Radiation Protection in Canada: Part II. * The Role of the Radiation Protection Division in Safeguarding the Health of Radiation Workers

The current status of radiation protection in Canada is discussed in the second of a three-part series and particular emphasis is placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. Administrative and operational control procedures have been developed, involving prior approval of health safeguards in the radioisotope user''s facilities and techniques, and systematic monitoring and inspection. Where necessary, a medical follow-up of accidents and excessive radiation exposures is carried out. In 1963 more than 1600 radioisotope licences were issued. Filmmonitoring service was provided to about 15,500 isotope and x-ray workers. Semiautomatic handling procedures have been developed to meet the increasing demand for film-monitoring services.Monitoring and inspection services have been provided for x-ray workers, and a committee has been formed to develop administrative procedures for health and safety control in x-ray work. Committees have also been set up to review the health and safety aspects of the operation of nuclear reactors and particle accelerators.     

Radiation Protection in Canada: Part I *

The current status of radiation protection in Canada has been summarized in the present paper, the first of a three-part series. Particular emphasis has been placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. Somatic and hereditary effects of radiation exposure are briefly discussed as a basis for an understanding of the radiation protection standards which have been developed at national and international levels. The rapid increase in use of radioactive materials and x-ray apparatus in medicine, industry and research, and the extensive atmosphere testing of nuclear weapons have led to the development of comprehensive radiation protection activities in Canada, especially in the Department of National Health and Welfare. Well-established lines of communication and liaison exist among the various agencies responsible for these activities.     

Radiation Protection in Canada: Part VII. The Role of Industrial Hygiene in the Field of Radiation Protection

The main emphasis of a provincial radiation protection program is on ionizing radiation produced by machines, although assistance is given to the Federal Radiation Protection Division in its program relating to radioactive substances. The basis for the Saskatchewan program of radiation protection is the Radiological Health Act 1961. An important provision of the Act is annual registration of radiation equipment. The design of the registration form encourages a “do-it-yourself” radiation and electrical safety inspection.Installations are inspected every two years by a radiation health officer. Two hundred and twenty-one deficiencies were found during inspection of 224 items of radiation equipment, the commonest being failure to use personal film badges. Insufficient filtration of the beam, inadequate limitation of the beam, and unnecessary exposure of operators were other common faults.Physicians have a responsibility to weigh the potential advantages against the hazards when requesting radiographic or fluoroscopic procedures.     

Radiation Protection in Canada: Part V. Radiobiological and Radiological Health Research in Canada

A recent survey was carried out with respect to radiobiological and radiological health projects in Canada. Letters of inquiry, followed by two questionnaires, were sent out to every institution where radiation research was likely to have been undertaken. Approximately 75% of those contacted replied. Of the total of 200 studies, 84% were classified as biological and medical studies, the remaining 16% as environmental radiation studies. Responses to the inquiry stressed the inadequacy of the present governmental budget for radiation research, the need for higher salaries for research workers, and the necessity of a more intensive teaching program for technicians and professional personnel. The granting of longer-term grants, rather than annually renewable grants, is urged.     

Radiation Protection in Canada: Part VII. Setting Standards for Radiation Protection

The current recommendations of the International Commission on Radiological Protection have as a basic objective the limitation of the radiation dose to “that which involves a risk that is not unacceptable to the individual and to the population at large”. The problem is to decide what degree of risk is acceptable, in relation to the benefits of a practice that necessitates a radiation exposure. At the present time it is not possible to make more than very rough estimates of some of the risks of exposure to radiation, but such estimates can be usefully compared with some of the other risks that are tolerated by society. On the assumption that it would be possible to make quantitative assessments of both the benefits and the risks, the question is raised as to how and by whom an appropriate balance should be made.     

Radiation Protection in Canada: Part VI. Problems in the Assessment of Genetic Damage from Exposure of Individuals and Populations to Radiation

Estimates of the genetic damage from radiation exposures of human populations are needed in order to set reasonable limits for future exposures. In addition to the three rads per generation received by the gonads from natural sources, a similar amount is currently contributed by medical radiology and a further five rads per generation has been suggested as an upper limit for exposures from the future peaceful uses of atomic energy. Two methods of estimating the genetic damage from such an increase suggest that there might be in the vicinity of 250 to 800 severely affected individuals per year in a population of 20 million people, or within an order of magnitude of the current highway fatality rate for Canada of about 4000 per year. Although the true value may be less, or greater, by as much as tenfold, the effect is in any case large enough to justify continued scrutiny.     

The Role of Microtubules in Macronuclear Division of Blepharisma*

SYNOPSIS. The macronucleus of the heterotrich ciliate Blepharisma undergoes a spectacular change in form in preparation for its division. The elongation phase of this cycle has been examined by light and electron microscopy. Coincident with elongation, microtubules appear closely applied to the outer surface of the macronucleus and parallel to the direction of elongation, and disappear as elongation is completed. It is demonstrated that the antimitotic drugs colchicine and podophyllotoxin reversibly block macronuclear elongation but do not entirely inhibit morphogenetic events including cell division. The failure of colchicine-treated macronuclei to begin or continue elongation is correlated with the prevention of formation, disruption, and/or disorientation of the extranuclear microtubules.     

Radiation Protection in Canada: Part IV Factors of Importance in Minimizing Radiation Exposure of Patients,Operators and Others Involved in Diagnostic and Therapeutic Radiology

Factors that may reduce the dose of radiation, from diagnostic and therapeutic x-ray procedures, to the patient and to the occupational and non-occupational worker are outlined. Suitable basic radiation measuring apparatus is described. It is recommended that, in diagnostic radiography, relatively high kilovoltage, proper cones, collimation and adequate filtration be used. Some specific recommendations are made concerning fluoroscopic, photoroentgen and portable x-ray examinations. Film monitoring of personnel is advisable. Examples are given of protective devices to lessen the dosage to the occupational worker. It is the responsibility of the radiologist or physician in charge to ensure that the x-ray equipment is safe to operate and the radiation dose to the patient is kept to a minimum. The roentgen output for all radiographic examinations should be known by the responsible user.