**2.13 Exposure to Nuclear Agents:**

Types of nuclear warfare agents

Effects of exposure

Evaluation and management of exposure

Prevention and countermeasures

Radiation is the third part of the CBR (Chemical, biological and
radiological) mode of warfare. Until recently, medical toxicology texts
did not deal with radiation "poisoning" but it has been included as a
regular part of the newer toxicology texts and is a recurrent subject at
medical toxicology seminars, workshops and general meetings.

**DEFINITIONS**

-   Ionizing radiation may take the form of an energetic subatomic
    particle (e.g. alpha particle, beta particle, neutron) or
    electromagnetic radiation (e.g. X-ray, gamma ray). Biological
    alterations and cellular changes/damage can occur from the effects
    of radiation transfer to the human tissues. Type of radiation and
    their description is, as follows:

-   Alpha particles are helium nuclei stripped of their electrons.
    Charged particles, such as this are heavy in mass and their range is
    limited to a few centimeters in the air and less than 100 µm is
    tissue. It is for this reason that alpha particles are of little
    hazard to the external body due to the keratinized layer of the
    skin. If the particles are internal, however, they can be harmful.

-   Beta particles are high energy electrons that can penetrate a
    several mm of tissue. They are generally hazardous if taken
    internally. There can be a skin hazard if large areas of the body
    surface are affected by significant amounts of radionuclide emitting
    high energy Beta particles.

-   Gamma rays and X-rays are high energy photons that can penetrate
    several cm of tissue. Dense metals such as iron or lead, however,
    can significantly attenuate their effect.

-   Neutron emission is also a potent ionizing radiation, capable of
    deep penetration and creating dense ionization trails. Reactors
    and/or accelerators are source examples of major neutron sources. An
    industrial example of the use of neutrons are moisture density
    gauges.

-   \[LET: or "low energy transfer". The LET of ionizing radiation is
    the energy lost in a medium per unit length traversed. The
    biological effects/damages of a specific radiation is generally
    directly correlated with increasing LET\]. Alpha and neutron
    particles are considered high-LET radiation.

**MODES OF INJURY**

There are four types of radiation exposure:

-   Irradiation: radiation exposure without contamination which is not
    considered a health hazard and does not require patient
    decontamination.

-   External contamination: Radionuclides present on external body
    surfaces that can be spread to others.

-   Internal contamination: Radionuclides that can be introduced in the
    body via ingestion, inhalation or injection (including wound
    contamination). These radionuclides undergo deposition in the body
    via a portal or entry. They, then, undergo translocation by
    solubization in the bloodstream, becoming bioavailable at target
    organs. Incorporation may keep these radionuclides within the target
    organs or the organ may undergo clearance as equilibrium of
    radionuclide deposition and release from the organ is established.

-   Combined injury: The sequelae of nuclear explosions, consisting of
    combinations of components of radiation injury and burns or
    mechanical injury. One would expect to see a higher
    morbidity/mortality with combined injuries.

**PATHOPHYSIOLOGY**

The biological effects or radiation depend on (1) Dose: the amount of
energy absorbed per tissue unit mass measured in rads and (2) Radiation
quality, referring to different biological effects that different
radiation types can have on tissue, depending on their LET's. Radiation
exposure above certain threshold levels causes an inflammatory cascade
that has, as its endpoint, fibrosis and vascular insufficiency,
particularly at the microvascular level. The effects on organ systems
would be organ dysfunction, insufficiency or failure. Example should be
hematopoietic depression, hepatic veno-occlusive disease, pneumonia,
enteritis, and epithelial skin injury.

**CLINICAL PRESENTATION**

Exposure between one and fifty rads are usually asymptomatic. Exposure
above 50 rads are likely to produce nausea, vomiting, diarrhea, and
malaise within three hours after exposure. Higher doses produce fever,
severe abdominal pain, and eye burning sensations. With higher doses
into the supralethal levels one sees confusion known as early transient
incapacitation (ETI). If contaminated internally, the patient may react
with anxiety, somatization, and depression. Rarely will these patients
be exposed to systemic threshold doses. The diagnosis can only be
confirmed by way of positive bioassay, chest counts or whole body
counts. (See table below) Externally contaminated patients should be
evaluated for local radiation injury and decontaminated after life and
limb-threatening conditions have been stabilized.

I![](media/image1.png){width="5.666666666666667in"
height="3.9868055555555557in"}

**CHRONIC EXPOSURE**

Chronic radiation exposure (CRS) presents with vague symptomatology and
is, therefore, difficult to classify and quantitate. Ninety individuals
with CRS have been described, primarily in the Chinese and Russian
literature. Chronic radiation exposure should be expected if there has
been a history of radiation exposure, in conjunction with serial and
progressive multiorgan system dysfunction and in the absence of other
etiologies in the differential diagnosis. Gastroenteritis may be
misdiagnosed early in the presentation but radiation will cause later
mucosal desquamation. Aplastic anemia could cause pancytopenia.

NB: Children and infants are considerably more susceptible to radiation
exposure than adults, due to higher mitotic and metabolic rates.

**LOCAL INVOLVEMENT**

Pemphigoid lesions are large blisters that may appear identical to
lesions caused by radiation exposure. Some spider bites will have a
necrotic center, but similar radiation lesions may be associated with
more blistering. High dose radiation can be associated with large skin
lesions and deep eschars. Microvascular ischemia may manifest in stasis
producing radiation ulcers. Sub acute epilation and hyperpigmentation
may also be a manifestation of radiation exposure. Dry radiation
epidermatitis can appear as skin neoplasms, particularly keratinizing
skin lesions. Radiation blistering can also appear as a local herpetic
eruption. The difference is that in the clinical course, since herpetic
lesion will resolve with therapy and over time, but the radiation
blister may continue to evolve and progressively erode further. Local
radiation injury may appear as a skin lesion that does not heal over
weeks or months.

**LABORATORY STUDIES**

A CBC (complete blood count) with a differential and urinalysis is
needed to establish a baseline following suspected irradiation
exposures. If overexposure of 10-25 rads is suspected, obtain baseline
sperm count initially at 6 weeks intervals post exposure, and
lymphocytic cytogenetics, lymphocyte micronuclei analysis and
fluorescent in situ hydridization (FISH) for delayed dose estimation.

Above 25 rads, studies should also include slit lamp exams to document
possible cataract formation, liver function tests and blood
agglutination studies, and testing of personal articles such as teeth or
tissue for electron spin resonance (ESR), for delayed dose estimation.

Systemic effects of radiation may be assessed by either the modified
USSR classification which relys on history, physical and laboratory
parameters or Andrews Lymphocyte Nomogram, which follows absolute
lymphocyte counts serially over a 48 hour period.

For evaluation of external contamination, take swabs from body orifices,
swipes from wounds, and skin wipes.

Internal contamination is assessed using the following specimens for
analysis at a health physics laboratory:

Urine: 24 hour specimens taken for 4 days

Feces: 24 hour specimens taken for 4 days

Vomitus and sputum samples

Serum creatinine assessment

Irrigating fluids

Other studies that may help evaluate internal contamination include
nuclear medicine gamma camera survey (may be used to screen for some
radionuclides). Chest counts (if inhalation of long-lived radionuclides
is suspected), and whole body radiation counts.

**TREATMENT**

Critical details of an accident must be obtained and verified by
credible sources and actual on-site measurements by appropriate
personnel. In treating patients with radiation exposure one must assume
a worst-case scenario. The five basic rules of toxicology must apply, as
with other ingested exposures.

Treat the patient before treating "the poison"

Prevent or reduce exposure

Enhance toxicant elimination

Use specific antidotes or adjuncts, if available and indicated

Consider the dose/ time exposure

**Recommended treatment of radiation accidents based on exposure
types:**

IRRADIATION: Supportive and symptomatic. Dose estimates and lymphocyte
cytogenetics will aid in determining prognosis. Bone marrow depression
can be treated with cytokines. For viral infections such as herpes
simplex, varicella or cytomegalovirus reactivation, antiviral agents can
be used.

EXTERNAL CONTAMINATION: Removal of clothing can significantly reduce the
exposure along with using soap and water. Medical personnel should avoid
self-contamination by strict barrier protection, using universal
precautions and Haz-Mat contamination control protocols. Wounds must be
decontaminated to decrease the chance of internal contamination. Using
dilute sodium hypochlorite (household bleach) 1:2-1:10 or with waterless
(grease) cleansers.

INTERNAL CONTAMINATION: For ingestion, standard use of lavage, activated
charcoal and catharsis, as indicated. (Lavage is preferable over emesis
induction) There is a greater likelihood of therapeutic enhancement if
decontamination is done early. Inhalation if large amounts of insoluble
radionuclides in the 50-100 of annual limit of intake (ALI) may be
treated by nonemergent bronchoscopic lavage 3-5 days later, similar to
techniques used for bronchogenic alveolar proteinosis.

COMBINED INJURY: Within 48 hours of exposure, lifesaving surgical
intervention should be performed in systemic exposure cases (prior to
the immunocompromise period). Elective surgery should occur only after
hematopoietic recovery is complete (usually 60+ days)

**The target organs of certain TOXIN-SPECIFIC AGENTS are as follows:**

Plutonium and Transuranics: Bone and lung

Uranium (unenriched) : Kidney Uranium hexafluoride can cause exothermic
creation of hydrofluoric acid (HF) leading to thermal and chemical burns
as well as inhalation injury.

Tritium: Electrolytes must be monitored periodically to correct any
imbalances

Iodine and Technetium: Thyroid

Cesium: Intracellular compartment

Internal and external contaminations usually occur as sub-threshold
events. In these cases, the individual may be followed as an outpatient.
Overexposures, on the other hand, with potential rapid threshold effects
will often have soft tissue manifestations such as swelling, erythema
and pain. Local injury may be manifest as early as 6 days in extreme
exposures but, more often, as late as 14 days after exposure. Systemic
effects are determined by the onset of nausea/vomiting and diarrhea,
usually within 3 hours of an overexposure, and should prompt
consideration of observation. Those presenting with prodromal symptoms
more than three hours following exposure may be followed as outpatients
with appropriate monitoring. Professionals such as nuclear medicine
physician, radiation oncologist, hematologist or occupational physicians
are valuable resources to consult for treatment advice. The
psychological as well as the physical aspects must be considered in any
treatment program.

**SEQUELAE**

After acute exposure, hematopoietic effects could include lymphopenia,
neutropenia and thrombocytopenia. Pulmonary effects may include
pneumonia and respiratory failure. Gastrointestinal effects may include
mucosal desquamation, severe diarrhea and electrolyte imbalances.
Veno-occlusive liver disease may occur in high dose exposures. Also,
neurovascular effects may be manifest by early transient incapacitation
and altered mental status, particularly in lethal exposures.

Long term effects can include the development of cancer later in life.
Tissue and organ sequelae may include fibrosis, vascular compromise and
organ insufficiency or failure.