The rate of cortical bone resorption was assessed from long-term in vivo measurements of (90)Sr content in the skeleton for men aged 50-80 years and for women 0-30 years after menopause. Measurements of (90)Sr were conducted with a whole body counter (WBC) for residents of the Techa Riverside communities (Southern Urals, Russia), who ingested large amounts of (90)Sr as a result of releases of liquid radioactive wastes into the river from the Mayak plutonium facility in early 1950s. The results of this study showed an increase in the rate of cortical bone resorption in both men and women, as based on the use of accidentally ingested (90)Sr as a tracer for bone metabolism. In men there was a continuous gradual increase in the rate of cortical bone resorption after 55 years from 2.8 to 4.5%/year by the age of 75 years. In women, there was a doubled increase in the rate of cortical bone resorption after menopause of up to 6%/year; then the rate remained unchanged for 10-12 years with a subsequent gradual decline down to 5-5.5%/year. Comparison of the rate of cortical bone resorption in men and women older than 55 years showed that women expressed significantly higher levels of cortical bone resorption.
The Techa River Dosimetry System (TRDS) has been developed to provide estimates of dose received by approximately 30,000 members of the Extended Techa River Cohort (ETRC). Members of the ETRC were exposed beginning in 1949 to significant levels of external and internal (mainly from (90)Sr) dose but at low to moderate dose rates. Members of this cohort are being studied in an effort to test the hypothesis that exposure at low to moderate dose rates has the same ability to produce stochastic health effects as exposure at high dose rates. The current version of the TRDS is known as TRDS-2000 and is the subject of this paper. The estimated doses from (90)Sr are supported strongly by approximately 30,000 measurements made with a tooth beta-particle counter, measurements of bones collected at autopsy, and approximately 38,000 measurements made with a special whole-body counter that detects the bremsstrahlung from (90)Y. The median doses to the red bone marrow and the bone surface are 0.21 and 0.37 Gy, respectively. The maximum doses to the red bone marrow and bone surface are 2.0 and 5.2 Gy, respectively. Distributions of dose to other organs are provided and are lower than the values given above. Directions for future work are discussed.
The Mayak Production Association, which began operation in 1948, was the first facility in the former Soviet Union for the production of plutonium. Significant worker and population exposure occurred as a result of failures in the technological processes in the late 1940's and early 1950's. Members of the public were exposed via discharge of about 1017 Bq of liquid wastes into the Techa River during 1949-1956, an explosion in the radioactive waste-storage facility in 1957, and gaseous aerosol releases within the first decades of the facility's operation. Residents of many villages downstream on the Techa River were exposed via a variety of pathways; the more significant included drinking of water from the river and external gamma exposure due to proximity to sediments and shoreline. The specific aim of this project is to enhance the reconstruction of external and internal radiation doses for individuals in the Extended Techa River Cohort. The purpose of this paper is to present the details of the methods that are being used in this enhanced dose-reconstruction effort and to provide example and representative results of the calculations. The methods of dose assessment currently being developed for the exposed population [termed the Techa River Dosimetry System-2000 (TRDS-2000)], which are a significant improvement on past methods (TRDS-1996), are presented. The new TRDS-2000 doses from the ingestion of radionuclides are substantially higher for the gastrointestinal tract, due to consideration of short-lived radionuclides. The TRDS-2000 doses from external exposure are substantially lower due to improvements in several factors. Assessment of uncertainty and validation of the "new" doses are significant issues currently under investigation.