Dr. Zablotska’s occupational health research adds to an emerging consensus that radiation risks for workers employed in uranium processing are substantially different from the risks of uranium miners, uranium enrichment workers, or nuclear workers.
A number of published pooled studies have assessed the health effects of both external radiation exposures of nuclear reactor workers and internal radiation exposures of uranium underground miners. Several recent studies indicate that uranium workers had substantially higher external exposures to gamma-rays compared to nuclear reactor workers, and that their internal exposures to radon decay products (RDP) were several times lower than in uranium miners. Thus, as stated above, there is an emerging consensus that exposures of uranium workers are substantially different from those of uranium underground miners or nuclear reactor workers, and that uranium workers should be carefully evaluated in separate studies. Only a few studies have conducted dose-response analyses of uranium workers with individual radiation doses, and they have all reported contradictory results, necessitating further research in this area. There are currently no pooled analyses of uranium workers and individual studies lack statistical power to assess health risks. Additionally, due to the small number of women in individual facilities, they have been generally excluded from analyses.
Uranium Processing Workers (UPW):
Dr. Zablotska is working on a pooled analysis of workers at four uranium-processing facilities from the U.S. and Canada that will include over 12,700 workers (Mallinckrodt Chemical Works in Missouri, Middlesex Sampling Plant in New Jersey, Fernald Feed Materials Production Center in Ohio, and Port Hope radium and uranium refinery and processing plant in Canada). This analysis will address critical gaps in our knowledge of the long-term health risks associated with occupational exposure to uranium, radium and silica in the uranium processing industry.
The cohorts share many similarities in occupational exposures, dose estimation and study design methods and background population mortality rates, providing a strong rationale for conducting a pooled study. The main analyses will be based on the pooled cohort of approximately 11,200 men, but we will also conduct exploratory analyses of around 1,500 women involved in uranium processing.
Aim 1: To complete the radiation dosimetry for Middlesex (from film badge readings, occupational medical x-rays, radon breath analyses, and radium and uranium urine samples), and estimate silica dust and radium exposures for workers at four uranium processing facilities: Port Hope, Fernald, Mallinckrodt and Middlesex.
Aim 2: To examine radiation-related risks of mortality from site-specific cancers and causes of death. To estimate radiation-related risks of morbidity from cardiovascular and renal diseases from exposures to uranium and radium. To estimate risk of lung and kidney disease from cumulative silica inhalation.
Aim 3: To estimate the risk of mortality from dementia, Alzheimer’s disease, Parkinson’s disease, and motor neuron disease associated with radium dose to brain.
International Pooled Analysis of Uranium Processing Workers (iPAUW):
In addition to conducting several studies of occupationally exposed workers in the U.S. and Canada, Dr. Zablotska is currently conducting pooled analyses with several European cohorts and actively participating in international consortia pooling the data from individual worker studies.
Workers involved in uranium milling, processing, enrichment and fuel fabrication (uranium workers) account for approximately 500,000 workers employed worldwide in the nuclear fuel cycle in the last 40-50 years. A better understanding of mortality patterns of uranium workers is essential to ensure that radiation protection programs appropriately protect workers’ health.
The five-year iPAUW study will address critical gaps in our knowledge of the long-term health risks associated with occupational exposure in the uranium processing industry. Over 100,000 workers (both male and female) are available for study and dose-response evaluations.
Aim 1: To harmonize the data from the cohorts in preparation for dose-response analyses.
Aim 2: To describe the overall mortality of uranium processing workers in contributing cohorts in comparison to the general population, by stages of uranium processing.
Aim 3: To examine RDP- and gamma- related risks of mortality from all solid cancers excluding lung cancer and from site-specific cancers and causes of death, including lung and bronchi, liver, kidney, bone, upper respiratory tract, and lymphatic and hematopoietic tissues, and temporal effect modifiers for radiation-associated risks.
Aim 4: To estimate risks of mortality from specific causes of death related to exposures to long-lived uranium radionuclides.
Aim 5: To consider uncertainties in exposure estimates and their potential effect on radiation risk estimates.
Public Health Relevance:
Both studies will be instrumental in developing evidence-based occupational safety recommendations. Study findings will vastly improve upon the current crude occupational safety risk projections based on the study of atomic bomb survivors from Japan whose exposures and population characteristics differ from U.S. workers of the uranium fuel industry. Using proven methods, we will increase collaboration and partnerships between study investigators and ensure that study findings will be disseminated to stakeholders and used for shaping public policies and government regulations.