Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
achieve in practice and interpretation may need to be based on a single sample. Faecal
monitoring is more often used in special investigations, particularly following a
known or suspected intake by inhalation of moderately soluble or insoluble
compounds. In these circumstances measurement of the quantity excreted daily may
be useful in the evaluation of clearance from the lungs and in the estimation of intake.
Early results may be useful in identifying exposed individuals.
(257) Radionuclides that emit photons may be determined in biological samples by
direct measurement with scintillation or semiconductor detectors. Analysis of a- and
b-emitting radionuclides usually requires chemical separation followed by appropriate
measurement techniques, including alpha spectrometry and liquid scintillation
counting. Measurement of so-called total a or b activity may occasionally be useful as
a simple screening technique.
(258) Increasing use is being made of mass spectrometric techniques for the analysis
of excreta samples. Examples are Inductively Coupled Plasma - Mass Spectrometry
(ICP-MS) that can achieve much lower detection limits for long-lived radionuclides
than is possible with alpha spectrometry and Thermal Ionization Mass Spectrometry
(TIMS), used to monitor very low activities of 239 Pu in urine (Inkret et al, 1998;
LaMont et al, 2005; Elliot et al, 2006).
(259) Measurement of activity in exhaled breath is a useful monitoring technique for
some radionuclides such as 226 Ra and 228 Th, since the decay chains of both these
radionuclides include gases which may be exhaled (Youngman et al, 1994;
Sathyabama et al, 2005). It can also be used to monitor 14 CO2 formed in vivo from the
metabolism of 14 C-labelled compounds (Leide-Svegborn et al, 1999; Gunnarsson et
al, 2003).
(260) Nasal smears may be employed as a useful screening technique. A positive
nasal swab gives an indication that an unexpected situation might have occurred.
Excreta measurements or lung monitoring should follow, to confirm the intake and to
provide a quantitative assessment.
4.4 Exposure Monitoring of the Workplace
(261) Workplace monitoring is useful for triggering bioassay measurements. In
addition, workplace characterization may be used as a complement to bioassay
monitoring as it provides useful information on physical and chemical composition of
the radionuclides present in the working environment (e.g. information on the particle
sizes (AMAD)).
(262) Two workplace monitoring methods may be used for monitoring individual
exposures: personal air sampling (PAS) and static air sampling (SAS). A Personal Air
Sampler is a portable device specifically designed for the estimation of intake by an
individual worker from a measurement of concentration of activity in air in the
breathing zone of the worker. A sampling head containing a filter is worn on the
upper torso within the breathing zone. Air is drawn through the filter by a calibrated
air pump carried by the worker. Ideally, sampling rates would be similar to typical
breathing rates for a worker (~1.2 m 3 h -1 ). However, sampling rates of current devices
are only about 1/5 th of this value. The activity on the filter may be measured at the end
of the sampling period to give an indication of any abnormally high exposures. The
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