Radioactivity of tobacco trichomes and insoluble cigarette smoke particles.
Airborne 210Pb concentrates on small Aitken particles which accumulate in tobacco trichomes. Prliminary measurements of 210Pb on cured tobacco leaves by analysis of surface particles removed by brushing and sonic cleaning showed concentrations of this radioactivity on leaf surfaces up to 20 times that of the bulk leaf per gm of ash. Preliminary results indicated that the type of insoluble smoke particle that will persist and accumulate in smoker's bronchi is between 10(4)pCi/gm, the activity of water-insoluble smoke particles, and 10(5)pCi/gm, the estimated activity of pyrolyzed trichome heads. Hence, tobacco curing and the combustion of trichomes in burning cigarettes produce insoluble particles of high 210Pb radioactivity which are inhaled and deposited in the bronchi. The subsequent ingrowth of 210Po (daughter isotope) results in high local alpha radiation which may account for bronchial cancer among smokers. For example, a single insoluble particle of North Carolina flue-cured tobacco trichomes carries an alpha radiation dose of about .5 rad or 5 rem/year of pulmonary accumulation.