Notes: Abstract  Excretion of trans,trans-muconic acid (2,4-hexadienedioic acid; t,t-MA), a potential biomarker of low-level exposure to benzene, was determined in 32 smokers and 82 nonsmokers. In smokers the median background excretion of t,t-MA was 0.13 (0.06–0.39) mg/g creatinine and was significantly higher (P〈0.05) than the value of 0.065 (0.02–0.59) mg/g creatinine in nonsmokers. For nonsmokers, the correlation between t,t-MA excretion and environmental exposure to benzene in ambient air, which was determined during the 8-day study period by personal diffusion samplers, was not significant (r=0.164, P=0.18). Nonsmokers living in the city tended to have higher t,t-MA excretion rates than nonsmokers living in the suburbs. However, the difference was only significant for nonsmokers from nonsmoking homes. For the same location (suburb or city), smoking at home leads to a marginal increase in t,t-MA excretion of the nonsmoking members of the household. In a further study with eight nonsmokers we found that dietary supplementation with 500 mg sorbic acid significantly increased (P〈0.001) the mean urinary t,t-MA excretion from 0.08 (0.04–0.12) to 0.88 (0.57–1.48) mg/24 h. Under study conditions 0.12% of the sorbic acid dose was excreted in urine as t,t-MA, thereby indicating that a typical dietary intake of 6–30 mg/day sorbic acid accounts for 10–50% of the background t,t-MA excretion in nonsmokers, and for 5–25% in smokers. As a consequence, sorbic acid in the diet is a significant confounding factor in assessing low-level benzene exposure if t,t-MA excretion in urine is used as a biomarker.

Notes: Abstract The DNA adduct 8-hydroxy-2′-deoxyguanosine (8-OHdG) has been widely used as a biomarker for oxidative stress. Bulky DNA adducts, which are detectable by the32P-postlabelling method, provide evidence for exposure to and metabolic activation of large, mainly apolar compounds, e.g. polycyclic aromatic hydrocarbons. We determined both types of adducts in placental tissues of 30 term pregnancies and related the adduct levels to the exposure to tobacco smoke and the plasma antioxidant status. Urine and plasma cotinine concentrations were used to select 10 nonsmokers, 9 nonsmokers exposed to environmental tobacco smoke (ETS) and 11 smoking women. Placental levels of 8-OHdG were 0.84±0.11, 0.90±0.21 and 0.83±0.20/105 deoxyguanosine bases (dG) for nonsmokers, nonsmokers exposed to ETS and smokers, respectively. The differences between the groups were not significant. Smoking women had significantly lower plasma vitamin C and β-carotene concentrations than nonsmoking women or nonsmoking women exposed to environmental tobacco smoke. The 8-OHdG adduct level in placental DNA was inversely correlated with the plasma vitamin E concentration (r=−0.47,P〈0.05). There was no association between placental 8-OHdG adducts and vitamin A, C and β-carotene in plasma. In total, 15 different adducts could be identified in the 30 placenta samples by the32P-postlabelling method. There was a strong inter-individual variation in both the number of adducts and adduct intensities. No smoking-related or vitamin-related effects on adduct patterns or intensities were found. Our findings suggests that, within the limits of the methods used, tobacco smoke exposure during pregnancy does not lead to a measurable increase in placental DNA adduct levels and that vitamin E appears to have a protective effect on placental 8-OHdG formation.

Notes: Summary The uptake of tobacco smoke constituents from gaseous and particulate phases of mainstream smoke (MS), inhaled by smokers, and of environmental tobacco smoke (ETS), breathed in by non-smokers, was investigated in two experimental studies. Tobacco smoke uptake was quantified by measuring carboxyhemoglobin (COHb), nicotine and cotinine in plasma and urine and the data obtained were correlated with urinary excretion of thioethers and of mutagenic activity. An increase in all biochemical parameters was observed in smokers inhaling the complete MS of 24 cigarettes during 8 h, whereas only an increase in COHb and, to a minor degree, in urinary thioethers was found after smoking the gas phase of MS under similar conditions. Exposure of non-smokers to the gaseous phase of ETS or to whole ETS at similar high concentrations for 8 h led to identical increases in COM, plasma nicotine and cotinine as well as urinary excretion of nicotine and thioethers which were much lower than in smokers. Urinary mutagenicity was not found to be elevated under either ETS exposure condition. As shown by our results, the biomarkers most frequently used for uptake of tobacco smoke (nicotine and cotinine) indicate on the one hand the exposure to particulate phase constituents in smoking but on the other hand the exposure to gaseous phase constituents in passive smoking. Particle exposure during passive smoking seems to be low and a biomarker which indicates ETS particle exposure is as yet not available. These findings emphasize that risk extrapolations from active smoking to passive smoking which are based on cigarette equivalents or the use of one biomarker (e.g. cotinine) might be misleading.

Notes: Abstract  Rationale: Compensation or compensatory smoking, accurately defined, deals with the question of whether switching to cigarette brands with different smoke yields is associated with a change in smoke uptake proportional to the change in machine-derived yields. The issue of compensation is important because it bears on whether switching to ”lighter” brands means lower overall smoke intake or not. Objectives: The present review investigated whether and to what extend low yield cigarettes are smoked more intensively. In addition, published data on whether nicotine, ”tar”, or any other smoke constituent or property influence compensational smoking are summarized. Methods: The studies on compensation were classified as follows: (1) studies on smoking behaviour in relation to cigarette yields (with and without brand switching); (2) studies on compensation for nicotine (switching between cigarettes which differ ”only” in their nicotine yield, nicotine supplementation, manipulation of renal nicotine excretion, administration of nicotine agonists or antagonists); (3) studies on compensation for other factors (influence of tar, taste, irritation, draw resistance). In order to quantify the degree of compensation, an index is defined and applied to selected brand switching studies. This compensation index determines, in relative units, the degree to which a smoker responds to a change in smoke yields with a change in smoke uptake measured by suitable biomarkers. The role of vent blocking is also briefly discussed. Results: Most of the studies which compare the smoking behaviour when smoking cigarettes with different smoke yields supply evidence for ”partial” compensation, suggesting that cigarettes with lower yields are smoked more intensively than those with higher yields. These studies also show that a change in the daily number of cigarettes is not a common mechanism of compensation. Effective vent blocking during smoking is a rare event and can therefore also be regarded as an uncommon mechanism of compensation. Evaluation of a suitable subset of brand-switching studies revealed an average compensation of 50–60% of the nicotine yield. Compensation tended to be more complete when changing to cigarettes with higher yields than when changing to cigarettes with lower yields. In general, brand-switching studies do not supply information on the underlying causal factors responsible for compensatory smoking. Results of the nicotine supplementation studies are not conclusive: some report evidence of nicotine titration, others do not. A general problem with this type of investigation is that continuous nicotine application does not mimic the spike-wise application with cigarette smoking, and may lead to nicotine tolerance. There is limited evidence that cigarettes were smoked more intensively when the urinary clearance of nicotine was increased. A small number of studies provide some evidence that smoking intensity increased after smokers were administered a nicotine antagonist. Several reports indicate that tar, taste and sensory properties of the smoke as well as the draw resistance of the cigarette may play a role in compensatory smoking. Low-yield cigarettes usually have reduced pressure drops which smoke researchers have suggested leads to increased puff volume. This effect seems to be independent of the smoke yield of the cigarette. There is also some evidence that some smokers maintain a consistent pattern of smoking which works independent of any changes in nicotine or tar yields, taste or design features of the cigarette (”functional autonomy”). Conclusions: The available data suggest that smokers partially compensate for a different smoke yield. While the factors and their interaction responsible for compensational smoking are not fully understood, there are data suggesting that a subgroup of smokers may partially compensate for nicotine. Even in this subgroup of smokers, however, the relative importance of the pharmacological versus the sensory effects of nicotine in smoke remains to be determined.

Notes: In genetic toxicology, the main fields of applications of the polymerase chain reaction (PCR) with subsequent electrophoretic characterization of amplificates include genotyping polymorphisms in the xenobiotic metabolism and mutant analysis. To assess the role of the individual sets of biotransformation enzymes for the internal dose resulting from xenobiotic exposure, we investigated blood samples from 69 healthy donors for the occurrence of known genetic polymorphisms in the xenobiotic metabolizing enzymes N-acetylaminotransfrase II (NAT2), glutathione-S-transferase (GST) μ and θ, and several cytochromes P450 (CYP), namely CYP1A1, CYP2E1 and CYP2A6. Using single strand conformation polymorphism (SSCP) analysis, five known single base substitutions located in the middle portion of 144 bp amplificates comprising exons 7 and 8 of the human hypoxanthine guanine phosphoribosyl transferase (hprt) cDNA, were clearly distinguished from wild type and from each other. Biomagnetic strand separation assigned the slower migrating single strand bands to the biotinylated sense strands.