THE FOLLOWING ARTICLE APPEARED IN THE

MARCH 2000 ISSUE

THE POISON SLEUTHS

DEATH BY RADON

-Dr. Anil Aggrawal

"Good morning doctor. Oh, my God, what are you doing today? You have the dead body of a middle aged man today. What happened to him? Please tell me.”

“Good morning Tarun. The name of this 45 year old man is Ramlal, and he was working in a drug factory. He was living with his invalid wife and a 20 year old son, in his ancestral house for the last so many years. For some months now, he was not feeling well. His friends and relatives were constantly advising him to see some doctor, but he refused to believe he was sick. He died today morning. Normally in such cases, no police enquiry occurs, but this man was a Union leader, and there have been widespread rumors that the management somehow managed slow poisoning in his case. It has been alleged that this was particularly easy for the management to do so, as he was working in a drug factory, and all sorts of harmful drugs were available to the management. The pressure of the workers was so much, that the police had to arrest the top management people. Currently they are in police custody, and can’t meet anyone."

"So what do you think doctor?"

"Tarun, I have just now conducted a thorough autopsy on him, and I found that he has died because of lung cancer. Now there is no poison except one that can induce lung cancer, and that is the Radon gas."

"You mean someone gave him radon gas to kill him? That sounds preposterous."

"I will talk about it later. But first some investigations that I did in this case. When I found that his body was unusually radioactive, I visited his house, and was not very surprised to find a great amount of radioactivity in his house too. In fact this is what I had expected."

"From where is that radioactivity coming doctor? Did someone from the management lace his house with radon gas?"

"Tarun, the radioactivity in all probability is coming from the underground."

"From the Underground? I really don't understand that. Now doctor, I feel I must know the radon story from the beginning. Otherwise I won't be able to follow you intelligently. Kindly tell me the radon story from the beginning."

"Tarun, Let me tell you about some general facts about Radon first. It is a colorless, odorless, and tasteless gas found in Group 0 of the Periodic Table. It has a density of 9.25 g per cubic decimeter. In fact, it is the heaviest gas known. It is 7.5 times heavier than air and more than 100 times heavier than hydrogen. The gas liquefies at -61.80 C (-800 F) and freezes at -710 C (-960 F). On further cooling, solid radon glows with a soft yellow light that becomes orange-red at the temperature of liquid air (-1950 C [-3190 F]). Natural radon consists of three isotopes. They have the atomic weights of 219, 220 and 222, and thus are written as radon-219, radon-220 and radon-222 respectively. In chemistry the usual practice of writing the atomic weights is on the upper left hand side of the element symbol; thus the three isotopes are often represented as 219Rn, 220Rn and 222Rn. The half life of all three varieties is very short. But among themselves, the shortest half life is that of the variety having least atomic weight, and the longest half life is that of the variety having the maximum atomic weight. Thus the half life of 219Rn is only 3.92 seconds. Half life, as you surely know is the period, in which the original amount of a radioactive material is reduced by half. The half life of 220Rn is slightly more; 51.5 seconds. The longest lived of all is 222Rn, but even this variety has a half life of just 3.823 days. All the three varieties do not occur in nature as such, but are produced as a result of decay of other radioactive materials. 222Rn is produced by the decay of Radium; 220Rn from the decay of Thorium, and 219Rn from the decay of Actinium. In fact their parent elements give them their more popular names. 222Rn, since it is produced from radium, is known as radon. For similar reasons, 220Rn and 219Rn are known as thoron and actinon respectively. Thus when we speak of radon, we usually refer only to the isotope 222Rn. The other varieties, i.e. thoron and actinon, may be referred to as the isotopes of radon. I may tell you that the first isotope of radon to be discovered was thoron, which was discovered in 1899 by the British scientists R.B. Owens and Ernest Rutherford, who noticed that some of the radioactivity of thorium compounds could be blown away with the passage of time. Radon was discovered in 1900 by the German chemist Friedrich E. Dorn. The last isotope of radon to be discovered was actinon which was found in 1904, independently by Friedrich O. Giesel and André-Louis Debierne. Although these three are the naturally occurring isotopes of radon, now more than a dozen artificial radioactive isotopes of radon are known. I may tell you that radon and all its isotopes are rare in nature because they are all short-lived and because their sources, radium, thorium and actinium are rare. The atmosphere contains traces of radon near the ground as a result of seepage from soil and rocks, all of which contain minute quantities of radium. You may ask where the radium comes from within the soil and rocks. Actually Radium occurs as a natural decay product of uranium which is present in various types of rocks. It is now known that some tracts of land contain unusually high amounts of uranium beneath. This gives rise to more radium and more radon, which seeps up through the soil and collects in homes if they happen to be built on that land. Radon is now known to cause lung cancer in populations which are exposed to it. Indeed, radon is now thought to be the single most important cause of lung cancer among nonsmokers. By the late 1980s, naturally occurring radon gas had come to be recognized as a potentially serious health hazard. The gas, arising from soil and rocks, seeps through the foundations, basements, or piping of buildings and can accumulate in the air of houses that are poorly ventilated. Exposure to high concentrations of this radon over the course of many years can greatly increase the risk of developing lung cancer. Radon levels are highest in homes built over geological formations that contain uranium mineral deposits. I may tell you that 222Rn is itself radioactive, and it decays into 218Po, which in turn decays into 214Pb, 214Bi, 214Po. These four radionuclides are called the radon daughters. They all become attached to particles in the air and get breathed into lungs. 222Rn, 218Po, 214Po are all alpha emitters. Radiation can cause damage to biological molecules, and can induce cancers, genetic defects and accelerated aging."

"Doctor, all this sounds very frightening indeed. You told me that by the late 1980s, radon had come to be recognized as a serious health hazard. Tell me how exactly scientists discovered that radon gas could be emanating from the soil and collecting in the houses."

"Tarun, it is a very remarkable story indeed. It started on December 2, 1984, in Pennsylvania, USA. Before that it was known that radon occurs as a serious health hazard in mines, but its occurrence in ordinary homes was not known. During December 1984, the alarm bells in the Limerick nuclear power plant (in Pennsylvania, near Philadelphia, USA) were constantly ringing, indicating that someone had been contaminated with radioactivity. But it was not known who it was. There were concerns that the radioactivity might escape and pollute the environment. Then on the fateful day of 2 December 1984, a worker Stanley Watras was found to be unusually radioactive. When more investigations were done, it was surprisingly discovered that the radioactivity was coming from his house. Some people believed that he was stealing some radioactive material from the work place and taking it home, but none was found. Still more investigations showed that unusual amounts of radon were leaking in his house from the underground. The house of Watras was so radioactive that the health risk of living there was the same as smoking hundreds of cigarettes a day! On detailed investigations it was found, that his house straddled a vein of uranium ore. The authorities decided to investigate the levels of radon in other nearby houses and the results were worrying. By the end of 1986, about 20,000 houses had been checked in Pennsylvania, and one in eight were found to be overloaded with radon! Well, here in the table you can find some important dates in radon research in America. (N.B. The table is quite complex and is very difficult to put over the net. Readers desirous of having the table may want to get in touch with the webmaster.)

"Oh, that is quite informative."

"Gradually, the public became so concerned about radon, that the government found it imperative to decide upon a safe level of radon, which could be allowed in the homes and at workplaces. These levels were called Action Levels. Levels above these Action Levels were considered unsafe and legislations were passed, which could prosecute managements if they allowed radon levels to rise above these prescribed limits. Action Levels for homes were 200 Becquerels per cubic meters (200 Bq m-3), while those for work places were 400 Becquerels per cubic meters (400 Bq m-3).”

“Sorry to interrupt you doctor, but I don’t quite understand the concept of Becquerels. Could you please explain me that?”

“Sure. Antoine Henri Becquerel, as you surely know was a French physicist who discovered radioactivity through his investigations of uranium and other substances. In 1903 he shared the Nobel Prize for Physics with Pierre and Marie Curie. In his honor, scientists have named the unit of radioactivity. A sample of radioactive substance would be said to have a radioactivity of one Becquerel if in that sample one atom disintegrates per second. So if I say that the level of Radon in a particular home is 200 Becquerels per cubic meters, it means that there is so much Radon in that house that in every cubic meter of that house, 200 atoms of Radon are disintegrating per second. This is a very small Unit. A bigger Unit is Curie, which is equivalent to 3.7 X 1010 Becquerels. You might be surprised at this odd figure. Actually one Curie is the amount of radioactivity given off by one gram of radium. And it is seen that in one gram of radium, about 3.7 X 1010 atoms disintegrate per second. Hence this figure. You might think that the unit Curie is named after Marie Curie, the joint winner of Nobel Prize with Becquerel, but it is actually named after her husband Pierre Curie, who too shared the Prize with them. This is a little known interesting fact. Most people wrongly think that this unit is named after Marie Curie. While I am on the subject, I may tell you something more about the safe levels of Radon in houses. It was found that houses with levels of 2000 Bq m-3 and more were very dangerous places to live in. The house of Stanley Watras had fifty time more radioactivity than this - a radioactivity of 100,000 Bq m-3!”

"Doctor, now I know enough about Radon and its dangers. Do you seriously think, someone from the management arranged for the radon gas to be accumulated in Ramlal's house so he could die of lung cancer?"

"Tarun, theoretically speaking it is possible, but practically such a possibility is exceedingly low. Radon is not an easy gas to prepare. Concentrated samples of radon are prepared synthetically for medical and research purposes only and that too in highly specialized labs. Typically a supply of radium is kept in a glass vessel in aqueous solution or in the form of a porous solid from which the radon can readily flow. At intervals of a few days, the accumulated radon is pumped off, purified, and compressed into a small tube, which is then sealed and removed. The tube of gas is a source of penetrating gamma radiation, which comes mainly from one of radon's decay products, bismuth-214 (214Bi). Such tubes of radon have been used for radiotherapy and radiography. My initial thought was that Ramlal's house is built on a tract of land which is rich in Uranium, but I had to get the opinion of a geologist before I could finally say anything. I have got that opinion now, and the report says that my guess was correct. Ramlal’s house indeed is constructed over a land rich in Uranium. Come let us tell the police that those management people are innocent, and it was Radon, which took the life of Ramlal.

"Unbelievable! This was a most interesting discussion doctor. Tell me what are you going to tell me the next time?"

"Tarun, next time, I would tell you about a very interesting poison - Hydrogen Peroxide."