|The establishment of criteria for the purpose of determining whether or
not a given situation should be subjected to radiation protection
requirements is especially complex when dealing with natural radioactivity.
Several concepts such as exclusion, exemption, clearance, action level
and intervention level have been developed to facilitate the selection
of the most appropriate way to address various situations involving
natural radiation. This document as most guidance documents including the
recent IAEA RS-G-1.7 recognize the need to consider other factors than
dose to an individual in the establishment of such concepts. But I
believe this draft "Scope of Radiological Protection Regulation" differs
somewhat from past guidance and may prompt a new tendency to lower
existing criteria unnecessarily by introducing the concept of a dose
criteria of "in the order of 1mSv" as an exemption concept for naturally
occurring radioactive material and introducing 40 Bq m-3 as the exclusion
criteria for indoor radon concentration.
Past guidance such as the IAEA BSS and RS-G-1.7 generally use the
concept of exclusion for radionuclide of natural origin and provide values
that limit the likelihood of individuals exceeding about 1 mSv in a
year. This approach is less prescriptive and also importantly is often
linked to the legal doctrine of de minimis non curat lex.
With regards to indoor radon concentration the use of an exclusion
criteria of 40 Bq m-3 does not seem to support the generally optimized
action levels (usually in the order of 200 Bq m-3). In contrast the
support for different exemptions for dwelling and workplace, in the context
that work activities are not related to naturally occurring radioactive
material and no specific consideration is given to radon exposure, is
difficult to understand based solely on occupancy factor. In this case
exposure of a working person spending 2000 hrs at work and 5000 hrs at
home (occupancy of 7000 hours) may be significantly higher than a
person spending most of the 7000 hours at home. Therefore, with some
specific exceptions, recommended radon action levels should be the same
for dwellings and workplace.