Handbook of Radon.
46. Occupational exposure to radon.
Radiation exposure to workers in the UK is controlled under the Ionising Radiation Regulations, 1985. These follow publication of an EC directive in 1980 and papers by ICRP in 1981 and 1982 giving general principles for the monitoring of workers exposed to radiation, and limits for inhalation of radon daughters.
The Ionising Radiation Regulations are very complicated and in parts difficult to understand. Clarity may not improve if they are updated to take account of revisions in the Euratom Directive on Safety Standards for Radiation Protection.
In simple terms however, the legal limit of exposure is 50 mSv per year (expressed as whole body effective dose), and with a requirement for monitoring individual doses where these exceed 15 mSv annually. In a house this would correspond to only 300 Bq/m3 but in a school up to 2100 Bq/m3 (see Section 41). However, not all the requirements of the 1985 Regulations apply where the only source of radiation in the work-place is from radon daughters.
Two classes of work area are defined under the Regulations: supervised and controlled. If calculated dose to a worker is in the region 5 to 15 mSv annually the area becomes 'supervised' and monitoring is required. Above 15 mSv it becomes 'controlled' and personal monitoring is required. It has been proposed that the upper limit of 50 mSv be reduced to 15 mSv, which could have had severe consequences for many Cornish tin mines had not all but one closed already for other economic reasons.
Because it is so much easier to measure average radon gas concentration than any other relevant quantity, the Regulations have been interpreted in terms of this. Thus, if a place of work is assessed at over 400 Bq/m3 it is deemed to require attention (or it would become a supervised area). A level of 1000 Bq/m3 or above, if not remedied by building or other methods, would result in controlled area designation.
To date, only a few thousand work-places have been monitored for radon in the UK, and about 300 found to be in breach of the Regulations. Implementation of mitigation measures and any necessary monitoring of workers seems unlikely, at the moment, to involve prosecutions. Much of the monitoring has been undertaken in schools - where the legal requirement is to protect the teachers rather than the children. Schools are discussed in more detail in Section 27.
Unlike artificial sources of radiation which are often well characterised and easily controlled, radon exposure in places of work can involve not only the building problems that have been experienced in houses but the difficulty of personal monitoring if an accurate measure of exposure is required. Any risk to an employer of being sued for not providing a safe working environment would seem slight so long as statutory requirements were met, but even at the lower limit of 5 mSv annually the implied risk is far greater than for many chemicals subjected to control under the COSHH Regulations (Control Of Substances Hazardous to Health).
Section 38 considers some of the legal implications of radon in the UK, including that insurance companies have paid out in claims cases to avoid creating case law, which might have resulted in many more claims. It is to be hoped that the absurdity of routinely measuring radon exposure for each individual in marginally affected buildings so as to defend any future claim can be avoided.