§ Mr. Ashdownasked the Secretary of State for the Environment what is the highest know level of radon in any dwelling in Truro constituency; what is the calculated 742W annual effective dose equivalent associated with such a level; what number of dwellings in Truro constituency have been found to have radon levels above the 20 milliSievert action level; what funds are available for remedial building work on such dwellings; and if he will make a statement.
§ Mr. Waldegrave[pursuant to his reply, 6 February 1987, c. 855–56]: I am advised by the National Radiological Protection Board that the highest level of radon found in any dwelling in Truro constituency in the course of its surveys to date is 7,725 becquerels per cubic metre, which is equivalent to an annual effective dose of 390 milliSieverts (mSv). This is more than twice the level found in any other house in the constituency, but 15 other dwellings were found in which the occupants receive annual doses above the 20 mSv action level.
The NRPB's preliminary survey identified a total of seven houses, all in Devon and Cornwall, where the annual effective dose was above 100 mSv. The NRPB is in touch with the householder concerned to offer confirmatory measurements and advice.
As I stated on 27 January, responsibility for remedial measures must rest with the house owner or landlord. The Government are prepared to consider offering financial assistance towards the costs of remedial work to the most needy owner-occupiers, but until we have received further evidence from NRPB on the extent of the problem and advice from the Building Research Establishment on the most effective remedial measures, it is too early to estimate the funds that may be needed for remedial building work.
As the participants in the NRPB's preliminary survey were given an assurance that the results would remain confidential it would not be appropriate for me to identify the properties concerned.