Hans J. Roethig

Population estimates for biomarkers of exposure to cigarette smoke in adult U.S. cigarette smokers

INTRODUCTION There are about 4,800 different chemical constituents in cigarette smoke. Therefore, the total systemic exposure evaluation of the population of smokers to cigarette smoke is challenging. Measurement of biomarkers as surrogates of cigarette smoke constituents is a realistic approach to assess exposure. OBJECTIVE To estimate cigarette smoke exposure of the U.S. smoker population. METHODS Stratified, cross-sectional, multicenter design (39 sites in 31 states); 3,585 adult cigarette smokers and 1,077 nonsmokers. Biomarkers were determined from 24-hr urine collections or blood samples. Population estimates were generated by weighting sample data with weights from a large U.S. probability sample (Behavioral Risk Factor Surveillance System). RESULTS The adult smoker population estimates for tobacco-specific biomarkers were nicotine equivalents 13.3 mg/24 hr (SE 0.14), serum cotinine 184 ng/ml (1.8), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol 439 ng/24 hr (5.5). The population estimates for smokers and nonsmokers for nontobacco-specific biomarkers were 1-hydroxypyrene 317 (6.8) and 110 (7.1) ng/24 hr, 4-aminobiphenyl Hb adducts 43.1 (1.04) and 11.4 (1.5) pg/g Hb, carboxyhemoglobin 5.26(0.04) in percent of hemoglobin saturation and 1.45(0.02), 3-hydroxypropylmercapturic acid 2,030 (24) and 458 (17) microg/24 hr, monohydroxy-butenyl-mercapturic acid 3.61 (0.1) and 0.30 (0.02) microg/24 hr, and dihydroxy-butyl-mercapturic acid 556 (4.9) and 391 (5.5) microg/24 hr. On average, young adult smokers had lower exposure than older smokers; female smokers had lower exposure than males, and Black smokers had lower exposure than Whites. DISCUSSION This study estimated the population exposure to cigarette smoke constituents in adult U.S. smokers and identified significant differences between subpopulations. The data may serve as a reference for monitoring the impact of changes in cigarette consumption and the introduction of potentially reduced exposure cigarettes.

Short-term exposure evaluation of adult smokers switching from conventional to first-generation electrically heated cigarettes during controlled smoking.

This randomized, controlled study in 110 male and female adult smokers evaluated biomarkers of tobacco smoke exposure (carbon monoxide [CO], carboxyhemoglobin [CO‐Hb], nicotine, urine mutagenicity) under controlled smoking conditions when adult smokers of 1 conventional cigarette brand (CC1) were switched to an electrically heated cigarette smoking system (EHCSS) or a low‐tar conventional cigarette (CC2). Baseline exposure was determined while all subjects smoked CC1. Subjects then were stratified for gender and cigarette consumption and randomized to 1 of 5 groups—EHCSS1, EHCSS2, CC1, CC2, or no smoking—and monitored for 8 days. Compared to baseline, biomarkers of exposure on day 8 decreased 53% to 93% (P < .0001) for EHCSS groups and 18% to 39% (P < .02) for CC2. Environmental tobacco smoke arising from the smoking activities of the different study groups was measured in the air of a separate smoking room over 1‐hour periods. Concentrations of respirable suspended particulates in both EHCSS groups were about 90% lower than in the CC1 and CC2 groups, similar to the 95% reduction in the no‐smoking group. CO was undetectable in the EHCSS and no‐smoking groups. Results from this short‐term clinical study indicate that switching from a conventional cigarette to a first‐generation EHCSS reduces the generation of environmental tobacco smoke and can reduce the exposure to the measured, potentially harmful constituents in tobacco smoke if smokers do not compensate by numbers of cigarettes. The study design was found to be suitable for the evaluation of the exposure of adult smokers to the measured smoke constituents and to allow the differentiation of different cigarette designs.

Short‐Term Clinical Exposure Evaluation of a Second‐Generation Electrically Heated Cigarette Smoking System

This randomized, controlled, forced‐switching, open‐label, parallel‐group study in 100 adult male and female smokers of conventional cigarettes evaluated 8 biomarkers of tobacco smoke exposure. After baseline exposure determinations, adult smokers were switched to a second‐generation electrically heated cigarette smoking system (EHCSS) for 8 days in a clinical setting. After 8 days of smoking the EHCSS biomarkers of exposure decreased by 43% to 85% compared to baseline. After correction for residual effects (carryover effects due to long elimination half‐life and non‐tobacco‐confounding sources of exposure), reductions in exposure ranged from 59% to 97%. Results from this short‐term clinical exposure study indicate that switching from a conventional cigarette to a second‐generation electrically heated cigarette smoking system substantially reduced the exposure to several measured potentially harmful constituents of tobacco smoke.

Biomarkers of Potential Harm Among Adult Smokers and Nonsmokers in the Total Exposure Study

INTRODUCTION There is overwhelming medical and scientific consensus that cigarette smoking causes lung cancer, heart disease, emphysema, and other serious diseases in smokers. In the Total Exposure Study, 29 biomarkers of potential harm (BOPH) were measured in a cross-sectional sample of 3,585 adult smokers (AS) and 1,077 nonsmokers (NS). The BOPH included markers of oxidative stress, inflammation, platelet activation, endothelial function, lipid metabolism, hematology, metabolism, the cardiovascular system, lung function, kidney function, and liver function. METHODS Multiple stepwise regression was used to examine the effect of demographic factors (age, gender, body mass index [BMI], and race) and smoking (number of cigarettes smoked per day or nicotine equivalents [NE] per 24 hr and smoking duration) on each BOPH. RESULTS As compared with NS, AS had >10% higher levels of 8-epi-prostaglandin F(2α) (8-epi-PG F(2α), 42%), 11-dehydrothromboxane B₂ (11-DHTB, 29%), white blood cell (WBC) count (19%), high-sensitivity C-reactive protein (15%), triglycerides (16%), and alkaline phosphatase (11%) and had 18% lower total bilirubin. Multiple stepwise regression revealed that although NE (milligrams per 24 hours) was statistically significant for 18 of the 29 BOPH, it was the most important factor only for WBCs and 11-DHTB. Smoking duration was the most important factor for forced expiratory volume in 1 second. In contrast, BMI was the most important factor for 12 BOPH. CONCLUSIONS These results contribute to the understanding of the relationship between tobacco smoking and potential biological effects.

Evaluation of biomarkers of exposure to selected cigarette smoke constituents in adult smokers switched to carbon-filtered cigarettes in short-term and long-term clinical studies

Cigarette smoke is a complex aerosol that includes a gas vapor phase and a particulate phase. Inclusion of activated carbon in the cigarette filter can reduce some of the gas-phase smoke constituents implicated as toxicologically relevant. The present study evaluated exposure to selected gas-phase constituents when adult smokers switched to prototype cigarettes with a highly activated carbon filter. Smokers (N = 160) in two separate studies were randomized to continue to smoke conventional cigarettes (either a 6-mg or 11-mg FTC tar product), to smoke test cigarettes containing carbon filters (comparable tar levels), or to stop smoking. After completing 8 days in controlled smoking conditions (short-term studies), smokers had the option to continue in 24-week long-term ambulatory studies with unrestricted smoking. Urinary excretion of mercapturic acid metabolites of 1,3-butadiene, acrolein, and benzene; nicotine and five of its metabolites, total NNAL, and 1-hydroxypyrene were measured at baseline in the conventional cigarette group, in all groups in the short-term studies, and every 4 weeks in the long-term studies. In the short-term studies, statistically significant reductions (>70%, p<.001) in gas-phase biomarker levels were observed in the test cigarette group for both tar level products compared with the conventional cigarette group. These reductions were similar to those observed in the stop-smoking groups. The reductions continued consistently (p<.001) throughout the long-term studies. Switching to test cigarettes minimally affected the particulate-phase biomarkers. Statistically significant and consistent reductions in selected gas vapor phase biomarkers were observed when smokers switched to activated carbon filter cigarettes.

Relationship between Biomarkers of Cigarette Smoke Exposure and Biomarkers of Inflammation, Oxidative Stress, and Platelet Activation in Adult Cigarette Smokers

Background: Cigarette smoking is a risk factor for several diseases, including cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer, but the role of specific smoke constituents in these diseases has not been clearly established. Methods: The relationships between biomarkers of potential harm (BOPH), associated with inflammation [white blood cell (WBC), high sensitivity C-reactive protein (hs-CRP), fibrinogen, and von Willebrand factor (vWF)], oxidative stress [8-epi-prostaglandin F2α (8-epiPGF2α)] and platelet activation [11-dehydro-thromboxin B2 (11-dehTxB2)], and machine-measured tar yields (grouped into four categories), biomarkers of exposure (BOE) to cigarette smoke: nicotine and its five metabolites (nicotine equivalents), 4-methylnitrosamino-1-(3-pyridyl)-1-butanol (total NNAL), carboxyhemoglobin, 1-hydroxypyrene, 3-hydroxypropylmercapturic acid, and monohydroxybutenyl-mercapturic acid, were investigated in 3,585 adult smokers and 1,077 nonsmokers. Results: Overall, adult smokers had higher levels of BOPHs than nonsmokers. Body mass index (BMI), smoking duration, tar category, and some of the BOEs were significant factors in the multiple regression models. Based on the F value, BMI was the highest ranking factor in the models for WBC, hs-CRP, fibrinogen, and 8-epiPGF2α, respectively, and gender and smoking duration for 11-dehTxB2 and vWF, respectively. Conclusions: Although several demographic factors and some BOEs were statistically significant in the model, the R2 values indicate that only up to 22% of the variability can be explained by these factors, reflecting the complexity and multifactorial nature of the disease mechanisms. Impact: The relationships between the BOEs and BOPHs observed in this study may help with the identification of appropriate biomarkers and improve the design of clinical studies in smokers. Cancer Epidemiol Biomarkers Prev; 20(8); 1760–9. ©2011 AACR.

Variability of peripheral arterial tonometry in the measurement of endothelial function in healthy men.

Measurement of endothelial function using peripheral arterial tonometry (PAT) has been reported to be significantly correlated with coronary blood flow. Repetitive PAT measurements were performed in 22 healthy male subjects at test intervals of 1 hour (5 times within a day) and 0.5 hours (7 times within a day) to evaluate the variability of the reactive hyperemia index (RHI). A total of 10 subjects underwent additional repetitive PAT at 2 hour intervals (7 times within a day) for 3 consecutive days to evaluate the diurnal effects and day‐to‐day reproducibility. The RHI from each test was computed automatically based on a 15 minute recording of pulse wave amplitude changes of the fingers in response to reactive hyperemia induced by a 5 minute occlusion of the brachial artery. Intrasubject variability of RHI at different test intervals, defined as the coefficient of variation (CV) was 15.3% ± 5.3%, 16.1%± 7.8%, and 22.6% ± 3.9% for the tests at 0.5 hour, 1 hour, and 2 hour intervals, respectively. Reactive hyperemia indices measured at the same time points on each of the 3 days were not statistically significant. The interday reproducibility, presented as intraclass correlation coefficients (ICC) ranged from − 0.07 to 0.47. We conclude that repetitive PAT measurements have no carryover effect on RHI at 1 hour, and 2 hour intervals, and the RHI measured at 0.5 hour intervals is associated with a trend of increase. The interday reproducibility is relatively low and the intrasubject variability of RHI is similar to those observed in studies of flow‐mediated dilation using brachial artery ultrasound scanning. Copyright

A 12‐Month, Randomized, Controlled Study to Evaluate Exposure and Cardiovascular Risk Factors in Adult Smokers Switching From Conventional Cigarettes to a Second‐Generation Electrically Heated Cigarette Smoking System

This randomized, controlled, forced‐switching, open‐label, parallel‐group study in 97 adult male and female smokers of conventional cigarettes evaluated biomarkers of tobacco smoke exposure and cardiovascular risk factors. After baseline measurements, smokers were either switched to a second‐generation electrically heated cigarette smoking system (EHCSS) or continued smoking conventional cigarettes for 12 months. Biomarkers of exposure and cardiovascular risk factors were measured at 0.5, 1, 2, 3, 4, 5, 6, 9, and 12 months. There was a rapid and sustained reduction in all biomarkers of exposure after switching to the EHCSS, with statistically significant reductions from baseline in nicotine equivalents (−18%), plasma cotinine (−16%), total 4‐(methylnitrosamino)‐1‐(3‐pyridyl)‐1‐butanol (−73%), total 1‐hydroxypyrene (−53%), urine mutagenicity (−52%), 4‐aminobiphenyl hemoglobin adducts (−43%), carboxyhemoglobin AUC7–23 h (−80%), and 3‐hydroxypropylmercapturic acid (−35%). These reductions in exposure in the EHCSS group were associated with statistically significant and pathophysiologically favorable changes in several cardiovascular risk factors, including white blood cell count (−0.78 × 103/μL), hemoglobin (−0.16 g/dL), hematocrit (−0.44%), urine 11‐dehydrothromboxane B2 (−374 ng/24 h), and high‐density lipoprotein cholesterol (+5 mg/dL).

The relationship between smoking machine derived tar yields and biomarkers of exposure in adult cigarette smokers in the US

UNLABELLED Comprehensive data on human exposure to smoke constituents from different machine-measured tar yield cigarettes is limited. METHODS This study used a stratified, cross-sectional, multi-center design to estimate biomarkers of exposure (BOE) from nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), pyrene, CO, acrolein, and 1,3-butadiene and their relationship to tar yield categories of cigarette in adult smokers in the U.S. 3625 adults smokers were enrolled into four tar categories < or =2.9 mg (T1), 3.0-6.9 mg (T2), 7.0-12.9 mg (T3), and > or =13.0mg (T4). Biomarkers were measured in blood (carboxyhemoglobin, 4-aminobiphenyl-hemoglobin (4-ABP-Hb)-adducts, serum cotinine) and 24h urine (nicotine and five metabolites, calculated as nicotine equivalents (NE), NNAL, 1-OH-pyrene, 3-HPMA, MHBMA and DHBMA). Data were analyzed using analysis of covariance (ANCOVA). RESULTS Tar was a significant factor for most biomarkers in the ANCOVA models. The largest least square mean differences between tar categories was 35% for NE per day, 28% for NE per cigarette, 36% for serum cotinine, 42% for NNAL per day, 29% for NNAL per cigarette, 26% for 1-OHP, 24% for COHb, 14% for 3-HPMA and 40% for 4-ABP-Hb. Variability in BOE ranged from 41% to 154% CV. CONCLUSIONS There was a statistically significant effect of machine-measured tar yield on most BOE, which were generally lower with lower tar yield.

A randomized, controlled exposure study in adult smokers of full flavor Marlboro cigarettes switching to Marlboro Lights or Marlboro Ultra Lights cigarettes.

Rationale. To date no state-of-the-art clinical study has been conducted to address the question as to whether switching to lower tar cigarettes reduces exposure to smoke constituents in humans. Methods. Randomized, controlled, forced switching study in 225 adult smokers of full flavor Marlboro (MFF) cigarettes for 8 days with a 24-week follow-up. Subjects smoked MFF (a 15-mg Federal Trade Commission (FTC) tar cigarette) at baseline and were randomized to smoke 11-mg Marlboro Lights (ML) or 6-mg Marlboro Ultra Lights (MUL) cigarettes. Biomarkers of exposure to nicotine, 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), pyrene, CO, benzene, acrolein, and mutagenic substances were measured. Results. In the short-term phase, switching from MFF to ML showed statistically significant decreases in nicotine exposure (-13%) and non-significant increases in CO exposure (+6%), while switching from MFF to MUL showed statistically significant decreases in nicotine (-27%) and CO (-13%) exposure. Both nicotine and CO biomarkers trended similarly in the 24-week follow-up as in the short-term phase. The other biomarkers of cigarette smoke constituents followed the same trend as nicotine at the end of the 24-week follow-up. Conclusions. Switching smokers to lower FTC tar yield cigarettes, on average, reduces nicotine and other biomarkers considered surrogates of tar exposure.