According to Dr. Ravenholt, former Director of World Health Surveys at the US Centres for Disease Control, 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.
Polonium-210 (Po-210) and lead -210 (Pb-210)are the two radioactive elements present in cigarettes
These volatilize 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.
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.
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. Polonium-210 and lead-210 are long-lived decay products of radon. Sticky hair-like structures on both sides of tobacco leaves collect these from the atmosphere. Tobacco roots also absorb some radioactivity from soil.
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 Po-210 and 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.
Shaw, Mitchell and Dorling of the University of Bristol showed that a cigarette reduces one’s life by 11 minutes! (British Medical Journal, January 1, 2000). This “frightening statistic” attracted 13 responses in the next two weeks. Dr Dorling declared that he himself is a 20-cigarettes-a-day smoker.
“Cigarette smoke contains radioactive fumes”. I warned the readers of the Journal. I wished to wean away Dorling and other smokers from smoking! I have received no feedback yet. I spread the message at all the fora.
A land mark study detailing cancer mortality in India published on March 28, 2012 in The Lancet Journal estimated that tobacco-related cancers represented 42·0% of male and 18·3% of female cancer deaths and there were twice as many deaths from oral cancers as lung cancers. This study is a wake up call.
An equally worrying fact is that a survey published in the March 2011 issue of the Indian Journal of Medical Research showed that 11.2 percent of students aged 11 to 19 used tobacco in one form or other.
We must do every thing possible now to prevent a lung cancer epidemic later.
Some news paper articles By Dr K S Parthasarathy
- Cigarettes are radioactive The Hindu June 5, 2003
- The Tribune December 26, 2002
- Polonium: a hazard, if ingested or inhaled The Hindu December 7, 2006