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Mortality among United States radiologic technologists, 1926-90
M M Doody1, J S Mandel, J H Lubin
1Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892, USA.
Cancer Causes & Control : CCC
|March 5, 1998
Summary
This study evaluated mortality risks for radiologic technologists, finding no increased lung cancer or leukemia. However, breast cancer showed a significant elevation, particularly for those employed earlier and longer, suggesting a possible radiation effect.
Area of Science:
- Occupational Health
- Radiation Epidemiology
- Medical Physics
Background:
- Assessing long-term health risks from chronic low-level ionizing radiation exposure is crucial for occupational safety.
- Radiologic technologists represent a unique cohort for studying radiation effects, particularly given the historical predominance of women in the field.
Purpose of the Study:
- To evaluate the potential mortality risk associated with chronic low-level ionizing radiation exposure in a large cohort of U.S. radiologic technologists.
- To investigate specific cancer risks, including lung, leukemia, and female breast cancer, in relation to occupational radiation exposure.
Main Methods:
- A cohort study of 143,517 U.S. radiologic technologists certified between 1926-1980, with follow-up through 1990 (2.8 million person-years).
- Analysis of mortality data (7,345 deaths) using standardized mortality ratios (SMRs) and internal referent groups.
- Examination of cancer-specific mortality, including lung cancer, leukemia, and female breast cancer, in relation to employment period and duration of certification.
Main Results:
- A strong healthy-worker effect was observed, with lower overall mortality (SMR=0.69) and cancer mortality (SMR=0.79).
- No increased risk for lung cancer or acute/myelogenous/monocytic leukemia was found.
- Female breast cancer mortality was not elevated relative to the general population (SMR=0.99) but was significantly higher relative to other cancers within the cohort (SMR ratio=1.3).
- Elevated breast cancer risk was associated with employment before 1940 (SMR=1.5) and certification exceeding 30 years (SMR=1.4).
- Internal analysis showed increased breast cancer risk with longer certification duration among those certified before 1940 (P-trend < 0.001).
Conclusions:
- While findings for breast cancer are suggestive of a radiation effect, potential exposure misclassification and confounding factors like reproductive history limit causal inference.
- The study highlights the importance of considering historical exposure levels and cumulative doses in radiation epidemiology.
- Further research with more precise exposure data is needed to confirm the association between occupational radiation and breast cancer risk in radiologic technologists.