Part 1. Efforts to Learn About Early Exposure in Radiological Occupations
It would be very difficult to believe that appreciable exposure to nurses, technicians, orderlies, physicians, office assistants, medical residents and fellows did not occur in the 1920, 1930, 1940, and 1950 periods. In the early 1950s we have a very good study from one of the leading institutions, the Cleveland Clinic, done for the purpose of estimating actual worker exposure in a reasonable manner.
Geist, Glasser and Hughes (1953) wrote:
"Within recent years there has been a considerable increase in the use of x-rays and radioactive substances in the diagnosis and treatment of disease. As a result the problem of adequate protection has become greatly magnified.
The Cleveland Clinic and its associated hospital is a very large and prestigious institution. Those who reported the study of worker exposure endeavored to ascertain the doses being received (or not received) by all categories of personnel involved in essentially every activity involving ionizing radiation within the Clinic and the hospital.
The study, involving 84 persons, was conducted over a period of three months. The technique employed for dose measurement was that of film badges. Badges were worn for one week by employees, returned to Tracerlab, Inc. in Boston, and developed by Tracerlab. The results were reported back in milli-Roentgens (mR) per week. New badges replaced the prior badge each week, for a total period of 3 months. We can presume that the measure being obtained is that of whole-body radiation, and that hence the breasts would have received some radiation from anterior, lateral, and posterior entry of x-rays.
A Drawback to the Study
There is every reason to consider that this study was well executed. However, there is a lesson from experience which teaches us that the measured doses were undoubtedly too low for a very specific reason. The employees know that it would be "inappropriate" for management to think they were being careless about doses being received, and would therefore be on their best behavior during the three-month period of such a trial evaluation. Anyone dealing with laboratory procedures knows that when employees know they are under test, the performance is far better than when the test is introduced unknown to the employees. We have had an extensive experience in this regard. There is no way that this particular test could have been done in a "blinded" fashion, so we must assume that the results obtained will show a lower dose than that which truly characterized operations at the Cleveland Clinic before or after the period of testing performance. We will therefore not be overestimating the true exposure by examining these results.
An Urge Which Could Not Be Suppressed
Consider a story from the 1941 paper by Dean Cowie and Leonard Scheele. They did a survey of 45 hospitals (in 24 states) to which radium had been provided for medical use. The purpose of their on-site visits was to study not only the storage and handling of the radium, but also the exposure of hospital personnel from the administration of diagnostic and therapeutic x-rays (1941, p.769). For example (p.777):
"In spite of adequate shielding, practices were noted that led to overexposure. One technician entered the deep therapy room to talk with the patients or to reposition them after they moved without turning off the high voltage on the tube. It was not possible to ascertain how often this occurred, but during our visit it was done spontaneously several times, and an ionization chamber in the technician's pocket showed that she received 0.75 r during her stay in the room."
It is very likely that this observed behavior represented only the residual "bad behavior" after everyone was trying to display "best behavior" for the evaluators.
Readers who doubt that occupational doses were higher than reported in the Cleveland Clinic Study, may well change their minds when they read some hair-raising stories of how radium in hospitals was often handled --- as observed by Cowie and Scheele in their survey (see Chapter 35).Part 2. The Actual Conduct of the Survey
We shall trace the various activities evaluated, and record the doses received in each activity. As a reference point, we can note that the so-called maximum permissible dose for exposure of the whole body to x, gamma, and beta radiation was 0.3 R per week, as recommended by the International Commission on Radiological Protection. Geist et al state that whenever the survey revealed that this level was exceeded as measured by the film badges, a further investigation was launched to determine the cause and ameliorative procedures were instituted. Such ameliorative procedures do not reduce exposures in any past activities. And, as a matter of realistic expectations, such ameliorative procedures tend to be forgotten once the test period is over.
The Major Divisions of the Study
The institution is divided into the outpatient Clinic and the Hospital. Separate facilities involving use of ionizing radiation were present in both Clinic and Hospital.
The radiation work is also subdivided by the categories of diagnostic roentgenology and radiation therapy. We shall consider the findings in both of these activities.
We shall describe the work by denoting (a) the department, (b) the number of persons involved, and (c) the estimated annual whole-body dose received for 50 weeks of work per year. The results provided to the Cleveland Clinic by the Tracerlab Company are in milli-Roentgens per week, since the badges were changed weekly. When a badge is returned with no exposure noted, we know that the dose received is somewhere between zero and the limit of detection of dose. Our prior experience indicates that the detection limit is between 10 and 20 mR (milli-Roentgens). We shall assume 20 mR as the detection limit, and record all doses as 10 mR when the report returned indicates no exposure.
Diagnostic Roentgenology in the Cleveland Clinic (Outpatient) Category Number Roentgens Person-Roentgens per year per year Radiological Technicians 12 15 180.0 Receptionists 4 0.5 2.0 Secretarial 5 0.5 2.5 Darkroom Operators 4 0.5 2.0 Film Transferers 6 0.5 3.0 Film Distribution ?? 0.5 ?? Staff Radiologists 5 5.1 25.5 Fellows in Radiology 8 5.1 40.8 Genito-Urinary Technician 1 4.5 4.5 Dental Technician 1 7.5 7.5 Catheterization Lab, Nurse 1 1.1 1.1 Catheterization Lab, Physician 1 4.5 4.5 Diagnostic Roentgenology in the Hospital (In-Patient) Radiological Technicians 2 2.43 4.9 Surgical Rad. Technician 1 5.0 5.0 Surgical, Cerebral Arterio- graphy, Neurosurgeon 1 6.9 6.9 Surgical, Angiocardiography Cardiologist 1 4.6 4.6 Cardiologist assistant 1 4.6 4.6 Radiologist 1 4.6 4.6 Radiologist assistant 1 4.6 4.6 Surgical, Aortography Urologist 1 1.6 1.6 Surgical, Cholangiography Surgeons 2 3.4 6.8 Therapeutic Roentgenology Departments Radiologists for x-ray therapy and isotope use. 2 4.5 9.0 Fellow in Radiology 1 0.8 0.8 Radium and Radon Handling Fellows in Radiology 2 10.7 21.4 Assistant in Biophysics 1 10.7 10.7 Otolaryngology; Radium applicator. Physician 1 3.1 3.1 Ophthalmology, Beta Sources. Physician 1 1.0 1.0 Therapeutic Roentgenology in the Hospital Dermatologists, Superficial Therapy (100 kv) 1 5.3 5.3 Biophysics, Head 1 1.0 1.0 Assistant 1 1.0 1.0 Total Persons Accounted For: 70 Sum 367.8 Pers.-Roent.
We must presume the remaining persons of the total of 84 were not engaged in operations that might result in exposure.
We may note a couple of features of this tabulation. The outpatient radiological technician data are given only as less than 300 mR per week. But we also have a note that there were nine exceptions, in which this limit was exceeded. We have therefore used 300 mR per week, assuming possible balance between the overexposures and some of the under-300 mR exposures.
Technicians Who Hold Patients While Beam Is "On"
In two categories, for the diagnostic radiologic technicians and the dermatologists, it was noted that exposures were increased by the practice of holding patients during radiological procedures. For the dermatologists, it was explicitly stated that the holding was of infants. The practice of staying with and holding patients was reported also by Cowie and Scheele (1941, p.777):
"A technician in another hospital sat with or held many foreign-language-speaking patients during superficial therapy. She did this on an average of three times weekly and received an average of 1.5 r per treatment. Her daily average on a 5-day basis was approximately 1.0 r.
What Happens without Perpetual Vigilance?
Cowie and Scheele continue (p.777): "A number of other improper practices leading to overexposures were noted, but in the majority of hospitals, practices were excellent. The radiologists in charge in the institutions where overexposure of roentgen-ray therapy technicians occurred had not been checking the work of their technicians and were unaware that these breaks in technique occurred. Close and careful supervision is important."Part 3. Analysis of the Data from the Cleveland Clinic
Mean Annual Exposure = 367.8 person-Roentgens / 84 persons = 4.38 Roentgens.
It would be difficult to estimate how we could extend these Cleveland Clinic data to the national scene directly, but we can place some likely limits on the national doses indirectly with some data from UNSCEAR 1977 (page 243, para.87 and 88). Klement and co-workers (1972) estimated 194,541 medical x-ray workers, and UNSCEAR 1977 (at p.243) cites a number of 38,000 individuals engaged in radium therapy work, for a total of 232,500 workers, rounded off, in the USA.
The Cleveland Clinic study was done 20 years earlier. A reasonable approximation would be for us to cut the 1972 worker total in half, which gives a total of 116,250 workers engaged in medical x-ray and radium work. We should cut this value in half again, to consider just female workers. Therefore, the estimated early period total for female medical x-ray workers would be 58,125 workers. And we consider this to be a reasonable approximation for the average year in 1920-1960.
We estimate 4.38 Roentgens as the annual exposure based on the Cleveland Clinic results.
(58,125 workers x 4.38 Roentgens) = 254,588 person-Roentgens.
We can distribute these person-Roentgens into 25 age-year categories, assuming the workers employed were equally distributed from age 20 to age 45 years.
254,588 person-Roentgens / 25 age-year categories = 10,184 person-Roentgens per category.
But our interest is in breast-doses. Since these person-Roentgens are for whole-body radiation exposure, and since essentially all film badges are worn on the front of the body, person-Roentgens received from the back are already corrected to rads by the passage through the body before reaching the film-badge. The posterior irradiation, after going through the body, contributes negligibly to the total dose. We shall therefore assign all 10,184 Roentgens to radiation received from the front of the body. But we must now convert the person-Roentgens to person-rads.
(10,184 person-Roentgens) x (0.693 rads per Roentgen) = 7,058 person-rads.
We must now convert the person-rads of the exposed workers into the population dose.
For this, we need the value in Column A of the Master Table. Let us illustrate by making the calculation for women in 20th age-year group. Column A entry is 885,914 women.
Average breast-dose = 7,058 person-rads / 885,914 women
= 0.00797 rads to the breasts.
We enter (7,058 person-rads / Column A population) into Column Q of the Master Table for ages 20 through 44 years, to provide the average breast-doses for medical occupational exposure. We consider that this approach represents a conservative underestimate of this dose.
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Unwelcome Evidence --- from the Irradiated Children
Below, we will quote from:
C. Lenore Simpson and Louis H. Hempelmann, "The Association of Tumors and Roentgen-Ray Treatment of the Thorax in Infancy," Cancer Vol.10 No.1: 42-56. January-February 1957.
Simpson and Hempelmann are extremely cautious in stating that their series of children treated for thymus enlargement really were experiencing radiation-caused neoplastic disease. We quote at pages 51-52:
"In all retrospective field studies of this nature, the establishment of suitable control material is a major difficulty. We have pointed out some of the advantages and disadvantages of our controls but feel we have established a definite increase in neoplastic disease among our treated children. We have raised the question whether radiation is responsible for this increase. Although we feel this point will be settled only when further studies have been made, it is of interest to examine the evidence at present available. There are indications from our own data that the tumor incidence varies with the type of radiation given. There are other clinical observations in man, and there is a large amount of evidence from animal experiments indicating that ionizing radiation is cancerogenic."
And at page 52:
"Malignant change occurring in heavily radiated tissue has been recognized for many years, first in the skin of the early radiologists and then in the bones. The part played by radiation in the etiology of such tumors has been recognized because the incidence is high, the tumor is in an unusual site, or chronic radiation damage preceded the onset of the cancer. The extensive literature on the subject has recently been reviewed by Hueper. Prior to the present study there has been little evidence tha tumors would follow doses of less than 1000 r. There was also little evidence that radiation could induce thyroid cancer in man."