Thirdhand smoke causes DNA damage in human cells

Thirdhand cigarette smoke: factors affecting exposure and remediation

Thirdhand smoke (THS) refers to components of secondhand smoke that stick to indoor surfaces and persist in the environment. Little is known about exposure levels and possible remediation measures to reduce potential exposure in contaminated areas. This study deals with the effect of aging on THS components and evaluates possible exposure levels and remediation measures. We investigated the concentration of nicotine, five nicotine related alkaloids, and three tobacco specific nitrosamines (TSNAs) in smoke exposed fabrics. Two different extraction methods were used. Cotton terry cloth and polyester fleece were exposed to smoke in controlled laboratory conditions and aged before extraction. Liquid chromatography-tandem mass spectrometry was used for chemical analysis. Fabrics aged for 19 months after smoke exposure retained significant amounts of THS chemicals. During aqueous extraction, cotton cloth released about 41 times as much nicotine and about 78 times the amount of tobacco specific nitrosamines (TSNAs) as polyester after one hour of aqueous extraction. Concentrations of nicotine and TSNAs in extracts of terry cloth exposed to smoke were used to estimate infant/toddler oral exposure and adult dermal exposure to THS. Nicotine exposure from THS residue can be 6.8 times higher in toddlers and 24 times higher in adults and TSNA exposure can be 16 times higher in toddlers and 56 times higher in adults than what would be inhaled by a passive smoker. In addition to providing exposure estimates, our data could be useful in developing remediation strategies and in framing public health policies for indoor environments with THS.

Exposure to nitrosamines in thirdhand tobacco smoke increases cancer risk in non-smokers

In addition to passive inhalation, non-smokers, and especially children, are exposed to residual tobacco smoke gases and particles that are deposited to surfaces and dust, known as thirdhand smoke (THS). However, until now the potential cancer risks of this pathway of exposure have been highly uncertain and not considered in public health policy. In this study, we estimate for the first time the potential cancer risk by age group through non-dietary ingestion and dermal exposure to carcinogen N-nitrosamines and tobacco-specific nitrosamines (TSNAs) measured in house dust samples. Using a highly sensitive and selective analytical approach we have determined 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. Using observations of house dust composition, we have estimated the cancer risk by applying the most recent official toxicological information. Calculated cancer risks through exposure to the observed levels of TSNAs at an early life stage (1 to 6years old) exceeded the upper-bound risk recommended by the USEPA in 77% of smokers' and 64% of non-smokers' homes. The maximum risk from exposure to all nitrosamines measured in a smoker occupied home was one excess cancer case per one thousand population exposed. The results presented here highlight the potentially severe long-term consequences of THS exposure, particularly to children, and give strong evidence of its potential health risk and, therefore, they should be considered when developing future environmental and health policies.

Nicotine, cotinine, and β-nicotyrine inhibit NNK-induced DNA-strand break in the hepatic cell line HepaRG

Recent in vitro work using purified enzymes demonstrated that nicotine and/or a nicotine metabolite could inhibit CYPs (CYP2A6, 2A13, 2E1) involved in the metabolism of the genotoxic tobacco nitrosamine NNK. This observation raises the possibility of nicotine interaction with the mechanism of NNK bioactivation. Therefore, we hypothesized that nicotine or a nicotine metabolite such as cotinine might contribute to the inhibition of NNK-induced DNA strand breaks by interfering with CYP enzymes. The effect of nicotine and cotinine on DNA strand breaks was evaluated using the COMET assay in CYP competent HepaRG cells incubated with bioactive CYP-dependent NNK and CYP-independent NNKOAc (4-(acetoxymethylnitrosoamino)-1-(3-pyridyl)-1-butanone). We report a dose-dependent reduction in DNA damage in hepatic-derived cell lines in the presence of nicotine and cotinine. Those results are discussed in the context of the in vitro model selected.

Children's exposure to secondhand and thirdhand smoke carcinogens and toxicants in homes of hookah smokers

INTRODUCTION

We examined homes of hookah-only smokers and nonsmokers for levels of indoor air nicotine (a marker of secondhand smoke) and indoor surface nicotine (a marker of thirdhand smoke), child uptake of nicotine, the carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and the toxicant acrolein by analyzing their corresponding metabolites cotinine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and NNAL-glucuronides (total NNAL) and 3-hydroxypropylmercapturic acid.

METHODS

Data were collected at 3 home visits during a 7-day study period from a convenience sample of 24 households with a child 5 years or younger. Three child urine samples and 2 air and surface samples from the living room and the child bedroom were taken in homes of nonsmokers (n = 5) and hookah-only smokers (n = 19) comprised of daily hookah smokers (n = 8) and weekly/monthly hookah smokers (n = 11).

RESULTS

Nicotine levels in indoor air and on surfaces in the child bedrooms in homes of daily hookah smokers were significantly higher than in homes of nonsmokers. Uptake of nicotine, NNK, and acrolein in children living in daily hookah smoker homes was significantly higher than in children living in nonsmoker homes. Uptake of nicotine and NNK in children living in weekly/monthly hookah smoker homes was significantly higher than in children living in nonsmoker homes.

CONCLUSIONS

Our data provide the first evidence for uptake of nicotine, the tobacco-specific lung carcinogen NNK, and the ciliatoxic and cardiotoxic agent acrolein in children living in homes of hookah smokers. Our findings suggest that daily and occasional hookah use in homes present a serious, emerging threat to children's long-term health.

Thirdhand smoke beliefs of parents

OBJECTIVE

To determine if the belief that thirdhand smoke is harmful to children is associated with smoking parents' attitudes, home or car smoking policies, and quitting behaviors.

METHODS

Data from a national randomized controlled trial, Clinical Effort Against Secondhand Smoke Exposure, assessed thirdhand smoke beliefs of 1947 smoking parents in an exit survey after a pediatric office visit in 10 intervention and 10 control practices. Twelve-month follow-up data were collected from 1355 parents. Multivariable logistic regression determined whether belief that thirdhand smoke harms the health of children is independently associated with parental behaviors and attitudes 12 months later. A χ(2) test assessed whether parents who disagreed that thirdhand smoke is harmful were more likely to make a quit attempt if they later believed that thirdhand smoke is harmful.

RESULTS

Belief at the exit survey that thirdhand smoke is harmful was independently associated with having a strictly enforced smoke-free home policy (adjusted odds ratio: 2.05; 95% CI: 1.37-3.05) and car policy (adjusted odds ratio: 1.69; 95% CI: 1.04-2.74) at the 12-month follow-up. A significantly higher percentage (71% vs 50%) of parents who did not hold the thirdhand smoke harm belief at baseline made at least 1 quit attempt if they agreed that thirdhand smoke is harmful at the 12-month follow-up (P = .02).

CONCLUSIONS

Thirdhand smoke harm belief was associated with a strictly enforced smoke-free home and car and attempts to quit smoking. Sensitizing parents to thirdhand smoke risk could facilitate beneficial tobacco control outcomes.

NEIL2 protects against oxidative DNA damage induced by sidestream smoke in human cells

Secondhand smoke (SHS) is a confirmed lung carcinogen that introduces thousands of toxic chemicals into the lungs. SHS contains chemicals that have been implicated in causing oxidative DNA damage in the airway epithelium. Although DNA repair is considered a key defensive mechanism against various environmental attacks, such as cigarette smoking, the associations of individual repair enzymes with susceptibility to lung cancer are largely unknown. This study investigated the role of NEIL2, a DNA glycosylase excising oxidative base lesions, in human lung cells treated with sidestream smoke (SSS), the main component of SHS. To do so, we generated NEIL2 knockdown cells using siRNA-technology and exposed them to SSS-laden medium. Representative SSS chemical compounds in the medium were analyzed by mass spectrometry. An increased production of reactive oxygen species (ROS) in SSS-exposed cells was detected through the fluorescent detection and the induction of HIF-1α. The long amplicon–quantitative PCR (LA-QPCR) assay detected significant dose-dependent increases of oxidative DNA damage in the HPRT gene of cultured human pulmonary fibroblasts (hPF) and BEAS-2B epithelial cells exposed to SSS for 24 h. These data suggest that SSS exposure increased oxidative stress, which could contribute to SSS-mediated toxicity. siRNA knockdown of NEIL2 in hPF and HEK 293 cells exposed to SSS for 24 h resulted in significantly more oxidative DNA damage in HPRT and POLB than in cells with control siRNA. Taken together, our data strongly suggest that decreased repair of oxidative DNA base lesions due to an impaired NEIL2 expression in non-smokers exposed to SSS would lead to accumulation of mutations in genomic DNA of lung cells over time, thus contributing to the onset of SSS-induced lung cancer.

Effects of tobacco smoke exposure in childhood on atopic diseases

Although the smoking prevalence in the United States continues to decline since the Surgeon General's first report in 1964, certain vulnerable populations continue to be disproportionately affected by the adverse consequences of tobacco smoke exposure. Children are particularly vulnerable to exposure and are likely to suffer from both short- and long-term adverse consequences after early life tobacco smoke exposure. An overwhelming amount of evidence supports an association between asthma development and tobacco smoke exposure, and evidence is mounting that tobacco smoke exposure may also increase risk of IgE sensitization. This manuscript will review the effects of tobacco smoke exposure in childhood on the development of asthma and allergic sensitization, and will review practical strategies to assist motivated parents with smoking cessation.

Cigarette smoke toxins deposited on surfaces: implications for human health

Cigarette smoking remains a significant health threat for smokers and nonsmokers alike. Secondhand smoke (SHS) is intrinsically more toxic than directly inhaled smoke. Recently, a new threat has been discovered - Thirdhand smoke (THS) - the accumulation of SHS on surfaces that ages with time, becoming progressively more toxic. THS is a potential health threat to children, spouses of smokers and workers in environments where smoking is or has been allowed. The goal of this study is to investigate the effects of THS on liver, lung, skin healing, and behavior, using an animal model exposed to THS under conditions that mimic exposure of humans. THS-exposed mice show alterations in multiple organ systems and excrete levels of NNAL (a tobacco-specific carcinogen biomarker) similar to those found in children exposed to SHS (and consequently to THS). In liver, THS leads to increased lipid levels and non-alcoholic fatty liver disease, a precursor to cirrhosis and cancer and a potential contributor to cardiovascular disease. In lung, THS stimulates excess collagen production and high levels of inflammatory cytokines, suggesting propensity for fibrosis with implications for inflammation-induced diseases such as chronic obstructive pulmonary disease and asthma. In wounded skin, healing in THS-exposed mice has many characteristics of the poor healing of surgical incisions observed in human smokers. Lastly, behavioral tests show that THS-exposed mice become hyperactive. The latter data, combined with emerging associated behavioral problems in children exposed to SHS/THS, suggest that, with prolonged exposure, they may be at significant risk for developing more severe neurological disorders. These results provide a basis for studies on the toxic effects of THS in humans and inform potential regulatory policies to prevent involuntary exposure to THS.

Nicotelline: a proposed biomarker and environmental tracer for particulate matter derived from tobacco smoke

Particulate matter (PM) derived from tobacco smoke contains numerous toxic substances. Since the PM and gas phase of tobacco smoke may distribute differently in the environment and substances in them may have different human bioavailability, multiple tracers and biomarkers for tobacco smoke constituents are desirable. Nicotelline is a relatively nonvolatile alkaloid present in tobacco smoke, and therefore, it has the potential to be a suitable tracer and biomarker for tobacco smoke-derived PM. We describe experiments demonstrating that nicotelline is present almost entirely in the PM, in both freshly generated cigarette smoke and aged cigarette smoke. An excellent correlation between the mass of nicotelline and the mass of the PM in aged cigarette smoke was found. We also describe experiments suggesting that the main source of nicotelline in tobacco smoke is dehydrogenation of another little-studied tobacco alkaloid, anatalline, during the burning process. We show that nicotelline metabolites can be measured in the urine of smokers and that nicotelline can be measured in house dust from homes of smokers and nonsmokers. We conclude that nicotelline should be useful as a tracer and biomarker for PM derived from tobacco smoke.

Strict smoke-free home policies among smoking parents in pediatric settings

OBJECTIVE

To examine strict smoke-free home policies among smoking parents assessed in pediatric offices.

METHODS

We analyzed baseline parental survey data from 10 control practices in a national trial of pediatric office-based tobacco control interventions (Clinical Effort Against Secondhand Smoke Exposure, CEASE). We used logistic regression models with generalized estimating equations to examine factors associated with strict smoke-free home policies.

RESULTS

Subjects were 952 parents who were current smokers. Just over half (54.3%) reported strict smoke-free home policies. Few reported being asked (19.9%) or advised (17.1%) regarding policies by pediatricians. Factors associated with higher odds of policies were child 5 years or younger (adjusted odds ratio [aOR] 2.43, 95% confidence interval [CI] 1.53, 3.86), nonblack race/ethnicity (aORs 2.17-2.60, 95% CIs 1.25-5.00), non-Medicaid (HMO/private (aOR 1.84, 95% CI 1.31, 2.58); self-pay/other aOR 1.76, 95% CI 1.12, 2.78); well-child versus sick child visit (aOR 1.61, 95% CI 1.11, 2.34), fewer than 10 cigarettes per day (aOR 1.80, 95% CI 1.31, 2.47), no other home smokers (aOR 1.68, 95% CI 1.26, 2.25), only father smoking (aOR 1.73, 95% CI 1.06, 2.83), and strict smoke-free car policy (aOR 3.51, 95% CI 2.19, 5.64).

CONCLUSIONS

Nearly half of smoking parents did not have strict smoke-free home policies. Parents were less likely to report policies if they were heavier smokers, black, living with other smokers, or attending a sick child visit; if they did not have a young child or smoke-free car policy; if they had a child on Medicaid; and if anyone other than only the father smoked. Few pediatricians addressed or recommended strict smoke-free home policies in an office visit. The pediatric office encounter represents a currently missed opportunity to intervene regarding smoke-free homes, particularly for high-risk groups.