An assessment of annual whole-body occupational radiation exposure in Ireland (1996-2005)

Abstract

Whole-body occupational exposure to artificial radiation sources in Ireland for the years 1996-2005 has been reviewed. Dose data have been extracted from the database of the Radiological Protection Institute of Ireland, which contains data on >95% of monitored workers. The data have been divided into three sectors: medical, industrial and education/research. Data on exposure to radon in underground mines and show caves for the years 2001-05 are also presented. There has been a continuous increase in the number of exposed workers from 5980 in 1996 to 9892 in 2005. Over the same time period, the number of exposed workers receiving measurable doses has decreased from 676 in 1996 to 189 in 2005 and the collective dose has also decreased from 227.1 to 110.3 man millisievert (man mSv). The collective dose to workers in the medical sector has consistently declined over the 10-y period of the study while that attributable to the industrial sector has remained reasonably static. In the education/research sector, the collective dose typically represents 5% or less of the total collective dose from all practices. Over the 10 y of the study, a total of 77 914 annual dose records have been accumulated, but only 4040 (<6%) of these represent measurable radiation doses in any given year. Over the same time period, there were 283 instances in which exposed workers received individual annual doses >1 mSv and 21 of these exceeded 5 mSv. Most of the doses >1 mSv were received by individuals working in diagnostic radiology (which also includes interventional radiology) in hospitals and site industrial radiography. There has been only one instance of a dose above the annual dose limit of 20 mSv. Evaluating the data for the period 2001-05 separately, the average annual collective dose from the medical, industrial and educational/research sectors are approximately 60, 70 and 2 man mSv with the average dose per exposed worker who received a measurable dose being 0.32, 0.79 and 0.24 mSv, respectively. Diagnostic radiology and site industrial radiography each represents >60% of the collective dose in their respective sectors. Available data on radon exposure in one underground mine and in three show caves indicate an annual collective dose of 75 man mSv from these work activities. By comparison, previous estimates of exposure of Irish air crew to cosmic radiation have given rise to an estimated collective dose of 12 000 man mSv. It can be concluded therefore that the natural radioactivity sources account for well >90% of all occupational exposure in Ireland. This evaluation does not include an estimate of exposure to radon in above-ground workplaces-these data are currently being evaluated and their inclusion will increase both the total occupational collective dose as well as the percentage of that dose due to natural radiation.