Comparative carcinogenicity of cigarette mainstream and sidestream smoke condensates on the mouse skin

Trends in tracheal, bronchial and lung cancer attributed to smoking in South America: Global Burden of Disease analysis 1990-2019

Objective

To investigate the burden of tracheal, bronchus, and lung (TBL) cancer due to tobacco exposure in the last 30 years in 12 South American countries.

Methods

We used the Global Burden of Disease (GBD) 2019 exposure-response function to analyze the total tobacco, smoking, and secondhand smoke exposure-related TBL cancer deaths and disability-adjusted life years (DALYs), for 12 South American countries, between 1990 and 2019. Metrics were described as absolute numbers or rates per 100 000 individuals. The relative change in burden was assessed by comparing the 1990-1994 to 2015-2019 periods.

Results

In 2019, the all-ages number of TBL cancer deaths and DALYs associated with tobacco exposure in South America was 29 348 and 658 204 in males and 14 106 and 318 277 in females, respectively. Age-adjusted death and DALYs rates for the region in 2019 were 182.8 and 4035 in males and 50.8 and 1162 in females, respectively. In males, 10/12 countries observed relative declines in TBL death rates attributed to tobacco exposure while only 4 countries reduced their mortality in females.

Conclusion

While significant efforts on tobacco control are under place in South America, substantial burden of TBL cancer persists in the region with significant sex-specific disparities. Increased country-specific primary data on TBL cancer and tobacco exposure is needed to optimize healthcare strategies and improve comprehension of regional trends.

Development and application of the Ames test using a direct-exposure module: The assessment of mutagenicity of incense and sidestream cigarette smoke

We had previously developed an improved Ames module to directly determine the mutagenicity of gaseous formaldehyde (HCHO) and toluene without liquid extraction. This study further evaluated the suitability and sensitivity of this module on whole and real polluted air samples. For this, two common brands of stick incense (A and B) and cigarettes (A and B) were harvested, and various types of incense smoke (IS) and sidestream cigarette smoke (SCS) samples were generated by lighting 3, 6, 12, 24, 30, or 36 incense sticks, and by lighting 1, 2, or 3 cigarettes, respectively, in an acrylic box. CO₂ , CO, total volatile organic compound (TVOC), PM_1.0, and HCHO concentrations in the air samples were determined, and all air samples did not partially fit the requirements of the air quality standards. The smoke samples were then directly exposed to TA100 for 10, 20, 30, or 60 min in our exposure module. Exposure to IS (brand A) for 30 to 60 min and exposure to IS (brand B) for 60 min led to statistically (p < 0.05) weak (below the twofold rule) but dose-dependent mutagenic activities either with or without metabolic activation. Furthermore, a short-term exposure (10-60 min) to SCS (brands A and B) displayed statistically significant (p < 0.05) direct-acting, indirect-acting, time- and dose-dependent mutagenic activities. Furthermore, our data also support that the liver S9 enzyme could enhance the mutagenic activities in most IS and SCS samples. This study confirmed that the modified Ames module can be applied to directly detect the mutagenic activities of real polluted air samples.

Association between secondhand smoke and cancers in adults in the US population

BACKGROUND

Tobacco use is the leading preventable cause of cancer and premature death, smoking has a clear causal relationship with a variety of cancers. However, the relationship between exposure to secondhand smoke (SHS) and other cancers besides lung cancer is not clear. In this study, we intend to investigate the cancers mortality risks especially other cancers besides lung cancer associated with exposure to SHS.

METHODS

The National Health and Nutrition Examination Survey is a longitudinal population-based, nationally representative health survey and mortality rates linked to the National Death Index (NDI) database. In this study, the participants completed a questionnaire assessing sociodemographic data, anthropometry, and lifestyle information, including smoking and alcohol consumption, meanwhile, all the participants were screened for serum cotinine. First, Spearman correlation analysis was performed to confirm the correlation between serum cotinine level and exposure status. And then, exposure to SHS was divided into two groups: low exposure group (serum cotinine level between 0.015 and 10) and high exposure group (serum cotinine level ≥ 10), Cox proportional hazards regression modeling was used to evaluate the association between exposure to SHS and eight different types of smoke-related cancer.

RESULTS

In this study, we evaluated a cohort of 25,794 US residents older than 19 years from 2005 to 2016 and were followed for mortality through the February 2019. We conducted Spearman correlation analysis to confirm the correlation between serum cotinine level and exposure status (including smoking and exposure to SHS), it demonstrated the correlation coefficient between serum cotinine level and exposure to smoke was 0.976, p < 0.00001. By Cox proportional hazards regression modeling, high exposure group were found to be positively associated with all neoplasms with a total Hazard Ratio (HR) of 1.748 (95% Confidence Interval (CI), 1.415-2.159), had higher all-cause mortality risks than non-exposure to tobacco smoke. Regarding the specific types, we found the following associations: cancer of the lung (HR, 1.484; 95% CI, 1.191-1.849), stomach (HR, 1.491; 95% CI, 1.199-1.854), bladder (HR, 1.487; 95% CI, 1.198,1.846), esophageal (HR, 1.487; 95% CI 1.194-1.852), kidney (HR, 1.497; 95% CI, 1.201-1.865), pancreatic (HR, 1.479; 95% CI 1.189-1.841), leukemia (HR, 1.479; 95% CI 1.190-1.839), cervical (HR, 1.490; 95% CI 1.198-1.853). However, low exposure group were non-existent statistically significant with a Hazard Ratio (HR) of 1.062 (95% Confidence Interval (CI), 0.953-1.183).

CONCLUSIONS

The research demonstrated that serum cotinine has a significant correlation with smoke exposure status, which confirmed serum cotinine can be used as an indicator to reflect human smoke exposure. What's more, our results confirmed high exposure of SHS (serum cotinine level ≥ 10) has a significant effect on lung, stomach, bladder, esophagus, kidney, pancreatic, leukemia, cervical cancer.

Implications of the Immune Landscape in COPD and Lung Cancer: Smoking Versus Other Causes

Cigarette smoking is reported in about one third of adults worldwide. A strong relationship between cigarette smoke exposure and chronic obstructive pulmonary disease (COPD) as well as lung cancer has been proven. However, about 15% of lung cancer cases, and between one fourth and one third of COPD cases, occur in never-smokers. The effects of cigarette smoke on the innate as well as the adaptive immune system have been widely investigated. It is assumed that certain immunologic features contribute to lung cancer and COPD development in the absence of smoking as the major risk factor. In this article, we review different immunological aspects of lung cancer and COPD with a special focus on non-smoking related risk factors.

DNA damage, DNA repair and carcinogenicity: Tobacco smoke versus electronic cigarette aerosol

The allure of tobacco smoking is linked to the instant gratification provided by inhaled nicotine. Unfortunately, tobacco curing and burning generates many mutagens including more than 70 carcinogens. There are two types of mutagens and carcinogens in tobacco smoke (TS): direct DNA damaging carcinogens and procarcinogens, which require metabolic activation to become DNA damaging. Recent studies provide three new insights on TS-induced DNA damage. First, two major types of TS DNA damage are induced by direct carcinogen aldehydes, cyclic-1,N2-hydroxy-deoxyguanosine (γ-OH-PdG) and α-methyl-1, N2-γ-OH-PdG, rather than by the procarcinogens, polycyclic aromatic hydrocarbons and aromatic amines. Second, TS reduces DNA repair proteins and activity levels. TS aldehydes also prevent procarcinogen activation. Based on these findings, we propose that aldehydes are major sources of TS induce DNA damage and a driving force for carcinogenesis. E-cigarettes (E-cigs) are designed to deliver nicotine in an aerosol state, without burning tobacco. E-cigarette aerosols (ECAs) contain nicotine, propylene glycol and vegetable glycerin. ECAs induce O6-methyl-deoxyguanosines (O6-medG) and cyclic γ-hydroxy-1,N2--propano-dG (γ-OH-PdG) in mouse lung, heart and bladder tissues and causes a reduction of DNA repair proteins and activity in lungs. Nicotine and nicotine-derived nitrosamine ketone (NNK) induce the same types of DNA adducts and cause DNA repair inhibition in human cells. After long-term exposure, ECAs induce lung adenocarcinoma and bladder urothelial hyperplasia in mice. We propose that E-cig nicotine can be nitrosated in mouse and human cells becoming nitrosamines, thereby causing two carcinogenic effects, induction of DNA damage and inhibition of DNA repair, and that ECA is carcinogenic in mice. Thus, this article reviews the newest literature on DNA adducts and DNA repair inhibition induced by nicotine and ECAs in mice and cultured human cells, and provides insights into ECA carcinogenicity in mice.

Exposure to Secondhand Smoke and Risk of Cancer in Never Smokers: A Meta-Analysis of Epidemiologic Studies

This is first meta-analysis to evaluate cancer risk associated with secondhand smoking across all cancers. A literature search was conducted for articles published before June 2014 on Pubmed, SCOPUS, Cochrane library, and CINAHL, and 40 articles on secondhand smoke and the prevalence of cancer among never smokers were selected for final analysis as per the inclusion criteria. Of the 40 articles, 27 were case-control studies and 13 were prospective cohort studies. With respect to overall cancer risk, odds ratio (OR) involving never smokers with significant exposure to secondhand smoke compared to never smokers without such exposure was 1.163 (95%CI 1.058–1.279). Subgroup meta-analyses by study design showed significant positive associations for both case-control studies and prospective cohort studies (OR 1.165, 95%CI 1.029–1.320; and OR 1.160, 95%CI 1.002–1.343, respectively). The association was stronger in the case of females (OR 1.253, 95%CI 1.142–1.374), lung cancer (OR 1.245, 95%CI 1.026–1.511), and breast cancer (OR 1.235, 95%CI 1.102–1.385). Secondhand smoking may increase the overall risk of cancer for never smokers, particularly lung and breast cancer, and especially in women. Strict implementation of smoking cessation programs should be encouraged, not only to reduce active smoking but also to limit exposure to secondhand smoke.

Never-Smoking Adolescents' Exposure to Secondhand Smoke in Africa

INTRODUCTION

Though Africa is in Stage 1 of the tobacco epidemic, lack of effective public smoking laws or political will implies that secondhand smoke (SHS) exposure may be high in youth. The study objective is to estimate prevalence and identify determinants of SHS exposure among never-smoker adolescents in Africa and make cross-country comparisons.

METHODS

Pooled data from the Global Youth Tobacco Surveys conducted in 25 African countries during 2006-2011 were used. Based on the venue of exposure in past 7 days, SHS was categorized into exposure inside, outside, and overall exposure (either inside or outside of the home), respectively. Data were analyzed in 2015 using logistic regression models to identify factors related to SHS exposure in three venues.

RESULTS

About 21% and 39% of adolescents were exposed to SHS inside or outside of the home, with overall exposure of 45%. In all 25 African countries, parental smoking was significantly associated with SHS exposure inside the home (ORs ranging from 3.02 [95% CI=2.0, 4.5] to 14.65 [95% CI=10.0, 21.5]). Peer smoking was associated with SHS exposure outside the home in 18 countries (ORs ranging from 1.45 [95% CI=1.0, 2.1] to 3.00 [95% CI=1.8, 5.1]). Parental smoking, peer smoking, and anti-smoking messages in media were identified as three major factors associated with SHS exposure.

CONCLUSIONS

A significant proportion of never-smoking adolescents in Africa are exposed to SHS, suggesting the need for countries to adopt policies to protect never smokers through the implementation of the WHO Framework Convention on Tobacco Control.

Association between Second-Hand Smoking and Laryngopathy in the General Population of South Korea

Purpose

The relationship between second-hand smoking and laryngopathy has not yet been reported. Thus, this study investigates the relationship between second-hand smoking and laryngopathy and suggests basic empirical data to prevent laryngopathy.

Methods

This study analyzed 1,905 non-smokers over the age of 19 (269 men and 1,636 women) who completed the health questionnaire, laryngeal endoscope test, and urine cotinine test in the 2008 Korea National Health and Nutrition Examination Survey (KNHANES). Second-hand smoking was defined as a urine cotinine concentration of 50ng/ml and over. Confounding factors included age, gender, education, household income, occupation, alcohol consumption, and coffee consumption. Risk ratios (RR) and 95% confidence intervals (CI) were presented for the relationship between second-hand smoking and laryngopathy by using Poisson regression analysis.

Results

There was a significant relationship between second-hand smoking and laryngopathy (p<0.05). After all compounding factors were adjusted, non-smokers exposed to second-hand smoking had a 2.5 times (RR = 2.47, 95% CI: 1.19–5.08) significantly higher risk of laryngopathy than non-smokers not exposed to second-hand smoking (p<0.05).

Conclusion

In this epidemiological study, there was a significant relationship between second-hand smoking and laryngopathy. More effective anti-smoking policies are required to protect the health of both non-smokers and smokers.

Secondhand Smoking and the Risk of Esophageal Squamous Cell Carcinoma in a High Incidence Region, Kashmir, India: A Case-control-observational Study

Studies have associated secondhand smoking (SHS) with cancers of the lung, larynx, and pharynx. Only a few studies have examined the association between SHS and esophageal squamous cell carcinoma (ESCC) and the findings are inconclusive. We aimed to investigate the association between SHS and risk of ESCC in a case-control study in Kashmir, where the incidence of ESCC is high. We recruited 703 histopathologically confirmed ESCC cases and 1664 hospital-based controls individually matched to the cases for age, sex, and district of residence. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated using conditional logistic regression models. Among never-tobacco users, the ORs for the association between SHS and ESCC risk were above unity with ever exposure to SHS (OR = 1.32; 95% CI, 0.43-4.02) and exposure to SHS for > 14 h/wk (median value) (OR = 2.69; 95% CI, 0.75-20.65). In the analysis of data from all participants, the OR (95% CI) for the association between SHS and ESCC was (OR = 1.02; 95% CI, 0.53-1.93) for SHS ≤ 14 h/wk and (OR = 1.91; 95% CI, 0.75-4.89) for SHS >14 h/wk in the models adjusted for tobacco use and several other potential confounding factors. We found an indication of increased risk of ESCC associated with exposure to SHS. Studies with larger numbers of SHS-exposed never tobacco users are required to further examine this association.

Secondhand smoke exposure-induced nucleocytoplasmic shuttling of HMGB1 in a rat premature skin aging model

Secondhand cigarette smoke exposure (SSE) has been linked to carcinogenic, oxidative, and inflammatory reactions. Herein, we investigated whether premature skin aging could be induced by SSE in a rat model, and assessed the cytoplasmic translocation of high mobility group box 1 (HMGB1) protein and collagen loss in skin tissues. Animals were divided into two groups: SSE and controls. Whole body SSE was carried out for 12 weeks. Dorsal skin tissue specimens were harvested for HMGB1 and Mallory's azan staining. Correlations between serum HMGB1 and collagen levels were determined. Rat skin exposed to secondhand smoke lost collagen bundles in the papillary dermis and collagen decreased significantly (p<0.05) compared with control rats. In epidermal keratinocytes, cytoplasmic HMGB1 staining was more diffuse and there were more HMGB1-positive cells after four weeks in SSE compared to control rats. A negative correlation between HMGB1 serum and collagen levels (r=-0.631, p=0.28) was also observed. Therefore, cytoplasmic HMGB1 expression in skin tissues might be associated with skin collagen loss upon the initiation of SSE. Additionally, long-term SSE might affect the appearance of the skin, or could accelerate the skin aging process.

Household ventilation may reduce effects of indoor air pollutants for prevention of lung cancer: a case-control study in a Chinese population

Background

Although the International Agency for Research on Cancer (IARC) has classified various indoor air pollutants as carcinogenic to humans, few studies evaluated the role of household ventilation in reducing the impact of indoor air pollutants on lung cancer risk.

Objectives

To explore the association between household ventilation and lung cancer.

Methods

A population-based case-control study was conducted in a Chinese population from 2003 to 2010. Epidemiologic and household ventilation data were collected using a standardized questionnaire. Unconditional logistic regression was employed to estimate adjusted odds ratios (OR_adj) and their 95% confidence intervals (CI).

Results

Among 1,424 lung cancer cases and 4,543 healthy controls, inverse associations were observed for good ventilation in the kitchen (OR_adj = 0.86, 95% CI: 0.75, 0.98), bedroom (OR_adj = 0.90, 95% CI: 0.79, 1.03), and both kitchen and bedroom (OR_adj = 0.87, 95% CI: 0.75, 1.00). Stratified analyses showed lung cancer inversely associated with good ventilation among active smokers (OR_adj = 0.85, 95% CI: 0.72, 1.00), secondhand smokers at home (OR_adj = 0.77, 95% CI: 0.63, 0.94), and those exposed to high-temperature cooking oil fumes (OR_adj = 0.82, 95% CI: 0.68, 0.99). Additive interactions were found between household ventilation and secondhand smoke at home as well as number of household pollutant sources.

Conclusions

A protective association was observed between good ventilation of households and lung cancer, most likely through the reduction of exposure to indoor air pollutants, indicating ventilation may serve as one of the preventive measures for lung cancer, in addition to tobacco cessation.

Meta-analysis of the association between secondhand smoke exposure and physician-diagnosed childhood asthma

INTRODUCTION

Studies suggest an association between secondhand smoke exposure and the development of childhood asthma. Several countries are considering legislation to protect children from exposure.

METHODS

A systematic review was conducted using MEDLINE, Embase, PubMed, and Web of Knowledge databases and a random effects meta-analysis was undertaken. Heterogeneity was assessed using the I (2) test. Publication and small study biases were examined visually using a funnel plot and tested formally using Egger test. Univariate and multivariate meta-regression analyses were undertaken, including a subgroup analysis of cohort studies to examine the effect of duration of follow-up.

RESULTS

Twenty relevant studies were identified (14 cross-sectional, 4 cohort, and 2 case-control) and provided 31 estimates of effect size. The pooled odds ratio was 1.32 (95% CI: 1.23, 1.42, p < .001). There was moderate heterogeneity (I (2) = 74.2%, p < .001). On multivariate meta-regression analysis, effect size estimates were significantly higher for case-control studies (p = .042) and those using self-reported exposure to secondhand smoke (p = .050). There was no evidence of significant publication or small study bias (Egger test, p = .121).

CONCLUSIONS

There is now consistent evidence of a modest association between secondhand smoke and physician-diagnosed childhood asthma. These results lend support to continued efforts to reduce childhood exposure to secondhand smoke.

Passive smoking and cervical cancer risk: a meta-analysis based on 3,230 cases and 2,982 controls

OBJECTIVE

Passive smoking has been considered as a risk factor of many cancers. To examine whether it might also pose a risk for cervical cancer, we performed a meta-analysis based on published case-control studies.

METHODS

We searched the PubMed database and references of included studies up to February 10th, 2012 for relevant studies. After two authors independently assessed the methodological quality and extracted data, a meta-analysis was conducted using CMA v2 software. Publication bias was evaluated by funnel plot, using Egger's and Begg's tests.

RESULTS

Finally 11 eligible studies yielded, involving 3,230 cases and 2,982 controls. The results showed that women who never smoke but exposed to smoking experience a 73% increase in risk of cervical cancer compared with non-exposed women (OR = 1.73, 95% CI = 1.35 - 2.21, p<0.001). Subgroup and sensitivity analyses indicated this result to be robust. Moderate publication bias was detected by visualing funnel plot, Egger's and Begg's tests.

CONCLUSION

Based on currently available evidence, the findings of this meta-analysis suggests that passive smoking significantly and independently increases the risk of cervical cancer.

Indoor air pollution and risk of lung cancer among Chinese female non-smokers

PURPOSE

To investigate indoor particulate matter (PM) level and various indoor air pollution exposure, and to examine their relationships with risk of lung cancer in an urban Chinese population, with a focus on non-smoking women.

METHODS

We conducted a case-control study in Taiyuan, China, consisting of 399 lung cancer cases and 466 controls, of which 164 cases and 218 controls were female non-smokers. Indoor PM concentrations, including PM(1), PM(2.5), PM(7), PM(10), and TSP, were measured using a particle mass monitor. Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95 % confidence intervals after adjusting for age, education, annual income, and smoking.

RESULTS

Among non-smoking women, lung cancer was strongly associated with multiple sources of indoor air pollution 10 years ago, including heavy exposure to environmental tobacco smoke at work (aOR = 3.65), high frequency of cooking (aOR = 3.30), and solid fuel usage for cooking (aOR = 4.08) and heating (aOR(coal stove) = 2.00). Housing characteristics related to poor ventilation, including single-story, less window area, no separate kitchen, no ventilator, and rarely having windows open, are associated with lung cancer. Indoor medium PM(2.5) concentration was 68 μg/m(3), and PM(10) was 230 μg/m(3). PM levels in winter are strongly correlated with solid fuel usage for cooking, heating, and ventilators. PM(1) levels in cases are more than 3 times higher than that in controls. Every 10 μg/m(3) increase in PM(1) is associated with 45 % increased risk of lung cancer.

CONCLUSIONS

Indoor air pollution plays an important role in the development of lung cancer among non-smoking Chinese women.

Biological evidence for the acute health effects of secondhand smoke exposure

A vast number of studies on the unfavorable effects of secondhand smoke (SHS) exist within the international literature, the majority of which evaluate longitudinal epidemiological data. Although limited, the experimental studies that assess the acute and short-term effects of exposure to SHS are also increasing in number. They include cellular, animal, and human studies that indicate a number of pathophysiological mechanisms through which the deleterious effects of SHS may arise. This current review evaluates the existing biological evidence regarding the acute health effects of SHS exposure. Analyses on the inhaled toxicants and the carcinogenicity of SHS are included as well as in-depth discussions on the evidence for acute SHS-induced respiratory, cardiovascular, metabolic, endocrine and immune effects, and SHS-induced influences on oxygen delivery and exercise. The influence of the length of exposure and the duration of the observed effects is also described. Moreover, recent findings regarding the underlying pathophysiological mechanisms related to SHS are depicted so as to generate models that describe the SHS-induced effects on different systems within the human body. Based on the presented biological evidence, it is concluded that brief, acute, transient exposures to SHS may cause significant adverse effects on several systems of the human body and represent a significant and acute health hazard. Future research directions in this area include research on the concentrations of tobacco smoke constituents in the alveolar milieu following SHS exposure, individual susceptibility to SHS, as well as the effects of SHS on neurobehavioral activity, brain cell development, synaptic development, and function.

Assessment of "gene-environment" interaction in cases of familial and sporadic pancreatic cancer

INTRODUCTION

Pancreatic cancer (PC) is the fourth leading cause of cancer death in the United States. This study characterizes one of the largest national registries of familial PC (FPC) and sporadic PC (SPC), focusing on demographics, clinical factors, self-reported environmental and occupational lifetime exposures, and survival status.

BACKGROUND

Reported risk factors for PC include advancing age, a family history of PC, high-risk inherited syndromes, cigarette, cigar, and pipe smoking, exposure to occupational and environmental carcinogens, African-American race, high fat/high cholesterol diet, obesity, chronic pancreatitis, and diabetes mellitus.

PATIENTS AND METHODS

This retrospective cross-sectional, case-only analysis includes cases of FPC (n = 569) and SPC (n = 689) from the Johns Hopkins National Familial Pancreas Tumor Registry (NFPTR) enrolled between 1994 and 2005.

RESULTS

FPC smokers with environmental tobacco smoke (ETS) exposure were diagnosed at a significantly younger mean age (63.7 years) as compared to FPC non-smokers without ETS exposure (66.6 years; p = 0.05). Non-smoker ETS-exposed cases were diagnosed with PC at a significantly younger mean age (64.0 years) compared to non-smoker non-ETS-exposed cases (66.5 years) (p < 0.0004). The mean age at diagnosis for Ashkenazi Jewish SPC subjects was significantly younger (by 2.1 years) than Ashkenazi Jewish FPC cases (p = 0.05). In addition, Ashkenazi Jewish FPC subjects who smoked were diagnosed 5.9 years earlier than Ashkenazi Jewish FPC non-smokers (p = 0.05). The median length of survival for unresected FPC cases was significantly shorter (168 days) as compared to unresected SPC cases (200 days) (p = 0.04). Survival was improved in resected cases, 713 days for FPC cases and 727 days for SPC cases, but was not significantly different between the groups (p = 0.4). Mild to moderate multiplicative interaction was found between a family history of PC and exposure to asbestos, environmental radon, and environmental tobacco smoke (ETS), as evidenced by odds ratios >1.0.

CONCLUSIONS

These are the first data to show that occupational and environmental exposures may act synergistically with inherited or acquired genetic polymorphisms, resulting in earlier occurrence of PC. Exposure to cigarette smoking and ETS exposure in non-smokers when younger than 21 years of age are associated with a younger mean age of diagnosis in FPC and SPC cases and Ashkenazi Jewish smokers, when compared to non-exposed cases. Risk prediction models which take into account environmental exposures as well as family history may more accurately predict the risk of PC. High-risk individuals will likely benefit from early identification of pre-malignant lesions and molecular profiling, as methods of early detection, prevention, and personalized therapy.

Differential sensitivity of male germ cells to mainstream and sidestream tobacco smoke in the mouse

Cigarette smoking in men has been associated with increased chromosomal abnormalities in sperm and with increased risks for spontaneous abortions, birth defects and neonatal death. Little is known, however, about the reproductive consequences of paternal exposure to second-hand smoke. We used a mouse model to investigate the effects of paternal exposure to sidestream (SS) smoke, the main constituent of second-hand smoke, on the genetic integrity and function of sperm, and to determine whether male germ cells were equally sensitive to mainstream (MS) and SS smoke. A series of sperm DNA quality and reproductive endpoints were investigated after exposing male mice for two weeks to MS or SS smoke. Our results indicated that: (i) only SS smoke significantly affected sperm motility; (ii) only MS smoke induced DNA strand breaks in sperm; (iii) both MS and SS smoke increased sperm chromatin structure abnormalities; and (iv) MS smoke affected both fertilization and the rate of early embryonic development, while SS smoke affected fertilization only. These results show that MS and SS smoke have differential effects on the genetic integrity and function of sperm and provide further evidence that male exposure to second-hand smoke, as well as direct cigarette smoke, may diminish a couple's chance for a successful pregnancy and the birth of a healthy baby.

Maternal exposure to tobacco smoke, alcohol and caffeine, and risk of anorectal atresia: National Birth Defects Prevention Study 1997-2003

.Anorectal atresia is a congenital anomaly with mostly unknown risk factors. Studies have provided evidence of teratogenic effects of alcohol and tobacco, and animal studies have suggested that caffeine may potentiate their teratogenicity. However, it is unclear how these factors affect the risk of anorectal atresia. We analysed data from maternal telephone interviews in a multistate case-control study with 464 infants with anorectal atresia and 4940 infants with no major birth defects. We used unconditional logistic regression to determine the association of exposure to smoking, environmental tobacco smoke (ETS), alcohol or caffeine with anorectal atresia. Effect modification by caffeine intake was assessed on additive and multiplicative scales. There was no association with alcohol intake in this analysis. However, there was some evidence of an association between anorectal atresia and maternal exposure to tobacco smoke and caffeine. Compared with non-smokers not exposed to ETS, the crude odds ratio (OR) and 95% confidence interval [CI] for cigarette smoking was 1.2 [95% CI 1.0, 1.5]. The association with anorectal atresia for non-smokers exposed to ETS at home and work was OR = 2.3 [95% CI 1.2, 4.1]. Compared with the lowest level of caffeine intake (<10 mg/day), the association for the highest caffeine intake (> or =300 mg/day) was OR = 1.5 [95% CI 1.0, 2.2]. Results did not change after adjustment for covariates. This study found evidence of associations between anorectal atresia and caffeine intake, cigarette smoking and exposure to ETS. Because there are currently few additional data to support these results, further study is needed.

Preneoplastic and neoplastic lesions in the lung, liver and urinary tract of mice exposed to environmental cigarette smoke and UV light since birth

It is difficult to reproduce the carcinogenicity of cigarette smoke (CS) in animal models. Recently, we showed that exposure of mice to mainstream CS (MCS) for 120 days, starting immediately after birth, resulted in an early and potent carcinogenic response. In parallel, we implemented studies evaluating intermediate biomarkers and tumors in mice exposed to environmental CS (ECS). To this purpose, we used 263 newborn CD-1 mice born from 27 dams. The whole-body exposure to ECS for 120 days, starting within 12 hr after birth, resulted in an early appearance of preneoplastic lesions in lung, which however tended to attenuate after discontinuing exposure. When the experiment was stopped, after 330 days, the number of lung adenomas was higher in ECS-exposed mice as compared to sham-exposed mice, but such increase was statistically significant only in mice co-exposed to smoke and halogen light mimicking solar irradiation. Moreover, exposure to ECS produced extensive histopathological changes, mainly parenchymatous degeneration, in liver. The alterations produced in both lung and liver require that exposure to ECS starts immediately after birth, no effect being observed when exposure started 8 days later. In contrast, induction by ECS of alterations in the urinary tract, such as microadenomas and adenomas in renal pelvis and kidney, papillary hyperplasia of urothelium, and urinary bladder papillomas, were unrelated to the exposure time after birth. The results obtained with ECS cannot be directly compared to those previously obtained with MCS, since the latter involved shorter daily exposures to more massive CS doses.

Second-hand smoke and human lung cancer

Since the early 1980s, there has been growing concern about potential health consequences of exposure to second-hand smoke (SHS). Despite SHS being established as a risk factor for lung cancer development, the estimated risk has remained small yet somehow debatable. Human exposure to SHS is complicated because of temporal variabilities in source, composition, and concentration of SHS. The temporality of exposure to SHS is important for human lung carcinogenesis with a latency of many years. To explore the causal effect of SHS in lung carcinogenesis, exposure assessments should estimate chronic exposure to SHS on an individual basis. However, conventional exposure assessment for SHS relies on one-off or short-term measurements of SHS indices. A more reliable approach would be to use biological markers that are specific for SHS exposure and pertinent to lung cancer. This approach requires an understanding of the underlying mechanisms through which SHS could contribute to lung carcinogenesis. This Review is a synopsis of research on SHS and lung cancer, with special focus on hypothetical modes of action of SHS for carcinogenesis, including genotoxic and epigenetic effects.

Meta-analysis of studies of passive smoking and lung cancer: effects of study type and continent

BACKGROUND

To calculate a pooled estimate of relative risk (RR) of lung cancer associated with exposure to passive smoking in never smoking women exposed to smoking spouses. This study is an updated meta-analysis that also assesses the differences between estimated risks according to continent and study type using meta-regression.

METHODS

From a total of 101 primary studies, 55 studies are included in this meta-analysis, of which, 7 are cohort studies, 25 population-based case-control and 23 non-population-based case-control studies. Twenty previously published meta-analyses are also reviewed. Fixed and random effect models and meta-regression are used to obtain pooled estimates of RR and P-value functions are used to demonstrate consistency of results.

RESULTS

The pooled RR for never-smoking women exposed to passive smoking from spouses is 1.27 (95% CI 1.17-1.37). The RR for North America is 1.15 (95% CI 1.03-1.28), Asia, 1.31 (95% CI 1.16-1.48) and Europe, 1.31 (1.24-1.52). Sequential cumulative meta-analysis shows no trend. There is no strong evidence of publication bias.

CONCLUSIONS

The abundance of evidence, consistency of finding across continent and study type, dose-response relationship and biological plausibility, overwhelmingly support the existence of a causal relationship between passive smoking and lung cancer.

Chronic nose-only inhalation study in rats, comparing room-aged sidestream cigarette smoke and diesel engine exhaust

Nose-only exposure of male and female Wistar rats to a surrogate for environmental tobacco smoke, termed room-aged sidestream smoke (RASS), to diesel engine exhaust (DEE), or to filtered, fresh air (sham) was performed 6 hours/day, 7 days/week for 2 years, followed by a 6-month post-exposure period. The particulate concentrations were 3 and 10 mg/m3. Markers of inflammation in bronchoalveolar lavage showed that DEE (but not RASS) produced a dose-related and persistent inflammatory response. Lung weights were increased markedly in the DEE (but not RASS) groups and did not decrease during the 6-month post-exposure period. Bulky lung DNA adducts increased in the RASS groups, but not in the DEE groups. Cell proliferation in the lungs was unaffected by either experimental treatment. Histopathological responses in the RASS groups were minimal and almost completely reversible; lung tumors were similar in number to those seen in the sham-exposed groups. Rats exposed to DEE showed a panoply of dose-related histopathological responses: largely irreversible and in some cases progressive. Malignant and multiple tumors were seen only in the DEE groups; after 30 months, the tumor incidence (predominantly bronchiolo-alveolar adenomas) was 2% in the sham-exposed groups, 5%in the high RASS groups, and 46% in the high DEE groups (sexes combined). Our results suggest that in rats exposed to DEE, but not to RASS, the following series of events occurs: particle deposition in lungs --> lung "overload" --> pulmonary inflammation --> tumorigenesis, without a significant modifying role of cell proliferation or DNA adduct formation.

Philip Morris toxicological experiments with fresh sidestream smoke: more toxic than mainstream smoke

BACKGROUND

Exposure to secondhand smoke causes lung cancer; however, there are little data in the open literature on the in vivo toxicology of fresh sidestream cigarette smoke to guide the debate about smoke-free workplaces and public places.

OBJECTIVE

To investigate the unpublished in vivo research on sidestream cigarette smoke done by Philip Morris Tobacco Company during the 1980s at its Institut für Biologische Forschung (INBIFO).

METHODS

Analysis of internal tobacco industry documents now available at the University of California San Francisco Legacy Tobacco Documents Library and other websites.

RESULTS

Inhaled fresh sidestream cigarette smoke is approximately four times more toxic per gram total particulate matter (TPM) than mainstream cigarette smoke. Sidestream condensate is approximately three times more toxic per gram and two to six times more tumourigenic per gram than mainstream condensate by dermal application. The gas/vapour phase of sidestream smoke is responsible for most of the sensory irritation and respiratory tract epithelium damage. Fresh sidestream smoke inhibits normal weight gain in developing animals. In a 21 day exposure, fresh sidestream smoke can cause damage to the respiratory epithelium at concentrations of 2 microg/l TPM. Damage to the respiratory epithelium increases with longer exposures. The toxicity of whole sidestream smoke is higher than the sum of the toxicities of its major constituents.

CONCLUSION

Fresh sidestream smoke at concentrations commonly encountered indoors is well above a 2 microg/m3 reference concentration (the level at which acute effects are unlikely to occur), calculated from the results of the INBIFO studies, that defines acute toxicity to humans. Smoke-free public places and workplaces are the only practical way to protect the public health from the toxins in sidestream smoke.

The complexities of an apparently simple lung tumor model: The A/J mouse

A simple animal model of tobacco smoke carcinogenesis works as follows: Strain A/J mice are exposed for 5 months to tobacco smoke. They are then given a 4-month recovery period in air before being killed. Lung surface tumors are counted and lung tumor multiplicity (average number of tumors per lung, including non-tumor bearing animals) is calculated. Results obtained in four different laboratories during the past 8 years have consistently shown significant increases in lung tumor multiplicities in tobacco smoke exposed animals. While inhaling to tobacco smoke, strain A mice (but not some other strains) fail to gain weight and immediately after smoke exposure only have about 75% of control weight; however, when removed into air, they regain weight rapidly up to control levels. The counting of surface tumors only may occasionally underestimate total number of lung tumors and thus yield false negatives. At the end of the experiment, the mice are 1-year old and about 80% of the tumors are adenomas, the remainder adenomas with carcinomatous foci or adenocarcinomas. Tobacco smoke does not increase the percentage of adenocarcinomas. Studies with filtered tobacco smoke have suggested that benzo(a)pyrene or tobacco smoke-specific nitrosamines cannot account for lung carcinogenesis in mice; the most likely single agent to cause lung tumors is 1,3-butadiene. A major disadvantage of the assay is its low statistical power. While it is easy to detect a 70-100% decrease in lung tumor multiplicity caused by a chemopreventive agent using group sizes of 20-30 animals, the detection of smaller reductions (20-50%) would require group sizes in the hundreds. From all available evidence it must be concluded that the complex mixture of tobacco smoke, a known human carcinogen, is a rather weak rodent carcinogen.

Analysis of complex mixtures--cigarette smoke

Mainstream cigarette smoke is a complex mixture that is inhaled into the respiratory system. The physical characteristics and chemical composition of mainstream smoke are reviewed and briefly compared with that of sidestream smoke. Special attention is paid to ageing effects and artifact formation during the sampling and testing of cigarette smoke, with specific examples of artifact formation during sampling discussed (nitrogen dioxide, methyl nitrite, etc.). Historically, the generation of cigarette smoke for chemical and biological testing has been based on standard smoke generation procedures that are intended for product comparisons. More recently, emerging global regulations have called for alternative smoke generation methods, with emphasis on results relevant to conditions of product use, e.g., estimates of maximum smoke emissions. Strategies for establishing such alternative smoke generation methods are discussed and the potential effects of alternative smoking conditions on analytical accuracy and precision are addressed. Current regulatory requirements that include Hoffmann analyte analysis (i.e., constituents reported to be associated with the risks of cigarette smoking) are also summarized and the potential effect of alternative smoke generation methods on individual constituent yields considered. Finally, a limited critique of emerging regulation that relates to mainstream cigarette smoke measurements, including a discussion of recent WHO recommendations, is offered.

Induction and modulation of lung tumors: genomic and transcriptional alterations in cigarette smoke-exposed mice

Cigarette smoke plays a major role in the epidemiology of lung cancer, and smoke components have extensively been investigated in carcinogenicity and chemoprevention studies in experimental animals. However, it is much more difficult to reproduce the tumorigenicity of the whole complex mixture in preclinical models. The authors review here some results obtained in their laboratories, dealing with the induction of lung tumors, and genomic and transciptional alterations in smoke-exposed mice. The authors were successful in inducing lung tumors in 4 strains of mice exposed whole-body to environmental cigarette smoke, including Swiss albino, A/J, SKH-1 hairless, and p53 mutant (UL533 x A/J)F1 mice. However, the tumorigenic response was rather weak in all strains. Much more intense were the smoke-induced alterations of a variety of intermediate biomarkers, such as cytogenetic end points in pulmonary alveolar macrophages, bone marrow and peripheral blood erythrocytes; apoptosis, p53 oncoprotein, and proliferating cell nuclear antigen in the bronchial epithelium; bulky DNA adducts, 8-hydroxy-2-deoxyguanosine; multigene expression, and thiobarbituric acid-reactive aldehydes in whole lung and several other organs. Smoke-induced genomic and transcriptional alterations were suitable for evaluating their modulation by chemopreventive agent, as shown in studies using the thiol N-acetylcysteine and the nonsteroidal anti-inflammatory drug sulindac.

Increased respiratory symptoms following surgery in children exposed to environmental tobacco smoke

OBJECTIVE

The aim of this study was to determine if children exposed to environmental tobacco smoke (ETS) via parental smoking (ETS+) developed more respiratory symptoms resulting in longer recovery times following surgical outpatient procedures compared with children of nonsmoking parents (ETS-).

METHODS

One hundred and forty six children (4.9 +/- 3 years) undergoing inguinal hernia repair were prospectively studied. Parental smoking behaviour was determined by survey and urine analysis. Seven respiratory symptoms were evaluated during induction and emergence from anaesthesia and during the recovery room (RR) stay.

RESULTS

Fifty-seven (39%) families admitted a smoking history while 89 (61%) denied it. This strongly correlated with the cotinine/creatinine ratio (Pearson correlation coefficient = 0.76; P = 0.01). ETS exposure was associated with an increased frequency of RR symptoms (ETS+: 56%; ETS-: 31%; P = 0.007).

CONCLUSIONS

In children undergoing general anaesthesia for inguinal hernia repair, ETS exposure was associated with an increased frequency of respiratory symptoms during emergence from anaesthesia and during postoperative recovery.

Modulation of cigarette smoke-related end-points in mutagenesis and carcinogenesis

The epidemic of lung cancer and the increase of other tumours and chronic degenerative diseases associated with tobacco smoking have represented one of the most dramatic catastrophes of the 20th century. The control of this plague is one of the major challenges of preventive medicine for the next decades. The imperative goal is to refrain from smoking. However, chemoprevention by dietary and/or pharmacological agents provides a complementary strategy, which can be targeted not only to current smokers but also to former smokers and passive smokers. This article summarises the results of studies performed in our laboratories during the last 10 years, and provides new data generated in vitro, in experimental animals and in humans. We compared the ability of 63 putative chemopreventive agents to inhibit the bacterial mutagenicity of mainstream cigarette smoke. Modulation by ethanol and the mechanisms involved were also investigated both in vitro and in vivo. Several studies evaluated the effects of dietary chemopreventive agents towards smoke-related intermediate biomarkers in various cells, tissues and organs of rodents. The investigated end-points included metabolic parameters, adducts to haemoglobin, bulky adducts to nuclear DNA, oxidative DNA damage, adducts to mitochondrial DNA, apoptosis, cytogenetic damage in alveolar macrophages, bone marrow and peripheral blood erytrocytes, proliferation markers, and histopathological alterations. The agents tested in vivo included N-acetyl-L-cysteine, 1,2-dithiole-3-thione, oltipraz, phenethyl isothiocyanate, 5,6-benzoflavone, and sulindac. We started applying multigene expression analysis to chemoprevention research, and postulated that an optimal agent should not excessively alter per se the physiological background of gene expression but should be able to attenuate the alterations produced by cigarette smoke or other carcinogens. We are working to develop an animal model for the induction of lung tumours following exposure to cigarette smoke. The most encouraging results were so far obtained in models using A/J mice and Swiss albino mice. The same smoke-related biomarkers used in animal studies can conveniently be applied to human chemoprevention studies. We participated in trials evaluating the effects of N-acetyl-L-cysteine and oltipraz in smokers from Italy, The Netherlands, and the People's Republic of China. We are trying to develop a pharmacogenomic approach, e.g. based on genetic metabolic polymorphisms, aimed at predicting not only the risk of developing cancer but also the individual responsiveness to chemopreventive agents.

Lung tumors in A/J mice exposed to environmental tobacco smoke: estimated potency and implied human risk

Directly inhaled tobacco smoke is a recognized human lung carcinogen, and epidemiological studies suggest relative risks of about 1.2-1.4 for nonsmoking spouses of smokers typically exposed to environmental tobacco smoke (ETS). While many individual ETS components have been shown experimentally to induce lung tumors, ETS itself was only recently shown to induce lung tumors in a series of studies in which strain A/J mice were exposed to well-defined ETS atmospheres. Data from these studies indicate that ETS exposure clearly can increase combined malignant and benign lung tumors in multiple experiments involving male and female A/J mice, and thus provide convincing evidence that ETS is a positive mouse carcinogen. Tumorigenic potencies estimated from these A/J mouse bioassay data predict a corresponding range of increased human risk (0.2-0.5%) that overlaps that implied by case-control studies showing increased lung cancer risks in lifelong nonsmokers married to smokers. In A/J mice exposed to a significantly tumorigenic ETS concentration, lung tumors were found to be significantly smaller than those in corresponding control mice, and mice so exposed for 9 months had significantly fewer tumors/animal than mice exposed for 5 months followed by 4 months in filtered ETS-free air. These findings support hypotheses that ETS does not promote growth of spontaneous neoplastic foci in A/J mice, and that ETS-induced lung-tumor risk in A/J mice occurs predominantly by genotoxic effects that can be suppressed by reduced cell proliferation associated with chronic, high-level ETS exposure. The results obtained add to evidence that A/J mouse lung tumors induced by ETS provide a relevant biological model of ETS-induced human lung tumors.

Synergistic mechanisms in carcinogenesis by polycyclic aromatic hydrocarbons and by tobacco smoke: a bio-historical perspective with updates

B[a]P (benzo[a]pyrene) has been used as a prototype carcinogenic PAH since its isolation from coal tar in the 1930's. One of its diol epoxides, BPDE-2, is considered its ultimate carcinogen on the basis of its binding to DNA, mutagenicity and extreme pulmonary carcinogenicity in newborn mice. However, BPDE-1 has a similar binding to DNA and mutagenicity but it is not carcinogenic. In addition, BPDE-2 is a weak carcinogen relative to B[a]P when repeatedly applied to mouse skin, the conventional assay site. Its carcinogenicity is increased when applied once as an initiator followed repeatedly by a promoter. This indicates a major role for promotion in carcinogenesis by PAHs. Promotion itself is a 2-stage process, the second of which is selective propagation of the initiated cells. Persistent hyperplasia underlies selection by promoters. The non-carcinogenicity of BPDE-1 has yet to be resolved. PAHs have long been considered the main carcinogens of cigarette smoke but their concentration in the condensate is far too low to account by themselves for the production of skin tumors. The phenolic fraction does however have strong promotional activity when repeatedly applied to initiated mouse skin. Several constituents of cigarette smoke are co-carcinogenic when applied simultaneously with repeated applications of PAHs. Catechol is co-carcinogenic at concentrations found in the condensate. Since cigarette smoking involves protracted exposure to all the smoke constituents, co-carcinogenesis simulates its effects. Both procedures, however, indicate a major role for selection in carcinogenesis by cigarette smoke. That selection may operate on endogenous mutations as well as those induced by PAHs. There are indications that the nicotine-derived NNK which is a specific pulmonary carcinogen in animals contributes to smoking-induced lung cancer in man. Lung adenoma development by inhalation has been induced in mice by the gas phase of cigarette smoke. The role of selection has not been evaluated in either of these cases.

Passive smoking and lung cancer: a cumulative meta-analysis

OBJECTIVE

To review the epidemiological evidence for the association between passive smoking and lung cancer.

METHOD

Primary studies and meta-analyses examining the relationship between passive smoking and lung cancer were identified through a computerised literature search of Medline and Embase, secondary references, and experts in the field of passive smoking. Primary studies meeting the inclusion criteria were meta-analysed.

RESULTS

From 1981 to the end of 1999 there have been 76 primary epidemiological studies of passive smoking and lung cancer, and 20 meta-analyses. There were 43 primary studies that met the inclusion criteria for this meta-analysis; more studies than previous assessments. The pooled relative risk (RR) for never-smoking women exposed to environmental tobacco smoke (ETS) from spouses, compared with unexposed never-smoking women was 1.29 (95% CI 1.17-1.43). Sequential cumulative meta-analysed results for each year from 1981 were calculated: since 1992 the RR has been greater than 1.25. For Western industrialised countries the RR for never-smoking women exposed to ETS compared with unexposed never-smoking women, was 1.21 (95% CI 1.10-1.33). Previously published international spousal meta-analyses have all produced statistically significant RRs greater than 1.17.

CONCLUSIONS

The abundance of evidence in this paper, and the consistency of findings across domestic and workplace primary studies, dosimetric extrapolations and meta-analyses, clearly indicates that non-smokers exposed to ETS are at increased risk of lung cancer.

IMPLICATIONS

The recommended public health policy is for a total ban on smoking in enclosed public places and work sites.

The miseries of passive smoking

Passive smoking is defined as an involuntary exposure to a combined but diluted cigarette sidestream smoke (SS, gas and particle phases that are evolved from the smoldering end of a cigarette while the smoker is not puffing) and the exhaled smoke from smokers. SS contains numerous cytotoxic substances such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, nitrosamines, heavy metals, poisonous gases, pesticide residues, and radioactive elements in quantities much higher than those found from the cigarette mainstream smoke (MS) which is puffed by smokers. Passive smoking is found to be the cause of death from cancers and cardiac disease. Furthermore, it damagingly involves reproductive organs, the nervous system, genetic materials, and is particularly hazardous to mother and child during pregnancy and to those with a history of asthma, chronic infections, induced or earned immune deficiency, or predisposed susceptibility.

Mainstream and sidestream cigarette smoke condensates suppress macrophage responsiveness to interferon gamma

Sidestream smoke evolves from the smoldering end of a cigarette while the smoker is not puffing, and contributes substantially to environmental tobacco smoke (ETS). In contrast, main stream smoke emerges from the butt end of the cigarette and is mainly inhaled by the smoker. This study was performed to compare the effects of short-term exposure to cigarette smoke condensates prepared from sidestream (CSC-SS) and mainstream cigarette smoke (CSC-MS) on macrophage basal metabolism and responsiveness to two different stimuli, bacterial lipopolysaccharide (LPS) and interferon gamma (IFNgamma). Despite their generation at different temperatures and their different chemical composition, CSC - SS and CSC - MS had similar effects on macrophages. Both enhanced macrophage basal metabolism and responsiveness to LPS. Macrophage responsiveness to IFNgamma, assessed by their expression of four functional capacities, was suppressed by both CSC-SS and CSC-MS. The four assessed IFNgamma-inducible functional capacities were: enhanced phagocytosis of immuoglobulin-opsonized sheep red blood cells, TPA-induced peroxide production, class II major histocompatibility complex expression, and nitric oxide synthesis with LPS co-stimulation. The effects of CSC - SS and CSC - MS were similar qualitatively; they differ quantitatively in some cases, with CSC-MS generally effective at lower concentrations (expressed as cigarette-equivalents) than CSC-SS. Considering dilution of sidestream smoke in room air and loss during passage through the respiratory system, we expect to deliver the maximal dose to lung macrophages in situ only in rooms dense with smokers. However, only a fraction of the maximal dose can partially suppress induction of some functions, such as nitric oxide production and MHC expression. Macrophages play critical roles in tissue modeling during development. Of particular concern are neonates, whose organs are still undergoing growth and development, and are therefore susceptible to impaired development. If involuntary exposure to ETS hinders induction of macrophage functional capacities by cytokines, then development of the lungs and perhaps other organs would be impaired. In general, since macrophages are potent effectors and regulators of immunity, impairment of their responsiveness to cytokine must disrupt the proper functioning of the immune system.

The toxicology of environmental tobacco smoke

It has by now become obvious that environmental tobacco smoke (ETS) may pose a health risk to nonsmokers. Epidemiological data suggest that exposure to ETS may increase the risk of developing lung cancer, cardiovascular disease, intrauterine growth retardation, predisposition to chronic lung disease, and sudden infant death syndrome. The human populations most at risk from ETS exposure appear to be neonates, young children, and possibly the fetus while in utero. Experimental studies with cigarette sidestream smoke (SS) have successfully duplicated several of these disease conditions in laboratory animals, particularly the effects of SS on fetal growth, lung maturation, and altered airway reactivity. The availability of animal models may open the way to fruitful experimental studies on mechanisms that help us to better understand disease.