Estimating Historical Radiation Doses to a Cohort of U.S. Radiologic Technologists

Abstract

Data have been collected and physical and statistical models have been constructed to estimate unknown occupational radiation doses among 90,000 members of the U.S. Radiologic Technologists cohort who responded to a baseline questionnaire during the mid-1980s. Since the availability of radiation dose data differed by calendar period, different models were developed and applied for years worked before 1960, 1960- 1976 and 1977-1984. The dose estimation used available film-badge measurements (approximately 350,000) for individual cohort members, information provided by the technologists on their work history and protection practices, and measurement and other data derived from the literature. The dosimetry model estimates annual and cumulative occupational badge doses (personal dose equivalent) for each technologist for each year worked from 1916 through 1984 as well as absorbed doses to organs and tissues including bone marrow, female breast, thyroid, ovary, testes, lung and skin. Assumptions have been made about critical variables including average energy of X rays, use of protective aprons, position of film badges, and minimum detectable doses. Uncertainty of badge and organ doses was characterized for each year of each technologist's working career. Monte Carlo methods were used to generate estimates of cumulative organ doses for preliminary cancer risk analyses. The models and predictions presented here, while continuing to be modified and improved, represent one of the most comprehensive dose reconstructions undertaken to date for a large cohort of medical radiation workers.

Childhood cancer in the offspring born in 1921–1984 to US radiologic technologists

“…Electronic files of film-badge doses were not routinely available until late 1970s. To estimate these doses, we undertook a comprehensive dose reconstruction that used hundreds of thousands of badge doses from electronic files from 1977 onward, thousands of badge doses from hard copy records for the period 1960 -76, and literature-based dose data for the period before 1960 (Simon et al, 2006). This dose reconstruction, although imperfect, is likely to be superior to proxy measures of exposure such as job title.…”

“…Annual occupational radiation doses received by RTs were estimated as described previously (Simon et al, 2006), using all relevant literature on doses received by RTs (mainly for those working before 1960, when dosimetry was not available), film-badge measurements from a commercial dosimetry provider or military dose registries, dose records provided by employers, and individual work history and protection practices from three cohort surveys. Annual ovary and testes organ dose estimates were used as the best approximations for foetal and germline exposures.…”

“…As 73% USRT cohort participants are female, both preconception and in utero occupational radiation exposure effects on offspring cancer risk could be studied. In addition, much effort was devoted to reconstructing probable dose levels during periods when workers were not routinely monitored (Simon et al, 2006), allowing quantitative evaluation of parental exposures. To date, this is the largest study of childhood cancer risk in RT offspring.…”

Polymorphisms in Apoptosis- and Proliferation-Related Genes, Ionizing Radiation Exposure, and Risk of Breast Cancer among U.S. Radiologic Technologists

“…Unique features of this study were its large size (859 cases and 1,083 controls), carefully reconstructed cumulative occupational radiation breast dose estimates (18,19), cumulative questionnaire-based diagnostic radiation breast dose scores, and the availability of detailed information about reproductive, demographic, and lifestyle factors derived from interviews of all subjects. Our risk estimates for both occupational and personal diagnostic radiation exposure were consistent with the entire cohort (data not shown) and from studies of radiation effects on breast cancer risk (ref.…”

“…The occupational dosimetry system used to estimate absorbed dose to the breast has been described in detail elsewhere (18,19), with some significant refinements (20) introduced for this work. The present dosimetry version incorporates new dose factors [i.e., Gray (Gy) to breast per Sievert (Sv) of badge dose] that reflect temporal changes in X-ray machine tube potentials and filtration, more reliable estimates of photon transmission through protective aprons and shields, more precise estimates of individual-specific apron use during the years worked, and substantially greater number of occupational radiation monitoring badge readings from cohort members in the period before 1977.…”