Building a job-exposure matrix for early plutonium workers at the Sellafield nuclear site, United Kingdom

Anthony Riddell,Richard Wakeford,Mark Peace,Jacqueline O’Hagan,Christine Wilson,David Macgregor,Frank De Vocht,Hanhua Liu,Raymond Agius

doi:10.1088/1361-6498/ab1168

Abstract

The potential for adverse health effects from internal exposure to Plutonium has been recognised since its discovery in the 1940s. However, in the absence of specific information, potential risks from Plutonium exposure have always largely been controlled through knowledge of radiation exposure risks in general, much of which comes from external radiation exposures. To try to obtain more direct estimates of potential internal exposure risks, epidemiological studies of Plutonium workers need to be conducted. Such epidemiological analyses require individual Plutonium exposure estimates that are as accurate and unbiased as possible. The UK Sellafield workforce includes one of the world’s largest cohorts of Plutonium workers, which constitutes, by some considerable margin, the group of workers most comprehensively monitored for internal exposure to this alpha-particle-emitter. However, for several hundred workers employed at the start of Plutonium work at the facility, during the period from 1952 through to 1963, the historical urinalysis results available cannot provide sufficiently accurate and unbiased exposure assessments needed for use in epidemiological studies. Consequently, these early workers have had to be excluded from epidemiological analyses and this has significantly reduced the power of these studies. A promising quantitative methodology to overcome the issue of missing or deficient exposure data, is to use exposure data from other sources to estimate the average exposure a ‘typical worker’ would have received, and to collate this information for specific occupations and years. This approach is called a Job-Exposure Matrix (JEM). Work on a pilot study to construct a population-specific quantitative JEM for the early Plutonium workers at Sellafield during 1952–1963, for whom reliable urinalysis results do not exist, has shown the potential for a JEM approach to produce more reliable and useful exposure estimates for epidemiological research.

Highlights

IntroductionEpidemiological analyses of populations exposed to ionising radiation have the potential to directly investigate any health effects of such exposures
Plutonium has been recognised as a human health hazard since the 1940s; primarily because its main isotopes undergo radioactive decay through alpha particle emission [1].Epidemiological analyses of populations exposed to ionising radiation have the potential to directly investigate any health effects of such exposures
In the absence of specific information, potential risks from Plutonium exposure have always largely been controlled through knowledge of radiation exposure risks in general, much of which comes from external radiation exposures

Summary

Introduction

Epidemiological analyses of populations exposed to ionising radiation have the potential to directly investigate any health effects of such exposures. Most epidemiological studies have largely been concerned with exposures to highly penetrating photon radiation (i.e. gamma and x rays) with sources external to the body, because such exposures are more common and much easier to evaluate than doses from internally deposited radionuclides. Owing to its high linear energy transfer rate, alpha particle radiation exhibits significantly enhanced biological effects at the cellular level relative to gamma radiation, so there is a specific need to investigate the health risks of exposures to alpha particle emitters such as Plutonium. The Plutonium worker cohort at the Sellafield site (originally Windscale Works) in the North-West of England is one of the largest and longest standing cohorts of this type in the world. The production of Plutonium requires the reprocessing of uraniumbased nuclear fuel, involving the chemical dissolution of irradiated fuel to separate out any Plutonium, remaining uranium, and waste fission products in the fuel; the separated

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