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Comments on: ENVIRONMENTAL TOBACCO SMOKE: A GUIDE TO WORKPLACE SMOKING POLICIES (Dratt) EPA 400/6-90/004 Response Addressing: Chapter 1: What Is ETS? Section: Differences Between Mainstream and Sidestream Smoke Prepared by: David W. Boldridge, Ph.D. Senior R&D Chemist R.J. Reynolds Tobacco Company October 1990

SUMMARY: The statements in the EPA Public Review draft document "Environmental Tobacco Smoke: A Guide to Workplace Policies" which relate to particle size distributions of mainstream and sidestream smokes are inaccurate and reflect a general lack of understanding of aerosol science. The draft document argues that the particles are substantially different in size, a position which contradicts the currently accepted scientific literature. Subsequent arguments, inferences and insinuations depend on the presence of a substantial difference in particle size between mainstream and sidestream smokes, and should be eliminated. COMMENTARY: The treatment of the physical nature of environmental tobacco smoke in "Environmental Tobacco Smoke: *A Guide to Workplace Policies" is seriously flawed in several respects. Each of the flaws will be addressed independently. On page 7 of the document a misleading definition of ETS is provided. Page 7, paragraph 5 begins with the statement "ETS is a cloud of fine particles and liquids suspended in gases." This suggests that the suspended "fine particles" in some way differ from "liquids", thereby implying that they are solid. There is no scientific evidence that there are solid particles present in ETS. Tobacco smoke is generally considered to be an aerosol of tiny liquid droplets suspended in a gas. The sentence should therefore be changed to read "ETS is an aerosol composed of fine liquid particles suspended in a gas mixture." OG 11 In paragraph 5, the authors then proceed to misinterpret the definition of an aerosol. M .A They erroneously subdivide the aerosol into "particulate phase" particles and "gas phase" ~

particles. The widely accepted range for aerosol particulate sizes is from 0.01 to 100 micrometers [1]. The minimum particle size is not normally set at 0.1 micrometer as stated in this EPA definition of ETS. (Some investigators extend the "particle" definition to 0.001 micrometer [2].) The gas phase is just that - a gas. The gas phase consists primarily of air admixed with some combustion gases. It is inaccurate to call any particles gas phase. The resolution of the objections raised above requires that the first four sentences of paragraph 5 be rewritten. The following is suggested: "ETS is an aerosol composed of fine liquid particles suspended in a gas mixture. For the purpose of study and discussion, scientists view ETS as consisting of two fractions, called "phases". The particulate phase consists of the tiny droplets of condensed material; the gas phase consists primarily of air components admixed with combustion gases." Under "DIFFERENCES BETWEEN MAINSTREAM AND SIDESTREAM SMOKE: Particle Size" (page 7, paragraphs 6,7 & 8) there are several significant errors. The initial error is semantic: In paragraph 6, the authors state that particles are "absorbed deep into the ...lungs." Aerosol particles are not absorbed into the lungs; they are breathed, inspired, respired, transported or carried. Absorption implies the dispersal of a op ~ substance throughout a physical matrix. ~ ~ 1+ 2

The subsequent error is more subtle but much more critical. In paragraphs 7 and 8, a comparison is made of the average particle size in mainstream and sidestream smoke. Mainstream smoke is said to have an average diameter of 0.7 micrometer, while "most sidestream particles, on the other hand, are much smaller - between two and four tenths of a micrometer." The 0.7 micrometer diameter for mainstream is attributed to Wells [3], a secondary source, who does not provide a further reference for the number. Primary literature sources suggest a smaller diameter for mainstream smoke [4-10], with significant variation depending on how the measurement was made. These reports uniformly place the mass mean diameter at 0.5 micrometer or less. Most notably, the Surgeon General in his 1986 report [11) describes two studies of mainstream and sidestream smoke particulate size measurements in which the instrumentation and techniques were comparable. The report concluded that 'These results also show that studies utilizing similar instruments provide similar size distribution of both SS and MS particles." This conclusion is not in agreement with the stated claim that most sidestream particles are much smaller. The EPA draft document should not compare mainstream and sidestream particle sizes at all, unless the authors can verify that the measurements are consistent with current state-of-the-art aerosol measurements, and that both mainstream and sidestream measurements were made under comparable conditions, with similar instruments. 3

The last sentence in this section has no direct connection to particle size. The sentence reads "The dose absorbed is small, but after absorption, the chemicals circulate widely in the body, tending to remain in the body longer than mainstream smoke in active smokers." This statement is derived from statements made by Wells and is based upon the assumption that the deposition patterns for mainstream and sidestream smoke are significantly different. The assumption that the deposition patterns are different is, in turn, based on the assumption that the average particle size of sidestream smoke is substantially smaller than the average particle size of mainstream smoke. Since the two particle sizes are not substantially different, the validity of arguments based on an assumed difference is questionable. This sentence should be deleted or moved to an appropriate location and substantiated. The technical quality of this section, as written, is very poor. The references cited by the authors do not necessarily reflect the main body of aerosol science as it applies to ETS and mainstream smoke aerosols. It is particularly disturbing that the authors use information from one source [11, p. 135] on the size of sidestream smoke and then contradict both data and conclusions pertaining to mainstream smoke which occur two pages later [11, p. 137]. Instead of using one source for their data, the authors cite an obscure second source for their mainstream data [3]. This source is not consistent with the bulk of the literature, but happens to support the argument they wish to make. This type of selective citation damages both the technical accuracy and scientific credibility of the document. 4

There is a significant body of recent literature pertaining to the aerosol properties of sidestream and mainstream smokes. The authors should try to present either the current, widely accepted data or convincing, technically sound arguments for alternate interpretations. Failure to strive for one of these goals reflects either a lack of competence or intellectual dishonesty. This section of the document, as written, reflects poorly on the EPA. RECOMMENDATION: I recommend that the section be rewritten as follows: DIFFERENCES BETWEEN MAINSTREAM AND SIDESTREAM SMOKE ETS may differ from mainstream smoke in three ways: particle size, quantitative and qualitative chemical composition. Particle Size ETS particles are approidmately the same size as those in mainstream smoke [6,11,12]. ~ ~ CA .A ~ S ,p

Recent measurements of mainstream particle mean diameter vary in the range 0.2 to 0.5 micrometer, depending on the method of measurement [4-10]. ETS is much more dilute than mainstream smoke. Measurements of sidestream smoke give particle size results similar to those for mainstream smoke when consistent measurement techniques are used [11]. Sidestream smoke is much more dilute than mainstream smoke. There is no evidence of differences in particle size which would lead to significant changes in the deposition patterns in the lung. 6

REFERENCES 1) Reist, P.C., Introduction to Aerosol Science, MacMillan Publishing Company, New York, 1984, p.8. 2) Friedlander, S.K., Smoke, Dust and Haze: Fundamentals of Aerosol Behavior, John Wiley and Sons, New York, 1977, p.5. 3) Wells, AJ., An Estimate of Adult Mortality in the United States from Passive Smoking, Envir. Internat., 14, 249-265(1988). 4) Hiller, F.C., McCusker, K.T., Mazumder, M.K., Wilson, J.D. and Bone, R.C., Deposition of Sidestream Cigarette Smoke in the Respiratory Tract, Am. Rev. Respir. Dis., 12S, 406-408(1982). 5) Ingebrethsen, B.J., Evolution of the Particle Size Distribution of Mainstream cigarette Smoke During a Puff, Aerosol Sci. Tech., 5, 423-433(1986). 6) Ishizu, Y., Ohta, K. and Okada, T., The Effect of Moisture on the Growth of Cigarette Smoke Particles, Beitr. Tabakforsch. Internat., 10, 161-168(1980). 7) Keith, C.H., Particle Size Studies on Tobacco Smoke, Beitr. Tabakforsch. Internat., 11, 123-131(1982). 8) McCusker, K., Hiller, F.C., Wilson, J.D., Mazumder, M.K. and Bone, R., Aerodynamic Sizing of Tobacco Smoke Particulate from Commercial Cigarettes, Arch. Environ. Health, 38, 215-218(1983). 9) Okada, T. and Matsunuma, K., Determination of Particle-Size Distribution and Concentration by a Light Scattering Method, J. Coll. Interface Sci., 48, 461-469(1974). 10) Stober, W., Lung Dynamics and Uptake of Smoke Constituents by Nonsmokers - A Survey, Prev. Med., 13, 589-601(1984). 11 U.S.DEPARTMENT OF HEALTH AND HUMAN SERVICES, The Health Consequences of Involuntary Smoking, a Report of the Surgeon General,1986, pp.135-138. 12 Leaderer, B.P., Cain, W.S., Isseroff, R. and Berglund, LG., Ventilation Requirements in Buildings-II. Particulate Matter and Carbon Mono~dde from Cigarette Smoking, Atmos. Envir., 18, 99-106(1984). 7 d ~