Tobacco Documents Online

A recent study' in Circulation contains technical errors and omissions in the inhalation exposure methodology which prevent a useful analysis of the morphometry data presented. The authors state that "moderate levels were chosen so that exporure conditions would be more relevant to those encountered in indoor environments by passive smokers." No reference was given to target concentrations, or how these targets would relate to field measurements. Instead, the reader finds that the mean values obtained in four identical chambers (no reason is given as why four separate units were needed) for total suspended particulates (TSP) were between 7.5 and 8.5 milligramsJm3. A recent review of TSP concentrations in 951 smoking homes and 905 non-smoking homes2 indicated an average of 0.049 milligrams/m3 for the former and 0.022 milligrams/m3 for the latter, for an overall difference (which may be due to smoking) between the two of 0. 327 milligrams/m3- This is more than 300 times less than the "moderate" concentrations used by Penn & Snyder. Clearly, the statement made in the Discussion ("comparable to the dose that can be expected under heavy smoking conditions at home") brings a new insight as to what constitutes "heavy" smoking for these authors, especially as their cockerels were exposed to this massive concentration continuously for 6 hours per day. The calculations made by Penn & Snyder in the Discussion contain a number of assumptions and produce results that are starkly at variance with actual field measurements.2 Hclcomb showed similarly 3

small differences in TSP concentrations between smoking and non-smoking restaurants, offices and transportation.2 In our laboratory3 we have shown no histopathological effects in the vascular systems of rats exposed to aged and diluted sidestream smoke at the p-ossly exaggerated TSP concentration of 10 mg/m3, 6 hours per day for 13 weeks (370 times the mean difference noted above between smoking and non-smoking homes). Cigarette mainstream smoke, sidestream smoke and environmental tobacco smoke (ETS) are not synonymous.4 The aging process, a major factor in thc: formation of ETS from sidestream smoke and exhaled mainstream smoke,5 is not pre:;ent in Penn & Snyder's design. Exposure to fresh sidestream smoke, as generated by Penn & Snyder, is totally inappropriate. It is then unclear as to how much of the aerosol presented to the cockerels was actually inhaled or ingested by them: whole-body exposures are known to produce large body burdens by the latter route when compared to the fornner.6 No reasons are given for the extensive modification of the smoke generator7 to remove design features that were incorporated to produce standard Fuffs and smoke with a constant composition. Together these unreferenced modificadons from our original design7 would produce an extremely variable aerosol over the fi hours of exposure (no 4

> _4c::__ data presented); the non-standard methods preclude verification of the results by other researchers. References 1. Penn A, Snyder, CA. Inhalation of sidestream cigarette smoke accelerates development of arteriosclerotic plaques. Circulation 1993; 88:1820-1825. 2. Holcomb, LC. Indoor air quality and environmental tobacco smoke: concentration and exposure. Env. Intl 1993; 19:9-40. 3. Coggins, CRE, Ayres, PH, Mosberg, AT, Sagartz, JW, Haye:;, AW. Sub-chronic inhalation study in rats, using aged and diluted sidestream smoke from a reference cigarette. Inha1. Toxicol. 1993; 5: 77-96. 4. Rodgman, A. Environmental tobacco smoke. Regul. Toxico,'. Pharmacol. 1992; 16: 223-244. 5. Guerin, MR, Jenkins, RA, Tomkins, BA. 1992. The chemistry of environmental tobacco smoke: composition and measurement. Lewis Publishers, Michigan. 6. Langard, S, Nordhagen, AL. Small animal inhalation chambers and the significance of dust ingestion from the contaminated coat when exposing rat> to zinc chromate. Acta Pharmacol. Toxicol. 1980; 46:43-46. 7. Ayres, PH, Mosberg, AT, Coggins, CRE. Modernization of nose-only smoking machines for use in animal inhalation studies. J. Am. Coll. Toxicol. 1990; 9:441-446. 5