|Comments | Additions/Updates|
The First Fifty Years of Radiation Protection
Introduction: The First Fifty Years of Radiation Protection--A Brief Sketch
The science and art of radiation protection or health physics as it is more properly called grew out of the parallel discoveries of x-rays and radioactivity in the closing years of the nineteenth century. The x-ray, discovered by German physicist Wilhelm Konrad Roentgen on November 8, 1895, was reported to the world shortly after the first of the year 1896. Roentgen's discovery was a scientific bombshell, and was received with extraordinary interest by both scientist and laymen. Many scientist dropped other lines of research to pursue the mysterious rays, and the newspapers and magazines of the day provided the public with numerous stories, some true, others fanciful, about the properties of the newly discovered rays
The public fancy was caught by the invisible ray with the ability to pass through solid matter, and, in conjunction with a photographic plate, provide a picture, albeit a shadowy diffuse one, of the bones and interior of the body. Scientific fancy was captured by an extraordinary new radiation, of shorter wavelength than light, that presaged new and great vistas in physics, and the structure of matter. Both the scientist and the public were enthusiastic about potential applications of the newly discovered rays as an aid in medicine and surgery. Thus, within a month after the announcement of the discovery, several medical radiographs had been made in Europe and the United States which were used by surgeons to guide them in their work.
Only two months after the general announcement of the discovery of the x-rays, Henri Becquerel, a french physicist, communicated to the world his discovery of similar penetrating rays emitted from salts of uranium. His discovery was, unlike that of the x-rays, virtually unnoted by the layman and scientist alike. Only a relatively few scientist were interested in Becquerel's findings, and it was not until the discovery of radium by the Curies two years later that interest in radioactivity became wide spread.
The initial lack of popular interest in radioactivity was more than made up for by the enormous activity with regards to x-rays. Experimenters and physicians, laymen and the physicists alike set up x-ray generating apparatus and proceeded about their labors with a blithe lack of concern regarding potential dangers. Such a lack of concern is quite understandable, for there was nothing in previous experience to suggest that x-rays would in any way be hazardous. Indeed, the opposite was the case, for who would suspect that a ray similar to light but unseen, unfelt, or otherwise undetectable by the senses would be damaging to the person? More likely, or so it seemed to some, x-rays would be beneficial, both for the prophylaxis and therapy
Inevitably, the widespread and unrestrained use of x-rays led to frank injury. Often, injuries were not attributed to x-ray exposure, in part because of the latent period before the onset of systems, and more so because there was simply no reason to suspect x-rays as the cause. Whatever some early experimenters may have thought about the skin effects they noted, others soon began to tie x-ray exposure and skin burns together. The first warning of possible adverse effects of x-rays came from Thomas Edison, William J. Morton, and Nikila Tesla who reported independently of eye irritations from experimentation with x-rays and fluorescent substances. These effects were most likely not attributable to x-rays but rather to eye strain, or possibly, ultraviolet from the fluorescence.
However, other reports, describing skin effects similar to those associated with a bad sunburn, began to appear. So frequent and persistent were these reports that in late 1896, less than a year after Roentgen's announcement, Elihu Thomson, an American physicist, deliberately exposed the little finger of his left hand to an x-ray tube for several days, half an hour per day. The resultant effects - pain, swelling, stiffness, erythema and blistering - were convincing for Thomson and others, but not for all. Many prominent physicians still denied that x-rays were in any way harmful, although oft times the denial was tempered by a qualification that the effects noted were attributable to misuse of the x-ray.
By 1900, four years after the discovery, it was apparent to most of the medical and scientific community that x-ray exposures, if too frequent or intensive, could produce skin burns. Reduction of exposure time and frequency were the most obvious ways to limit dose to patients, and experimenters sometimes used enclosed tubes or distance to protect themselves. Filtration of the x-ray beam was advocated prior to 1900 as was limitation of beam size (collimation). Other techniques, including the use of intensifying screens to reduce exposure time and higher x-ray generating voltages were also used about 1900 to minimize patient doses to x-rays. Impetus to providing patient protection was spurred by malpractice law suits decided in favor of patients who had been injured as a result of diagnostic x-ray exposure.
Although the basic techniques of x-ray protection were well known by 1905, ten years after the discovery, implementation was spotty. Thus, even during the 1920's and into the '30's and even '40's it was not uncommon to find medical x-ray units with virtually no safety precautions. The hazards of radioactivity were better controlled, primarily because of the high monetary value of the radium sources in use in medicine, coupled with their continuous output of very penetrating rays. Thus, storage of radium in locked shielded safes was common, and applicators, necessitated by sterile techniques and surgical application, were generally used.
The early chronology of radiation protection efforts is given in Table 0.1. Three distinct periods are noted:
The Pioneer Era has already been briefly described, and needs only mention of an extraordinary x-ray protection pioneer to complete the description. William Herbert Rollins was a Boston dentist, who, during the period 1896-1904, made numerous original contributions to the emerging science of radiology. Among his contributions were several pertaining to radiation protection: leaded tube housings, collimators, and other techniques (including the development of high voltage tubes) to limit patient dose. Rollins also performed a series of experiments that showed x-rays could kill guinea pigs. His experiments included exposure of a pregnant guinea pig which resulted in killing of the fetus and which led to Rollins expressing concern about the use of x-rays in pelvic exams of pregnant women. For a period of several years, Rollins was the quintessential promulgator of radiation protection techniques. He was a true pioneer of x-ray protection.
The Dormant Era (1905-1925) was a period of two decades in which applications of x-rays and radium along with the development of improved equipment seemed dominant. In the protection area, little overt progress was made, although latent effects of radiation exposures, particularly at low level, began to be recognized. However, gains in the radiation protection area were relatively slow and few, although in some respects highly significant.
One little known event that is of historical significance in health physics was reported at the October 1907 meeting of the American Roentgen Ray Society. At that meeting, Rome Vernon Wagner, an x-ray tube manufacturer, reported that in an effort to control his personal exposures, he had begun to carry a photographic plate in his pocket and to develop the plate each evening to determine if he had been exposed. This practice, which apparently did not come into widespread use until later, was clearly the forerunner of the film badge. Unfortunately, Wagner's concerns for his personal exposure came too late, for he had already developed cancer and died 6 months later in 1908.
A major development in the period was the adoption of radiation protection recommendations by the British Roentgen Society (1915) and the American Roentgen Ray Society (1922). Simple as these were by modern standards, they provided a sound basis for users of x-rays, and more importantly, signified an active organizational interest in x-ray protection. Not was radium ignored, the British X-ray and Radium Protection Committee jointly sponsored by several organizations, issued its first memorandum in 1921 and included a rather lengthy section specifically addressed to radium protection.
The real gains were yet to come. The year 1925 marked the start of what might be termed "Era of Progress" (1925-1945). In that year(1), Arthur Mutscheller put forth the first tolerance dose or permissible exposure limit, equivalent to about 0.2 rem per day. Mutscheller, a German-American physicist, based this limit on 1/100 of the quantity known to produce a skin erythema per month noting that recovery would occur swiftly enough to obviate any untoward effects. Swedish physicist Rolf Sievert also put forth a tolerance dose- 10% of the skin erythema dose - in the same year.
The 1920's saw other gains in radiation protection: the introduction of film badges for routine personnel monitoring, recognition of the genetic effects of x-rays (for which Hermann Muller won the Nobel Prize in 1946), and the adoption of a unit for measuring radiation by the Second International Congress on Radiology in 1928. The definition and adoption of the Roentgen, as this unit was named, provided a physical basis for the quantitative measurement, heretofore lacking, thus permitting in a more or less unequivocable way, documentation of radiation exposures.
Recognition of radiation hazards and the need for control led to the formation of the International X-ray and Radium Protection Committee, forerunner of the current International Commission on Radiological Protection, and the following year the formation of the U.S. Advisory Committee on X-ray and Radium Protection (ACXRP), direct ancestor of the modern day National Council on Radiation Protection and Measurements. These bodies undertook a study of the so-called tolerance dose and promulgated the establishment of definitive, scientifically based radiation protection guides, the first of which was published in 1931, a 114 page document which, among other things, considered the hazards of toxic chemicals from burning x-ray film as well as protective measures for protection of both patients and those occupationally exposed.
The decade of the 1930's also saw the first reduction in recommended exposure limits, when in 1936 the ACXRP recommended the reduction of the so-called tolerance dose to 0.1 R/day, reducing it by half. Five years later, in 19441, the ACXRP established the first permissible body burden fro radioactivity in the body - 0.1 microcurie for radium. The body burden was based on the pioneering work of Robley D. Evans, MIT physicist, with radium dial painters. The year 1941 also saw an article by Lauriston Taylor that recommended an even further reduction in the permissible level for external exposure to 0,02 R/day, or roughly the equivalent of 5 rem/year.
Note 1: Mutscheller's proposal was published in the American Journal of Roentgenology in 1925 although he actually made the recommendation in 1924 at the American Roentgen Ray Society Meeting.
It was the Manhattan District of U.S. Army Corps of Engineers that the name "health physics" was born, and great advances were made in radiation safety. From the onset, the leaders of the Manhattan District recognized that a new and intense source of radiation and radioactivity would be created, and thus, in the summer of 19424, asked Ernest O. Wollan, a cosmic ray physicist at the University of Chicago, to form a group to study and control radiation hazards. Thus, Wollan was the first to bear the title of health physicist. He was soon joined by Carl G. Gamertsfelder, recently graduated physics baccalaureate, and Herbert M. Parker, the noted British-American medical physicist. By mid 1943, six others had been added: Karl Z. Morgan, James C. Hart, Robert R. Coveyou, O.G. Landsverk, L.A. Pardue and John E. Rose.
Within the Manhattan District, the name "health physicist" seems to have been derived in part from the need for secrecy (and hence a code name for radiation protection activities) and the fact that there was a group of mostly physicists working on health related problems. Thus, their activities included development of appropriate monitoring instruments, developing physical controls, administrative procedures, monitoring areas and [personnel, radioactive waste disposal-- in short, the entire spectrum of modern day radiation protection problems. It was in the Manhattan District that many of the modern concepts of protection were born, including the rem unit, which took into account the biological effectiveness of the radiation, and the maximum permissible concentration (MPC) for inhaled radioactivity. In deed, it was in the Manhattan District that modern day radiation protection effects, born in the early days of x-ray and radium, realized their maturity.
Permission was granted by Ronald L. Kathern for use of this article at this WWW site. It was reproduced from the book: Health Physics: A Backward Glace, R. Kathren and P. Ziemer (Editors), Pergamon Press, 1980.