Physical, chemical, and physiological protection from radiation can be provided.  Physical protection is used to prevent radiation exposure of individuals from occurring.  Chemical protection is provided to protect when a possible radiation exposure is anticipated or after an exposure has occurred. Physiological protection is provided after a radiation incident has occurred to lessen the harm from the radiation exposure.

Physical protection is based on the principal of radiation attenuation.  This principal relates to the fact that the radiation intensity decreases as the radiation penetrates a given material.  If the material is thick enough, it can essentially stop the radiation.  Figure 4.1 shows how protective gear can stop some radiation.

The density of a radiation-shielding material determines its penetration by gamma and x-rays.  The denser the material, the more the gamma- or x-ray intensity is reduced. 

Lead is the densest of commonly available material.  It has been used to provide shielding from gamma and x-rays.  However, it should be recognized that lead is not the densest element. For example, tantalum, tungsten, and thorium are higher on the density scale, but lead is readily available, easily fabricated, and cost less than these materials.  Lead bricks can be purchased and arranged in various ways to shield radiation.

Motor vehicles (e.g., ambulance) will provide some protection from gamma rays from surface soil contaminated with gamma-emitting radionuclides.  However, the exterior of a vehicle maneuvering in radionuclide-contaminated soil will likely get contaminated. The contamination can be passed on to the passengers when leaving and entering the vehicle.  Others could also be contaminated when using the vehicle.  However, some of the external contamination can be removed by showering of the passengers and putting water over the vehicle. The water used in showering and in cleansing the car will however then become radioactive.

Some U.S. military troops in the Persian Gulf War entered military vehicles previously hit by depleted uranium (DU) penetrators.  DU has both chemical and radiation toxicity. The DU spontaneously combusts upon impact producing DU particles in sizes that can be inhaled.  It has been reported that many servicemen and women climbed on and/or entered DU-impacted vehicles without protective gear in carrying out some of their assignments. This likely led to some DU intakes (e.g., via inhalation) by the soldiers.

Some Persian Gulf War troops also reported breathing smoke from burning vehicles that had been impacted by DU rounds. In addition, an unknown number of medical personnel who treated wounded soldiers may have been exposed to DU dust from clothing and wounds.

Although the DU is slightly radioactive, its chemical toxicity may be more of a hazard to exposed individuals than the radiation hazard.

Protective garments and devices (e.g., respirators) can provide physical protection from airborne DU as well as from other airborne radioactive particles.

Nuclear workers at the Mayak plutonium production facility in the Former Soviet Union did not have respirators to protect them from plutonium intake during their early years of employment at the facility.  As a consequence, many workers inhaled large amounts of plutonium, which led to a variety of health effects.  See Section 3 for a discussion of harm arising from radiation exposure.

Shielding can be used to protect from neutron exposure.  However, shielding from neutron exposure is somewhat complicated.  This is because neutrons interact with the shielding material producing gamma rays.  Thus the shielding material must protect not only from the neutrons but also from the gamma rays that are produced.  The amount of gamma rays produced depends on the shielding material.

Normal clothing provides some protection from airborne, beta-emitting radionuclides (e.g., from nuclear weapons and nuclear accident fallout).  However, radioactive material could deposit on uncovered areas of the skin and lead to radiation burns of the skin and possibly ulcers.

Airborne radioactive material can also deposit in the eyes and cause damage if no protective devices are worn.  Rinsing the eyes can remove some of the radioactive material.

Many active chemicals can reduce the harm produced by radiation when given before radiation exposure.  These substances have different chemical structures and include such agents as sulfhydryl compounds, amino acid groups, hormones, and many pharmacological agents and metabolic inhibitors.

Aminothiols and their derivatives have been some of the most effective chemicals in providing protection from radiation injury.  However, most of these agents cause side effects.

Side effects of aminothiols used as radiation protectors include:

• Nausea
• Vomiting
• Hypotension
• Weakness
• Fatigue

When conducting military operations, such side effects are undesirable.  Thus, much research has been done to develop chemical agents that protect from radiation harm while minimizing side effects.

• Significant dose modifying factor (DMF, explained below)
• Oral administration, preferably no more than once a day
• Minimal reduction in effectiveness when administered soon after exposure rather than before exposure
• Minimal side effects

A DMF value like 1.5 could provide a great benefit because of the steepness of radiation dose-response curves for effects that involve damage to large numbers of cells (e.g., lethal damage to the hematopoietic system).  Providing chemical protection with a DMF of 1.5 is equivalent to the biologically relevant dose being 1.5 times smaller than the actual dose.  Such a reduction by chemical protection could lead to a biologically relevant dose below the threshold for causing the effect of interest.  If the effect of interest is lethality, then many lives could be saved via use of the chemical protection.

Chelation treatment with specific chemicals can provide protection from some inhaled radionuclides (e.g., plutonium).  This is explained below and relates to an actual radiation incident that occurred at Los Alamos National Laboratory on March 16, 2000.

Eight workers at the U.S. Department of Energy's Los Alamos National Laboratory were exposed by inhalation to plutonium-238 while working at Technical Area 55, the Laboratory's plutonium facility.

Four of the employees underwent chelation therapy at the Laboratory's Occupational Medicine facility within 2 hours of the incident.  This took place after tests of the employees' nasal passages indicated possible exposure to plutonium at levels that would warrant the treatment.

In the chelation therapy, the exposed workers received a drug known as calcium trisodium pentatate that captures plutonium so it can be excreted from the body before it is incorporated into the bone, liver, and other sites.  The treatment is most effective when given within hours of plutonium intake.

The presence of plutonium on nasal swipes did not necessarily mean that plutonium was deposited in the lungs of the Los Alamos workers.  However, the four employees underwent chelation therapy as a precaution.

Additional monitoring of the plutonium-exposed workers excreta over weeks and months and follow-up testing will determine their actual intake of radioactivity.  The four employees may undergo further chelation treatment if warranted.

Radiation damages specific tissue/organs in the body.  One of the most sensitive targets is the hematopoietic system.  Thus, after significant radiation exposure, blood cell counts can drop dramatically leading to bleeding from loss of platelets and infection from loss of white blood cells.  One form of protection called supportive treatment is to administer blood (e.g., fresh platelets), electrolytes, antibiotics, etc.

More elaborate treatments have recently emerged including the use of agents that stimulate reproduction of blood cells.  Bone marrow transplants are also sometimes used in cases of very severe radiation injury.