The less harmful cigarette

A summary of toxicological and chemical data relevant to the evaluation of cast sheet tobacco

A tiered testing strategy based on a comparative chemical and biological testing program has been developed to evaluate the potential of tobacco processes, ingredients, or other technological developments to change the biological activity that results from burning tobacco. Cast sheet tobacco is a specific type of reconstituted tobacco sheet that can be used in the manufacture of cigarettes. The comparative chemical and biological testing program was used to compare the mainstream smoke and cigarette smoke condensate (CSC) from a Reference cigarette that did not contain cast sheet to that collected from Test cigarettes containing cast sheet at a final blend level of either 10% or 15%. Testing included mainstream cigarette smoke chemistry studies, in vitro studies (Ames assay, sister chromatid exchange assay, and neutral red cytotoxicity assay), and in vivo toxicology studies (13-week rat nose-only inhalation assay and 30-week mouse dermal tumor promotion assay). Certain statistically significant differences were observed in the chemical and biological studies when the Reference cigarette was compared to each of the Test cigarettes. However, when viewed collectively, the chemical and biological studies demonstrated that inclusion of cast sheet up to 15% in the final blend did not increase the inherent biological activity of mainstream cigarette smoke or CSC.

Phase-out filter perforation: effects on human tobacco smoke exposure

Phase-Out is a mechanical device that dilutes the cigarette smoke stream by mechanically perforating cigarette filters. Machine testing of Phase-Out-treated cigarettes suggested that smoke exposure reductions of 90-95% could be achieved with the device. This study evaluated exposure to carbon monoxide (CO) and nicotine when humans (N = 10) smoked Phase-Out-treated cigarettes under controlled laboratory conditions. Using boost (i.e., change from baseline) measures of constituent exposure, reductions ranging from 30-80% were seen for both nicotine and carbon monoxide. Orderly graded reductions in constituent exposure were observed for both nicotine and carbon monoxide as the number of filter perforations increased from zero to six holes, with no further reduction at the eight-hole condition. Percentage reductions in constituent exposure generally corresponded well to those anticipated from machine testing, indicating that the controlled smoking technology was valid and that the Phase-Out device operated as expected in a human smoking assay. The utility of partial constituent-level reductions is discussed both with regard to lowered health risks of smoking and ease of quitting when partial reduction is used as a gradual weaning preparation for quit attempts.

Cellular and molecular biological aspects of human bronchogenic carcinogenesis

This is a time of rapid progress in the field of human bronchogenic carcinogenesis due to recent advances in cellular and molecular biology. Important developments over the last 10 years include establishment of methods for culturing NHBE cells under defined conditions, and molecular biological and biochemical epidemiological techniques for identifying genetic changes that are associated with malignant transformation of these cells. Most progress in defining genes associated with human carcinogenesis has been due to discoveries related to oncogenes and more recently, tumor suppressor genes. As was described in Section II.B.3.a, we now know that oncogene products serve as growth factors, growth factor receptors, and cytosolic and nuclear regulatory proteins. In addition, although the actions of putative tumor suppressor genes are less well understood, the first isolated tumor suppressor gene Rb, interacts with the products of DNA viruses which, in turn, are involved in regulation of transcription as was described in Section II.B.3.b. Thus, not surprisingly, both oncogenes and tumor suppressor genes code for classes of proteins that are known to play an important role in regulation of cell proliferation. Recently, a second gene that appears to possess tumor suppression activity (p53) has been identified on the short arm of chromosome 17 (17p). The initial data suggesting a possible tumor suppressor gene on chromosome 17p came from cytogenetic and RFLP studies associating loss of heterozygosity in the chromosome 17p13 region with tumor cells and tissues. Since the p53 gene is located in this region it was evaluated and found to be frequently or always altered in several types of tumor cells. Recently, it was determined that introduction of the wild-type p53 gene into NIH3T3 cells will inhibit subsequent malignant transformation. Thus, the preponderance of evidence now supports the hypothesis that while mutated p53 acts as an oncogene, the wild-type p53 gene codes for a tumor suppressor function. The role of balance between oncogenes and tumor suppressor genes in control of proliferation is presently an active area of investigation. As discussed, introduction of a chromosome containing a tumor suppressor gene will suppress tumorigenicity of a malignant cell line, even though that cell line possesses an active c-Ha-ras oncogene. Whether or not the level of expression of an activated oncogene is related to tumorigenicity is presently being investigated.(ABSTRACT TRUNCATED AT 400 WORDS)

Smoking and lung cancer: risk as a function of cigarette tar content

The hypothesis of reduction in lung cancer risk associated with the adoption of low-tar cigarettes was examined in a subset of subjects from a population-based, case-control study of incident primary lung cancer among New Jersey white men. Risk was related to time-weighted average tar levels of cigarettes smoked in 1973-1980. Unadjusted estimates of risk were significantly low for the lowest tar (less than 14 mg/cig) smokers [odds ratio = 0.53 (0.29,0.97)] compared with the highest (21.1-28 mg/cig). However, adjustment by age and total pack-years rendered the risk reduction insignificant. Of note was the finding that cases who smoked low-tar cigarettes compensated for reducing tar by increasing the number of cigarettes they smoked by almost half a pack per day from the years 1963-1972 to 1973-1980, while in the same period controls and high-tar cigarette smoking cases did not increase the numbers smoked.

Towards the reduction of lung cancer

The epidemiology of lung cancer clearly demonstrates the preventive opportunities that exist for major causes of cancer death. We have the opportunity to affect lung cancer rates by reducing the effects of smoking. Such activities, in increasing order of importance, include low-yield cigarettes, tobacco smoking cessation and tobacco smoking prevention. Within a community these activities could best be conducted and carried out through a Disease Prevention Unit (DPU), the nature of which is briefly described in this paper.

Tobacco sidestream smoke: uptake by nonsmokers

Some epidemiological studies indicate an association between passive smoking and an increased risk for cancer, especially for cancer of the lung. Other reports, however, have failed to confirm these findings. Biochemical analyses of the physiological fluids for markers of exposure to tobacco smoke are needed as measurements of the uptake of smoke components by nonsmokers and for the estimation of relative cancer risk to passively exposed persons compared with that to active cigarette smokers. This communication reports the uptake of carbon monoxide, hydrogen cyanide, and nicotine after passive smoke exposure under controlled conditions. The results indicate that salivary nicotine values reflect the level of recent passive smoke exposure within an hour and that urinary cotinine values indicate the level of passive smoke exposure in the preceding hours. N-Nitrosoproline has been shown to serve as an indicator of endogenous N-nitrosamine formation in cigarette smokers: yet, preliminary studies do not indicate that urinary excretion of N-nitrosoproline is increased following short-term passive smoke exposure. In infants, first field studies suggest a correlation between exposure to tobacco-smoke-polluted environments and levels of cotinine in both serum and urine.

Maintain levels of nicotine but reduce other smoke constituents: a formula for "less-hazardous" cigarettes?

Twenty-two volunteers who smoked more than 20 cigarettes with "high" nicotine yields (0.8 to 1.2 mg) per day participated in an 8-week study designed to test the hypothesis that smoking cigarettes with a constant level of nicotine but reduced deliveries of tar, carbon monoxide, and hydrogen cyanide leads to a decrease in smoke absorption. All subjects smoked their usual high-nicotine brand for the first 3 weeks (P1), and the absorption of smoke constituents was determined from levels of thiocyanate and cotinine in saliva and serum, levels of carbon monoxide in expired air, and levels of carboxyhemoglobin in the blood. During the final 5 weeks (P2), the treatment group (16 subjects) switched to the "light" version of their usual brands (similar yields of nicotine but with reduced yields of tar, carbon monoxide, and hydrogen cyanide); the control group (6 subjects) smoked their usual brands for the duration of the study. Average levels of cotinine for the subjects who switched during P2 were not significantly different from those of the control group as was expected. Slight reductions were noted in average expired-air carbon monoxide levels, blood carboxyhemoglobin, and saliva thiocyanate, but these reductions were smaller than anticipated based on brand characteristics. The results suggest that the ratio of smoke constituents is different when individuals, rather than machines, smoke cigarettes. Yields determined under subject-defined conditions are necessary in order to properly evaluate the role of nicotine in the design of "less-hazardous" cigarettes.

Reported cigarette smoke values: a closer look

Effects of mechanical compression of the filter tips and of blocking the air channels of a special filter design on the smoke yields of seven brands of commercial filter cigarettes were investigated. In addition, the influence of these variables on actual uptake of smoke constituents by smokers was studied with four subjects. Compression of filter tips produced major increases in smoke yields for the cigarette which features a filter tip with four longitudinal air channels at its periphery. Blocking of these air channels increased tar yields by 51 per cent, nicotine by 69 per cent, and carbon monoxide by 147 per cent. Subjects who smoked the cigarette with this special filter design tended to smoke fewer cigarettes per day than when they smoked cigarettes with perforated filter tips, yet their plasma cotinine levels were significantly higher. Blood pressure and pulse rate were markedly elevated after first exposure to smoke from the special filter cigarette, as were plasma nicotine levels. These results point out that individuals inhale different quantities of smoke constituents from cigarettes with reportedly similar smoke yields according to Federal Trade Commission methods. A redefinition of "average" smoking parameters readjustment of standard laboratory methodology are suggested.

The misuse of 'less-hazardous' cigarettes and its detection: hole-blocking of ventilated filters

Smokers of low-yield, ventilated-filter cigarettes sometimes defeat the purpose of the smoke-dilution holes by occluding them with fingers, lips, or tape. Blocking the holes is shown to have large effects on the delivery by these cigarettes of toxic products (nicotine, tar, and carbon monoxide). Techniques for detecting this misuse of "less hazardous" cigarettes are discussed, with particular emphasis on the distinctive signs of hole-blocking which are left in the spent filters.