Researchers in the UK have developed a new method of evaluating the historical internal radiation exposure of plutonium workers in a study funded by the National Institute for Health Research.
They focused their efforts on workers employed at the start of plutonium operations in the UK Sellafield (formerly Windscale) nuclear reprocessing facility.
In a paper published today in the Journal of Radiological Protection, the researchers describe how they have developed this approach and the need for this research.
Tony Riddell of the Center for Radiation, Chemical and Environmental Hazards (Public Health England), and the lead author explained: "With very little specific information available, potential risks of plutonium exposure have been largely controlled information about radiation exposure risks in general, much of which comes from external radiation exposures.
"In order to obtain more direct estimates of potential internal exposure risks, epidemiological studies of plutonium workers are required. These studies require individual plutonium exposure estimates that are as accurate and impartial as possible.
"The UK Windscale / Sellafield workforce consists of one of the world's largest cohorts of plutonium workers and, through the support of the workforce, has been subject to previous epidemiological analyzes.
However, accurate and unbiased exposure assessments for more than 600 employees employed there at the start of plutonium operations cannot be produced, between 1952 and 1963, using the results of urinalysis monitoring available to them: while these results are t suitable for operational protection purposes in the time, they tend to be highly exposed and this would result in any risks being underestimated if used in epidemiological analysis.
"This means that these early workers are excluded from epidemiological studies of exposure risks, which significantly reduce the power of these studies. Early workers are important to assess potential exposure risks because they are usually accepting some of the highest plutonium outcrops and, because of a time journey, health outcomes for these workers will now be largely known. "
In the paper, the researchers show how they tried to solve this problem with a method called the Job Disclosure Matrix (JEM).
Dr Frank De Vocht, from the University of Bristol, and the main researcher of the study, explained: "The JEM method is a standard exposure assessment methodology for epidemiological studies of chemical and physical occupational exposures but little use was made for internal radiation assessment. T exposures.
"It means estimating the level of average exposure that a typical worker in a homogeneous exposure group would have received in a given period, assuming that individual worker exposures are in the same group (often described by the job / occupation). ) comes from the same distribution.
"To overcome the problem of missing or defective exposure data, we used more reliable data from other relevant workers ('exposure analogues') along with statistical, mathematical and empirical analyzes to estimate the average exposures for A typical worker in Windscale / Sellafield is for every combination of occupation and a certain year that is required to build the JEM.
The method of exposure analogues developed in this study provides a generic methodological movement that can be transferred to other employees who have manifested their in-house, and can t allow other epidemiological cohorts to include significant groups of workers who might otherwise have been excluded because of the lack of information about reliable information. "
Replacing this missing data with these JEM estimates allowed the researchers to build a more reliable picture of early workers' radiation exposure.
Dr De Vocht added: "It is likely that the missing or unreliable exposure data with JEM values in future epidemiological studies could have a significant impact on the risk estimates that can be generated."
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