Crotonaldehyde exposure in U.S. tobacco smokers and nonsmokers: NHANES 2005-2006 and 2011-2012

Exposure to volatile organic compounds is a risk factor for diabetes: A cross-sectional study

Currently, more studies showed that environmental chemicals were associated with the development of diabetes. However, the effect of volatile organic compounds (VOCs) on diabetes remained uncertain and needed to be studied. This cross-sectional study examined whether exposure to low levels of VOCs was associated with diabetes, insulin resistance (TyG index) and glucose-related indicators (FPG,HbA1c, insulin) in the general population by using the NHANES dataset (2013-2014 and 2015-2016). We analyzed the association between urinary VOC metabolism (mVOCs) and these indicators in 1409 adults by multiple linear regression models or logistic regression models, further Bayesian kernel machine regression (BKMR) models were performed for mixture exposure analysis. The results showed positive associations between multiple mVOCs and diabetes, TyG index, FPG, HbA1c and insulin, respectively. Among them, HPMMA concentration in urine was significantly positively correlated with diabetes and related indicators (TyG index, FPG and HbA1c), and the concentration of CEMA was significantly positively correlated with insulin. The positive association of mVOCs with diabetes and its related indicators was more significant in the female group and in the 40-59 years group. Thus, our study suggested that exposure to VOCs affected insulin resistance and glucose homeostasis, further affecting diabetes levels, which had important public health implications.

Urinary metabolites of multiple volatile organic compounds among pregnant women across pregnancy: Variability, exposure characteristics, and associations with selected oxidative stress biomarkers

Volatile organic compounds (VOCs) are a group of pollutants pervasive in daily life with identified adverse health effects. However, no study has investigated the variability in VOC metabolites during pregnancy and their relationships with oxidative stress biomarkers in pregnant women. In the present study, the variability of 21 selected VOC metabolites was examined and their relationships with three selected oxidative stress biomarkers measured in spot urine samples at three trimesters of 1094 pregnant women were analyzed. Nineteen VOC metabolites were ubiquitous in the urine samples with detection rates ranging from 75.9% to 100%. Monohydroxybutenyl mercapturic acid (MHBMA) and s-phenyl mercapturic acid (PMA) had detection rates lower than 1.00%. Intraclass correlation coefficients (ICCs) of the detected analytes at three trimesters ranged 0.07-0.24, and the concentrations were highest in the first trimester. Higher concentrations of some VOC metabolites were related with participant characteristics including higher pre-pregnancy body mass index (BMI), lower education level, unemployment during pregnancy, multiparity, and sampling season of summer or winter. In repeated cross-sectional analyses, interquartile range (IQR) increases in the 19 detected VOC metabolites were positively related with 8-hydroxy-2'-deoxyguanosine (8-OHdG), 8-hydroxyguanosine (8-OHG), and 4-hydroxy nonenal mercapturic acid (HNEMA) with the estimates ranging from 9.00% to 204%. The mixture effect of the VOC metabolites on the oxidative stress biomarkers was further assessed using weighted quantile sum regression (WQS) models and the results showed that the WQS index of VOC metabolite mixture was significantly associated with 8-OHdG (β: 0.37, 0,32, and 0.39 at the 1st, 2nd, and 3rd trimester, respectively), 8-OHG (0.38, 0.32, and 0.39) and HNEMA (1.21, 1.08, and 1.10). Glycidamide mercapturic acid (GAMA), and trans,trans-muconic acid (MU) were the strongest contributors of the mixture effect on 8-OHdG, 8-OHG, and HNEMA, respectively. Overall, urinary concentrations of the VOC metabolites during pregnancy were strongly associated with the oxidative stress biomarkers.

Particulate matters, aldehydes, and polycyclic aromatic hydrocarbons produced from deep-frying emissions: comparisons of three cooking oils with distinct fatty acid profiles

It is recognized that hazardous emissions produced from frying oils may be related to oil properties, particularly the fatty acid composition. However, investigations have been limited and partial. In this work, the emissions from deep-frying foods with three oils (palm, olive, and soybean oils) with distinct fatty acid profiles were comprehensively examined in a simulated kitchen, and the interrelationship among emitted substances, oil quality parameters, and fatty acids profiles was explored. Firstly, palm oil emitted the highest number concentration of total particle matters ((3895 ± 1796) × 10³ #/cm³), mainly in the Aitken mode (20–100 nm). We observed a positive correlation between particle number concentration and levels of palmitic acid, a major saturated fatty acid (SAFA) (r_s = 0.73, p < 0.05), and total polar compounds (TPC) (r_s = 0.68, p < 0.05) in the fried oil, a degradation marker which was also positively correlated with that of black carbon (BC) (r_s = 0.68, p < 0.05). Secondly, soybean oil emitted the highest level of gaseous aldehydes (3636 ± 607 μg/m³), including acrolein, propinoaldehyde, crotonaldehyde, hexanal, and trans-2-heptenal; the total aldehyde concentration were positively correlated with α-linolenic acid (ALA) percentage (r_s = 0.78, p < 0.01), while hexanal and trans-2-heptenal were with linoleic acid (LA) (r_s = 0.73 and 0.67, p < 0.05). LA and ALA were two major polyunsaturated fatty acids in non-tropical plant oils. Thirdly, palm oil emitted the most particle-bound polycyclic aromatic hydrocarbons (PAHs), and a positive association was discovered between two PAHs and SAFA percentage. Olive oil seems superior to soybean and palm oils with regards to toxic emissions during deep-frying.

Repeated measurements of 21 urinary metabolites of volatile organic compounds and their associations with three selected oxidative stress biomarkers in 0-7-year-old healthy children from south and central China

Human beings are extensively and concurrently exposed to multiple volatile organic compounds (VOCs, including some Class I human carcinogens), which may induce oxidative stress in human body. Data on urinary metabolites of VOCs (mVOCs) among young children are limited. No studies have examined their inter-day variability of mVOCs and their associations with oxidative stress biomarkers (OSBs) using repeated urine samples from children. In this study, we measured twenty one mVOCs and three OSBs [8-hydroxy-2'-deoxyguanosine (8-OHdG; for DNA), 8-hydroxyguanosine (8-OHG; for RNA], and 4-hydroxy nonenal mercapturic acid (HNEMA; for lipid)] in 390 urine samples of 130 children (three samples on three consecutive days provided by each participant) aged 0-7 years from September 2018 to January 2019 in Shenzhen, south China, and Wuhan, central China. HPMMA (3-hydroxypropyl-1-methyl mercapturic acid/N-Acetyl-S-(3-hydroxypropyl-1-methyl)-l-cysteine), 3HPMA (3-hydroxypropyl mercapturic acid/N-Acetyl-S-(3-hydroxypropyl)-l-cysteine), and ATCA (2-aminothiazoline-4-carboxylic acid) had higher specific gravity-adjusted median concentrations (1 383, 286, and 273 μg/L, respectively) than the others. Intraclass correlation coefficients of mVOCs ranged from 0.29 to 0.71. After false-discovery rate (FDR, defined as FDR q-value < 0.05) adjustment, linear mixed-effects models revealed that 14 mVOCs were positively associated with 8-OHdG (β range: 0.09-0.37), 11 mVOCs were positively associated with 8-OHG (β range: 0.08-0.30), and 11 mVOCs were positively associated with HNEMA (β range: 0.21-0.70) in urine. Considering the weight of the mVOC index accounted for the associations, based on the weighted quantile sum regression model, parent compounds of DHBMA (3,4-dihydroxybutyl mercapturic acid/N-Acetyl-S-(3,4-dihydroxybutyl)-l-cysteine) and t,t-MA (trans,trans-muconic acid) should be listed as priority VOCs for management to mitigate health risks. For the first time, this study characterized the inter-day variability of urinary mVOCs and their associations with selected OSBs (8-OHdG, 8-OHG, and NHEMA) in young, healthy Chinese children.

Joint effect of 25-hydroxyvitamin D and secondhand smoke exposure on hypertension in non-smoking women of childbearing age: NHANES 2007-2014

BACKGROUND

Vitamin D deficiency (VDD) may increase the risk of hypertension in women of childbearing age, who may be exposed to secondhand smoke (SHS) simultaneously. Till now, few studies have investigated the joint effects of VDD and SHS on hypertension in this population. We evaluated whether exposure to SHS modified the association between VDD and hypertension.

METHODS

Data from National Health and Nutrition Examination Surveys (NHANES) 2007-2014 were analyzed. Our research subjects were 2826 nonsmoking and nonpregnant women of childbearing age (20-44 years old). Hypertension was defined based either on systolic blood pressure (SBP) ≥ 130 mmHg and/or diastolic blood pressure (DBP) ≥ 80 mmHg or on now taking prescribed medicine for hypertension. The directed acyclic graphs (DAG) and the back-door criterion were used to select a minimal sufficient adjustment set of variables (MSAs) that would identify the unconfounded effect of 25(OH)D and hypertension. The interactive effect of VDD and SHS on hypertension was evaluated by using logistic regression models, followed by strata-specific analyses.

RESULTS

The prevalence of VDD in the hypertension group was significantly higher than that in the non-hypertension group (48.2% vs 41.0%, P = 0.008), as well as the exposure rate of SHS (39.1% vs 33.8%, P = 0.017). VDD was independently associated with nearly 50% increased risk of hypertension [adjusted odds ratio (aOR) = 1.43, 95% confidence interval (CI): 1.01, 2.04], while no significant association was observed between SHS and hypertension. However, SHS showed a significant synergistic effect on VDD with a higher aOR of 1.79 (95% CI: 1.14, 2.80) (P_interaction = 0.011). This synergistic effect was more obvious when stratified by BMI (in overweight women, aOR, 95% CI =4.74, 1.65-13.60 for interaction vs 2.33, 1.01-5.38 for VDD only) and race (in Non-Hispanic Black women, aOR, 95% CI =5.11, 1.58-16.54 for interaction vs 2.69, 1.10-6.62 for VDD only).

CONCLUSION

There exist synergistic effects of SHS and VDD on the prevalence of hypertension in American women of childbearing age, with more significant effects in women who were overweight or Non-Hispanic Black. Further studies are warranted to verify this finding in other populations, and the molecular mechanisms underlying the joint effect of SHS and VDD need to be elucidated.

Urinary metabolites of multiple volatile organic compounds among general population in Wuhan, central China: Inter-day reproducibility, seasonal difference, and their associations with oxidative stress biomarkers

General population are concurrently and extensively exposed to many volatile organic compounds (VOCs), including some Group 1 human carcinogens, such as 1,3-butadiene. However, only a few studies assessed internal exposure levels of VOCs; particularly, very limited studies have examined associations between the urinary concentrations of multiple VOC metabolites (mVOCs) and oxidative stress biomarkers (OSBs) among the general population. In this study, 21 mVOCs and three OSBs including 8-hydroxy-2'-deoxyguanosine (8-OHdG; for DNA), 8-hydroxyguanosine (8-OHG; for RNA), and 4-hydroxy nonenal mercapturic acid (HNEMA; for lipid) were measured in 406 urine samples collected from 128 healthy adults during autumn and winter of 2018 in Wuhan, central China, including repeated samples taken in 3 d from 75 volunteers. Inter-day reproducibility for most mVOCs was good to excellent; urinary concentrations of mVOCs in winter were generally higher than those in autumn. Risk assessment was conducted by calculating hazard quotients for the parent compounds, and the results suggested that acrolein, 1,3-butadiene, and cyanide should be considered as high-priority hazardous ones for management. After false-discovery adjustment, 16 of the studied mVOCs were positively associated with 8-OHdG and 8-OHG (β values ranged from 0.04 to 0.48), and four mVOCs were positively associated with HNEMA (β values ranged from 0.21 to 0.78). Weighted quantile sum regression analyses were used to assess associations of mVOC mixture and OSBs, and we found significantly positive associations between the mixture index and OSBs, among which the strongest mVOC contributors for the associations were 2-methylhippuric acid for both DNA (20%) and RNA (17%) oxidative damage, and trans,trans-muconic acid (50%) for lipid peroxidation. This study firstly reported good to excellent short-term reproducibility, seasonal difference in autumn and winter, and possible health risk in urinary concentrations of multiple mVOCs among the general population.

Characterization of the association between cigarette smoking intensity and urinary concentrations of 2-hydroxyethyl mercapturic acid among exclusive cigarette smokers in the National Health and Nutrition Examination Survey (NHANES) 2011-2016

BACKGROUND

2-Hydroxyethyl mercapturic acid (2HEMA, N-acetyl-S-(2-hydroxyethyl)-L-cysteine) is a urinary metabolite of several volatile organic compounds including acrylonitrile and ethylene oxide, which are found in cigarette smoke.

METHODS

We measured 2HEMA concentrations in urine specimens collected during the National Health and Nutrition Examination Survey (2011-2016) from eligible participants aged >12 years (N = 7,416). We developed two multiple linear regression models to characterize the association between cigarette smoking and 2HEMA concentrations wherein the dependent variable was 2HEMA concentrations among participants who exclusively smoked cigarettes at the time of specimen collection and the independent variables included sex, age, race/ethnicity, creatinine, diet, and either cigarettes smoked per day (CPD) or serum cotinine.

RESULTS

We detected 2HEMA in 85% of samples tested among exclusive cigarette smokers, and only 40% of specimens from non-smokers. When compared to exclusive cigarette smokers who smoked 1-9 CPD, smoking 10-19 CPD was associated with 36% higher 2HEMA (p < 0.0001) and smoking >19 CPD was associated with 61% higher 2HEMA (p < 0.0001). Additionally, 2HEMA was positively associated with serum cotinine.

CONCLUSIONS

This study demonstrates that cigarette smoking intensity is associated with higher urinary 2HEMA concentrations and is likely a major source of acrylonitrile and/or ethylene oxide exposure.

Harmonization of acronyms for volatile organic compound metabolites using a standardized naming system

Increased interest in volatile organic compound (VOC) exposure has led to an increased need for consistent, systematic, and informative naming of VOC metabolites. As analytical methods have expanded to include many metabolites in a single assay, the number of acronyms in use for a single metabolite has expanded in an unplanned and inconsistent manner due to a lack of guidance or group consensus. Even though the measurement of VOC metabolites is a well-established means to investigate exposure to VOCs, a formal attempt to harmonize acronyms amongst investigators has not been published. The aim of this work is to establish a system of acronym naming that provides consistency in current acronym usage and a foundation for creating acronyms for future VOC metabolites.

Assessment of Serum Concentrations of 12 Aldehydes in the U.S. Population from the 2013-2014 National Health and Nutrition Examination Survey

Aldehydes are known carcinogens and irritants that can negatively impact health. They are present in tobacco smoke, the environment, and food. The prevalence of aldehyde exposure and potential health impact warrants a population-wide study of serum aldehydes as exposure biomarkers. We analyzed 12 aldehydes in sera collected from 1843 participants aged 12 years or older in the 2013-2014 National Health and Nutrition Examination Survey. Several aldehydes were detected at high rates, such as isopentanaldehyde (99.2%) and propanaldehyde (88.3%). We used multiple linear regression models to examine the impact of tobacco smoke and dietary variables on serum concentrations of isopentanaldehyde and propanaldehyde. Although 12 serum aldehydes were analyzed and compared to tobacco smoke exposure, only isopentanaldehyde and propanaldehyde showed any significant association with tobacco smoke exposure. Survey participants who smoked 1-10 cigarettes per day (CPD) had 168% higher serum isopentanaldehyde and 28% higher propanaldehyde compared with nonusers. Study participants who smoked 11-20 CPD had higher serum isopentanaldehyde (323%) and propanaldehyde (70%). Similarly, study participants who smoked >20 CPD had 399% higher serum isopentanaldehyde and 110% higher serum propanaldehyde than nonexposed nonusers. The method could not, however, differentiate between nonexposed nonusers and nonusers exposed to secondhand smoke for either of these two aldehydes. No dietary variables were consistently predictive of serum isopentanaldehyde and propanaldehyde concentrations. This report defines baseline concentrations of serum aldehydes in the U.S. population and provides a foundation for future research into the potential health effects of aldehydes. In addition, this study suggests that tobacco smoke is a significant source of exposure to some aldehydes such as isopentanaldehyde and propanaldehyde.

Exposure to 1,3-Butadiene in the U.S. Population: National Health and Nutrition Examination Survey 2011-2016

1,3-Butadiene is a volatile organic compound with a gasoline-like odour that is primarily used as a monomer in the production of synthetic rubber. The International Agency for Research on Cancer has classified 1,3-butadiene as a human carcinogen. We assessed 1,3-butadiene exposure in the U.S. population by measuring its urinary metabolites N-acetyl-S-(3,4-dihydroxybutyl)-L-cysteine (34HBMA), N-acetyl-S-(1-hydroxymethyl-2-propenyl)-L-cysteine (1HMPeMA), N-acetyl-S-(2-hydroxy-3-butenyl)-L-cysteine (2HBeMA), and N-acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine (4HBeMA). Urine samples from the 2011 to 2016 National Health and Nutrition Examination Survey were analysed for 1,3-butadiene metabolites using ultrahigh-performance liquid chromatography/tandem mass spectrometry. 34HBMA and 4HBeMA were detected in >96% of the samples; 1HMPeMA and 2HBeMA were detected in 0.66% and 9.84% of the samples, respectively. We used sample-weighted linear regression models to examine the influence of smoking status (using a combination of self-reporting and serum-cotinine data), demographic variables, and diet on biomarker levels. The median 4HBeMA among exclusive smokers (31.5 µg/g creatinine) was higher than in non-users (4.11 µg/g creatinine). Similarly, the median 34HBMA among exclusive smokers (391 µg/g creatinine) was higher than in non-users (296 µg/g creatinine). Furthermore, smoking 1-10, 11-20, and >20 cigarettes per day (CPD) was associated with 475%, 849%, and 1143% higher 4HBeMA (p < 0.0001), respectively. Additionally, smoking 1-10, 11-20, and >20 CPD was associated with 33%, 44%, and 102% higher 34HBMA (p < 0.0001). These results provide significant baseline data for 1,3-butadiene exposure in the U.S. population, and demonstrate that tobacco smoke is a major exposure source.

Characterization of US population levels of urinary methylcarbamoyl mercapturic acid, a metabolite of N,N-dimethylformamide and methyl isocyanate, in the National Health and Nutrition Examination Survey (NHANES) 2005-2006 and 2011-2016

Methylcarbamoyl mercapturic acid (MCAMA, N-acetyl-S-(N-methylcarbamoyl)-L-cysteine) is a urinary metabolite of N,N-dimethylformamide and methyl isocyanate, which are volatile organic compounds that are harmful to humans. N,N-dimethylformamide exposure causes liver damage, and methyl isocyanate inhalation damages the lining of the respiratory tract, which can increase risk of chronic obstructive pulmonary disease and asthma. This study characterizes urinary MCAMA levels in the US population and explores associations of MCAMA concentrations with select demographic and environmental factors. We used liquid chromatography tandem mass spectrometry to measure MCAMA in urine collected from study participants ≥ 12 years old (N = 8272) as part of the National Health and Nutrition Examination Survey 2005-2006 and 2011-2016. We produced multiple regression models with MCAMA concentrations as the dependent variable and sex, age, fasting time, race/ethnicity, diet, and cigarette smoking as independent variables. Cigarette smokers and nonsmokers had median urinary MCAMA concentrations of 517 μg/g creatinine and 127 μg/g creatinine, respectively. Sample-weighted multiple regression analysis showed that MCAMA was positively associated with serum cotinine (p < 0.0001). Compared to non-exposed participants (serum cotinine ≤ 0.015 ng/mL), presumptive exposure to second-hand tobacco smoke (serum cotinine > 0.015-≤ 10 ng/mL and 0 cigarettes smoked per day) was associated with 20% higher MCAMA (p < 0.0001). Additionally, smoking 1-10 cigarettes per day was associated with 261% higher MCAMA (p < 0.0001), smoking 11-20 cigarettes per day was associated with 357% higher MCAMA (p < 0.0001), and smoking > 20 cigarettes per day was associated with 416% higher MCAMA (p < 0.0001). These findings underscore the strong association of tobacco smoke exposure with urinary MCAMA biomarker levels.

Characterization of acrylonitrile exposure in the United States based on urinary n-acetyl-S-(2-cyanoethyl)-L-cysteine (2CYEMA): NHANES 2011-2016

BACKGROUND

Acrylonitrile is a possible human carcinogen that is used in polymers and formed in tobacco smoke. We assessed acrylonitrile exposure in the US population by measuring its urinary metabolites N-acetyl-S-(4-hydroxy-2-methyl-2-buten-1-yl)-L-cysteine (2CYEMA) and N-acetyl-S-(1-cyano-2-hydroxyethyl)-L-cysteine (1CYHEMA) in participants from the 2011-2016 National Health and Nutrition Examination Survey.

OBJECTIVE

To assessed acrylonitrile exposure using population-based biomonitoring data of the US civilian, non-institutionalized population.

METHODS

Laboratory data for 8057 participants were reported for 2CYEMA and 1CYHEMA using ultrahigh-performance liquid chromatography/tandem mass spectrometry. Exclusive tobacco smokers were distinguished from non-users using a combination of self-reporting and serum cotinine data. We used multiple linear regression models to fit 2CYEMA concentrations with sex, age, race/Hispanic origin, and tobacco user group as predictor variables.

RESULTS

The median 2CYEMA level was higher for exclusive cigarette smokers (145 µg/g creatinine) than for non-users (1.38 µg/g creatinine). Compared to unexposed individuals (serum cotinine ≤0.015 ng/ml) and controlling for confounders, presumptive second-hand tobacco smoke exposure (serum cotinine >0.015 to ≤10 ng/ml and 0 cigarettes per day, CPD) was significantly associated with 36% higher 2CYEMA levels (p < 0.0001). Smoking 1-10 CPD was significantly associated with 6720% higher 2CYEMA levels (p < 0.0001).

SIGNIFICANCE

We show that tobacco smoke is an important source of acrylonitrile exposure in the US population and provide important biomonitoring data on acrylonitrile exposure.

Examination of xylene exposure in the U.S. Population through biomonitoring: NHANES 2005-2006, 2011-2016

Aim: Xylenes are aromatic hydrocarbons used for industrial applications such as the production of petrochemicals and plastics. Acute xylene exposures can negatively impact health through neurotoxicity and irritation of respiratory and dermal tissues. We quantified urinary biomarkers of xylene exposure [2-methylhippuric acid (2MHA) and a mixture of 3- and 4-methylhippuric acids (34MH)] in a representative sample of the U.S. population. Methods: Spot urine obtained during the National Health and Nutrition Examination Survey 2005-2006 and 2011-2016 was analysed using ultra-high-performance liquid chromatography/tandem mass spectrometry. Exclusive smokers were distinguished from non-users using a combination of self-report and serum cotinine data. Results: The median 2MHA and 34MH levels were higher for exclusive smokers (100 µg/g and 748 µg/g creatinine, respectively) than for non-users (27.4 µg/g and 168 µg/g creatinine, respectively). Participants who smoked cigarettes had significantly higher 2MHA and 34MH levels (p < 0.0001) than unexposed participants. Smoking 1-10, 11-20, and >20 cigarettes per day (CPD) was significantly associated with 181%, 339% and 393% higher 2MHA levels, respectively. For 34MH, smoking 1-10, 11-20, and >20 CPD was significantly associated with 201%, 398%, and 471% higher 34MH levels, respectively. Conclusion: We confirm that tobacco smoke is a significant source of xylene exposure as measured by urinary 2MHA and 34MH levels.

A review of the analysis of biomarkers of exposure to tobacco and vaping products

Quantification of exposure to different chemicals from both combustible cigarettes and vaping products is important in providing information on the potential health risks of these products. To assess the exposure to tobacco products, biomarkers of exposure (BOEs) are measured in a variety of biological matrices. In this review paper, current knowledge on analytical methods applied to the analysis of biomarkers of exposure to tobacco products is discussed. Numerous sample preparation techniques are available for the extraction and sample clean up for the analysis of BOEs to tobacco and nicotine delivery products. Many tobacco products-related exposure biomarkers have been analyzed using different instrumental techniques, the most common techniques being gas and liquid chromatography coupled with mass spectrometry (GC-MS, GC-MS/MS and LC-MS/MS). To assess exposure to emerging tobacco products and study exposure in dual tobacco users, the list of biomarkers analyzed in urine samples has been expanded. Therefore, the current state of the literature can be used in preparing a preferred list of biomarkers based on the aim of each study. The information summarized in this review is expected to be a handy tool for researchers involved in studying exposures to tobacco products, as well as in risk assessment of biomarkers of exposure to vaping products.

Association between Metabolites and the Risk of Lung Cancer: A Systematic Literature Review and Meta-Analysis of Observational Studies

Globally, lung cancer is the most prevalent cancer type. However, screening and early detection is challenging. Previous studies have identified metabolites as promising lung cancer biomarkers. This systematic literature review and meta-analysis aimed to identify metabolites associated with lung cancer risk in observational studies. The literature search was performed in PubMed and EMBASE databases, up to 31 December 2019, for observational studies on the association between metabolites and lung cancer risk. Heterogeneity was assessed using the I2 statistic and Cochran's Q test. Meta-analyses were performed using either a fixed-effects or random-effects model, depending on study heterogeneity. Fifty-three studies with 297 metabolites were included. Most identified metabolites (252 metabolites) were reported in individual studies. Meta-analyses were conducted on 45 metabolites. Five metabolites (cotinine, creatinine riboside, N-acetylneuraminic acid, proline and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene) and five metabolite groups (total 3-hydroxycotinine, total cotinine, total nicotine, total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (sum of concentrations of the metabolite and its glucuronides), and total nicotine equivalent (sum of total 3-hydroxycotinine, total cotinine and total nicotine)) were associated with higher lung cancer risk, while three others (folate, methionine and tryptophan) were associated with lower lung cancer risk. Significant heterogeneity was detected across most studies. These significant metabolites should be further evaluated as potential biomarkers for lung cancer.

Tobacco Smoke and Endothelial Dysfunction: Role of Aldehydes?

PURPOSE OF REVIEW

Tobacco smoking is the most significant modifiable risk factor in the development of cardiovascular disease (CVD). Exposure to mainstream cigarette smoke (MCS) is associated with CVD through the development of endothelial dysfunction, a condition characterized by an imbalance of vasoactive factors in the vasculature. This dysfunction is thought to be induced in part by aldehydes generated at high levels in MCS.

RECENT FINDINGS

Electronic cigarettes (e-cigs) may also pose CVD risk. Although the health effects of e-cigs are still largely unknown, the presence of aldehydes in e-cig aerosol suggests that e-cigs may induce adverse cardiovascular outcomes similar to those seen with MCS exposure. Herein, we review studies of traditional and emerging tobacco product use, shared harmful and potentially harmful constituents, and measures of biomarkers of harm (endothelial dysfunction) to examine a potential and distinct role of aldehydes in cardiovascular harm associated with cigarette and e-cig use.

Urinary Biomarkers of Exposure to Volatile Organic Compounds from the Population Assessment of Tobacco and Health Study Wave 1 (2013-2014)

Volatile organic compounds (VOCs) are ubiquitous in the environment. In the United States (U.S.), tobacco smoke is the major non-occupational source of exposure to many harmful VOCs. Exposure to VOCs can be assessed by measuring their urinary metabolites (VOCMs). The Population Assessment of Tobacco and Health (PATH) Study is a U.S. national longitudinal study of tobacco use in the adult and youth civilian non-institutionalized population. We measured 20 VOCMs in urine specimens from a subsample of adults in Wave 1 (W1) (2013-2014) to characterize VOC exposures among tobacco product users and non-users. We calculated weighted geometric means (GMs) and percentiles of each VOCM for exclusive combustible product users (smokers), exclusive electronic cigarette (e-cigarette) users, exclusive smokeless product users, and tobacco product never users. We produced linear regression models for six VOCMs with sex, age, race, and tobacco user group as predictor variables. Creatinine-ratioed levels of VOCMs from exposure to acrolein, crotonaldehyde, isoprene, acrylonitrile, and 1,3-butadiene were significantly higher in smokers than in never users. Small differences of VOCM levels among exclusive e-cigarette users and smokeless users were observed when compared to never users. Smokers showed higher VOCM concentrations than e-cigarette, smokeless, and never users. Urinary VOC metabolites are useful biomarkers of exposure to harmful VOCs.

Acute and chronic vascular effects of inhaled crotonaldehyde in mice: Role of TRPA1

Although crotonaldehyde (CR) is an abundant α,β-unsaturated aldehyde in mainstream cigarette smoke (MCS), the cardiovascular toxicity of inhaled CR is largely unexplored. Thus, male C57BL/6 J mice were exposed acutely (1 h, 6 h, and 4d) and chronically (12 weeks) to CR (at levels relevant to MCS; 1 and 3 ppm), and cardiovascular and systemic outcomes were measured in vivo and in vitro. Diastolic blood pressure was decreased (hypotension) by both acute and chronic CR exposure. Vascular toxicity of inhaled CR was quantified in isolated aorta in response to agonists of contraction (phenylephrine, PE) and relaxation (acetylcholine, ACh; sodium nitroprusside, SNP). Although no change in contractility was observed, ACh-induced relaxations were augmented after both acute and chronic CR exposures whereas SNP-induced relaxation was enhanced only following 3 ppm CR exposure. Because CR is a known agonist of the transient receptor potential ankyrin 1 (TRPA1) channel, male TRPA1-null mice were exposed to air or CR (4d, 1 ppm) and aortic function assessed in vitro. CR exposure had no effect on TRPA1-null aortic function indicating a role of TRPA1 in CR effects in C57BL/6 J mice. Notably, CR exposure (4d, 1 ppm) had no effect on aortic function in female C57BL/6 J mice. This study shows that CR inhalation exposure induces real-time and persistent vascular changes that promote hypotension-a known risk factor for stroke. Because of continued widespread exposures of humans to combustion-derived CR (environmental and tobacco products), CR may be an important cardiovascular disease risk factor.

Isoprene Exposure in the United States Based on Urinary IPM3: NHANES 2015-2016

Isoprene is the 2-methyl analog of 1,3-butadiene and is a possible human carcinogen (IARC Group 2B). We assessed isoprene exposure in the general US population by measuring its urinary metabolite, N-acetyl-S-(4-hydroxy-2-methyl-2-buten-1-yl)-l-cysteine (IPM3) in participants (≥3 year old) from the 2015-2016 National Health and Nutrition Examination Survey. Spot urine samples were analyzed for IPM3 using ultrahigh-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Exclusive tobacco smokers were distinguished from non-users using a combination of self-reporting and serum cotinine data. IPM3 was detected in 80.2% of samples. The median IPM3 level was higher for exclusive cigarette smokers (39.8 μg/g creatinine) than for non-users (3.05 μg/g creatinine). Sample weighted regression analysis, controlling for creatinine, sex, age, race, body mass index, and diet, showed that IPM3 was positively and significantly associated with serum cotinine. Smoking 1-10 cigarettes per day (CPD, 0.5 pack) was significantly associated with an IPM3 increase of 596% (p < .0001), and smoking >20 CPD (>1 pack) was significantly associated with an IPM3 increase of 1640% (p < .0001), controlling for confounding variables. Drinking beer/ale at median and 90th percentile levels (compared to zero consumption) was associated (p < 0.05) with 0 and 2.9% increase in IPM3 in non-users, respectively. We conclude that tobacco smoke is a major source of isoprene exposure in the US population. This study provides important public health biomonitoring data on isoprene exposure in the general US population.

Resolution and Quantitation of Mercapturic Acids Derived from Crotonaldehyde, Methacrolein, and Methyl Vinyl Ketone in the Urine of Smokers and Nonsmokers

Using improved HPLC analysis conditions, we report the separation of three isomers of mercapturic acid conjugates previously assigned in the literature only to 3-hydroxy-1-methylpropylmercapturic acid (HMPMA-1), a human urinary metabolite of crotonaldehyde. The new conditions, employing a biphenyl column cooled to 5 °C and eluted with a gradient of formic acid, acetonitrile, and methanol, allow the analysis of human urinary mercapturic acids derived not only from crotonaldehyde but also from its isomers methacrolein (3-hydroxy-2-methylpropyl mercapturic acid, HMPMA-2) and methyl vinyl ketone (3-hydroxy-3-methylpropyl mercapturic acid, HMPMA-3). The mercapturic acids were detected and quantified by LC-ESI-MS/MS using the corresponding stable isotope labeled mercapturic acids as internal standards. The analysis was validated for accuracy and precision and applied to urine samples collected from cigarette smokers and nonsmokers. Smokers had significantly higher levels of all three mercapturic acids than did nonsmokers. The results demonstrated that HMPMA-3 from methyl vinyl ketone comprised the major portion of the peaks previously ascribed in multiple studies to HMPMA-1. HMPMA-1 had concentrations intermediate between those of HMPMA-2 and HMPMA-3 in both smokers and nonsmokers. This study reports the first quantitation of HMPMA-2 and HMPMA-3 in human urine. The observation of higher levels of HMPMA-3 than in the other two mercapturic acids suggests a previously unrecognized potential significance of methyl vinyl ketone as a toxicant in smokers and nonsmokers.

Autophagy in Crotonaldehyde-Induced Endothelial Toxicity

Crotonaldehyde is an extremely toxic α,β-unsaturated aldehyde found in cigarette smoke, and it causes inflammation and vascular dysfunction. Autophagy has been reported to play a key role in the pathogenesis of vascular diseases. However, the precise mechanism underlying the role of acute exposure crotonaldehyde in vascular disease development remains unclear. In the present study, we aimed to investigate the effect of crotonaldehyde-induced autophagy in endothelial cells. Acute exposure to crotonaldehyde decreased cell viability and induced autophagy followed by cell death. In addition, inhibiting the autophagic flux markedly promoted the viability of endothelial cells exposed to high concentrations of crotonaldehyde. Crotonaldehyde activated the AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK) pathways, and pretreatment with inhibitors specific to these kinases showed autophagy inhibition and partial improvement in cell viability. These data show that acute exposure to high concentrations of crotonaldehyde induces autophagy-mediated cell death. These results might be helpful to elucidate the mechanisms underlying crotonaldehyde toxicity in the vascular system and contribute to environmental risk assessment.

Biomarkers of Exposure to Secondhand and Thirdhand Tobacco Smoke: Recent Advances and Future Perspectives

Smoking is the leading preventable disease worldwide and passive smoking is estimated to be the cause of about 1.0% of worldwide mortality. The determination of tobacco smoke biomarkers in human biological matrices is key to assess the health effects related to the exposure to environmental tobacco smoke. The biomonitoring of cotinine, the main nicotine metabolite, in human biofluids-including urine, serum or saliva-has been extensively used to assess this exposure. However, the simultaneous determination of cotinine together with other tobacco biomarkers and the selection of alternative biological matrices, such as hair, skin or exhaled breath, would enable a better characterization of the kind and extent of tobacco exposure. This review aims to perform a critical analysis of the up-to-date literature focused on the simultaneous determination of multiple tobacco smoke biomarkers studied in different biological matrices, due to the exposure to secondhand smoke (SHS) and thirdhand smoke (THS). Target biomarkers included both tobacco-specific biomarkers-nicotine and tobacco specific nitrosamine biomarkers-and tobacco-related biomarkers, such as those from polycyclic aromatic hydrocarbons, volatile organic compounds, metals and carbon monoxide. To conclude, we discuss the suitability of determining multiple biomarkers through several relevant examples of SHS and THS exposure.

Quantification of 19 Aldehydes in Human Serum by Headspace SPME/GC/High-Resolution Mass Spectrometry

Sources of human aldehyde exposure include food additives, combustion of organic matter (tobacco smoke), water disinfection byproducts via ozonation, and endogenous processes. Aldehydes are potentially carcinogenic and mutagenic, and chronic human aldehyde exposure has raised concerns about potential deleterious health effects. To aid investigations of human aldehyde exposure, we developed a novel method to measure 19 aldehydes released from Schiff base protein adducts in serum using controlled acid hydrolysis, solid-phase microextraction (SPME), gas chromatography (GC), and high-resolution mass spectrometry (HRMS). Aldehydes are released from Schiff base protein adducts through acid hydrolysis, and are quantified in trace amounts (μg/L) using stable isotope dilution. Detection limits range from 0.1 to 50 μg/L, with calibration curves spanning 3 orders of magnitude. The analysis of fortified quality control material over a three-month period showed excellent precision and long-term stability (3-22% CV) for samples stored at -70 °C. The intraday precision is also excellent (CV, 1-10%). The method accuracy ranges from 89 to 108% for all measured aldehydes, except acrolein and crotonaldehyde, two aldehydes present in tobacco smoke; their analysis by this method is not considered robust due in part to their reactivity in vivo. However, results strongly suggest that propanal, butanal, isobutanal, and isopentanal levels in smokers are higher than levels in nonsmokers, and thus may be useful as biomarkers of tobacco smoke exposure. This method will facilitate large epidemiological studies involving aldehyde biomonitoring to examine nonoccupational environmental exposures.

Clinical and radiographic periodontal status and whole salivary cotinine, IL-1β and IL-6 levels in cigarette- and waterpipe-smokers and E-cig users

The aim was to compare the clinical (plaque index [PI], bleeding on probing [BOP], probing pocket depth [PPD] and clinical attachment loss [CAL]) and radiographic (marginal bone loss [MBL]) periodontal parameters and whole salivary cotinine, interleukin (IL)-1β and IL-6 levels among cigarette-smokers, waterpipe-smokers, E-cig users and never-smokers. In total, 154 male individuals (39 cigarette-smokers, 40 waterpipe-smokers, 37 E-cig users and 38 never-smokers) were included. Full mouth PI, BOP, PPD and CAL were measured on all teeth (excluding third molars); and MBL was measured in digital intra-oral radiographs. Unstimulated whole salivary flow rate (UWSFR) and whole salivary cotinine, IL-1β and IL-6 levels were measured. Group comparisons were performed using one way analysis of variance and Bonferroni post-hoc tests. P-values less than 0.05 were considered statistically significant. There was no difference in UWSFR among the groups. Cotinine levels were significantly higher among cigarette- (P < 0.001) and waterpipe-smokers (P < 0.001) and E-cig users (P < 0.001) than never-smokers. IL-1β (P < 0.01) and IL-6 (P < 0.01) levels were significantly higher among cigarette- and waterpipe-smokers than E-cig users and never-smokers. There was no difference in PPD, CAL, mesial and distal MBL and whole salivary IL-1β and IL-6 levels among E-cig users and never-smokers. In conclusion, clinical and radiographic parameters of periodontal inflammation were poorer in cigarette and waterpipe smokers than E-cig users and never-smokers; and whole salivary cotinine levels were similar in all groups. Whole salivary IL-1β and IL-6 levels were higher in cigarette- and waterpipe-smokers than E-cig users and never-smokers.