelia Ramirez, a Postdoctoral Research Fellow from York’s Wolfson Atmospheric Chemistry Laboratories who started this research line, said: “While TSNAs have been suspected to form part of third hand smoke as a result of laboratory studies, we have demonstrated for the first time the presence of carcinogenic tobacco-specific compounds, such as TSNAs, in settled house dust found in a panel of smokers’ and non-smokers’ homes.
“The TSNAs concentrations found in smoke-free homes would suggest that TSNAs formed in smoking environments can persist for extended periods, possibly due to partitioning to ambient particles, and subsequently be transported into non-smokers’ homes from outside.”
Nitrosamines (#-nitrosoamines), typified by #-nitrosodimethylamine and #-nitrosodiethanolamine (Fig. 1), are mutagens and are reactive compounds that readily alkylate DNA via an reaction (slow formation of an alkylcarbenium ion and rapid reaction of this with nitrogen, oxygen, and phosphorus atoms on DNA). N-Nitrosoamines are widespread in the environment and can be formed endogenously in humans (1-3). For example, workers in the rubber industry are exposed to high levels of N-nitrosodiethanolamine, which is a potent carcinogen over a considerable dose range and in more than one species. A wide range of volatile N-nitrosoamines are found in fried bacon and other pork products, while a different range of N-nitrosoamines are present in tobacco products and believed to play a significant role in human cancers associated with tobacco use. N-Nitrosoamines are potent carcinogens in every animal species tested; and although their role in human cancer is not definitively proved, it is considered highly likely that they are human carcinogens (2, 4).
Figure 1. Structures of the nitrosamines N-nitrosodimethylamine and N-nitrosodiethanolamine.
One of the most extensively studied compounds in this class is N-nitrosodimethylamine (NDMA). This chemical is nonreactive per se, but can be metabolized to an S^-type methylating agent, primarily by cytochrome P450 IIE1. Although the metabolite reacts primarily to form around 60% Ny-methylguanine DNA adducts, it also generates a significant amount (approximately 6%) of O6- methylguanine, as well as other minor N- and O-alkylated bases. ^-Methylguanine and other O- alkylated adducts are directly miscoding, and they introduce base pair substitutions upon DNA replication; extensive evidence exists to link these lesions with mutagenesis and carcinogenesis by NDMA and related agents. NDMA has been described as the most powerful methylating agent known (5).
Nitrosamines are chemical compounds of the chemical structure R¹N(-R²)-N=O, most of which are carcinogenic. Nitrosamines are used in the manufacture of some cosmetics, pesticides, and in most rubber products.
These nitrosamine carcinogens are formed from nicotine and related compounds by a nitrosation reaction that occurs during the curing and processing of tobacco. They are called tobacco-specific nitrosamines because they are found only in tobacco products, and possibly in some other nicotine-containing products. The tobacco-specific nitrosamines are present in cigarette smoke and to a lesser degree in “smokeless” tobacco products such as dipping tobacco and chewing tobacco. They are present in trace amounts in snus, a Swedish style snuff that is not fermented (a type of curing) and is pasteurized. They are among the most important carcinogens in cigarette smoke, along with combustion products and other carcinogens.
Among the tobacco-specific nitrosamines, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N’-nitrosonornicotine (NNN) are the most carcinogenic. NNK and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are potent systemic lung carcinogens in rats. Tumors of the nasal cavity, liver, and pancreas are also observed in NNK- or NNAL-treated rats. NNN is an effective esophageal carcinogen in the rat, and induces respiratory tract tumors in mice, hamsters, and mink. A mixture of NNK and NNN caused oral tumors when swabbed in the rat oral cavity. Thus, considerable evidence supports the role of tobacco-specific nitrosamines as important causative factors for cancers of the lung, pancreas, esophagus, and oral cavity in people who use tobacco products.
- The presence of nicotine, eight N-nitrosamines and five tobacco-specific nitrosamines in forty-six settled dust samples from homes occupied by both smokers and non-smokers.
- Cancer risk through ingestion and dermal exposure.
- Carcinogenic materials can be passed from smokers to non-smokers during shared contact, for example between clothes and surfaces and also enter homes via airborne transport of cigarette smoke.”
No less than 4000 irritating, suffocating, dissolving, inflammable, toxic, poisonous, carcinogenic gases and substances and even radioactive compounds (nickel, polonium, plutonium, etc.) have been identified in tobacco smoke. Some of these are listed hereafter: Benzopyrene, dibenzopyrene, benzene, isoprene, toluene (hydrocarbon); naphthylamines; nickel, polonium, plutonium, arsenic, cadmium (metallic constituents); carbon dioxide, methane, ammonia, nitric oxide, nitrogen dioxide, hydrogen sulphide (gases); methyl alcohol, ethanol, glycerol or glycerine, glycol (alcohols and esters); acetaldehyde, acrolein, acetone (aldehydes and ketones); cyanhydric or prussic acid, carboxyl derivatives (acids); chrysene, pyrrolidine, nicoteine, nicotinine, nicoteline, nornicotine, nitrosamines (alkaloids or bases); cresol (phenols), etc.
Sources: http://www.sciencedirect.com/science/article/pii/S0160412014001962 , http://what-when-how.com/molecular-biology/nitrosamines-molecular-biology/ , http://en.wikipedia.org/wiki/Tobacco-specific_nitrosamines , http://digitalsmoking.ge/en/faq/about-old-cigarettes