Dr. John CunninghamTo ask the Secretary of State for the Environment what is his Department's comparative assessment of the annual radiation exposure to individuals from (i) natural background radiation in the environment, (ii) iodine 125 discharged from hospitals in sewers, (iii) iodine 125 in drinking water and (iv) krypton 85 discharges from the thermal oxide reprocessing plant received by the public in the vicinity of Sellafield.
§ Mr. Maclean[holding answer 20 November 1992]: (i) Exposure of individuals to natural background radiation is kept under review by the National Radiological Protection Board. An NRPB report published in 1989 gave the average effective dose from background radiation to the United Kingdom population as 2,200 microsieverts per year.
558W(ii) NRPB estimated the effective dose to sewer workers from iodine 125 to be 1.2 microsieverts per year.
(iii) A study by St. Bartholomew's medical school funded by Her Majesty's inspectorate of pollution found the effective dose to the public from iodine 125 in drinking water to be in the range 0 to 7 microsieverts per year.
(iv) The THORP plant is not operational. However, the effective dose from krypton 85 emissions from THORP under proposed discharge limits contained in draft authorisations recently published by HMIP would not exceed 6.4 microsieverts per year to members of the critical group in the Sellafield area.
For comparison, the International Commission on Radiological Protection has recommended a limit on effective doses from man-made sources—other than doses received by a patient undergoing medical treatment—for members of the public of 1,000 microsieverts per year.