Breath Carbon Monoxide Levels Research Articles

Varenicline OTC Trial on Efficacy and Safety.

Varenicline helps people who smoke quit at rates 2-3 times greater than placebo. Currently in the U.S., varenicline is not available over the counter (OTC). In this study, we assessed the safety and efficacy of 1mg and 0.5mg varenicline as an OTC medication for smoking cessation in comparison to placebo. This randomized, double-blind, placebo-controlled study was performed at two clinical sites in the United States of n=313 people. The treatment period was 12 weeks. During the COVID pandemic, the protocol was modified to allow remote participation; verification of smoking status was via breath carbon monoxide levels for in-person visits and mailed urine cotinine kits for the remote participants. There was no difference in biologically confirmed continuous abstinence by condition between Weeks 8-12; however, the odds of biologically confirmed point prevalence abstinence were higher for those in the 1mg b.i.d. condition than for those in the placebo condition at Week 12 (OR 3.39; 95% CI 1.49, 7.71), and were higher for those assigned to the 1.0mg b.i.d. condition than the 0.5mg b.i.d. condition at Week 12 (OR 2.37; 95% CI 1.11, 5.05). Adverse events were modest, and as expected (vivid dreams and nausea in the medication conditions). The results are suggestive that varenicline is safe and effective as an OTC medication.

Efficacy of nutritional supplement (Haras) on carbon monoxide levels in smokers and non-smokers: An observational study.

Carbon monoxide (CO) concentrations in exhaled air may impart a quick, non-invasive method to determine smoking status. Haras is a nutraceutical medication, which is slowly gaining recognition for its antioxidant and anti-inflammatory activities. The effectiveness of the Haras therapy in smokers and non-smokers will be assessed by evaluating breath CO levels. The study included 101 test subjects with 76 subjects of smokers and 25 subjects of non-smokers. Both the test groups were given 10 mL of Haras juice in divided doses per day for 30 days. The CO levels were evaluated using a breath analyser before drug trial and then on the 8th, 15th, 22nd and after the conclusion of the drug trial. The Wilcoxon signed-rank test was used to compare the CO and carboxyhemoglobin levels among smokers and non-smokers. Smokers had higher mean percent carboxyhemoglobin and mean parts per million CO values than non-smokers, and the difference between the two was shown to be statistically significant (P < 0.001). It was also found to be statistically significant from the first day to the eighth day, the first day to the 15th day, the first day to the 20th second day, first day to the 30th day (P < 0.001). Haras can be used effectively as an alternative supportive treatment for the diminution of CO levels in smokers and non-smokers.

Whole person care: Outcomes from a 5-year care model integrating primary care into a behavioral health clinic.

Integrated mental and physical health care has the potential to improve health outcomes. A behavioral health organization established a reverse integration program site using a co-located model to provide primary care services to patients receiving behavioral health services. We ask whether this model of co-located care was effective in improving a range of physical health outcomes for clients. This program was funded with a grant from the Substance Abuse and Mental Health Services Administration Primary and Behavioral Health Care Integration. Patients received services in a community mental health setting that embedded primary care services. The population included adult patients with mental illness, substance use disorder (SUD), or co-occurring medical diagnoses in an urban setting. Just under half of the patients identified as non-White, and over one quarter identified as Hispanic. These characteristics demonstrate a medically complex and underserved population. This description and exploratory analysis utilized National Outcome Measures data and clinical health measures from electronic health records. We stratified data by SUD and mental illness diagnoses. We measured changes in health outcomes for this complex population of 532 patients from 2015 to 2019. From enrollment to last visit, patient outcomes improved for blood pressure and cholesterol. Conversely, waist circumference and breath carbon monoxide levels significantly worsened. This reverse integration co-location program demonstrates that positive health outcomes can be achieved through evidence-based care, adaptable clinic arrangements, and robust community connections and support. More work is needed to generate positive health outcomes in medically complex patients. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Breath Carbon Monoxide Level of Non-Smokers Exposed to Environmental Tobacco Smoke

Environmental tobacco smoke (ETS) exposure is a health hazard for non-smokers. To measure breath carbon monoxide (CO) levels of non-smoking subjects exposed to ETS and of non-smoking subjects not exposed to ETS. The study was conducted with the help of a pre-designed questionnaire. One hundred male subjects were selected for the study; group I consisted of 50 non-smokers (waiters in hotels/restaurants/bars) exposed to ETS and group II consisted of 50 non-smokers not exposed to ETS. All subjects underwent clinical examination. Breath CO levels of both the groups were measured by the Mini Smoklyzer. The mean breath CO level (ppm) was higher in group I compared to group II (9.18 +/- 2.84 versus 4.56 +/- 1.62; p < 0.001). The mean breath CO level was also significantly higher in ETS exposed subjects who worked for more than nine hours a day in bars, restaurants and hotels (p = 0.018) and in subjects suffering from respiratory diseases (p < 0.001) compared to normal subjects. The abnormally high level of breath CO observed in passive smokers exposed to ETS may suggest that, these subjects may be prone to develop the tobacco related diseases.

Breath Carbon Monoxide Levels in Different Forms of Smoking

Bidi, cigarette, hookah and chillum are common modes of tobacco smoking in India. Many people consider hookah and chillum smoking less toxic because smoke is filtered through water or wet cloth. We evaluated the toxicity of tobacco smoking by measuring end-tidal carbon monoxide (eCO) levels after various modes of smoking. Eighteen healthy smokers who smoked bidi, cigarette, hookah and chillum on six days were studied. They smoked one bidi, one cigarette, five minutes hookah, one serve (15 minutes) hookah, five minutes chillum and one serve (15 minutes) chillum on six days randomly. The eCO values were measured before initiation of smoking and for a period of one hour after the smoking session. Increase in eCO values in comparison to baseline after different modes of smoking was compared. In comparison to baseline, mean eCO levels were raised by 4.94 (0.96) parts per million (ppm) immediately and 4.17 (1.07) ppm 60 minutes after cigarette smoking. Bidi smoking caused slightly less increase in mean eCO levels (3.17 [0.82]). One serve of hookah and chillum smoking caused elevation of mean eCO values by almost eight-folds higher than that of cigarette smoking. Five minutes of smoking with hookah (22.18 [5.29]) and one serve of hookah (33.0 [8.76]) and chillum (40.14 [12.73]) caused significantly higher values of mean increase in eCO in comparison to cigarette smoking (p<0.001). With regard to eCO levels, hookah and chillum smoking are much more toxic than cigarette smoking.

Effect of cigarette smoking on smoking biomarkers, blood pressure and blood lipid levels among Sri Lankan male smokers

Study purposeThe aim of this study was to determine the fractional exhaled nitric oxide (FeNO) levels, exhaled breath carbon monoxide (eCO) levels, blood pressure, blood lipid levels between smokers and...

An innovation involving self-surveillance and serious gaming to increase smoking quit rate: Protocol for a pilot randomized controlled trial.

Smoking is a health hazard. Current smoking cessation measures such as behavioral change counselling by trained professionals, nicotine replacement therapy and medications have limited success. Smoking intensity is assessed using a portable device to measure the smokers’ exhaled breath carbon monoxide (eCO) level. A systematic review suggests the potential of serious gaming to increase smoking quit rate. However, the related studies were unable to explain and determine the effect gamification on smoking cessation.A handy personalized eCO measurement device linked to a smart-phone applications (app) has been developed (integrated STEADES-2 system). This novel system incorporates app-based video and print learning resources, authentication function and gamification using the eCO data as game element. Trained multidisciplinary healthcare professionals access the STEADES-2 data to monitor smoking status and support smokers via asynchronous virtual coaching. The pilot randomized controlled trial will enroll 20 smokers to use the STEADES-2 system (intervention group) and another 20 to the existing smoking cessation programme (control group) in primary care. The primary feasibility outcomes will include the recruitment response rate, the smokers’ usability of the STEADES-2 system, their self eCO monitoring, frequencies of participation in the serious games and interactions with their virtual coaches. Their smoking literacy, utility and experience of the STEADES-2 system are other outcomes. Smokers in both groups will be compared on their cigarette abstinence as secondary outcome based on eCO levels and urine cotinine test (primary outcomes after 12 weeks).The results will be disseminated via conferences and publications.

A pilot study of wellness coaching for smoking cessation among individuals with mental illnesses

Background Smoking continues to be a major health concern among persons with mental illnesses. Aims This pilot study compared smoking outcomes between wellness-coaching for smoking cessation and a control group. Methods Thirty-one individuals were enrolled in an educational group on smoking cessation and 23 completed an eight-session manualized education. Following this educational group, 11 of 23 participants were randomly assigned to wellness coaching for four months and 12 to a control condition. ANCOVAs were used to compare group differences in smoking outcomes. Results Fagerström Nicotine Dependence Index (FTND) score of the participants who received the wellness coaching intervention decreased significantly as compared to the control group, indicating a lower level of nicotine dependence. The outcomes of average number of cigarettes smoked daily and breath carbon monoxide level showed tendencies towards reductions for wellness coaching, although not statistically significant compared to the control condition. Conclusions Suggestions are shared about the feasibility of wellness coaching as well as barriers and challenges learned in implementing such an intervention to assist individuals with mental illnesses in quitting or reducing smoking.

The Preliminary Efficacy and Feasibility of Group-Based Smoking Cessation Treatment Program for Incarcerated Smokers.

Group-based tobacco dependence treatment has been known to help smokers to quit in general adult populations, but the feasibility and efficacy of this type of smoking cessation treatment in correctional settings remain uncertain. A 6-week group-based smoking cessation treatment with nicotine replacement therapy (NRT) in the form of nicotine patches was implemented in seven male prison facilities, in the Northeast, among smokers who were born biologically as male. Exhaled breath carbon monoxide (CO) levels were collected from participants at each session to confirm smoking status. Participants were evaluated at the 1-month post-group treatment follow-up to determine abstinence. Those who were lost to follow-up were recorded as continued smoking and not using NRT nicotine patches. The goal of the study was to explore the feasibility and preliminary efficacy of conducting a smoking cessation treatment program for incarcerated smokers. A total of 350 inmates were screened, 177 inmates were enrolled across the prison sites for the 6-week program, and 102 inmates completed the program. A majority of those enrolled reported that they began smoking when they were between 15 and 19 years of age (44.9%) and were smoking on average for 26 years. Less than half (21.3%) reported ever using electronic cigarettes at baseline and in Session 1,116 individuals who attended reported a median CO level of 18.0 parts per million (ppm). At a 1-month follow-up, 43 individuals reported a median CO level of 5.00 ppm. The study demonstrated preliminary efficacy and feasibility of group-based smoking cessation treatment with NRT nicotine patches in incarcerated smokers.

Nicotine Replacement Therapy and Healthy Lifestyle Psychoeducation for Smoking Reduction in Acute Psychiatric Inpatients: A Cluster-Randomized Parallel Study.

Effectiveness of nicotine replacement therapies in acute psychiatric inpatient settings remains under-researched. The aim of this study was to compare effectiveness and acceptability of 3 different forms of nicotine replacement therapy in achieving smoking reduction among acute psychiatric inpatients. This cluster-randomized, parallel study compared effectiveness and acceptability of nicotine inhalers, nicotine gum, and nicotine patches for smoking reduction in the acute psychiatric inpatient setting. The primary outcome was the exhaled breath carbon monoxide (CO) level change from baseline at weeks 4 and 8. Secondary outcomes included changes in nicotine withdrawal symptoms and psychiatric symptom severity. Three hundred ten inpatients on the acute care wards were randomly assigned to nicotine inhalers (n = 184), gum (n = 71), and patches (n = 55). Only the nicotine inhaler group showed statistically significant reduction in CO level from baseline at both weeks 4 and 8 (P < 0.001 and P = 0.032, respectively). The nicotine inhaler and the patch group showed significant decrease in nicotine withdrawal symptoms from baseline at both weeks 4 and 8. Meanwhile, the nicotine inhaler and the gum group showed significant decrease in psychiatric symptom severity from baseline at both weeks 4 and 8. Post hoc comparisons revealed that the inhaler group had a greater decrease in psychiatric symptom severity compared with the patch group. Nicotine inhalers may be an effective choice for smoking reduction in acute psychiatric inpatient settings given its significant effects on CO level, withdrawal symptoms, and psychiatric symptom severity, particularly during the first 4 weeks of treatment.

Effects of 6-Week Use of Very Low Nicotine Content Cigarettes in Smokers With Serious Mental Illness.

IntroductionThe US Food and Drug Administration is considering implementing a reduced-nicotine standard for cigarettes. Given the high rate of smoking among people with serious mental illness (SMI), it is important to examine the responses of these smokers to very low nicotine content (VLNC) cigarettes.MethodsThis trial compared the effects of VLNC (0.4 mg nicotine/g tobacco) and normal nicotine content cigarettes (15.8 mg/g) over a 6-week period in non-treatment-seeking smokers with schizophrenia, schizoaffective disorder, or bipolar disorder (n = 58). Linear regression was used to examine the effects of cigarette condition on cigarettes per day, subjective responses, nicotine and tobacco toxicant exposure, craving, withdrawal symptoms, and psychiatric symptoms.ResultsAt week 6, participants in the VLNC condition smoked fewer cigarettes per day, had lower breath carbon monoxide levels, lower craving scores, and rated their study cigarettes lower in satisfaction, reward, enjoyment, and craving reduction than those in the normal nicotine content condition (ps < .05). Week 6 psychiatric and extrapyramidal symptoms did not differ by condition, except for scores on a measure of parkinsonism, which were lower in the VLNC condition (p < .05). There were no differences across conditions on total nicotine exposure, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, withdrawal symptoms, or responses to abstinence.ConclusionsThese results suggest that a reduced-nicotine standard for cigarettes would reduce smoking among smokers with SMI. However, the lack of effect on total nicotine exposure indicates VLNC noncompliance, suggesting that smokers with SMI may respond to a reduced-nicotine standard by substituting alternative forms of nicotine.ImplicationsResults from this trial suggest that a reduced-nicotine standard for cigarettes would reduce smoking rates and smoke exposure in smokers with SMI, without increasing psychiatric symptoms. However, noncompliance with VLNC cigarettes was observed, suggesting that these smokers might respond to a reduced-nicotine standard by substituting alternative forms of nicotine.

A Pilot Study of E-Cigarette Naïve Cigarette Smokers and the Effects on Craving After Acute Exposure to E-Cigarettes in the Laboratory.

Recent surveys confirm continued increases in the use of electronic-cigarettes (e-cigarettes) in adolescents and adults. Users often state that e-cigarettes reduce tobacco craving and withdrawal symptoms in addition to their smoking. Data from laboratory studies and clinical trials have confirmed these statements, though there are inconsistencies in the outcomes. In this pilot study, we set out to evaluate the effects of e-cigarettes, as compared to the participants' own cigarettes, on baseline craving and smoking severity. Using a within-subjects, placebo-controlled study design, 15 tobacco-dependent, e-cigarette naïve participants sustained abstinence overnight. They completed distinct phases of this protocol during four separate study sessions. Participants were randomized to an e-cigarette device containing one of three doses of nicotine (0, 18, or 36 mg/ml) or their own cigarette. Each study visit was ~3 hours long and separated by at least 7 days. Visits included assessments of craving and smoking severity. The data showed that after 10 puffs in both the Own cigarette and e-cigarette conditions, breath carbon monoxide levels increased significantly in the former but not the latter. Questionnaire of Smoking Urges and Choices to Smoke scores were not statistically different across groups after two distinct bouts of 10 puffs each. Additionally, E-cigarette Perceptions Questionnaire responses were not significantly different according to dose. This experiment provides data demonstrating that e-cigarettes did not reduce craving or smoking severity in e-cigarette naïve users. However, since this was a pilot study, the conclusions that can be drawn are limited. (Am J Addict 2019;28:361-366).

Effectiveness and cost-effectiveness of repeated implementation intention formation on adolescent smoking initiation: A cluster randomized controlled trial.

Objective: Forming implementation intentions (if–then plans) about how to refuse cigarette offers plus antismoking messages was tested for reducing adolescent smoking. Method: Cluster randomized controlled trial with schools randomized (1:1) to receive implementation intention intervention and messages targeting not smoking (intervention) or completing homework (control). Adolescents (11–12 years at baseline) formed implementation intentions and read messages on 8 occasions over 4 years meaning masking treatment allocation was not possible. Outcomes were: follow-up (48 months) ever smoking, any smoking in last 30 days, regular smoking, and breath carbon monoxide levels. Analyses excluded baseline ever smokers, controlled for clustering by schools and examined effects of controlling for demographic variables. Economic evaluation (incremental cost effectiveness ratio; ICER) was conducted. Trial is registered (ISRCTN27596806). Results: Schools were randomly allocated (September–October 2012) to intervention (n = 25) or control (n = 23). At follow-up, among 6,155 baseline never smokers from 45 retained schools, ever smoking was significantly lower (RR = 0.83, 95% CI [0.71, 0.97], p = .016) in intervention (29.3%) compared with control (35.8%) and remained so controlling for demographics. Similar patterns observed for any smoking in last 30 days. Less consistent effects were observed for regular smoking and breath carbon monoxide levels. Economic analysis yielded an ICER of $134 per ever smoker avoided at age 15–16 years. Conclusions: This pragmatic trial supports the use of repeated implementation intentions about how to refuse the offer of a cigarette plus antismoking messages as an effective and cost-effective intervention to reduce smoking initiation in adolescents.

Salivary cotinine concentration and carbon monoxide levels in young adults smoking midwakh in comparison with cigarette smokers

ObjectivesTo estimate and compare the salivary cotinine levels using a semiquantitative method, called NicAlert, between three groups: non-smokers, daily smokers of cigarettes and daily smokers of midwakh, and to compare...

The implications of high carbon monoxide levels in early pregnancy for neonatal outcomes

ObjectivesThe aim of this study was to examine the implications of increased maternal Breath Carbon Monoxide (BCO) levels at the first antenatal visit for subsequent birthweight (BW) and neonatal outcomes. Study designSecondary analysis of a prospective, observational study. Pregnant women aged ≥18years who understood English were recruited (n=250). However, only women who delivered a normally formed baby weighing ≥500g were analysed (n=234). At the first antenatal visit, a research questionnaire was completed and a BCO test was performed. Obstetric and neonatal data computerised by midwives at the first antenatal visit and updated after delivery were also analysed. ResultsResults from the receiver operating characteristic (ROC) curve indicated the highest combined sensitivity and specificity for smoking was observed at a BCO cut-off level of 3ppm (sensitivity 85%, specificity 90%). Of the 234 women, 53 (22.6%) had a BCO ≥3ppm but only 36 (15.4%) disclosed smoking to the midwife on routine questioning. A further 23 (9.8%) were classified as non-disclosers based on a research questionnaire and/or a BCO measurement ≥3ppm. No relationship was found between the self-reported number of cigarettes daily in early pregnancy and BW (r=0.05, p=0.78). However, an inverse relationship was found between maternal BCO levels and BW (r=−0.31, p<0.001). BCO levels ≥3ppm in early pregnancy were associated with an increased risk of emergency caesarean section, low birth weight, BW <25th centile, fetal distress and having two or more adverse pregnancy events (all p<0.05). Smoking non-disclosers had babies with decreased BWs (−400.1g, 95% CI 141.1–659.0g, p<0.001), and higher rates of BW <25th centile (56.5% versus 25.3%, p<0.001), small-for-gestational-age (21.7% versus 9.1%, p<0.001) and fetal distress (39.1% versus 16.0%, p<0.01) compared to non-smokers Non-disclosers at the first antenatal visit also had a 22% higher rate of having two or more adverse pregnancy events (p<0.05). ConclusionThe results showed that an increased BCO level was associated with a lower BW and increased risk of adverse pregnancy and neonatal outcomes. This strengthens the case for universal BCO screening at the first antenatal visit. A high BCO reading should be an indication for referral to stop smoking services referral and close fetal surveillance.

Conscientiousness explains the link between childhood neglect and cigarette smoking in adults from a low-income, urban area-the differential effects of sex.

Cigarette smoking represents the leading cause of preventable morbidity and mortality in the US and understanding its risk factors remains a critical public health endeavor. Low-income individuals and individuals with a history of childhood maltreatment are at heightened risk for cigarette smoking, yet the underlying factors between this association are understudied. Conscientiousness is one construct with potential explanatory relevance to both smoking and childhood neglect. The current investigation examined the association between childhood physical and emotional neglect with smoking (i.e., self-reported cigarette smoking and breath carbon monoxide levels) via conscientiousness. The sample was comprised of 115 adults (Mage = 50.46, SDage = 5.86; 76.4% Black) recruited from a community center serving low-income and homeless individuals. Mediation analyses showed the indirect effect of childhood emotional neglect on cigarette smoking through conscientiousness; for physical neglect, this relationship was only present among males. The current study provides preliminary evidence that conscientiousness may be a particularly important vulnerability factor when examining the association between childhood neglect and smoking.

Dimensions of impulsive behavior: Predicting contingency management treatment outcomes for adolescent smokers

BackgroundBehavioral measures of impulsive behavior include the dimensions of behavioral disinhibition, decision-making, and lapses of attention. These behaviors are associated with a range of risky activities during adolescence, including cigarette smoking; however, few studies have evaluated their associations with tobacco treatment outcomes. The current study examined the relationship between impulsive behavior and contingency management treatment outcomes for adolescent smokers. MethodsData from two contingency management smoking cessation trials were combined (N = 189 adolescents). Participants provided breath carbon monoxide (CO) samples with incentives delivered contingent (i.e., active treatment [AT] condition) or non-contingent (i.e., control treatment [CT] condition) on CO level. Dimensions of impulsive behavior were assessed pre- and post-treatment using the Go/Stop Task, a measure of delay discounting, a continuous performance task, while self-reported impulsivity was assessed with the Barratt Impulsiveness Scale-Adolescent. Relationships between impulsive behavior and treatment outcomes (efficacy and adherence) were assessed using linear mixed effects models. ResultsParticipants in the AT condition had significantly lower program CO levels at each treatment phase. Delay discounting in the AT condition predicted CO levels, with those discounting the most lowering their breath CO levels the least. Delay discounting also predicted program adherence across both conditions. ConclusionsDelay discounting may be the most relevant dimension of impulsive behavior to predict outcomes for adolescent smokers completing CM programs, both in terms of successful reductions in smoking and program adherence. Suggestions are made to reduce the effects of delay discounting for adolescent smokers using this treatment approach.

A prospective, observational study investigating the use of carbon monoxide screening to identify maternal smoking in a large university hospital in Ireland

ObjectivesThis study evaluated breath carbon monoxide (BCO) testing in identifying maternal smokers as well as the difference between disclosers and non-disclosers of smoking status. We also investigated if other extrinsic...

Promoting smoking abstinence among patients with chronic obstructive pulmonary disease: Initial feasibility

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the U.S., with the majority of COPD deaths attributable to cigarette smoking. Despite this, individuals with COPD have a higher prevalence of smoking, poorer quit rates, and higher relapse rates compared to smokers without a COPD diagnosis. We examined the feasibility of an incentives-based intervention for producing an initial period of biochemically-verified smoking abstinence among daily smokers with COPD. Participants were randomly assigned to a Contingent (n = 13) or Noncontingent (n = 16) incentives condition and visited the clinic for 14 consecutive days. Contingent participants earned vouchers with monetary value contingent on breath carbon monoxide (CO) levels during Study Days 1–5 and urinary cotinine during Days 6–14. Voucher earnings began at $9.00 and increased by $1.50 with each subsequent negative sample for maximum possible of $362.50. Noncontingent participants received vouchers of comparable value independent of smoking status. Differences between conditions varied across study days for daily smoking abstinence (X2 = 45.27, p < 0.0001), CO (F(13, 280) = 1.95, p = 0.025), and cotinine (F(13, 279) = 2.20, p = 0.010), with generally higher rates of abstinence and lower CO and cotinine levels observed in the Contingent vs. Noncontingent conditions. Results from this randomized pilot study support the potential efficacy of an incentives-based intervention for reducing cigarette smoking among individuals with COPD. Further research efforts should seek to promote and evaluate longer-term abstinence and associated changes in respiratory function.

Analysis of breath carbon monoxide among urban automobile drivers

Background: Air pollution caused by automobiles can pose serious health hazard due to urbanization. Carbon monoxide (CO) is one of the six criteria for air pollution related to urbanization. Urban drivers are occupationally at risk of exposure to CO. Aims and Objectives: This study was undertaken to assess the levels of CO in breath among the exposed group of urban automobile drivers and to compare breath CO levels among various group of drivers based on their years of experience or duration of exposure. Materials and Methods: A cross-sectional analysis of breath sample for the presence of CO was conducted on automobile drivers (n = 101) using different type of motor vehicles in urban Chennai using breath CO analyzer (Vitalograph 29700). Mean CO levels were compared among groups using ANOVA. Proportion in groups was assessed by χ2/Fisher’s exact test. Results: The mean CO of the breath analysis was 2.45 parts per million (ppm) which corresponds to the mean carboxyhemoglobin of 0.68%. Exhaled breath CO was 3–4 ppm in 22.8% of the drivers. 8.9% of the drivers had exhaled breath CO above 9 ppm. Statistically significant difference was observed between duty hours and exhaled breath CO (P < 0.01). Drivers who were smokers had a significantly higher breath CO (P < 0.00). Drivers who used gas as fuel were having statistically significant higher breath CO (P < 0.05). Conclusions: CO is potential environmental toxin of air due to vehicle exhaust. Drivers are constantly exposed, which is evident by our report of having higher breath CO with long duty hours. Smoking adds to environmental exposure of CO to automobile drivers.