title: Occupational exposure to natural radiation.
abstract: Natural sources of radiation can make an important contribution to the exposures of people at work. Two areas of interest are work with minerals having elevated concentrations of activity and work in buildings where radon daughter concentrations are elevated. The Euratom Directive on ionising radiation requires that the handling of radioactive substances be reported to national authorities. National authorities may waive this requirement where the activity per unit mass is below 100 Bq g-1, or for solid natural radioactive substances, 500 Bq g-1. An investigation was undertaken in five factories to determine whether work with minerals having levels of natural activity below these might lead to significant doses. Models based on the data collected were used to relate the activity in the minerals to the effective dose equivalent arising from gamma radiation, inhalation of radon daughters, and intake of long-lived activity. These assessments show that the activity concentration at which exposures to airborne dust could lead to doses equal to one-tenth of the dose limit for workers are 0.3 Bq g-1 for thorium-232 and 1 Bq g-1 for uranium-238. Above these values, radiological supervision may be necessary. In a separate study, measurements of radon daughter concentrations were made in seventy workplaces. Concentrations in some premises approached or exceeded the derived air concentration for occupational exposure. The highest concentrations were found in premises with low ventilation rates.
mesh_terms: D000388:Air / Q000032:analysis; D004391:Dust; D004781:Environmental Exposure; D006801:Humans; D008903:Minerals / Q000032:analysis; D008906:Mining; D011827:Radiation; D011868:Radioisotopes / Q000032:analysis; D011883:Radium / Q000032:analysis
chemical_list: D004391:Dust; D008903:Minerals; D011868:Radioisotopes; D011883:Radium