EXTERNAL AND INTERNAL CONTAMINATION DECONTAMINATION AND DECORPORATION

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EXTERNAL AND INTERNAL CONTAMINATION
DECONTAMINATION AND DECORPORATION

• Module XV

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IntroductionContamination risk
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Contamination sourcesreactor accidents
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Goiania accident
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 victims 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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Decontamination
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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
• 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

Mouth
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
• - rinse auditory canal using ear
  syringe

Eyes
Ears

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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 radionuclides metabolic pathway

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Extent of hazard

• 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 (size,
  chemical composition, solubility in body fluids)
• 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 lt5 microns in diameter may reach
  alveolar area
• Particles gt10 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 lt10 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
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Internal contamination measurement direct
methods
Whole body counters
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

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Bioassay sampling
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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

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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

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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

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Diluting agentswater 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 exchangeprussian blue for 137Cs

• 137Cs - physical half-life Tp30 years
  biological half-life in adults average Tb110
  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 agentsDTPA 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 Zn-DTPA daily
  up to five days if bioassay results indicate need
  for additional chelation
• Pregnancy - First dose Zn-DTPA instead of Ca-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 (Wilsons 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