Urinary excretion of mutagens in passive smokers

The miseries of passive smoking

Passive smoking is defined as an involuntary exposure to a combined but diluted cigarette sidestream smoke (SS, gas and particle phases that are evolved from the smoldering end of a cigarette while the smoker is not puffing) and the exhaled smoke from smokers. SS contains numerous cytotoxic substances such as polycyclic aromatic hydrocarbons (PAHs), aromatic amines, nitrosamines, heavy metals, poisonous gases, pesticide residues, and radioactive elements in quantities much higher than those found from the cigarette mainstream smoke (MS) which is puffed by smokers. Passive smoking is found to be the cause of death from cancers and cardiac disease. Furthermore, it damagingly involves reproductive organs, the nervous system, genetic materials, and is particularly hazardous to mother and child during pregnancy and to those with a history of asthma, chronic infections, induced or earned immune deficiency, or predisposed susceptibility.

Urinary mutagenicity and thioethers in nonsmokers: role of environmental tobacco smoke (ETS) and diet

The urinary excretion of mutagens and thioethers was investigated in a controlled diet study and in two field studies. A diet containing charcoal-broiled meat and other items rich in mutagenic compounds increased the urinary mutagenicity as assessed in Salmonella typhimurium strain TA98 with metabolic activation approximately 46-fold compared to a diet low in mutagens. The excretion of thioethers after ingestion of the diet rich in mutagens also increased significantly when compared to the diet low in mutagens. The increase was associated with the content of preformed thioethers in the diet. In the first field study with 21 nonsmokers, urinary mutagenicity as assessed in Salmonella typhimurium strain TA98 and excretion of thioethers showed no relation to either the self-reported exposure to environmental tobacco smoke (ETS) or to serum cotinine concentrations used as an objective marker for ETS exposure. In the second field study, urinary mutagenicity was determined with a tobacco-smoke sensitive Salmonella typhimurium strain YG1024 with metabolic activation. No correlation was found between the mutagenic activity in urine and ETS exposure duration, nicotine on the personal sampler, cotinine in saliva and cotinine in urine. Our results suggest that real-life ETS exposure does not measurably increase either urinary mutagen or urinary thioether excretion. Furthermore, diet seems to be the most important source for both urinary mutagen and thioether excretion in nonsmokers.

Mutagens in urine sampled repetitively from municipal refuse incinerator workers and water treatment workers

Municipal refuse incinerator workers may be exposed to mutagenic compounds from combustion gases and particulates during plant operation, maintenance, and ash removal procedures. The frequency of mutagens was measured by the Ames assay in 3 urine samples collected from each of 37 workers in 4 refuse incinerators and 35 (control) workers from 8 water treatment plants during June-August 1990. When comparing the first urine samples contributed by workers in each cohort, incinerator workers had a significantly (p < .05) increased risk of both direct-acting mutagens and promutagens (8/37 or 22% for each mutagen type) compared with water treatment workers (2/35 or 6% for each mutagen type). Smoking within 24 h before urine sampling was not a confounder of these results. Interestingly, there was no significant (p > .05) difference for risk of urinary mutagens or promutagens between the two cohorts when comparing, respectively, the second and third urine samples from each cohort. The repeatability of demonstrating urinary mutagens in individual incinerator workers was poor, suggesting that their exposure was highly variable and/or that these workers modified their exposure (e.g., wore masks) as a consequence of being studied. Factors that influence production of mutagenic compounds during refuse incineration and subsequent worker exposure are discussed.

Mainstream and environmental tobacco smoke

Environmental tobacco smoke (ETS) is derived from cigarette smoldering and active smoker exhalation. Its composition displays broad quantitative differences and redistributions between gas and respirable suspended particulate (RSP) phases when compared with the mainstream smoke (MSS) that smokers puff. This is because of different generation conditions and because ETS is diluted and ages vastly more than MSS. Such differences prevent a direct comparison of MSS and ETS and their biologic activities. However, even assuming similarities on an equal mass basis, ETS-RSP inhaled doses are estimated to be between 10,000- and 100,000-fold less than estimated average MSS-RSP doses for active smokers. Differences in effective gas phase doses are expected to be of similar magnitude. Thus the average person exposed to ETS would retain an annual dose analogous to the active MSS smoking of considerably less than one cigarette dispersed over a 1-year period. By contrast, consistent epidemiologic data indicate that active smoking of some 4-5 cigarettes per day may not be associated with a significantly increased risk of lung cancer. Similar indications also obtain for cardiovascular and respiratory diseases. Since average doses of ETS to nonsmoking subjects in epidemiologic studies are several thousand times less than this reported intake level, the marginal relative risks of lung cancer and other diseases attributed to ETS in some epidemiologic studies are likely to be statistical artifacts, derived from unaccounted confounders and unavoidable bias.

Importance of exposure to gaseous and particulate phase components of tobacco smoke in active and passive smokers

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 COHb, 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.

Urinary mutagens in municipal refuse incinerator workers and water treatment workers

Municipal refuse incineration workers may be exposed to mutagenic compounds from gaseous and particulate emissions and during ash removal operations. The frequency of urinary mutagens was measured by the Ames test among a sample of 104 refuse incinerator workers in seven incinerator plants during March-May 1988. The frequency was compared to that observed in 61 water treatment employees in 11 municipal water treatment facilities during the same period. Incinerator workers had a significantly higher risk for urinary mutagens and promutagens as compared to water plant workers after controlling for age. Among incinerator workers, increased risk of having urinary mutagens was associated with workers who wore protective clothing (defined as clothing other than masks or gloves) or whose job classification was equipment repair. It also showed a weak positive association with increasing age. There was an increased risk of urinary promutagens associated with not wearing gloves. The presence or absence of mutagenicity in workers' urine varied with plant location. Incinerator operating conditions affecting the production of toxicants and mutagens are discussed and the results of other studies involving toxicant exposure of humans near incinerators are cited.

Biomonitoring after controlled exposure to environmental tobacco smoke (ETS)

A rough estimation of the amounts of tobacco smoke components taken up by active and passive smoking suggests that, in the case of passive smoking, gas phase constituents in ETS are of greater relevance than particle-bound substances. Since this aspect is of importance for the risk evaluation of passive smoking, it was decided that it should be investigated further in a series of exposure studies with human volunteers. The ETS exposure conditions were characterized by measuring tobacco smoke components such as carbon monoxide (CO), nitrogen oxides (NOx), nicotine, formaldehyde, tobacco-specific nitrosamines (N-nitrosonornicotine (NNN), 4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), benzo(a)pyrene (BaP) and particulate matter in the air of the exposure room. The biomonitoring covered carboxyhemoglobin (COHb), thioethers and mutagenic activity in urine. These parameters were compared to those observed after controlled active smoking. It was found that urinary thioether excretion increased in non-smokers after extremely high ETS exposure. This effect could be attributed to gas phase ETS components. Urinary mutagenicity was not measurably increased in non-smokers under these conditions. This indicates that in passive smoking, as opposed to smoking, the gas phase might be more important in terms of possible effects than the particulate matter. It would, therefore, be misleading to make extrapolations based on the burden of smoking to establish the burden of passive smoking.

Mutagenicity of urine from greenhouse workers

The mutagenicity of urine from spray applicators in 12 greenhouses in 1986 has been evaluated. The workers served as their own controls. Urine samples reflecting pesticide exposure were collected at the end of the day of application and a corresponding control sample was collected 3 d later. Using Salmonella typhimurium bacterial tester strains TA98 and TA100 with and without S9 activation, seven workers showed no significant differences (p less than 0.05) in the mutagenicity of their exposed and control urine. Of the five remaining workers, three, who wore no respirators, showed significantly higher (p less than 0.05) concentrations of mutagens in their exposed urine sample as compared to their respective controls. The mutagenicity of certain of the compounds applied by these latter workers is discussed.

Passively inhaled tobacco smoke: a challenge to toxicology and preventive medicine

The difficulties in defining the exposure of a passive smoker might explain the controversial results regarding an association between passive smoking on one hand and lung cancer, tumors of all sites and ischemic heart diseases on the other. The plausibility of these epidemiological observations will be discussed in the light of analytical, toxicological, biochemical and oncological data. The minute amounts of nicotine and particulate matter, even the much higher concentrations of volatile substances, such as nitrosamines, NOx, acroleine and formaldehyde, present in diluted sidestream compared to mainstream smoke and breathed by involuntarily smoking people, cannot explain their relatively high cancer risk. It is plausible if one considers the high capacity of cigarette smoke to induce drug metabolizing enzymes. Diluted sidestream smoke, however, lacks compounds which induce several iso-enzymes of cyt. P-450 monooxygenase in the tissues. The best evidence is the up to 100-fold increase in placental enzymes if pregnant women smoke, whereas passively inhaled tobacco smoke is ineffective as inducer. The small amounts of paternal smoke inhaled by pregnant women, containing teratogenic and carcinogenic compounds, which are supposedly not detoxified in the placenta, seem to explain the higher risk for malformations of the fetus and the same or even increased risk for perinatal mortality, compared with the outcome of pregnancy if the mother smoked. The induction of placental enzymes very probably protects the fetus against the much higher amounts of toxic agents inhaled by the smoking mother. The increased activity of placental enzymes seems to be a model for the probably greater capacity of certain cyt. P-450 iso-enzymes in the lung and other tissues to convert carcinogens to inactive metabolites when the individual smokes actively. It is well known that concomitant administration of carcinogens with inducing agents inhibits tumor growth in animals because of a shift in the metabolism which favours the formation of ineffective substances. The negligible amounts of nicotine and CO in passively inhaled tobacco smoke cannot be responsible for the surprisingly high risk for ischemic heart diseases of passive smokers. A plausible explanation is offered by experiments with doves and chicken, which develop atherosclerotic lesions due to the action of carcinogens which are metabolized by certain inducible cyt. P-450 iso-enzymes in the aortic wall. Much circumstantial evidence will be presented, indicating that PAHs, contrary to the propagated opinion, play a minor role for the initiation of cancer in active smokers.(ABSTRACT TRUNCATED AT 400 WORDS)