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Alpha-particle-induced cancer in humans
1Radiobiology Division, University of Utah, Salt Lake City 84112.
Health Physics
|October 1, 1988
Summary
Internal exposure to alpha-particle-emitting radionuclides like radon progeny and Thorotrast increases cancer risk, particularly lung and liver cancers. Skeletal cancers are also observed following exposure to radium isotopes, with minimal latency periods.
Area of Science:
- Radiobiology
- Radiation Oncology
- Environmental Health
Background:
- Internal exposure to alpha-particle-emitting radionuclides poses significant health risks, including cancer.
- Radon progeny (222Rn), Thorotrast, and radium isotopes (226Ra, 228Ra, 224Ra) are key sources of internal alpha particle exposure.
- Understanding cancer risks from these exposures is crucial for public health and radiation protection.
Purpose of the Study:
- To provide updated information on alpha-particle-induced cancers in humans.
- To assess cancer risks associated with specific internal alpha emitters.
- To evaluate the latency and dose-response relationships for radiation-induced cancers.
Main Methods:
- Review and analysis of epidemiological data from human populations exposed to internal alpha emitters.
- Comparison of observed cancer cases with predicted risks based on dose-response models.
- Consideration of animal study findings to inform human risk assessment.
Main Results:
- Increased lung cancer risk observed in individuals exposed to radon (222Rn) progeny.
- Significant liver cancer incidence among German Thorotrast patients, with radioactivity identified as the primary driver.
- Occurrence of skeletal cancers in individuals exposed to radium isotopes (226Ra, 228Ra, 224Ra), with minimal appearance times around 4 years and majority expressed by 30 years post-exposure.
- Observed skeletal sarcomas in low-dose 224Ra patients align with predictions.
Conclusions:
- Internal alpha emitters represent a substantial cancer risk, necessitating ongoing monitoring and risk assessment.
- The findings challenge the "practical threshold" hypothesis for radiation-induced cancers.
- Follow-up studies of individuals exposed to alpha particles are vital for understanding high-LET radiation effects, especially given revised neutron dose estimates for atomic-bomb survivors.