Cigarette Smoke Constituents Research Articles

“My First Thought was Croutons”: Perceptions of Cigarettes and Cigarette Smoke Constituents Among Adult Smokers and Nonsmokers

“My First Thought was Croutons”: Perceptions of Cigarettes and Cigarette Smoke Constituents Among Adult Smokers and Nonsmokers

Histomorphometrical evaluation in testis and epididymis of rats with pulmonary emphysema experimentally induced by prolonged exposure to cigarette smoke

The study evaluated the histomorphometrical aspects of testis and epididymis of adult rats with pulmonary emphysema experimentally induced by exposure to cigarette smoke for 30 weeks. Previous studies related to effects of the cigarette smoke on male reproductive tissue were performed in relatively shorter time periods and thus, it does not allow a direct correlation between smoke exposure and damage to reproductive structures like testis and epididymis. In order to evaluate the effect of cigarette smoke for long period on the testis and epididymis, twelve adult Wistar rats were divided into two groups: Control (CG; exposed to ambient air) and Smoking (SG; exposed to cigarette smoke). The weight of the testes, epididymides, seminal glands and prostate were not affected (p>0.05) by experimental treatment. In the SG, the testes presented cellular desquamation, significant decrease in the number of germ cells and Sertoli cell, and reduction (p<0.05) in area and diameter of seminiferous tubules. The exposure of animals to cigarette smoke did not promoted histological changes in the epididymis, but decreased significantly the ductular area and epithelial height in the caput and corpus regions. It was concluded that testis was more susceptible than the epididymis to the effects of cigarette smoke constituents in rats with pulmonary emphysema experimentally induced by prolonged cigarette-smoke exposure.

Heterocyclic aromatic amines and their contribution to the bacterial mutagenicity of the particulate phase of cigarette smoke.

Heterocyclic aromatic amines (HAAs) rank among the strongest known mutagens. Approximately 30 HAAs have been found in cooked foods (broiled, fried, and grilled) and several HAAs have been characterized as animal carcinogens. Nine HAAs have also been reported to be constituents of cigarette smoke (CS) raising concerns that HAAs might contribute significantly to the known carcinogenicity of CS. As HAAs are found predominantly in the total particulate matter (TPM) of CS, an improved method for the quantification of HAAs in TPM is reported allowing detection and quantification of 8 HAAs in a single run. The mutagenic potency of these HAAs and that of TPM from the reference cigarette 2R4F was determined in the Salmonella Reverse Mutation Assay (Ames assay) with tester strain TA98 and a metabolic activation system. The 8 HAAs, when applied together in the Ames assay, showed a clear sub-additive response. Likewise, the combination of HAAs and TPM, if at all, gave rise to a slight sub-additive response. In both cases, however, the sub-additive response in the Ames assay was observed at HAA doses that are far above the amounts found in CS. The contribution of the individual HAAs to the total mutagenic activity of TPM was calculated and experimentally confirmed to be approximately 1% of the total mutagenic activity. Thus, HAAs do not contribute significantly to the bacterial in vitro mutagenicity of CS TPM.

"My First Thought was Croutons": Perceptions of Cigarettes and Cigarette Smoke Constituents Among Adult Smokers and Nonsmokers.

Understanding what people think about harmful and potentially harmful constituents in cigarettes and cigarette smoke has new urgency given legislation requiring US Food and Drug Administration (FDA) to disclose constituent information. Our study sought to obtain qualitative information on what people think about these constituents and the language they use to talk about them. We conducted six focus groups in 2014 with 40 adults in North Carolina. Open-ended questions focused on cigarette and cigarette smoke constituents in general and on the 18 constituents on the FDA's abbreviated list. We coded the transcripts for emergent themes, and all four coders discussed themes until we reached consensus. Participants knew that cigarette smoke contains chemicals but did not know how many chemicals nor what those chemicals are, beyond tar and nicotine. Dangers of constituents mentioned included "chemicals," physical disease, and addiction. Participants incorrectly believed harmful constituents came primarily from tobacco companies' additives. For unfamiliar constituents, people tried to make associations based on similar-sounding words. Recognizable constituents that participants associated with health harms most discouraged them from wanting to smoke. Most participants wanted to know health harms associated with constituents and what else the chemicals were in. Participants showed enthusiasm for learning more information about constituents, and also showed substantial misunderstandings about the source of harmful constituents. Our findings contribute to the limited body of research on adults' knowledge and perceptions of cigarette smoke constituents and can aid the FDA as it plans to disclose constituent information to the public. Our study provides information about adults' understanding of cigarette smoke constituents and what adults would like to know about these constituents. This information can help communication campaigns describe cigarette smoke constituents in a way that discourages people from wanting to smoke.

Induction of thioredoxin reductase 1 by crotonaldehyde as an adaptive mechanism in human endothelial cells

Cigarette smoking is one of the main sources of toxic chemical exposure to humans and is the greatest cause of progression of vascular disease. Crotonaldehyde is one of the major constituents of cigarette smoke and a product of endogenous lipid peroxidation. Thioredoxin reductase (TrxR) is a key element of the intact thioredoxin (Trx) system, which is predominant in modulating the intracellular redox homeostasis. In this study, we showed the effects of crotonaldehyde on the induction of TrxR1 expression in human endothelial cells. Crotonaldehyde exposure caused notably increased phosphorylation of p38 mitogen-activated protein kinase (MAPK). Introduction of siRNA against nuclear factor erythroid 2-related factor 2 (Nrf2) downregulated TrxR1 expression. Furthermore, treatment with auranofin, a TrxR inhibitor, significantly increased the death rate of crotonaldehyde-exposed cells. In summary, these results suggest a role for TrxR1 upregulation through p38 MAPK-Nrf2 activation in the adaptive response of human endothelial cells to crotonaldehyde.

Triple Quad-ICP-MS Measurement of Toxic Metals in Mainstream Cigarette Smoke from Spectrum Research Cigarettes.

We previously reported toxic metal concentrations in the mainstream smoke from 50 varieties of commercial cigarettes available in the USA using quadrupole inductively coupled plasma-mass spectrometry (ICP-MS). However, efforts to continue producing high quality data on select mainstream cigarette smoke constituents demand continued improvements in instrumentation and methodology and application of the methodology to cigarettes that differ in design or construction. Here we report a new application of 'triple quad'-ICP-MS instrumentation to analyze seven toxic metals in mainstream cigarette smoke from the Spectrum variable nicotine research cigarettes. The Spectrum cigarettes are available for research purposes in different configurations of low or conventional levels of nicotine, mentholated or nonmentholated, and tar delivery ranges described as 'low tar' or 'high tar'. Detailed characterizations of specific harmful or potentially harmful constituents delivered by these research cigarettes will help inform researchers using these cigarettes in exposure studies, cessation studies and studies related to nicotine addiction or compensation.

Teratogenic, bioenergetic, and behavioral effects of exposure to total particulate matter on early development of zebrafish (Danio rerio) are not mimicked by nicotine

Cigarette smoke has been associated with a number of pathologies; however, the mechanisms leading to developmental effects are yet to be fully understood. The zebrafish embryo is regarded as a ‘bridge model’; however, not many studies examined its applicability to cigarette smoke toxicity. This study examined the effects of total particulate matter (TPM) from 3R4F reference cigarettes on the early development of zebrafish (Danio rerio). Zebrafish embryos were exposed to two concentrations of TPM (0.4 and 1.4μg/mL equi-nicotine units) or nicotine at equivalent doses. The exposures began at 2h post-fertilization (hpf) and lasted until 96hpf. Several physiological parameters were assessed during or after the exposure. We show that TPM increased mortality, delayed hatching, and increased the incidence of deformities in zebrafish. TPM exposure also increased the incidence of hemorrhage and disrupted the angiogenesis of the major vessels in the brain. Moreover, TPM exposure reduced the larval body length, decreased the heart rate, and reduced the metabolic rate. Biomarkers of xenobiotic metabolism and oxidative stress were also affected. TPM-exposed zebrafish also differed behaviorally: at 24hpf the embryos had a higher frequency of spontaneous contractions and at 144hpf the larvae displayed swimming hyperactivity. This study demonstrates that TPM disrupts several aspects of early development in zebrafish. The effects reported for TPM were not attributable to nicotine, since embryos treated with nicotine alone did not differ significantly from the control group. Collectively, our work illustrates the utility of zebrafish as an alternative model to evaluate the toxic effects of cigarette smoke constituents.

Effects of MAO inhibition and a combination of minor alkaloids, β-carbolines, and acetaldehyde on nicotine self-administration in adult male rats

IntroductionAlthough nicotine is the primary reinforcing constituent in cigarettes, there is evidence that other constituents in cigarette smoke may interact with nicotine to reinforce smoking behavior. MethodsThe present experiments investigated whether a novel combination of these cigarette smoke constituents would increase nicotine self-administration in adult male rats. The constituents included five minor alkaloids (anabasine, nornicotine, cotinine, myosmine, and anatabine), two β-carbolines (harman and norharman), and acetaldehyde. All doses were indexed to be proportional to concentrations in cigarette smoke given a standard dose of nicotine used in rodent self-administration, or ten times higher than this standard. To model MAO inhibition seen in chronic smokers, some groups received separate injections of tranylcypromine prior to each self-administration session. ResultsTranylcypromine increased low-dose nicotine self-administration independent of other smoke constituents, which had no effect on self-administration behavior. The effect of tranylcypromine was confirmed across a large range of reinforcement schedules. The effect of tranylcypromine on low-dose nicotine self-administration was observed regardless of whether the injection was delivered 1-h or 23-h prior to the self-administration session, consistent with the interpretation that MAO inhibition was responsible for the increase in self-administration, instead of acute off-target effects. ConclusionsThese data suggest that this cocktail of constituents does not significantly alter the primary reinforcing effects of nicotine, but constituents that inhibit MAO may increase the primary reinforcing effects of nicotine, especially at low doses.

Considerations for comparative tobacco product assessments based on smoke constituent yields

Cigarette smoke is a complex mixture of more than 8000 smoke constituents. The quantification of selected mainstream smoke constituent yields is one of the methods to evaluating and comparing the performance of different products. Numerous regulatory and scientific advisory bodies have used cigarette smoke constituent yield data for reporting and product comparison purposes. For more than a decade limitations of the indiscriminate application of traditional statistical methods such as the t-test for differences in comparative smoke constituent yield assessments lacking a specific study design, have been highlighted. In the present study, the variability of smoke constituent yields is demonstrated with data obtained under the ISO smoking regime for the Kentucky reference cigarette 3R4F and one commercial brand, analyzed on several occasions between 2007 and 2014. Specifically it is shown that statistically significant differences in the yields of selected smoke constituents do not readily translate to differences between products, and that tolerances need to be defined. To this end, two approaches have been proposed in the literature – minimal detectable differences, and the statistical equivalence. It is illustrated how both approaches provide more meaningful comparison outcomes than the statistical t-test for differences. The present study provides considerations relevant for comparative tobacco product assessments both in the scientific and regulatory contexts.

Dioxin Exposure Impairs BMP-2-Mediated Spinal Fusion in a Rat Arthrodesis Model.

Cigarette smoking inhibits bone-healing and leads to increased rates of pseudarthrosis. However, the mechanisms behind these effects are controversial. Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin)--a cigarette smoke constituent and potent activator of the aryl hydrocarbon receptor (Ahr)--negatively impacts bone quality and osteoblast differentiation. We hypothesized that activation of the Ahr by dioxin would inhibit bone morphogenetic protein (BMP)-2-mediated spinal fusion in a rat arthrodesis model. Female Long-Evans rats were pretreated with dioxin or vehicle in six weekly doses, followed by bilateral posterior lumbar spinal fusion across the L4-L5 transverse processes using recombinant human BMP (rhBMP)-2. Treatments continued until sacrifice at four weeks postoperatively. A third group was treated with dioxin for six weeks, followed by a recovery period of four elimination half-lives to assess the reversible effects of dioxin exposure on spinal fusion capacity. Bone formation and fusion capacity were evaluated using fusion scoring, radiography, micro-computed tomography, and histologic analysis. Fusion scores for dioxin-treated and dioxin-recovery rats were significantly lower than those for controls. Although fusion rates were also significantly reduced in dioxin-treated animals relative to controls (50% versus 100%, respectively), rates were not significantly reduced in dioxin-recovery animals (80%). Dioxin treatment significantly inhibited spinal fusion in a rat arthrodesis model, and a prolonged cessation of dioxin exposure facilitated only a partial recovery of bone-healing capacity. This finding indicates that, although the effects of dioxin are persistent, an extended recovery from exposure could potentially restore bone regeneration in vivo. Development of a pharmacologic agent that reduces the adverse effects of cigarette smoke on bone-healing could prove useful to orthopaedic surgeons. Since dioxin and other similar cigarette smoke toxins exert their effects through Ahr pathway activation, the receptor represents a potential therapeutic target to improve spinal fusion rates in patients who smoke.

Red Wine Again? Commentary on an article by Erin L. Hsu, PhD, et al.: "Dioxin Exposure Impairs BMP-2-Mediated Spinal Fusion in a Rat Arthrodesis Model".

In their article, Hsu et al. describe how a specific constituent of cigarette smoke (dioxin) negatively influences bone morphogenetic protein (BMP)-2-mediated spinal fusion in rats. On the basis of their findings, they speculate on potential therapeutic options to improve fusion in spinal arthrodesis and bone-healing in other orthopaedic procedures in patients who continue smoking. Recently, a detailed overview of the adverse effects of smoking on the musculoskeletal system was published in The Journal of Bone & Joint Surgery 1 . These negative effects can be roughly summarized as (1) prothrombotic effects with, among others, an increased risk of osteonecrosis; (2) metabolic effects resulting in decreased bone strength with subsequent increased fracture risk; (3) anti-osteogenic effects with decreased healing capacity of fractures and osteotomy and arthrodesis sites; and (4) other general adverse effects increasing the risk of perioperative complications such as wound-healing disturbances. Although the specific effects of many toxic substances in cigarette smoke, such as carbon monoxide and nicotine, have been established in terms of tissue oxygenation, carcinogenesis, and addiction, it is unclear which toxic substances specifically cause adverse musculoskeletal effects. The role of nicotine, the main addictive substance, is especially controversial regarding the often-reported positive effect …

Mercapturic Acids Derived from the Toxicants Acrolein and Crotonaldehyde in the Urine of Cigarette Smokers from Five Ethnic Groups with Differing Risks for Lung Cancer.

The Multiethnic Cohort epidemiology study has clearly demonstrated that, compared to Whites and for the same number of cigarettes smoked, African Americans and Native Hawaiians have a higher risk for lung cancer whereas Latinos and Japanese Americans have a lower risk. Acrolein and crotonaldehyde are two important constituents of cigarette smoke which have well documented toxic effects and could play a role in lung cancer etiology. Their urinary metabolites 3-hydroxypropylmercapturic acid (3-HPMA) and 3-hydroxy-1-methylpropylmercapturic acid (HMPMA), respectively, are validated biomarkers of acrolein and crotonaldehyde exposure. We quantified levels of 3-HPMA and HMPMA in the urine of more than 2200 smokers from these five ethnic groups, and also carried out a genome wide association study using blood samples from these subjects. After adjusting for age, sex, creatinine, and total nicotine equivalents, geometric mean levels of 3-HPMA and HMPMA were significantly different in the five groups (P<0.0001). Native Hawaiians had the highest and Latinos the lowest geometric mean levels of both 3-HPMA and HMPMA. Levels of 3-HPMA and HMPMA were 3787 and 2759 pmol/ml urine, respectively, in Native Hawaiians and 1720 and 2210 pmol/ml urine in Latinos. These results suggest that acrolein and crotonaldehyde may be involved in lung cancer etiology, and that their divergent levels may partially explain the differing risks of Native Hawaiian and Latino smokers. No strong signals were associated with 3-HPMA in the genome wide association study, suggesting that formation of the glutathione conjugate of acrolein is mainly non-enzymatic, while the top significant association with HMPMA was located on chromosome 12 near the TBX3 gene, but its relationship to HMPMA excretion is not clear.

Polycyclic aromatic hydrocarbons and cytochrome P450 in HIV pathogenesis.

High prevalence of cigarette smoking in HIV patients is associated with increased HIV pathogenesis and disease progression. While the effect of smoking on the occurrence of lung cancer has been studied extensively, the association between smoking and HIV pathogenesis is poorly studied. We have recently shown the possible role of cytochrome P450 (CYP) in smoking/nicotine-mediated viral replication. In this review, we focus on the potential role of CYP pathway in polycyclic aromatic hydrocarbons (PAH), important constituents of cigarette smoke, mediated HIV pathogenesis. More specifically, we will discuss the role of CYP1A1 and CYP1B1, which are the major PAH-activating CYP enzymes. Our results have shown that treatment with cigarette smoke condensate (CSC) increases viral replication in HIV-infected macrophages. CSC contains PAH, which are known to be activated by CYP1A1 and CYP1B1 into procarcinogens/toxic metabolites. The expression of these CYPs is regulated by aryl hydrocarbon receptors (AHR), the cellular target of PAH, and an important player in various diseases including cancer. We propose that PAH/AHR-mediated CYP pathway is a novel target to develop new interventions for HIV positive smokers.

Hierarchical Composites to Reduce N-Nitrosamines in Cigarette Smoke.

In order to reduce the harmful constituents in cigarette smoke, two hierarchical composites were synthesized. Based on, zeolites HZSM-5 or NaY fragments were introduced into the synthetic system of mesoporous silica SBA-15 or MCM-41 and assembled with the mesoporous materials. These porous composites combine the advantages of micro- and mesoporous materials, and exhibit higher effects than activated carbon on reducing tobacco specific nitrosamines (TSNA) and some vapor phase compounds in smoke.

Smoking-induced skeletal muscle dysfunction: from evidence to mechanisms.

Smoking is the most important risk factor for the development of chronic obstructive pulmonary disease (COPD). Patients with COPD commonly suffer from skeletal muscle dysfunction, and it has been suggested that cigarette smoke exposure contributes to the development of skeletal muscle dysfunction even before overt pulmonary pathology. This review summarizes the evidence that muscles of nonsymptomatic smokers are weaker and less fatigue resistant than those of nonsmokers. Although physical inactivity of many smokers contributes to some alterations observed in skeletal muscle, exposure to cigarette smoke per se can also induce skeletal muscle dysfunction. Cigarette smoke constituents and systemic inflammatory mediators enhance proteolysis and inhibit protein synthesis, leading to loss of muscle mass. Reduced skeletal muscle contractile endurance in smokers may result from impaired oxygen delivery to the mitochondria and ability of the mitochondria to generate ATP due to interaction of carbon monoxide with hemoglobin, myoglobin, and components of the respiratory chain. Besides hampering contractile function, smoking may have immediate beneficial effects on motor skills, which are attributable to nicotine. In contrast to pulmonary pathology, many of the effects of smoking on skeletal muscle are most likely reversible by smoking cessation.

A study to investigate changes in the levels of biomarkers of exposure to selected cigarette smoke constituents in Japanese adult male smokers who switched to a non-combustion inhaler type of tobacco product

In a clinical study, changes in 14 biomarkers of exposures (BOEs) from 10 tobacco smoke constituents and mutagens detected by the urine mutagenicity test were investigated using a non-combustion inhaler type of tobacco product (NCIT) by switching from a conventional cigarette. This study was conducted in 80 Japanese healthy adult males with a 4-week residential, controlled, open-label, parallel group design. After randomization, 40 smokers used NCIT with approximately 750 aspirations, other 20 smokers smoked approximately 20 pieces of an assigned 1-mg ISO tar conventional cigarette (CC1) every day. Twenty non-smokers (NS) did not use any tobacco product. Under this study condition, switching from cigarette to NCIT showed significant reduction in all BOEs measured. On day 29, the levels of these BOEs were almost the same as those in the NS group, except BOEs of nicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). This suggested that the exposure to 8 constituents and mutagens in the NCIT group was similar to that in the NS group, while the exposure to nicotine was higher. Although the precise exposure level to NNK was not estimated because of the long half-life of its BOE, it would be substantially lower in the NCIT group than in the CC1 group.

NADPH oxidase and the cardiovascular toxicity associated with smoking.

Smoking is one of the most serious but preventable causes of cardiovascular disease (CVD). Key aspects of pathological process associated with smoking include endothelial dysfunction, a prothrombotic state, inflammation, altered lipid metabolism, and hypoxia. Multiple molecular events are involved in smokinginduced CVD. However, the dysregulations of reactive oxygen species (ROS) generation and metabolism mainly contribute to the development of diverse CVDs, and NADPH oxidase (NOX) has been established as a source of ROS responsible for the pathogenesis of CVD. NOX activation and resultant ROS production by cigarette smoke (CS) treatment have been widely observed in isolated blood vessels and cultured vascular cells, including endothelial and smooth muscle cells. NOX-mediated oxidative stress has also been demonstrated in animal studies. Of the various NOX isoforms, NOX2 has been reported to mediate ROS generation by CS, but other isoforms were not tested thoroughly. Of the many CS constituents, nicotine, methyl vinyl ketone, and α,β-unsaturated aldehydes, such as, acrolein and crotonaldehyde, appear to be primarily responsible for NOX-mediated cytotoxicity, but additional validation will be needed. Human epidemiological studies have reported relationships between polymorphisms in the CYBA gene encoding p22phox, a catalytic subunit of NOX and susceptibility to smoking-related CVDs. In particular, G allele carriers of A640G and -930A/G polymorphisms were found to be vulnerable to smoking-induced cardiovascular toxicity, but results for C242T studies are conflicting. On the whole, evidence implicates the etiological role of NOX in smoking-induced CVD, but the clinical relevance of NOX activation by smoking and its contribution to CVD require further validation in human studies. A detailed understanding of the role of NOX would be helpful to assess the risk of smoking to human health, to define high-risk subgroups, and to develop strategies to prevent or treat smoking-induced CVD.

Comparative Study of Cigarette Smoke Cytotoxicity Using Two In Vitro Assay Systems

SUMMARY The aim of this study was to compare the results obtained from two in vitro cytotoxicity assays that depend upon different mechanisms/modes of action. The Neutral Red Uptake (NRU) assay is based on endocytotic activity whereas the Water Soluble Tetrazolium Salts (WST-1) assay is based on mitochondrial dehydrogenase activity. Both were investigated in light of their wide use and documented validation. The total particulate matter (TPM) and gas vapor phase (GVP) of main stream smoke derived from Kentucky reference cigarettes 3R4F and 10 test cigarettes made of 100% flue-cured or 100% Burley tobacco were individually applied to the two assays using CHO-K1 cells. In addition, cigarette smoke constituents and known cytotoxic agents, documented to affect specific endpoints, were evaluated within both assays. Although the NRU assay was primarily more sensitive than the WST-1 assay, both assays provided comparable results in terms of the rank order for the cytotoxicity of cigarette smoke samples. In addressing the cytotoxicity of constituents in cigarette smoke, acrolein, hydroquinone and catechol gave clear dose-related decreases in cell viability (an end point common in both assays). Moreover, enzyme inhibitors of the mitochondrial respiratory chain and chemicals causing membrane disruption also showed similar responses regardless of the specific endpoint addressed within the cytotoxicity assay. In conclusion, results from the NRU and WST-1 assay are comparable therefore indicating results were independent of the different assay detection mechanisms/modes of action. [Beitr. Tabakforsch. Int. 26 (2014) 98-108]

Exposure evaluation of adult male Japanese smokers switched to a heated cigarette in a controlled clinical setting

The objective of this clinical study was to investigate changes in levels of biomarkers of exposure (BOEs) in healthy Japanese male smokers who switched to a prototype heated cigarette (HC). This was a controlled, semi-randomized, open-label, residential study conducted in Japan. A total of 70 healthy Japanese male smokers were enrolled. Following enrollment, subjects smoked their usual brand of cigarette for 2days and were subsequently randomized either to an HC group or a 10mg tar conventional cigarette (CC10) group for four consecutive weeks. Levels of BOEs for ten selected cigarette smoke constituents (nicotine, carbon monoxide (CO), benzene, 1,3-butadiene, acrolein, hydrogen cyanide, crotonaldehyde, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone [NNK], pyrene, 4-aminobiphenyl), and urine mutagenicity were measured at several time points during the study period. At the end of the study period, except for blood carboxyhemoglobin, levels of BOEs for the other nine constituents and urine mutagenicity were significantly lower in the HC group compared to the CC10 group. These results suggest that exposure to most cigarette smoke constituents, except CO, can be reduced by switching from CC10 to HC.

Maternal smoking, xenobiotic metabolizing enzyme gene variants, and gastroschisis risk

Maternal smoking during pregnancy is one proposed risk factor for gastroschisis, but reported associations have been modest, suggesting that differences in genetic susceptibility might play a role. We included 108 non-Hispanic white and 62 Hispanic families who had infants with gastroschisis, and 1,147 non-Hispanic white and 337 Hispanic families who had liveborn infants with no major structural birth defects (controls) in these analyses. DNA was extracted from buccal cells collected from infants and mothers, and information on periconceptional smoking history was obtained from maternal interviews, as part of the National Birth Defects Prevention Study. We analyzed five polymorphisms in three genes that code for enzymes involved in metabolism of some cigarette smoke constituents (CYP1A1, CYP1A2, and NAT2). Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) independently for maternal smoking and maternal and infant gene variants, and to assess joint associations of maternal smoking and maternal or infant gene variants with gastroschisis. In analyses adjusted for maternal age at delivery and stratified by maternal race-ethnicity, we identified three suggestive associations among 30 potential associations with sufficient numbers to calculate ORs: CYP1A1*2A for non-Hispanic white mothers who smoked periconceptionally (aOR = 0.38, 95% CI 0.15-0.98), and NAT2*6 for Hispanic non-smoking mothers (aOR = 2.17, 95% CI 1.12-4.19) and their infants (aOR = 2.11, 95% CI 1.00-4.48). This analysis does not support the occurrence of effect modification between periconceptional maternal smoking and most of the xenobiotic metabolizing enzyme gene variants assessed.