Accidental exposures in medical

 Accidental exposures in medical applications of radiation uses of radiation, particularly in radiotherapy, can be of concern, w.r.t patient safety, and occupational exposure considerations. New technologies may bring in improvement to the therapy. However, these technologies involve increase in the complexities of the systems, which in turn may cause new types of human error and problems with the equipment.

It is very important that any errors leading to or likely to lead (near misses) to serious consequences need to be investigated in time, and in detail. Dissemination of the information on these errors is crucial in preventing re-occurrence. Lessons learnt from accidental exposures form an invaluable resource for revealing vulnerable aspects of the practice of radiotherapy. For details refer: ICRP 112.

Radon at home

Exposure to radon has been a major health hazard in uranium mines. Radiological safety aspects of the mine workers are adequately addressed in ICRP/IAEA/WHO documents. The issues are discussed in detail in the reference book on Radiological Protection and Safety - A Practitioner’s Guide.

Radon is also found airborne in homes, particularly in dwellings of cold countries, like United States and Canada where the air in the dwellings and work areas is recirculated.

Radon comes from the radioactive decay of natural of uranium/radium present in trace quantities in bricks, soil, rock, and water. Being gaseous, it gets into the air you breathe. Basement areas are more radon prone due to exhalation of radon from the floor and walls. Radon typically moves up through the basement/ground to the air above and into your living areas through cracks and other cavities in the foundation. There is a guide “Home Buyers and Sellers Guide to Radon” by US EPA (www.epa.gov) which covers all the radon related issues.  

What is radon (Rn-222)?

 Radon-222 is a gaseous radioactive, short-lived (half-life is 3.82d), inert gas produced by the alpha decay of radium-226 in the naturally occurring uranium-238 series. Radon is ubiquitous. 

Uranium and thorium are natural radioactive elements present in the earth and rocks in very small amounts. Hence, building materials such as sand, bricks and cement also contain some amount of uranium, thorium, radium-226 or radium 224. Since they are present in the earth, the water-soluble elements present, such as uranium and radium in the decay series, get into water resources and land mass. The gaseous radionuclides radon and thoron seep out of soil and get mixed with the atmospheric air.  

Thus, we get exposed to these gaseous radionuclides in dwellings as well as outside the dwellings. They contribute maximum to the radiation dose received by the world population by inhalation of the air contaminated with these radionuclides. The concentration of these radionuclides varies from place to place, dwelling to dwelling depending on the ventilation/air supply available for dilution and dispersion, and the concentration uranium and thorium in the materials. In cold countries, the concentration of radon in dwelling is likely to be of concern, since the dwellings are closed most of the time, and recirculation of the indoor air facilitates build-up of radon and its daughter products, thus create potential inhalation hazard.  

Ignorant members of public - About ionizing radiation

Let us frankly expose the TRUTH – Common man (person) including illiterate, semi-illiterate, and so-called literate or educated, hardly know anything about ionizing radiation, its benefits, and harmful effects. They only know that radiation is dangerous, so many thousands have died in the explosions of the atom bombs in Japan; the exposed person will lose hair and become impotent, etc etc. How we are going to explain all the benefits we are talking about to such a large percentage, maybe more than 90% of the population who are lacking an understanding of elementary radiation physics, mathematics, biology and medicine?

Communication is the key. All the practitioners of radiation and radiological protection, facility operators, and the government authorities should focus on ways and means to create awareness amongst the people about radiation: benefits of low-level exposures; medical uses in health-care; industry and food preservation; health effects at high levels of exposures, and how safely the radioactive waste is managed by well-informed experts. We should use mass media communication systems and school/college syllabus to the maximum possible extent. Desist from use of words, like probability, ALARA, risk analysis, etc when communicating with members of the public.

Integrated risk assessment – radiation and chemicals

Occupational workers work in an environment where there are mixed pollutants, some of them are cancer-causing and some may cause non-cancer diseases. For worker’s overall safety considerations, it may become necessary to assess health risks from individual pollutants, as well as combined risk from all the pollutants existing in the work environment. The pollutants may include chemicals, radiation, physical pollutants, etc.

Health effects of radiation or chemicals are classified as acute or chronic. Acute affects results from a single exposure to a high radiation dose rate or exposure to a high concentration of a chemical. The effect, deterministic in nature sets in rapidly and could be mild to severe. The dosage of chemicals or radiation plays a significant role in the level of severity of the effect. Chronic effects develop over a long period of exposure to a low concentration of chemical or low dose rate of radiation. The effect may remain invisible for a relatively long period, called the latent period. Carcinogenicity is included in chronic effects, which are stochastic in nature.

 For a given end-point, say cancer, the risk from the exposure/intake may be added to get an integrated risk, which may be expressed in terms of the risk equivalent radiation dose. As of now, ICRP assumes a total lifetime stochastic risk of 0.01 per Sievert of radiation dose received as tolerable. This is in the absence of ALARA.

An integrated risk assessment system needs to be in place to have an overall risk perspective for the benefit of policymakers and decision-makers to try to achieve risk reduction of the workers in totality – from radiation as well as chemicals. Thus, the total detriments will have different components. Once the risk from exposure to all the pollutants is quantified for a given end-point by some acceptable methodology, it can be expressed in terms of Risk Equivalent Radiation Dose (RERD).

Dose reductions for radiological safety in occupational scenarios can consider the risk of both the radiation and possible presence of chemical pollutant in the work environment. Similarly, environmental safety should take into account the ambient levels of chemical pollutants and the corresponding risk to the members of the public. 

Additional small contributions to the environmental pollution by the discharges from nuclear industry cause negligible risk as compared to the multiple chemicals risks, as seen by the calculated RERD values.

[More details, references in Harmonization of Risk Management Approaches-Radiation and Chemical Exposures, Pushparaja, and P. Srinivasan, Proc. IRPA 11, Madrid, Spain, 2011].

At the end of 2018 - good news to curb CO2 emissions

It is well know that powders like finely divided carbon, silica, etc can adsorb gaseous matter on their surface to a great extent.

Professor Zhongwei Chen, at the University of Waterloo in Canada has developed optimized carbon powders (spheres) to absorb carbon dioxide, which is the main gaseous emission which is linked to the on-going climate change.  Work is going on to further increase the efficiency of the adsorption process by increasing the size and concentration of pores on the carbon material. Carbon is cost effective, environmental friendly and can be used in any shape and size, like columns.

The ultimate use is to employ the material at the carbon dioxide discharge lines of fossil fuel burning power plants to capture the CO2 gas. After saturation, the carbon can be stored deep underground, at geological formations to prevent its escape into the environment – in competition to disposal of high level radioactive waste in geological formations! 

The system needs to be developed in massive industrial scale to make any significant effect to control climate change. Better option still will be to exploit solar power or wind power to a much larger extent.  It is well know that powders like finely divided carbon and silica can adsorb gaseous matter on their surface to a great extent.

Use of chemical weapons

As per the Geneva Protocol 1925, the use of chemical weapons, through the implementation of the provisions of the “CONVENTION ON THE PROHIBITION OF THE DEVELOPMENT, PRODUCTION, STOCKPILING AND USE OF CHEMICAL WEAPONS AND ON THEIR DESTRUCTION 2005” is prohibited world-wide as a method of warfare for the benefit of mankind.

There are many toxic chemicals /gases which can create devastation/death in areas where the chemical weapons are used. However, chemicals are used often by some governments and other terror organizations to strike terror and induce fear amongst the public at large.  Often, we hear of accidental toxic gas leak causing death of people in the vicinity. Recently, in Douma, Syria chemical weapon was used and so many deaths.  

It is time that the UNSC urgently step-in and enforce the provisions /obligations of the Convention in letter and spirit and ensure that the chemical weapons are never used as a means of warfare or civil war to destroy population groups. The incidents of use of chemicals/chemical weapons should be investigated by UN authorities. Adequate resources for monitoring and for providing medical care for affected should be provided by the rich nations.