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| Risk assessment |
| The risk immanent to the use of a radiopharmaceutical
is the exposure to radiation – either of patients, of
health personnel or of the public. The risk assessment of the
use of HeliCap capsules containing 37 kBq (14C) was given in
the toxicological/pharmacological documentation (Part III).
The points considered were and are the following: |
| 1. |
Risk to patients:
The physical half-life of (14C) is 5730 years.
Studies on the biological half-time have, however, demonstrated
that ingested (14C) urea, administered e.g.
as one HeliCap capsule, is eliminated quickly, and that
determined pharmacokinetic parameters clearly indicate
a negligible risk to no risk at all: |
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Munster et al
investigated 18 subjects who received either 185
kBq or 37 kBq (14C) urea. Elimination
via breath and urine were examined up to 72 hours.
Maximum recoveries of (14C) were between 1 and 2
hours after ingestion. Overall elimination of (14C)
independent of the amount ingested (185 kBq vs 37
kBq) was ca 87% in “high expirers” and
ca 99% in “low expirers”. Long-term
retention was low. When compared to daily exposure
to natural sources of radiation which on average
figure 3.7 kBq/day, then the remaining activity
3 days after ingestion of a HeliCap capsule is not
more and even less than the average natural daily
exposition to radiation. |
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Like Munster et al, the
detailed studies by Leide-Svegborn et al. also conclude
that the exposure from a test dose of 110 kBq and
of 55 kBq in children both correspond to about a
day of natural radiation from the environment. The
majority of (14C) excreted in urine was
found in the first 24 hours, and peak expiration
of (14C) occurred within the first hour
after ingestion. Leide-Svegborn et al also conclude
that there is no reason for restrictions on even
repeated screening investigations with 14C-urea
in whole families, including children when administering
a dose of 55 kBq 14C-urea (48% more than
what is administered with the HeliCap. |
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Further, exposure to radioactivity
associated with the use of HeliCap is hundreds to
thousands of times less than well accepted procedures
performed in departments of radiology. |
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| 2. |
Risk to health personnel:
The council directive 96/29/Euroatom, Article 9(1) states
that the limit on effective dose for exposed workers shall
be 100mSv in a consecutive five year period, subjected
to a maximum effective dose of 50mSv in any single year.
A positive patient taking a HeliCap is exposed to a maximum
effective dose of 0.003mSv. By definition the effective
dose for a health personnel carrying out the test being
at risk for contamination from the patient must be much
less. This is confirmed by the analysis performed by the
US Nuclear Regulatory Commission. |
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The analysis
made by the US Nuclear Regulatory Commission on
exposure of workers administrating the 14C-urea
breath test led to the conclusion that a full-time
worker administrating 8000 capsules per year containing
37 kBq 14C-urea followed by breath testing would
get exposed to 0.007 mSv per year which is by magnitudes
below the annually permitted effective dose stipulated
by Council Directive 96/29/Euroatom (maximum effective
dose of 50 mSv in any single year). |
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The analysis made by the
US Nuclear Regulatory Commission also included analysis
of exposure due to potential accidents in the administration
facility: They calculated that rupture of a capsule
causing skin contamination of the worker or the
patient (100 cm2 exposed for one hour
prior to washing resulting in 2.775 kBq skin absorption)
would lead to an effective dose of 0.00029 mSv. |
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| 3. |
Risk to the public: The Council
Directive 96/29/Euroatom, Article 13(2) states that the
limit for effective dose for members of the public shall
be 1 mSv in a year. The analysis made by the US Nuclear
Regulatory Commission on the environmental impact concluded
that “The earth’s atmosphere contains an inventory
of naturally occurring (14C) of about 1.4 x 1017 Bq (equivalent
to the activity of 3.8 x 1012 breath tests), which is
in addition to the huge inventory of about 8.9 x 1018
Bq in the world’s oceans” Further, “the
current world inventory of naturally occurring 14C results
in an average dose to the public of about 0.0125 mSv per
year, and the release of 2,22 x 1010 Bq of 14C from total
600 000 tests would result in an additional average annual
dose of 2.0 x 10-9 mSv per year”. This amount is
negligible compared to the 1 mSv limit stated in the above
mentioned European Council Directive. |
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Taking the European
Commission Publication – Radiation Protection
97. Radiation Protection following Iodine-131 therapy
(exposures due to out-patients or discharged in-patients)
into consideration, which states that the following
dose constraints will be applied: |
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Children (including unborn
children) 1 mSv |
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Adults (under 60 years of
age) 3 mSv |
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Adults (60 years of age
and older) 15 mSv |
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Other persons (members of
the public) 0.3mSv |
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| Then the maximum radiation dose of 3
microSv following one diagnostic test in a Helicobacter pylori
positive patient is still 100 times less than even the tightest
dose constraint stipulated for the public in the above mentioned
Radiation Protection Publication to safeguard them from radiation
exposition through Iodine-131 treated patients. |
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| Noster System AB’s overall
conclusion concerning radiation risk and the use of HeliCap
is: For patients, health personnel and the public there is potentially
no radiation risk involved in the use of HeliCap. |
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