Effect of race and glucuronidation rates on the relationship between nicotine metabolite ratio and nicotine clearance.

OBJECTIVES: To investigate if the nicotine metabolite ratio (NMR, the ratio of nicotine metabolites 3'-hydroxycotinine/cotinine) is a reliable phenotypic biomarker for nicotine clearance across races, and as a function of differences in the rate of nicotine, cotinine and 3'-hydroxycotinine glucuronidation and UGT genotypes. METHODS: Participants [Caucasians (Whites), African Americans (Blacks) and Asian-Americans (Asians)] received an oral solution of deuterium-labeled nicotine and its metabolite cotinine. Plasma and saliva concentrations of nicotine and cotinine were used to determine oral clearances. Rates of glucuronidation were assessed from urine glucuronide/parent ratios, and UGT2B10 and UGT2B17 genotypes from DNA. RESULTS: Among the 227 participants, 96 (42%) were White, 67 (30%) Asian and 64 (28%) Black. Compared to the other two races, Whites had higher nicotine and cotinine total oral clearance, Blacks had lower nicotine and cotinine glucuronidation rates and Asians had lower 3'-hydroxycotinine glucuronidation rates. A strong positive correlation (correlations coefficients 0.77-0.84; P < 0.001) between NMR and nicotine oral clearance was found for all three races, and NMR remained a strong predictor for the nicotine oral clearance while adjusting for race, sex and age. Neither the metabolite glucuronidation ratios nor the UGT genotypes had significant effects on the ability of NMR to predict nicotine oral clearance. CONCLUSION: NMR appears to be a reliable phenotypic biomarker for nicotine clearance across races, glucuronidation phenotypes and genotypes. Racial differences in the relationships between NMR, smoking behaviors and addiction are unlikely to be related to an inadequate estimation of nicotine clearance on the basis of NMR.

The influence of nicotine metabolic rate on working memory over 6 hours of abstinence from nicotine.

BACKGROUND: A faster rate of nicotine metabolism has been associated with smoking more cigarettes, greater nicotine withdrawal symptoms, and lower smoking quit rates. However, the association between nicotine metabolic rate (NMR) and cognitive functioning during withdrawal has not been determined. METHODS: We compared cognitive function in 121 fast or slow nicotine metabolizers after smoking, and at 3 and 6 h of nicotine abstinence. Cognitive functioning was assessed using N-back working memory tests with outcomes of accuracy and processing speed. Participants smoked two cigarettes and then abstained from smoking for 6 h. N-back tests were administered after smoking (0 h) and at 3 and 6 h of nicotine abstinence. RESULTS: An effect of processing speed was found over time on the 2-back, in that participants had significantly longer average reaction times when the stimuli presented did not match the target letter. NMR was not significantly associated with the processing speed change over time. Within-race differences in working memory were evident in that Caucasian fast metabolizers had significantly poorer accuracy and processing speed. CONCLUSIONS: Minimal change in working memory over 6 h of nicotine abstinence was observed. Overall, NMR was not significantly associated with the change in processing speed, however Caucasian fast metabolizers displayed poorer accuracy and processing speed at discrete time points.

Effects of Nicotine Metabolic Rate on Cigarette Reinforcement.

INTRODUCTION: The rate of nicotine metabolism, estimated by the nicotine metabolite ratio (NMR), is an important determinant of tobacco dependence. This study investigated the effect of NMR on smoking behavior due to nicotine reinforcement during ad libitum smoking. AIMS AND METHODS: As part of a larger study, participants were stratified based on saliva NMR as fast and slow metabolizers. After smoking a cigarette and measuring nicotine blood concentrations, participants smoked as desired over a 90-minute period. Analysis included time to first cigarette, total number of cigarettes, total number of puffs, and weight of tobacco consumed. RESULTS: Sixty-one (48%) participants were fast metabolizers and 66 (52%) slow metabolizers by NMR. No significant differences were found regarding the smoking topography variables by NMR. Normal metabolizers by genotype (n = 79) had a shorter time to first cigarette than reduced metabolizers (n = 39; p = .032). Blacks smoked fewer cigarettes (p = .008) and took fewer total puffs (p = .002) compared with Whites. Among Whites, fast metabolizers by NMR had a shorter time to first cigarette compared with slow metabolizers (p = .014). Among fast metabolizers, Whites had, compared with Blacks, shorter latency to first cigarette (p = .003) and higher number of total puffs (p = .014) and cigarettes smoked (p = .014). Baseline cigarettes per day and nicotine elimination half-life significantly predicted topography outcomes. CONCLUSIONS: Saliva NMR did not predict cigarette reinforcement during a relatively brief period of ad libitum smoking. Differences were seen by race, with White fast metabolizers by NMR having shorter time to first cigarettes compared with slow metabolizers. IMPLICATIONS: After a 90-minute period of nicotine abstinence, NMR was not significantly associated with smoking reinforcement. Slow and fast metabolizers had similar time to first cigarette, number of cigarettes smoked, total number of puffs, and tobacco consumed; however, within-race differences show that within Whites, fast metabolizers had a faster time to first cigarette than slow metabolizers.

Differences in nicotine intake and effects from electronic and combustible cigarettes among dual users.

AIM: To describe systemic nicotine exposure and subjective effects of electronic cigarettes (e-cigarettes) in people who use both e-cigarettes and cigarettes (dual users), including within-subject comparisons of e-cigarette and cigarette use. DESIGN: Two-arm, counterbalanced cross-over study. Participants used their usual brand of e-cigarette or cigarette during a standardized session in a 2-week study. SETTING: Hospital research ward, San Francisco, CA, USA. PARTICIPANTS: Thirty-six healthy (eight women, 28 men) participants. MEASUREMENTS: Plasma nicotine was analyzed by gas chromatography-tandem mass spectrometry; nicotine withdrawal, urge to smoke and vape, affective states, craving, satisfaction and psychological reward were measured by standardized questionnaires. FINDINGS: Compared with cigarettes, average maximum plasma nicotine concentration (Cmax ) was lower with e-cigarettes [6.1 ± 5.5 ng/ml, mean ± standard deviation (SD) versus 20.2 ± 11.1 ng/ml, P < 0.001] and time of maximal concentration (Tmax ) was longer (6.5 ± 5.4 versus 2.7 ± 2.4 minutes, P < 0.001). Use of both products resulted in a reduction in the severity of withdrawal symptoms, negative affect and urge to use either product. E-cigarettes were less rewarding and satisfying and reduced craving to a lesser degree than cigarettes. We were not able to detect any differences in withdrawal symptoms, affective states and urge to smoke cigarettes between e-cigarette and cigarette use. CONCLUSION: Systemic nicotine exposure was, on average, lower with single use of e-cigarettes compared with cigarettes, and e-cigarettes were judged to be less satisfying and rewarding and reduced craving less than cigarettes.

Relationship between skin melanin index and nicotine pharmacokinetics in African American smokers.

BACKGROUND: Blacks bear a disproportionate burden of smoking-related diseases and experience greater difficulty quitting smoking than Whites. Nicotine has a high affinity for melanin, and it has been hypothesized that melanin levels might influence nicotine pharmacokinetics and enhance dependence. The aim of this study was to evaluate the hypothesis that melanin affects nicotine disposition kinetics in humans. METHODS: Forty-four Black participants were administered intravenous infusions of deuterium-labeled nicotine and cotinine. Plasma concentrations of nicotine and cotinine were measured, and pharmacokinetic parameters were estimated. The constitutive and facultative melanin indexes were measured using a dermaspectrophotometer. RESULTS: The median constitutive melanin index was 60.7 (32.8-134.7) and the median facultative melanin index 68.1 (38.6-127.1). The mean (±SD) nicotine elimination half-life was 136 min (±33.5), clearance was 1237 mL/min (±331), and Vss was 204 L (±66), or 2.6 L/kg (±0.7). No evidence of significant differences was found in nicotine pharmacokinetic parameters by comparing participants in different melanin index quartiles (outliers with very high melanin index had similar pharmacokinetic values to others). Differences were not statistically significant when adjusted for age, BMI, sex and CYP2A6 genotype or the nicotine metabolite ratio (NMR), and no evidence of significant correlations were found between melanin (facultative or constitutive) and the pharmacokinetic parameters of nicotine or cotinine or tobacco dependence measures. CONCLUSIONS: Based on our finding in this group of Black smokers, we could not confirm the hypothesis that melanin significantly affects nicotine disposition kinetics or measures of tobacco dependence.

Effects of Nicotine Metabolic Rate on Withdrawal Symptoms and Response to Cigarette Smoking After Abstinence.

This study investigated the influence of the rate of nicotine metabolism, as indicated by the nicotine metabolite ratio (NMR), on tobacco dependence. We stratified 136 smokers on the basis of saliva NMR as fast (n = 65) and slow (n = 71) metabolizers. Two "loading cigarettes" were smoked after overnight, and a "reward cigarette" was smoked after 6 hours of daytime, abstinence. Blood nicotine concentrations, expired carbon monoxide, withdrawal/craving, and reward questionnaires were collected before/after smoking and during daytime abstinence. Compared with slow metabolizers, fast metabolizers had a shorter nicotine elimination half-life (P < 0.001), lower plasma nicotine concentrations (P < 0.001), and higher withdrawal/craving scores (P < 0.05) for most times during daytime abstinence, indicating that fast metabolizers are likely smoking more to relieve withdrawal symptoms (negative reinforcement). Reward/satisfaction scores were similar in fast and slow metabolizers, suggesting that faster nicotine metabolism, assessed by NMR, is not associated with greater positive reinforcement. CYP2A6 normal (n = 82) and reduced (n = 42) genotype predicted plasma nicotine concentrations but not withdrawal symptoms.

Butanediol Conversion to Gamma-Hydroxybutyrate Markedly Reduced by the Alcohol Dehydrogenase Blocker Fomepizole.

1,4-Butanediol (BDO)-used as solvent and abused for its euphoric effects-is converted to gamma-hydroxybutyrate (GHB) by the enzyme alcohol dehydrogenase. This double-blind, placebo-controlled crossover study with six healthy volunteers is the first to date investigating the role of the ADH inhibitor fomepizole (4-methylpyrazole (4MP)) in moderating this conversion in humans. Participants received on two different days either intravenous placebo or 15 mg/kg 4MP followed by oral administration of 25 mg/kg BDO. Pretreatment with 4MP resulted in significantly higher BDO maximal plasma concentration (P = 0.001) and area under the concentration-time curve (AUC; P = 0.028), confirming that ADH is the primary pathway for the conversion of BDO to GHB in humans. With 4MP, the mean arterial pressure was significantly lower at 105 minutes compared to baseline (P = 0.003), indicating that blood pressure lowering, observed not with a temporal relationship to 4MP administration but after the maximum BDO concentration was reached, may be an intrinsic effect of BDO.

Effect of γ-hydroxybutyrate (GHB) on driving as measured by a driving simulator.

RATIONALE: Gamma-hydroxybutyrate acid (GHB), a GABAB receptor agonist approved for treatment of narcolepsy, impairs driving ability, but little is known about doses and plasma concentrations associated with impairment and time course of recovery. OBJECTIVE: To assess effects of oral GHB (Xyrem®) upon driving as measured by a driving simulator, and to determine plasma concentrations associated with impairment and the time course of recovery. METHODS: Randomized, double-blind, two-arm crossover study, during which 16 participants received GHB 50 mg/kg orally or placebo. GHB blood samples were collected prior to and at 1, 3, and 6 h post dosing. Driving simulator sessions occurred immediately after blood sampling. RESULTS: Plasma GHB was not detectable at baseline or 6 h post dosing. Median GHB concentrations at 1 and 3 h were 83.1 mg/L (range 54-110) and 24.4 mg/L (range 7.2-49.7), respectively. Compared to placebo, at 1 h post GHB dosing, significant differences were seen for the life-threatening outcome collisions (p < 0.001) and off-road accidents (p = 0.018). Although driving was not faster, there was significantly more weaving and erratic driving with GHB as measured by speed deviation (p = 0.002) and lane position deviation (p = 0.004). No significant impairment regarding driving outcomes was found in the GHB group at 3 and 6 h post dose. CONCLUSION: GHB in doses used to treat narcolepsy resulted in severe driving impairment at 1 h post dosing. After 3 to 6 h, there was full recovery indicating that safe driving is expected the next morning after bedtime therapeutic GHB use in the absence of other substances.

Comparison of Urine 4-(Methylnitrosamino)-1-(3)Pyridyl-1-Butanol and Cotinine for Assessment of Active and Passive Smoke Exposure in Urban Adolescents.

Background: Many adolescents are exposed to tobacco smoke, from either active smoking (CS) or secondhand smoke (SHS) exposure. Tobacco-specific biomarkers of exposure include cotinine (detects use in past 2-4 days) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL; detects use for a month or longer). NNAL is expected to detect more intermittent tobacco exposure. We compared NNAL and cotinine as biomarkers of exposure to tobacco in urban adolescents and determined the optimal NNAL cutoff point to distinguish CS from SHS exposure.Methods: Surplus urine samples, collected from 466 adolescents attending pediatric well or urgent care visits at Zuckerberg San Francisco General Hospital in 2013 to 2014, were assayed for cotinine and NNAL.Results: Ninety-four percent of adolescents had measurable levels of NNAL compared with 87% for cotinine. The optimal NNAL cutoff point to distinguish CS from SHS was 9.6 pg/mL by latent class or 14.4 pg/mL by receiver-operating characteristic analysis. Cotinine and NNAL were strongly correlated, but the correlation slopes differed for active versus SHS-exposed adolescents. Among nonsmokers, NNAL levels were significantly higher in African American (median, 3.3 pg/mL) compared with other groups (0.9-1.9 pg/mL), suggesting greater exposure to SHS.Conclusions: Urine NNAL screening finds a large majority (94%) of urban adolescents are exposed to tobacco. African Americans are exposed to higher levels of SHS than other ethnic/racial groups.Impact: SHS is associated with significant medical morbidity in adolescents. Routine biochemical screening with NNAL or cotinine detects high prevalence of SHS exposure and should be considered as a tool to reduce SHS exposure in high-risk populations. Cancer Epidemiol Biomarkers Prev; 27(3); 254-61. ©2018 AACR.

Impact of e-liquid flavors on nicotine intake and pharmacology of e-cigarettes.

OBJECTIVES: To describe the effect of e-liquid flavors on nicotine intake and pharmacology of e-cigarettes. METHODS: 11 males and 3 females participated in a 3-day inpatient crossover study with strawberry, tobacco, and their usual flavor e-liquid. Nicotine levels were nominally 18mg/mL in the strawberry (pH 8.29) and tobacco (pH 9.10) e-liquids and ranged between 3-18mg/mL in the usual brands (mean pH 6.80). Each day consisted of a 15-puff session followed by 4h of abstinence, then 90min of ad libitum use. Subjects used a KangerTech mini ProTank 3. RESULTS: After 15 puffs, the amount of nicotine inhaled and systemically retained were not significantly different between the strawberry and tobacco e-liquids but plasma AUC(0→180) was significantly higher with the strawberry e-liquid. While not significantly different, Cmax was 22% higher and various early time point AUCs to measure rate of rise of nicotine in blood ranged between 17 and 23% higher with the strawberry e-liquid compared to the tobacco e-liquid. During ad libitum use, systemic exposure to nicotine (AUC(0→90)) was the same for the tobacco and usual brand e-liquids but were both significantly lower than after using the strawberry e-liquid. The usual flavors were more liked and satisfying than the strawberry and tobacco e-liquids. CONCLUSION: Flavors influence nicotine exposure through flavor liking, may affect rate of nicotine absorption possibly through pH effects, and contribute to heart rate acceleration and subjective effects of e-cigarettes. E-cigarette users titrate their nicotine exposure but the extent of titration may vary across flavors.

Urine Cotinine Screening Detects Nearly Ubiquitous Tobacco Smoke Exposure in Urban Adolescents.

INTRODUCTION: Routine biochemical assessment of tobacco smoke exposure could lead to more effective interventions to reduce or prevent secondhand smoke (SHS)-related disease in adolescents. Our aim was to determine using urine cotinine (major nicotine metabolite) measurement the prevalence of tobacco smoke exposure among adolescents receiving outpatient care at an urban public hospital. METHODS: Surplus urine was collected in 466 adolescents attending pediatric or urgent care clinics at Zuckerberg San Francisco General Hospital, serving families with lower levels of income and education, in 2013-2014. The majority were Hispanic or African American. Urine cotinine cut points of 0.05 to 0.25 ng/ml, 0.25 to 30 ng/ml, and 30 ng/ml were used to classify subjects as light SHS or thirdhand smoke exposed, SHS or light/intermittent active users, and active tobacco users, respectively. RESULTS: Among subjects 87% were exposed, including 12% active smoking, 46% SHS and 30% lightly exposed. The SHS exposed group adjusted geometric mean cotinine values were significantly higher in African Americans (1.48 ng/ml) compared to other groups (0.56-1.13 ng/ml). CONCLUSIONS: In a city with a low smoking prevalence (12%), a large majority (87%) of adolescents seen in a public hospital clinic are exposed to tobacco. This is much higher than reported in national epidemiological studies of adolescents, which used a plasma biomarker. Since SHS is associated with significant respiratory diseases and parents and adolescents underreport exposure to SHS, routine biochemical screening should be considered as a tool to reduce SHS exposure. The clinical significance of light exposure needs to be investigated. IMPLICATIONS: Urine biomarker screening found that a large majority (87%) of adolescents treated in an urban public hospital are exposed to tobacco. Since SHS is associated with significant respiratory diseases and parents and adolescents underreport exposure to SHS, routine biochemical screening should be considered as a tool to reduce SHS exposure.

Disposition kinetics and metabolism of nicotine and cotinine in African American smokers: impact of CYP2A6 genetic variation and enzymatic activity.

OBJECTIVE: The rate of nicotine metabolism, determined primarily by CYP2A6 activity, influences tobacco dependence and smoking-induced disease risk. The prevalence of CYP2A6 gene variants differs by race, with greater numbers in African Americans compared with Caucasians. We studied nicotine disposition kinetics and metabolism by the CYP2A6 genotype and enzymatic activity, as measured by the nicotine metabolite ratio (NMR), in African American smokers. METHODS: Participants were administered intravenous infusions of deuterium-labeled nicotine and cotinine. Plasma and urine concentrations of nicotine and metabolites were measured and pharmacokinetic parameters were estimated. RESULTS: Pharmacokinetic parameters and urine metabolite excretion data were analyzed by CYP2A6 genotype and by NMR. A number of gene variants were associated with markedly reduced nicotine and cotinine clearances. NMR was strongly correlated with nicotine (r=0.72) and cotinine (r=0.80) clearances. Participants with higher NMR excreted significantly greater nicotine C-oxidation and lower non-C-oxidation products compared with lower NMR participants. CONCLUSION: CYP2A6 genotype, NMR, and nicotine pharmacokinetic data may inform studies of individual differences in smoking behavior and biomarkers of nicotine exposure.

The Influence of Puff Characteristics, Nicotine Dependence, and Rate of Nicotine Metabolism on Daily Nicotine Exposure in African American Smokers.

BACKGROUND: African American (AA) smokers experience greater tobacco-related disease burden than Whites, despite smoking fewer cigarettes per day (CPD). Understanding factors that influence daily nicotine intake in AA smokers is an important step toward decreasing tobacco-related health disparities. One factor of interest is smoking topography, or the study of puffing behavior. AIMS: (i) to create a model using puff characteristics, nicotine dependence, and nicotine metabolism to predict daily nicotine exposure, and (ii) to compare puff characteristics and nicotine intake from two cigarettes smoked at different times to ensure the reliability of the puff characteristics included in our model. METHODS: Sixty AA smokers smoked their preferred brand of cigarette at two time points through a topography device. Plasma nicotine, expired CO, and changes in subjective measures were measured before and after each cigarette. Total nicotine equivalents (TNE) was measured from 24-hour urine collected during ad libitum smoking. RESULTS: In a model predicting daily nicotine exposure, total puff volume, CPD, sex, and menthol status were significant predictors (R(2) = 0.44, P < 0.001). Total puff volume was significantly greater and inter-puff intervals were significantly shorter after ad lib smoking compared with the first cigarette of the day, but puffing behaviors for both cigarettes were highly correlated (r range = 0.69-0.89, P < 0.001) within-subjects. CONCLUSION: This is the first study, to our knowledge, to show that puff characteristics of individual cigarettes are predictive of daily nicotine intake. IMPACT: These findings enhance our understanding of the relationship between smoking behavior and nicotine intake in AA smokers. Cancer Epidemiol Biomarkers Prev; 25(6); 936-43. ©2016 AACR.

Nicotine delivery, retention and pharmacokinetics from various electronic cigarettes.

AIMS: To measure the systemic retention of nicotine, propylene glycol (PG) and vegetable glycerin (VG) in electronic cigarette (e-cigarette) users, and assess the abuse liability of e-cigarettes by characterizing nicotine pharmacokinetics. DESIGN: E-cigarette users recruited over the internet participated in a 1-day research ward study. Subjects took 15 puffs from their usual brand of e-cigarette. Exhaled breath was trapped in gas-washing bottles and blood was sampled before and several times after use. SETTING: San Francisco, California, USA. PARTICIPANTS: Thirteen healthy, experienced adult e-cigarette users (six females and seven males). MEASUREMENTS: Plasma nicotine was analyzed by gas chromatography-mass spectrometry (GC-MS/MS) and nicotine, VG and PG in e-liquids and gas traps were analyzed by LC-MS/MS. Heart rate changes and subjective effects were assessed. FINDINGS: E-cigarettes delivered an average of 1.33 (0.87-1.79) mg [mean and 95% confidence interval (CI)] of nicotine, and 93.8% of the inhaled dose, 1.22 (0.80-1.66) was systemically retained. Average maximum plasma nicotine concentration (Cmax ) was 8.4 (5.4-11.5) ng/ml and time of maximal concentration (Tmax ) was 2-5 minutes. One participant had Tmax of 30 minutes. 84.4% and 91.7% of VG and PG, respectively, was systemically retained. Heart rate increased by an average of 8.0 beats per minute after 5 minutes. Withdrawal and urge to smoke decreased and the e-cigarettes were described as satisfying. CONCLUSIONS: E-cigarettes can deliver levels of nicotine that are comparable to or higher than typical tobacco cigarettes, with similar systemic retention. Although the average maximum plasma nicotine concentration in experienced e-cigarette users appears to be generally lower than what has been reported from tobacco cigarette use, the shape of the pharmacokinetic curve is similar, suggesting addictive potential.

Nicotine Delivery and Vaping Behavior During ad Libitum E-cigarette Access.

OBJECTIVE: To characterize vaping behavior and nicotine intake during ad libitum e-cigarette access. METHODS: Thirteen adult e-cigarette users had 90 minutes of videotaped ad libitum access to their usual e-cigarette. Plasma nicotine was measured before and every 15 minutes after the first puff; subjective effects were measured before and after the session. RESULTS: Average puff duration and interpuff interval were 3.5±1.4 seconds (±SD) and 118±141 seconds, respectively. 12% of puffs were unclustered puffs while 43%, 28%, and 17% were clustered in groups of 2-5, 6-10, and >10 puffs, respectively. On average, 4.0±3.3 mg of nicotine was inhaled; the maximum plasma nicotine concentration (Cmax) was 12.8±8.5 ng/mL. Among the 8 tank users, number of puffs was positively correlated with amount of nicotine inhaled, Cmax, and area under the plasma nicotine concentration-time curve (AUC0→90min) while interpuff interval was negatively correlated with Cmax and AUC0→90. CONCLUSION: Vaping patterns differ from cigarette smoking. Plasma nicotine levels were consistent with intermittent dosing of nicotine from e-cigarettes compared to the more bolus dosing from cigarettes. Differences in delivery patterns and peak levels of nicotine achieved could influence the addictiveness of e-cigarettes compared to conventional cigarettes.

Effect of reducing the nicotine content of cigarettes on cigarette smoking behavior and tobacco smoke toxicant exposure: 2-year follow up.

BACKGROUND AND AIMS: A broadly mandated reduction of the nicotine content (RNC) of cigarettes has been proposed in the United States to reduce the addictiveness of cigarettes, to prevent new smokers from becoming addicted and to facilitate quitting in established smokers. The primary aim of this study was to determine whether following 7 months of smoking very low nicotine content cigarettes (VLNC), and then returning to their own cigarettes, smokers would demonstrate persistently reduced nicotine intake compared with baseline or quit smoking. METHODS: In a community-based clinic 135 smokers not interested in quitting were randomized to one of two groups. A research group smoked their usual brand of cigarettes, followed by five types of research cigarettes with progressively lower nicotine content, each for 1 month, followed by 6 months at the lowest nicotine level (0.5 mg/cigarette) (53 subjects) and then 12 months with no intervention (30 subjects completed). A control group smoked their usual brand for the same period of time (50 subjects at 6 months, 38 completed). Smoking behavior, biomarkers of nicotine intake and smoke toxicant exposure were measured. RESULTS: After 7 months smoking VLNC, nicotine intake remained below baseline (plasma cotinine 149 versus 250 ng/ml, P<0.005) with no significant change in cigarettes per day or expired carbon monoxide (CO). During the 12-month follow-up, cotinine levels in RNC smokers rose to baseline levels and to those of control smokers. Quit rates among RNC smokers were very low [7.5 versus 2% in controls, not significant). CONCLUSIONS: In smokers not interested in quitting, reducing the nicotine content in cigarettes over 12 months does not appear to result in extinction of nicotine dependence, assessed by persistently reduced nicotine intake or quitting smoking over the subsequent 12 months.

Intake of toxic and carcinogenic volatile organic compounds from secondhand smoke in motor vehicles.

BACKGROUND: Volatile organic compounds (VOC) from tobacco smoke are associated with cancer, cardiovascular, and respiratory diseases. The objective of this study was to characterize the exposure of nonsmokers to VOCs from secondhand smoke (SHS) in vehicles using mercapturic acid metabolites. METHODS: Fourteen nonsmokers were individually exposed in the backseat to one hour of SHS from a smoker seated in the driver's seat who smoked three cigarettes at 20-minute intervals in a stationary car with windows opened by 10 cm. Baseline and 0- to 8-hour postexposure mercapturic acid metabolites of nine VOCs were measured in urine. Air-to-urine VOC ratios were estimated on the basis of respirable particulate matter (PM2.5) or air nicotine concentration, and lifetime excess risk (LER) of cancer death from exposure to acrylonitrile, benzene, and 1,3-butadiene was estimated for adults. RESULTS: The greatest increase in 0- to 8-hour postexposure concentrations of mercapturic acids from baseline was MHBMA-3 (parent, 1,3-butadiene; 2.1-fold), then CNEMA (acrylonitrile; 1.7-fold), PMA (benzene; 1.6-fold), MMA (methylating agents; 1.6-fold), and HEMA (ethylene oxide; 1.3-fold). The LER of cancer death from exposure to acrylonitrile, benzene, and 1,3-butadiene in SHS for 5 hours a week ranged from 15.5 × 10(-6) to 28.1 × 10(-6) for adults, using air nicotine and PM2.5 to predict air VOC exposure, respectively. CONCLUSION: Nonsmokers have significant intake of multiple VOCs from breathing SHS in cars, corresponding to health risks that exceed the acceptable level. IMPACT: Smoking in cars may be associated with increased risks of cancer, respiratory, and cardiovascular diseases among nonsmokers.

Biomarkers of secondhand smoke exposure in automobiles.

OBJECTIVES: The objectives of this study were: (1) to characterise the exposure of non-smokers exposed to secondhand smoke (SHS) in a vehicle using biomarkers, (2) to describe the time course of the biomarkers over 24 h, and (3) to examine the relationship between tobacco biomarkers and airborne concentrations of SHS markers. METHODS: Eight non-smokers were individually exposed to SHS in cars with fully open front windows and closed back windows over an hour from a smoker who smoked three cigarettes at 20 min intervals. The non-smokers sat in the back seat on the passenger side, while the smoker sat in the driver's seat. Plasma cotinine and urine cotinine, 3-hydroxycotinine (3HC) and 4-(methylnitrosoamino)-(3-pyridyl)-1-butanol (NNAL) were compared in samples taken at baseline (BL) and several time-points after exposure. Nicotine, particulate matter (PM2.5) and carbon monoxide (CO) were measured inside and outside the vehicle and ventilation rates in the cars were measured. RESULTS: Average plasma cotinine and the molar sum of urine cotinine and 3HC (COT+3HC) increased four-fold, urine cotinine increased six-fold and urine NNAL increased ∼27 times compared to BL biomarker levels. Plasma cotinine, urine COT+3HC and NNAL peaked at 4-8 h post-exposure while urine cotinine peaked within 4 h. Plasma cotinine was significantly correlated to PM2.5 (Spearman correlation rs=0.94) and CO (rs=0.76) but not to air nicotine. The correlations between urine biomarkers, cotinine, COT+3HC and NNAL, and air nicotine, PM2.5 and CO were moderate but non-significant (rs range = 0.31-0.60). CONCLUSIONS: Brief SHS exposure in cars resulted in substantial increases in levels of tobacco biomarkers in non-smokers. For optimal characterisation of SHS exposure, tobacco biomarkers should be measured within 4-8 h post-exposure. Additional studies are needed to better describe the relationship between tobacco biomarkers and environmental markers of SHS.

Particulate mass and polycyclic aromatic hydrocarbons exposure from secondhand smoke in the back seat of a vehicle.

CONTEXT: Exposure to secondhand smoke (SHS) has been reduced in the USA by banning smoking in public places. These restrictions have not had the same effect on children's exposure to SHS as adults suggesting that children are exposed to SHS in locations not covered by bans, such as private homes and cars. OBJECTIVES: Assess exposure to SHS in the backseat of a stationary vehicle where a child would sit, quantify exposures to fine particulates (PM2.5), polycyclic aromatic hydrocarbons (PAH), carbon monoxide (CO) and nicotine. Estimate the impact on a child's mean daily exposure to PM2.5. METHODS: SHS exposures in stationary vehicles with two different window configurations were monitored. A volunteer smoked three cigarettes in a one-hour period for twenty-two experiments. PM2.5, CO, nicotine and PAH where measured in the backseat of the vehicle. 16 PAH compounds were measured for in gas and particle phases as well as real-time particle phase concentrations. RESULTS: The mean PAH concentration, 1325.1 ng/m(3), was larger than concentrations measured in bars and restaurants were smoking is banned in many countries. We estimate that a child spending only ten minutes in the car with a smoker at the mean PM2.5 concentration measured in the first window configuration--1697 mg/m(3)--will cause a 30% increase to the daily mean PM2.5 personal average of a child. CONCLUSIONS: Estimates made using the measured data and previously reported PM2.5 daily mean concentrations for children in California showing that even short exposure periods are capable of creating large exposure to smoke.

Comparison of nicotine and carcinogen exposure with water pipe and cigarette smoking.

BACKGROUND: Smoking tobacco preparations in a water pipe (hookah) is widespread in many places of the world and is perceived by many as relatively safe. We investigated biomarkers of toxicant exposure with water pipe compared with cigarette smoking. METHODS: We conducted a crossover study to assess daily nicotine and carcinogen exposure with water pipe and cigarette smoking in 13 people who were experienced in using both products. RESULTS: When smoking an average of 3 water pipe sessions compared with smoking 11 cigarettes per day (cpd), water pipe use was associated with a significantly lower intake of nicotine, greater exposure to carbon monoxide (CO), and a different pattern of carcinogen exposure compared with cigarette smoking, with greater exposure to benzene, and high molecular weight polycyclic aromatic hydrocarbon (PAH), but less exposure to tobacco-specific nitrosamines, 1,3-butadiene, acrolein, acrylonitrile, propylene oxide, ethylene oxide, and low molecular weight PAHs. CONCLUSIONS: A different pattern of carcinogen exposure might result in a different cancer risk profile between cigarette and water pipe smoking. Of particular concern is the risk of leukemia related to high levels of benzene exposure with water pipe use. IMPACT: Smoking tobacco in water pipes has gained popularity in the United States and around the world. Many believe that water pipe smoking is not addictive and less harmful than cigarette smoking. We provide data on toxicant exposure that will help guide regulation and public education regarding water pipe health risk.