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4& 44 , FROM: SUBJ ECT: -LICvVwHTT &% MYNI[tS IrOTC®YII'®lRA7CED CIGARETTE AND TOBACCO DIVISION Comments on Recent News Releases Concerning. Lead-210 and Polonium-210 in Cigarette Smoke Tobacco leaf, as do all plant tissues, contains small amounts of many inorganic constituents, amon.g them some lead, and polonium. The lead~content has been found to be somewhat variable as re- ported by different investigators, the average content being about 40 parts per. million (40 micrograms per gram of tobacco ),. Upon pyrolysis of the tobacco iri the burning cigarette cone, , 1C _ ., acLLL . _ cL~J~1CcW.'.~ lLV , flJt`lIl sCJIIle i'ecd.5UilcLUly' volatile prodi-i'CLs ?11CL1cCh transfer into main.stream.smoke. The transfer efficiency has been reported to be of the order of 4%. -This is in contrast to most of, the major inorganic species in. tobacco which have very low transfer efficiencies (e.g., calciumi- present 26,000 ppm, transfer 0.001%, aluminum - present 700 ppm, transfer 0.003%, etc.). Nevertheless, the level of lead er se in smoke is so low that it is generally considered to be of little biological significance. Lead is made up of many isotopes, i.e., atoms of slightly different atomic weight, one of whic.hy the radioactive lead-210, ~ 600 s mentioned in the recent newspaper articles. T.^d-210 is principally a.~-emitter and probably not harm1 ~ to Poloniumi-210 which is an d,-emitter with a snort ha_ -life 138 days ) and it is this ~,-radiation given off by. Po-210 that

.; . Memo to Mr. Ted Cramer Page 2 July 25, 1974 most of the recent articles have focused on. The levels of Po-210 in tobacco and smoke are so low that .they are generally expressed not in weight but in radiation units,(usually picocuries/gram of tobacco or per cigarette in smoke; pico = 10-12). The reported levels are usually of the order of 0.3 - 0.6 pc/g of tobacco and 0.02 - G.01 pc/cigarette volatility. in mainstream smoke. Thus, polonium transfers into smoke more efficiently than lead, as would be expected from its higher Some of the recent publication.s'have made some very strong- sfcsll_:emPtlf,;s about the Gign,ifi_ca.nc? of .thesP levels of radiation such as: E. A. Martell, Nature, 249, 217 (1974): "Thus, it seems that ~C-radiation from Po-210 in insoluble smoke particles may be the primary agent of bronchial cancer in smoking." We will have to counterbalance this by opposing opinions of equally reputable scientists such as: B. Rajewski and W. Stahlhofen, Nature, 209, 1313 (1966 ): (the calculated dose rate) "would seemto show that carcinogenesis caused by inhalation of Po-210 with the tobacco smoke is rather unlikely". grar,t monies or some other laurels, have been known to occasion- Researchers, particularly when~in pursuit of rese arch aaly u;rcrstate what is warranted by facts in order to enhance the

Memo to Mr. Ted Cramer Page 3 July 25, 1974 . t merits of their own thing. As it stands, we shall have to delay , objective judgement as -to just how significan.t Po-210 in. smoke is.until considerable additional research is completed.- We,have carried out some studies on the filtration efficiency of various filters for Po-210. Standard cellulose acetate filters, such as the L+" M filter, remove of the order of ~+10~ of Po-210 from smoke. This appears to be very nicely in. line with the filtration. efficiency for "tar" which is also -about 40/. In a Lark study, we found.a Po-210 removal efficiency of 58% which, if true, indicates that part of the polonium in smoke mav be in the form of some compounds that are considerably more volative than metallic polonium itself. These experiments were relatively cursory and, due to the low levels of polonium with"which we are dealing, the data scatter was considerable, however, the results appear plausible. RESEARCH DEPARTMENT Vello Norman VN/sbs