Cigarettes are radioactive

IN THE year 1987, I received some anxious queries from smokers when a national news agency prominently published a news item titled `cigarette is radioactive' and attributed it to me. I cannot claim any originality in the matter. In 1976, scientists at the Bhabha Atomic Research Centre, where I then worked, measured Polonium-210 levels in tobacco. I provided them the equipment to measure polonium. Polonium-210 is an alpha particle emitting radioactive element.

In 1982, an article titled `Radioactivity in Cigarette Smoke' in the New England Journal of Medicine by T.H.Winters and J.R.DiFranza of the University of Massachusetts Medical Centre, provided the wake up call. They showed that cigarette contains radioactivity in the form of polonium-210 (Po-210) and lead-210 (Pb-210). They claimed that a person smoking 1 and 1/2 packs of cigarettes per day receives a radiation dose to certain regions of the lung equal to 300 x-ray films of the chest per year. Others estimated that the dose is over 70 times more. The dose rate depends on the radioactive content of the tobacco, the puff size and the frequency and number of cigarettes smoked.

Dr. Ravenholt, former Director of World Health Surveys at the US Centres for Disease Control, declared that Americans receive more radiation from tobacco smoke than from any other source. In 1990, the then US Surgeon General C.Everett Koop declared on US national television that radioactivity in cigarette accounts for at least 90 per cent of all smoking related cancers.

T.C. Tso, a former researcher of the US Department of Agriculture, found out that phosphatic fertilizers, which contained uranium and its decay product radium-226, are the sources of radioactivity in tobacco. Radium-226 decays into radon, an inert gas. Po-210 and Pb-210 are long-lived decay products of radon. Sticky hairlike structures on both sides of tobacco leaves collect these from the atmosphere. Tobacco roots also absorb some radioactivity from soil.

Scientists found high concentrations of Po-210 in certain regions of the lungs in seven out of the 37 smokers studied. Lung cancers developed in these regions. Scientists could induce lung tumours in laboratory animals by instilling Po-210 in various amounts down to less than one-fifth of that inhaled by heavy cigarette smokers during 25 years. Also, Po-210 is the only compound in cigarette smoke that has produced cancers by itself in laboratory animals by inhalation.

Indirect evidence revealed the role of radioactivity in cigarettes in the induction of lung cancer. Between 1938 and 1956, lung cancer rates in USA increased almost ten-fold.

The polonium levels in American tobacco also tripled from 1938 to 1960. Lung cancer rates increased in women as in men though ladies generally used filtered cigarettes. Filters remove benzopyrene and nitrosamine, two well-known cancer-inducing compounds. But they are ineffective against Po-210 and Pb -210.

Polonium and lead volatilises in lighted cigarettes. Ten per cent of Pb-210 and 20 per cent of Po-210 contained in cigarettes enter the smoker's lung through the main smoke stream; remaining ninety percent of Pb-210 and 80 per cent of Po-210 float in the ambient air for the passive neighbours to inhale!

Lighted cigarettes produce Po-210 and insoluble Pb-210 in the main stream. Smokers inhale them deep into their lungs. The particles of smoke- bearing radioactive residues accumulate continuously in the narrow airways of smokers and form hotspots. These hotspots deliver high radiation doses. Not surprisingly, most lung cancers are formed in these regions.

Po-210 being soluble gets removed from the inner linings of the lung. Blood circulating in the lung absorbs it partly and carries it to every tissue and cell in the body. Alpha particles from Po-210 mutate the cells. Many of these cells will die. But a few partly damaged cells may survive and multiply uncontrollably to cause cancer.

Scientists have separated Po-210 from tobacco smoke, deeper inner linings of the lung and also from blood and urine of smokers. Smokers' urine contains six times more polonium than non-smokers'. Non radioactive cancer-inducing agents are not found in the urine of even heavy smokers.

Dr. Ravenholt studied smokers among war veterans over 16 years and found that pollutants in cigarettes cause cancer in buccal cavity, pharynx, stomach, kidney, bladder, etc. Fourteen different tissues in all.

It seems that radiation safety professionals are not deterred by presence of radioactivity in cigarettes. I noted this while attending the International Congress of the International Association for Radiation Protection at Hiroshima. After each session, I saw many delegates rushing to the `smoking room'. They were not a minority.

K.S. Parthasarathy

Secretary, AERB

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