Transcript EXTERNAL AND INTERNAL CONTAMINATION

EXTERNAL AND INTERNAL
CONTAMINATION
Radioactive sources
Radioactive sources are present in the sealed
(normally non spreadable) and unsealed form
(spreadable):
Gammagraphy essentially uses as sources
iridium-192 and sometimes cobalt-60
Neutrongraphy uses sources of neutrons like
californium-252 or an americium/beryllium
couple.
Betagraphy uses beta sources like carbon-14.
Chemical and biological radiation-treatment
uses gamma radiation sources cobalt-60 or
caesium-137.
Radioactive sources in medicine
In medicine there are three uses
for non-sealed radioactive nuclides:
Biological analyses: radio-markers have been replaced
progressively by non-radioactive markers.
Medical imaging: nuclear medicine department use
radio-pharmaceuticals for diagnostics, which are
ingested by the patient to obtain an image of the tissue
or organ while it is functioning.
Therapy: radio-pharmaceuticals can constitute the
treatment itself, for example iodine 131 for the
treatment of thyroid cancer.
Contamination risk
Contamination sources
reactor accidents involving damage to the core
leading to combined inhalation-peroral entry into the
body of a mixture of fission products (primarily of
volatile caesium and iodine isotopes)
accidental violation of the regulations or procedures
governing work with radioactive substances,
especially in form of powder or solution
accidents involving leaking or damaged sealed
sources (i.e. 192Ir, 137Cs, 60Co, 226Ra)
errors in dosage of radionuclides used for
diagnostic and therapeutic purposes
accidents involving the fabrication and reprocessing
of nuclear fuels and the transportation and disposal
of radioactive waste
Chernobyl accidents
Goiania accident
Area of contamination – 4 000 000 m2
249 contaminated (137Cs) persons,
129 with internal contamination, 4 deaths
Contamination sources
in nuclear accidents
External radionuclide
contamination
External contamination:
radioactive materials in form of dust,
solid particles, aerosols or liquid,
become attached to skin or clothes
External contamination
The risks linked to external exposure of the skin differ
according to the type of radiation:
alpha emitting radio-elements do not a priori present
any risk by external contamination,
beta emitting radio-elements do present a special risk
because they entail exposure which is almost
exclusively of the skin,
gamma emitting radio-elements pose the same
problems by external contamination as in external
exposure,
external contamination by a neutron emitting radioelement is impossible.
External contamination reveals a secondary potential risk of
internal contamination by inhalation, ingestion or breaking and
penetration of the skin.
People involved
in the Chernobyl accident in 1986
The Chernobyl accident, 26 April 1986, involved the very
serious irradiation and contamination of a number of people
working in the power station and those who immediately
intervened, it provides a good example of external contamination.
More than 200 patients were hospitalized in the hours
following the catastrophe. Before this massive flood of victims, the
initial efforts to manage the situation were limited to treatment of
the symptoms a full assessment of lesions, treatment of traumatic
lesions and summary external decontamination. The latter fact was
revealed to be particularly damaging as all the patients had external
contamination by fission products, such as Cs-137, Sr-90, or I-131,
all of them being beta and some gamma emitters. Beta emitters on
the skin caused severe radiological burns with complex
development.
It is estimated that 5 of the 28 premature deaths following the
accident were attributable in part to radiological burns. These 5
deaths, and perhaps others, could doubtless have been avoided if
good external decontamination of all the exposed subjects had
been carried out in the shortest time.
External contamination triage
Triage following known or suspected radiation accidents
includes both medical and radiological considerations
Medical triage should be based upon local procedures for
medical management of persons involved in accidents
with radioactive materials and on considerations
dependent on the severity of injuries.
Treatment in life threatening conditions has priority over
considerations for exposure to or contamination with
radioactive materials.
Following medical stabilization of the patient’s condition,
careful radiological assessment can be directed to
determining the presence of both external and internal
contamination.
External contamination
measurement
Proper monitoring of patient can detect and
measure alpha, beta or gamma emitters;
radiation type depends on isotope in
contaminant
Alpha monitor
Radiological survey
Initial external
contamination
survey (of skin,
eyes, lips)
should be made
with instruments
adequate for the
particular situation
The results of the radiological survey should be recorded on an
anatomical chart and made a part of the patient's medical record
Quick `frisk’
112 000 persons monitored in Goiania at olympic stadium
Decontamınatıon
Decontamination techniques
Decontamination procedures
Start with gentle stream of warm water
Use mechanical action of flushing and/or
friction of cloth, sponge or soft brush
For showering, begin with the head and
proceed to the feet
Keep materials out of eyes, nose, mouth
and wounds
Use waterproof draping to limit spread
Cover uncontaminated area with plastic
sheet and tape edges
Decontamination
techniques and control
• Use single inward movements or
circular motion
• Then rinse area with tepid water
and gently dry using the same
motions
• After drying, premonitory skin to
determine effectiveness of
decontamination
Decontamination procedures:
body orifices
Consideration:
 Orifices need special attention because
absorption of radioactive material more
rapid than through skin
Mouth
Nostrils
Procedures:
 Oral cavity:
brush teeth with
toothpaste, frequently rinse mouth with
3% citric acid
 Pharyngeal region: gargle with 3% H2O2
 Swallowed radioactive materials: gastric
lavage
 Nose: rinse with tap water or
physiological saline
Decontamination procedures:
body orifices
Procedures:
•Eyes: rinse by directing stream of
water or physiological saline from
inner to outer canthus while
avoiding
contamination
of
nasolacrimal gland
•Ears:
- rinse externally with water
- rinse auditory canal using
ear syringe
Eyes
Ears
Useful therapeutic agents
for skin decontamination
Common soap or detergent solution
for skin and hair; low acidity (pH ~5)
recommended
Chelating agents:
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solution of EDTA 10% for skin or hair
contamination with transuranium, rare earth
and transition metals
DTPA 1% in aqueous acid solution (pH ~4)
for washing skin after contamination with
transuranics, lanthanides or metals (cobalt,
iron, zinc, manganese)
Useful therapeutic agents
for skin decontamination
Potassium permanganate
5% aqueous solution should be used carefully
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not recommended for face, natural orifices and
genital regions
use when conventional washing ineffective
follow with application of reducing agent, then rinse
with water
Hydroxylamine or sodium hyposulfite
5% freshly prepared aqueous solutions

reducing agents - apply after KMn04 or Lugol, then
wash with water
Useful therapeutic agents
for skin decontamination
Antiphlogistic topical ointment:

To be applied for fixed contamination,
especially useful for contamination of fingers
Isotonic saline solution for eyes
Isotonic 1.4% bicarbonate solution for
removing uranium from body
Lugol solutions for iodine contamination
Acetic acid solution (pH 4 to 5) or simply
vinegar for decontamination of 32P
Internal contamination
Occurs when people ingest, inhale or
are injured by radioactive material. The
most frequent points of entry are by
inhalation and wounds.
Metabolism of non-radioactive analogue
determines radionuclide’s metabolic
pathway.
Paints for luminous watch faces
In the 1920s and 1930s the clock making industry used
radium 226 and 228 in radio-luminescent paint for watches.
At this time, the risk from alpha emitting radio-elements was
almost unknown.
The workers who painted the luminous faces had the bad
habit of tapering their brushes with their lips. Every time
they did this they ingested several becquerels of radium.
The fact that radium and calcium are chemical homologues,
resulted in rare bone cancers appearing starting from the
20s, in the form of carcinoma of the sinus of the face.
An epidemiological enquiry demonstrated the link between
exposure to radium and the risk of bone cancer in 2,403
workers, whose ingestion of quantities of radium could be
evaluated. 64 were suffering from osteosarcoma whereas 2
cases of this type of cancer would have been expected
statistically.
Extent of hazard
Factors determining extent of
contamination hazard:
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Amount of radionuclides
Energy and type of radiation
Biological and radiological half-life
Critical organ
Chemical and physical properties of
radionuclide
Intake routes
In order of decreasing frequency, contaminants
enter the body by four principle routes:

Inhalation:
Particularly likely with explosion or fire
Particle characteristics important
composition, solubility in body fluids)

Ingestion:
Critical for general public after
accidental environmental release
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Wound contamination
Absorption
(size,
chemical
Inhalation
Fate of inhaled particles dependent on
physicochemical characteristics
Soluble particles (3H, 32P, 137Cs) absorbed
directly into circulatory system
Insoluble particles (Co, U, Ru, Pu, Am)
are cleared by lymphatic system or by
mucociliary apparatus above alveolar
level. Most secretions reaching pharynx
swallowed, enter gastrointestinal system
Deposition and clearance from
respiratory tract
Contaminant's particle size determines deposition in
respiratory tract
 Particles <5 microns in diameter may reach alveolar
area
 Particles >10 microns too large to pass into alveoli,
deposited in upper airways
Pulmonary effects
Irradiated lung tissue
Pulmonary fibrosis
Ingestion
 All
swallowed radioactive material enters
digestive tract
 primarily from contaminated food and
water
 secondarily from respiratory tract
 Absorption
from the gastrointestinal tract
depends on
 chemical make-up and solubility of
contaminant
Parameters of ingestion
 Gastrointestinal absorption
< 10 % for most elements
 Elements of high absorption:
• radium
(20%)
• strontium (30%)
• tritium
(100%)
• iodine
(100%)
• caesium (100%)
Wound contamination
Any wound considered contaminated
until proven otherwise
Open fracture demonstrates wound contamination
with depleted uranium shrapnel
Percutaneous absorption
Generally, radionuclides do not cross intact
skin, so uptake by this route does not occur
Most important exceptions are: tritium,
iodine, caesium
Skin wounds, including acid burns,
abrasive scrabbing, create portal for
particulate contamination to subcutaneous
tissue, bypassing epithelial barrier
Distribution and deposition
Iodine
Uranium
Metabolism
Diagram of intake, metabolism and excretion of radionuclides
Internal contamination measurement:
direct methods
Whole body counters
Thyroid uptake system
Indirect contamination
measurement
Indirect measurement of contamination includes
nasal swipes to determine respiratory intake of
radioactive aerosols, and also urine and faeces
sampling to establish internal contamination
Alpha and beta emitters, the most hazardous
internal contaminants, detected through bioassay
sampling
Accurate bioassays require carefully executed
sampling over time and knowledge of type and
time of contamination
Bioassay sampling
Managment of internal contamination:
First Action
Life threatening conditions have priority
over considerations of radioactive exposure
or contamination. Attention to vital functions
and control of haemorrhage take priority
Contamination levels almost never serious
hazard to personnel for time required to
perform
lifesaving
measures
and
decontamination
Treatment of internal
contamination
Treatment
procedures:
the sooner started –
the more effective
In practice, initial
treatment decisions
based on accident
history rather than
careful dose estimates
Basic principles of treatment
Reduce absorption and
internal deposition
Enhance excretion of
absorbed contaminants
Current methods of treatment of
internal contamination
- Saturation of target organ, e.g. potassium iodide
for iodine isotopes
- Complex formation at site of entry or in body
fluids followed by rapid excretion, e.g. DTPA for Pu
isotopes
- Acceleration of metabolic cycle of radionuclide
by isotope dilution, e.g. water for 3H
- Precipitation of radionuclide in intestinal lumen
followed by faecal excretion e.g. barium sulphate
administration for 90Sr
- Ion exchange in gastrointestinal tract, e.g.
prussian blue for 137Cs
Diluting agents: water for tritium - 3H
Single exposures are treated by forced
fluid intake:
 Enhanced fluid intake e.g. water, tea, beer,
milk has dual value of diluting tritium and
increasing excretion (accelerated
metabolism)
 Biological half-life of tritium - 10 days
 Forcing fluids to tolerance (3-4 L/day)
reduces biological half-life to 1/3-1/2 of
normal value
Ion exchange: prussian blue for 137Cs
 137Cs - physical half-life Tp=30 years;
biological half-life in adults average
Tb=110 days, in children 1/3 of this

Prussian blue effective means to reduce
body's uptake of caesium, thallium and
rubidium from the gastrointestinal tract

Dosage of prussian blue: one gram orally
3 x daily for 3 weeks reduces Tb to about
1/3 normal value
Chelation agents: DTPA for heavy
metals and transuranic elements
 Ca-DTPA is 10 times more effective
than Zn-DTPA for initial chelation of
transuranics. Must be given as soon as
possible after accident
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After 24 hours, Ca-DTPA and Zn-DTPA
equally effective
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Repeated dosing of Ca-DTPA can
deplete body of zinc and manganese
Dosage of Ca-DTPA and Zn-DTPA
 1 g iv. or inhalation in a nebulizer
 Initially: 1 g Ca-DTPA, repeat 1 g
Zn-DTPA daily up to five days if
bioassay results indicate need for
additional chelation
 Pregnancy: First dose Zn-DTPA
instead of Ca-DTPA
Additional chelating agents

Dimercaprol (BAL) forms stable chelates, and
may therefore be used for the treatment of
internal contamination with mercury, lead,
arsenic, gold, bismuth, chromium and nickel

Deferoxamine (DFOA) effective for chelation
of 59Fe

Penicillamine (PCA) chelates with copper,
iron, mercury, lead, gold. Superior to BAL and
Ca-EDTA for removal of copper (Wilson’s
disease)
Treatment of uranium contamination
In any route of internal contamination,
treatment consists of slow intravenous
transfusion of 250 mL of isotonic
1.4 % sodium bicarbonate
Local
treatment:
for
skin
contamination, wash with isotonic
1.4% solution of sodium bicarbonate
Summary of lecture
Attend to life-threatening injuries first
Earlier skin decontamination decreases
degree of beta burns, lowers risk of internal
contamination, reduces chance of further
contamination
Goal of internal contamination treatment:
decrease uptake into circulatory system,
decrease deposition in critical organs, increase
excretory rate contaminant
Health physicists and medical specialists should
advise on risks and benefits of decorporation
Lecture is ended
THANKS FOR ATTENTION
In lecture materials
of the International Atomic Energy Agency (IAEA),
kindly given by doctor Elena Buglova, were used