Philip Morris clinical study of carbon filtered cigarettes challenged by nondisclosure issues

Abstract

Scientists from Philip Morris USA recently reported a clinical study in which they claim a significant reduction in biomarkers of exposure to “gas vapor” phase smoke constituents among smokers who switched from conventional filter cigarettes to cigarettes with filters containing activated carbon (Sarkar et al., 2008). The test cigarettes were prototypes, made in-house, and coded as TC-6 and TC-11. Each test cigarette filter contained a charcoal form of activated carbon from an undisclosed supplier. Properties widely known to be critical for appraising charcoal’s potential effectiveness, including surface area and absorbance activity (British American Tobacco Company Limited, London, 1985), were not disclosed. Also not disclosed was whether the charcoal had been surface modified, a subject that has been of considerable interest to Philip Morris (Zhuang, Fournier, Paine, & Xue, 2008). The manner in which the carbon was distributed in the filter was also not disclosed (e.g., cavity filter vs. carbon on tow filter; Philip Morris USA, 2005; Polzin et al, 2008; Zhuang et al.). Thus, the absence of these vital pieces of information precludes comparison of the results of this study with those of prior or future research which examines the influence of smoking charcoal filter tipped cigarettes on biomarkers of exposure. Paradoxically, a recent review of the literature by another group of investigators at Philip Morris concluded that scientific evaluation of charcoal filtration of cigarette smoke has been hindered by a lack of documentation regarding the activity of the charcoal used and information on filter design. The authors concluded that this makes it difficult to reach a definitive conclusion regarding the potential health benefits of using charcoal as a smoke filtration technology (Coggins & Gaworski, 2008). The report by Coggins and Gaworski was not referenced in the publication by Sarkar et al.