§ Mr. Muddasked the Secretary of State for Employment (1) pursuant to his reply of the 31 March, why there is a wide disparity between the radon exposure levels of the National Radiological Protection Board and those of the Euratom Directive on Radiological Protection: and whether on present readings there is any likelihood of danger to miners working at the South Crofty tin mine, Cornwall;
(2) if he is satisfied that, subject to improved ventilation, no danger from radon gas exists to men employed underground at South Crofty tin mine, Cornwall.
§ Mr. Mayhew[pursuant to his reply, 3 April 1980]: The exposure level for radon and radon daughters as recommended by the National Radiological Protection Board, is based upon USA and International Commission on Radiological Protection recommendations and corresponds to levels of risk associated with exposures to other ionising radiation and radioactivity at the presently set dose limits.
441WThe Euratom directive level for radon and radon daughters was specified in the 1968 directive and remained unchanged in the 1976 directive. It is based upon an earlier interpretation of International Commission on Radiological Protection recommendations, which are currently under review.
The recent survey at South Crofty of radon and radon daughter product concentrations shows that about one-third of the measurements taken gave indications of levels which, if maintained throughout the year, would somewhat exceed the exposure level recommended by NRPB. Bearing in mind that any exposure to radiation inevitably carries some risk present proposals to improve ventilation sufficiently to reduce long term average exposures below the level recommended by NRPB will correspondingly reduce the risk to exposed miners from radon to a point where it is small by comparison with other risks in mining.