Missing annual external radiation dosimetry data among Hanford workers

Abstract

Epidemiological studies of workers employed at the Hanford Site have been underway for nearly 30 years. Although the external radiation dosimetry program at Hanford has been fairly comprehensive, some workers included in previous epidemiological analyses have periods of employment during which there are missing annual external radiation dosimetry records. In this report, employment history records and annual external dosimetry records have been used to investigate the extent of missing annual external dosimetry records for workers at the Hanford facility. A``nearby'' procedure for estimating values for missing annual external dosimetry records was evaluated. Among the 33,459 workers who were employed at least 180 days and had at least one annual external dosimetry record, annual external dosimetry records were missing for 8% of the years of employment ( 32,323 missing annual external dosimetry records ) . Missing annual external dosimetry records were more common for female Hanford workers than for male workers, and for workers employed in the early years of Hanford's operation than for workers employed in later years of operation. The nearby procedure provided reliable estimates of values for missing annual external dosimetry records. Using this procedure, 18,937.5 mSv were estimated for missing annual external dosimetry records; this was 2% of the total recorded cumulative external radiation dose for these workers. Missing annual external dosimetry records should be considered as a potential source of bias and uncertainty in investigations of radiation ± cancer associations among Hanford workers.

Evaluation of external radiation dosimetry records at the Savannah River Site, 1951–1989

“…The percentage of missing annual external dosimetry records among male SRS workers (4%) is comparable to the 6% missing annual external dosimetry records among male Hanford workers (Richardson et al, 1999) and the 5% missing annual dose records reported among white males employed at ORNL (Wing et al, 1991). Also similar to previous findings from evaluations of the dosimetry programs at ORNL and Hanford, we found that coverage was more complete in later historical periods than in earlier years of operation.…”

“…So, the nearby estimation procedure tends to lead to a small overestimate of the value for an unmonitored dose year in which the true dose was zero and a small underestimate of the value for an unmonitored year in which the true dose was greater than zero. These findings are similar to patterns reported in a previous application of the nearby procedure to data for workers from the Hanford Site (Richardson et al, 1999). If we had information that indicated that a clerical worker was employed in an area in which the dose rate was zero then we could assign a zero dose to that year.…”

“…In previous studies of workers employed at US Department of Energy sites, estimated dose values were derived for person-years of employment that were missing annual dosimetry information via a ''nearby'' method (Watson et al, 1994;Richardson et al, 1999). Under this method, a series of hierarchical steps are followed in order to calculate an estimated value for each missing annual dosimetry record (i.e., if there were no adequate data to calculate an estimated value using the first step in the procedure, an estimated value was calculated using a subsequent step).…”

Age at exposure to ionising radiation and cancer mortality among Hanford workers: follow up through 1994

“…21 Although annual dose records were available for most production workers in most years, a substantial proportion of missing values occurred in earlier time periods, especially for clerical workers and women. 20 Missing values were estimated by a 13 step algorithm that relied on each worker's dose in neighbouring years, and, if not available, on the mean dose for workers of the same occupation and sex in the same year. 20 Statistical analysis An SAS computer program 22 was used to tabulate persondays and deaths in categories defined by the crossclassification of cumulative radiation dose and covariates of interest: age-at-risk, birth cohort, race, sex, socioeconomic status (SES), employment status, in vivo monitoring, and plutonium exposure potential.…”

Plutonium‐related work and cause‐specific mortality at the United States Department of Energy Hanford Site

“…The primary occupational exposure under investigation at Hanford has been external penetrating ionizing radiation. These external exposures have been routinely quantified using personal dosimeters for a majority of workers included in epidemiologic studies [Gilbert, 1990;Kneale et al, 1991;Gilbert and Fix, 1996;Richardson et al, 1999Richardson et al, , 2000. Epidemiologic studies have demonstrated dose-response relationships for cancer mortality and external radiation exposures at older ages [Stewart and Kneale, 1989Stewart, 1993, 1995], but not for cumulative exposures across all ages [Gilbert et al, 1989[Gilbert et al, , 1993a.…”