Goiania’s radiation accident – down the memory lane

In 1987, a scrap yard in Goiânia suffered one of the worst accident involving a radioactive source. Two families live and work at the scrap yard in the Brazilian city. Plastic and metal scrap collected off the streets is sorted out for recycling. Scrap merchants sold a metal canister left at an abandoned medical clinic. It looked harmless but valuable. They had no idea that it contained a powerful radioactive source used to treat cancer. The equipment was opened and the glittering radioactive Caesium chloride powder was shown to the friends and relatives of the junk-yard owner. Small fractions of the powder were gifted as souvenirs.

Thus, unknowingly, the contamination became wide spread over two weeks period. 250 people were contaminated. Four died in the first month. The management of the accident generated 3000 cubic meters of radioactive waste, which was disposed off in near surface repositories on the outskirts of the city.

The incident brought global changes in radiation safety. Lessons drawn from the accident are still helping to shape actions on radiation safety and security decades later. Before the accident, the regulations were weak when it came to controlling radiation used in medicine and industry worldwide. There was no awareness that radioactive sources must be controlled from ´cradle to grave´, and to prevent the public accessing them. Since the accident, the gradual replacement of sealed sources containing the soluble, powdery form of cesium chloride has been considered. The task is not easy. The IAEA has been developing rigorous safety standards for dealing with orphaned sources of this kind in the metal recycling industry. .

Fly-ash waste from thermal power plants

Coal-based thermal power plants burn train-loads of coal in a day and the percentage of ash generated is of the order of 35-40%. This waste needs disposal, and the target buyers are cement manufacturers and brick makers. The bricks made out of this fly-ash are cheaper as compared to the conventional bricks. The fly ash contains the naturally occurring radionuclides coming from uranium and thorium series of elements and Potassium-40. These radionuclides are present in the coal in parts per million (ppm) levels and get concentrated in the fly ash. A few hundreds of Becquerel (unit to express the quantity of radioactivity) of the radioactivity per kg of the material are likely to be present in the fly-ash.

One of the daughter products in uranium and thorium series is the gaseous radon isotopes. Being gaseous, the radionuclides diffuse out of the bricks/walls made out of the fly ash. These are emitting alpha radiation, and give dose to the lungs when goes inside the lungs as an air contaminant via inhalation route.

From radiation protection considerations, it is suggested that before fly-ash is used for commercial exploitation, an assessment of the materials is made for their radioactive content and the probable dose it is likely to give. If necessary, the material should be processed to remove the radioactivity content as much as possible. Clearance from the appropriate national authorities such as Atomic Energy Regulatory Board in India, may be required before large scale use of the “waste” fly-ash materials in cement or bricks used for construction of residential buildings.

Radioprotectors

While the radiation therapy is used to effectively to destroy cancerous tissues, it can have devastating side effect on healthy cells. It is desirable to have a drug which can protect some healthy cells without reducing the treatment’s effectiveness? Radio-protectors are drugs that protect normal (non-cancerous) cells from the damage caused by the high radiation dose used in radiation therapy. These agents promote the repair of normal cells that are exposed to radiation.

Amifostine may be the only drug approved by the FDA as a radio-protector. A single dose given to the laboratory animals shortly before receiving radiation therapy significantly reduce the radiation damage.

It is reported that the researchers at the Roswell Park Cancer Institute, USA, have developed a new drug, code-named CBLB502 that can protect healthy cells and bone marrow during anticancer radiation therapy. The drug may even protect against the biological effects such as lethal gastrointestinal (GI) syndrome (as an antidote) which are likely to be caused due to excessive exposures of the full-body in radiation emergencies. However, these are studies involving animals and more research needs to be done in humans.

Everything is more or less radioactive

When we say radioactive material, we mean the material emits ionizing radiation, capable of producing ion pairs in biological materials. Examples are alpha particles, beta, gamma, X-rays and neutrons. So in all cases, the radiation produces electrical interactions in the absorbing material. X-rays are also produced artificially in machines by rapid slowing down of an electron beam.

Everything around us is radioactive. There is cosmic radiation and terrestrial radiation. Cosmic radiation comes from deep space. Its origin is uncertain and the radiation is highly energetic. It is a mixture of many different types of radiation. All these highly energetic radiation particles interact with the atmosphere and as a result cosmic radiation at ground level becomes primarily muons, neutrons, electrons, positrons and photons. Exposure of humans to this cosmic radiation is unavoidable. The resultant dose is called external dose. Depending upon the elevation from the sea level, the dose rate due to exposure of population is different, and varies considerably. During the interaction, gaseous radioactive isotopes (radionuclides) such as Tritium (H-3) and Carbon-14 are also produced. These gaseous radionuclides get mixed up in the air we are breathing. Over time, they get incorporated in the bio-sphere.

Terrestrial radiation comes from the naturally occurring radioactive material present in rocks, in the ocean, in the atmosphere and in living organisms. Humans are also exposed to the radiation emitted by these terrestrial radioactive materials. Examples of these long-lived radionuclides are: Potassium-40, uranium and thorium series (their decay products such as radioisotopes of radium, polonium and lead). The radionuclides are also found in our diet and they get incorporated in the body. One of the radioactive decay products in the uranium and thorium series is gaseous Radon. The two important radionuclide are Radon-220 (from thorium series) and Radon-222 (from uranium series). Being gaseous, they come out of the solid matrix (like: rock/soil/bricks) and get mixed up in the air we are breathing. These inhaled radionuclides result in internal dose to the body.

The unit of radioactivity is Becquerel (Bq). It represents the quantity of radioactive material that emits one one disintegration per second. The older unit is a Curie (Ci) and 1 Curie is equal to 37 billion Bq. Thus, Bq is a very small unit and prefixes of kilo, mega and giga are use for thousand, million and billion respectively are used to express the amount of radioactive material generally used. Curie is a very big unit and hence prefixes of milli, micro and nano are used to express the amount: one-thousandth, one-millionth and one-billionth of a Curie.

Lead healthy lifestyle with mobile phones

It is true that mobile phones have brought in revolution in telecommunications industry. The expected mobile phone usage in India is projected to be 500 million (half of the population) within a short period of time. As per the recent reports, of the service providers are planning to erect over 90,000 base stations all over India to meet the ever increasing demand from rural areas! Mobile phone usage is very predominant in the new lifestyle adopted by younger generation. Mobiles are often given to children to play by the ever obliging parents. The scenario is not different in other countries.

Communication between a mobile phone and the nearest base station is achieved by the microwave radiation emissions from the transmitters connected to the antennas mounted at the base stations. These base stations are erected on top of buildings or specially built towers. There is much apprehension worldwide about the long-term health effects due to the exposure of people residing near the base stations and the mobile phone users to the radiofrequency emissions. Health effects such as heating of the exposed tissues, increased risk of malignant tumors (cancers) in the head and ears, genetic effects due to exposure of body cells to the radiofrequency (RF) radiations, etc. are reported in the literature.

Keeping in mind of the above uncertainties, including scanty nature of the studies and the gaps in our knowledge about the health effects of RF radiation, it is advised to keep the exposures much below the prescribed international guidelines. Use mobile phones for messaging only. Hand-free phones are safer. Since children are more sensitive to the radiation, mobile phones should be kept away from children.

There is a need for strict regulation to ensure that the manufacturers of the mobile phones maintain the radiation emission levels of the mobiles much lower than the standards. The base stations should be shared among the service providers to minimize the required number of base stations. Base stations near schools and crowded areas should be avoided.

There should be a dedicated regulatory body for strict regulation of the mobile phone usage. The regulators should periodically monitor the ambient RF levels near the base stations and display the readings for public knowledge and for checking compliance with the set limits by regulators. House insurance/health insurance schemes should also look into the safety of erecting antenna on the residential building tops.

What is dirty bomb?

A “dirty bomb” is not a nuclear weapon or bomb, the type of which was exploded over Hiroshima and Nagasaki, Japan. Dirty bomb is also called as “radiological dispersal device” (RDD) that combines a conventional explosive, such as dynamite, with radioactive material. Most RDDs would not release enough radiation to kill people or to cause radiation induced severe illness. However, the effects of the conventional explosive itself would be more harmful to individuals than the radioactive material.

Terrorist organizations may use this type of explosion to create panic and fear amongst the target population groups. Making prompt, accurate information available to the public could prevent the panic situation sought by terrorist organizations.

However, depending on the scenario, RDD explosion could create fear and panic due to the radioactive part of the bomb. This is the main motive behind using radioactive material in the conventional bomb. The explosion will contaminate property, may be a few blocks or a few kilometers depending upon the quantity, type of radioactive material used, method used for the dispersal and the weather conditions at that point of time. The clean up of the contamination is potentially costly, need expert’s guidance and time consuming.

Prompt detection of the type of radioactive material used will greatly assist local authorities in advising the community on protective measures, such as sheltering in place, or quickly leaving the immediate area. Radiation can be readily detected with equipment already carried by many emergency responders. There are expert groups identified by the government to respond to such type of emergencies within minutes. Media such as television and mobile messaging system come handy in informing the public as to the protective actions to be taken to minimize the exposure to radiation. The experts also will asess the radiation dose received by the exposed persons and suggest remedial measures, if required.

Thumb rules for the protection are: i) minimize the time spent near the affected area and ii) keep sufficient distance from the site of contamination. The inhalation of the airborne radioactive material can be prevented by using a wet handkerchief over the nose or a respirator normally used by the hospital staff.

Radiation protection of non-human species.

ICRP Publication 91 (2003) provided the basic framework for assessing the impact of ionizing radiation on non-human species. In order to provide further guidance on the issue, the International Commission on Radiological Protection (ICRP) brought out a draft document, the work of an ICRP Task Group, to address “Environmental Protection: The Concept and Use of Reference Animals and Plants”.

This draft provides the practical basis for consideration of non-human species in radiological protection. The draft report can be downloaded from the ICRP site. It is said that the ICRP would much appreciate receiving comments and suggestions regarding this draft by all concerned not later than Friday 28 March, 2008.