Transcript External and Internal Contamination

EXTERNAL AND INTERNAL
CONTAMINATION
DECONTAMINATION AND DECORPORATION
Module XV
Introductıon
Contamination risk
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Contamination sources:
reactor accidents
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Goiania accident
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Area of contamination: 4 000 000 m2
249 contaminated (137Cs) persons,
129 with internal contamination, 4 deaths
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External radionuclide
contamination
 External
contamination: radioactive
material, as dust, solid particles,
aerosols or liquid, becomes attached to
victim’s skin or clothes
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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
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Radiological survey
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Radiological triage
Quick `frisk’
112 000 persons monitored in Goiania at olympic stadium
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Decontamınatıon
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Decontamination
techniques
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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

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Decontamination
techniques
• Use single inward movements or
circular motion
• Then rinse area with tepid water and
gently dry using the same motions
• After drying, remonitor skin to
determine effectiveness of
decontamination
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Decontamination procedures:
body orifices
Consideration:
 Orifices need special attention because
absorption of radioactive material more
rapid than through skin
Procedures:
Mouth
 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
Nostrils
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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
Eyes
Ears
- rinse auditory canal using
ear syringe
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Useful therapeutic agents for
skin decontamination-I
Common soap or detergent solution for skin
and hair; low acidity (pH ~5) recommended
 Chelating agents:

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)

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Useful therapeutic agents for
skin decontamination-II

Potassium permanganate, 5% aqueous solution should
be used carefully




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
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Useful therapeutic agents for
skin decontamination-III

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

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Internal contamination
 Occurs
when people ingest, inhale, or are
injured by radioactive material

Metabolism of non-radioactive analogue
determines radionuclide’s metabolic
pathway
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Extent of hazard
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Factors determining extent of
contamination hazard:
Amount of radionuclide(s)
Energy and type of radiation
Biological and radiological half-life
Critical organ
Chemical and physical properties of
radionuclide
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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)
(size,
chemical
Ingestion:
Critical for general public after accidental environmental
release
Wound contamination
Absorption
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Contamination sources
in nuclear accidents
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Inhalation
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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
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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
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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

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Ingestion
• GI absorption <10% for most elements
• Elements of high absorption:
• radium
(20%)
• strontium (30%)
• tritium
(100%)
• iodine
(100%)
• caesium (100%)
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Wound contamination
•Any wound considered contaminated until
proven otherwise
Open fracture demonstrates wound
contamination with depleted uranium shrapnel
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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
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Distribution and deposition
Iodine
Uranium
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Metabolism
Diagram of intake, metabolism and excretion of
radionuclides
Internal contamination
measurement : direct methods
Whole body counters
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Thyroid uptake system
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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

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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
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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 GIT

Dosage of prussian blue: one gram orally 3x
daily for 3 weeks reduces Tb to about 1/3 normal
value
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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

After 24 hours, Ca-DTPA and Zn-DTPA
equally effective

Repeated dosing of Ca-DTPA can deplete
body of zinc and manganese
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Dosage of Ca-DTPA and
Zn-DTPA
 1 g iv. or inhalation in a nebulizer
 Initially: 1 g Ca-DTPA, repeat 1 g ZnDTPA daily up to five days if bioassay
results indicate need for additional
chelation
Pregnancy - First
instead of Ca-DTPA
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Zn-DTPA
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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)
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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
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Summary

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
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