Health outcomes of low-dose ionizing radiation exposure among medical workers: a cohort study of the Canadian national dose registry of radiation workers

Abstract

Background: Medical workers can be exposed to low-dose ionizing radiation from various sources. The potential cancer risks associated with ionizing radiation exposure have been derived from cohort studies of Japanese atomic bomb survivors who had experienced acute, high-level exposure. Since such extrapolations are subject to uncertainty, direct information is needed on the risk associated with chronic low-dose occupational exposure to ionizing radiation. Objectives: To determine the occupational doses of ionizing radiation and examine possible associations with mortality rates and cancer incidence in a cohort of medical workers deriving from the National Dose Registry of Canada (NDR) over the period of 1951-1987. Methods: Standardized mortality and incidence ratios (SMR and SIR, respectively) were ascertained by linking NDR data for a cohort of 67 562 medical workers (23 580 males and 43 982 females) with the data maintained by the Canadian Mortality, and Cancer Incidence databases. Dosimetry information was obtained from the National Dosimetry Services. Results: During the follow-up period, 1309 incident cases of cancer (509 in males, 800 in females) and 1325 deaths (823 in males, 502 in females) were observed. Mortality from cancer and non-cancer causes was generally below expected as compared to the general Canadian population. Thyroid cancer incidence was significantly elevated both among males and females, with a combined SIR of 1.74 and 90% CI: 1.40-2.10. Conclusions: The findings confirm previous reports on an increased risk of the thyroid cancer among medical workers occupationally exposed to ionizing radiation. Over the last 50 years, radiation protection measures have been effective in reducing radiation exposures of medical workers to the current very low levels.

Reproductive Risk Factors for Thyroid Cancer: A Prospective Cohort Study in Khon Kaen, Thailand

“…Thus, it is known that exposure to ionizing radiation, especially in childhood, increases the risk of developing thyroid cancer (Silverman, 1984;IARC, 2001;Zielinski et al, 2009;Furukawa et al, 2013) However, it is still not clear why thyroid cancer is markedly predominant in females. Previous observational studies on the reproductive system have produced conflicting results (Akslen et al, 1992;Pham et al, 2009;Horn-Ross et al, 2011;Kabat et al, 2012).…”

Effects of Ionising Radiation on Micronucleus Formation and Chromosomal Aberrations in Chinese Radiation Workers

“…Diagnostic and therapeutic applications, such as X rays and other medical devices, are an important source of IR and pose a significant risk of occupation-related exposure to IR. This poses a huge problem with regard to health of the exposed occupational group and for hospitals in managing occupational health risks (2,6,7) . Considering the serious radiological effects of IR on human health, the health risk to Chinese workers in different occupations, particularly in a healthcare setting, is important to understand (2) .…”

Occupational Cancer

“…There was also evidence of an increased risk of lung and thyroid tumors in radiological technologists who were frequently exposed to radiation as they assisted patients during x-rays, 85À86 and lung cancer in those who allowed others to practice x-rays on them. 86 Studies in various countries have also observed increased risks of leukemia, breast cancer, and skin cancer, 87 as well as thyroid cancer 88 in female workers exposed to ionizing radiation.…”

“…However, few studies of thyroid cancer and occupational risk factors among women have been conducted. Increased risk of thyroid cancer has been observed in women with exposure to ionizing radiation, 88 such as x-rays, 72,80 including health care workers, 70À71 radiological technologists, 85 dentists, and dental assistants. 72 Increased risk has also been observed in women employed as dry cleaners, 25 tailors, shoemakers and shoe cutters, 70,72 shop managers, 70 teachers, 72 warehouse workers, 72 the textile industry, 154 electric installation work, 70 and in women exposed to silica, 296 video display terminals, 72 and solvents in the shoe and leather industry.…”