A complication of external contamination or of close contact with a radioactive source is the effect of local radiation on tissues and organ systems (Figure 6.10). This scenario along with partial body exposure has occurred more often than incidents involving whole body irradiation in past radiation mishaps. Local radiation injury will also alter the clinical course of patients suffering from acute radiation syndrome (ARS). In fact, significant morbidity and mortality in these cases may result from local injury rather than from ARS itself. The damage to tissues results in the release of endogenous toxins into the circulatory system, resulting in high body temperatures, metabolic disorders and neurological complications.
The basic pathophysiology involves the response of the various cell types of the skin and organs that are exposed to radiation. That response is a function of the relative radioresponsiveness of the tissues involved. Individual cell types respond differently based on the amount of radiation delivered. The individual cellular response to radiation is also a function of its lineage, its level of development or maturity, and the stage during cell division when it is irradiated. Cell lineage is important because some cells are more radiosensitive (e.g., erythroblasts) than others (e.g., muscle cells). The developmental stage during which a cell is irradiated also is an important determinant of cellular response. Precursor/stem cells are more sensitive than fully developed, mature cells. Similarly, cells that are actively replicating (going through mitosis) are also more responsive.
After receiving a radiation dose, a progressive, chronic, and complex inflammatory process begins. The clinical course is a function of the following:
Although only a small superficial area may initially appear to be affected, because of the amount of energy involved, deeper tissues and organ systems may also be affected. Depending on the individual cells involved, onset of clinical symptoms will be variable. Perhaps the most pertinent rule of thumb in these types of injuries is that there is no pathognomonic sign or symptom of radiation injury. There is not always a specific linear relationship between the dose of radiation that a tissue receives and the subsequent somatic manifestations that result. Skin damage evolves over time according to the local dose with the tissue furthest from the direct local injury being the slowest to display damage. The extent of tissue damage or involvement is inversely proportional to the square of the distance from the source of radiation. There is no definite correlation between specific symptoms and cell types.
CRS has been divided into five time-related stages: prodromal erythematous, manifestational, subacute, chronic, and late.
This stage may last minutes to hours after exposure to doses >5-6 Gy. The time to onset, intensity, and duration are used to predict prognosis. The early erythema is likely due to release of vasoactive amines and secondary vasodilation. A clinically asymptomatic latent period may follow. At this stage, high-dose and low-dose casualties cannot be distinguished. If additional symptoms (e.g., nausea, vomiting, central nervous system [CNS] changes) develop along with relevant patient history, then further assumptions or conclusions will be possible.
After a latency period of 7-21 days, clinical signs develop that range from bright erythemas with a burning sensation to painful blisters and ulcers. These changes are due to injury to blood vessels and underlying connective tissue and death of skin stem cells. From 8 to 12 Gy, there is dry desquamation, and from 15 to 20 Gy, moist desquamation ensues. Moist desquamation occurs less commonly in children undergoing radiation therapy than in adults. This is probably because of the ability of the epithelium to recover more quickly in children than in adults. More changes are also observed in fair-skinned individuals and at the more radiosensitive areas of the body such as the axilla, groin, and skin folds. Radiation sensitivity in other areas of the body decreases in the following order:
Least sensitive areas are the nape of the neck, scalp, palms, and soles. Dry desquamation usually leads to complete recovery. However, recovery from moist desquamation depends on the extent of injury.
The subacute stage is characterized by initiation of progressive dermal and subcutaneous fibrosis leading to a second ulcerative phase and cutaneous ischemia in affected areas.
Onset is usually from 16 weeks to 2 years after initial irradiation with epidermal atrophy and erosions associated with dermal and subcutaneous fibrosis being the main clinical manifestations. Concomitant inflammation tends to progress indefinitely with no endpoint. As such, long-term evaluation and management may be required.
This occurs 10-30 years after irradiation in the exposed field with development of "spontaneous" angiomas, keratoses, ulcers, and squamous and basal cell carcinomas.
There are no specific protocols published to guide treatment. However, treatment of past victims provides a valuable point of reference for treating future victims. The clinical situation helps guide whether the treatment approach should be conservative or surgical, based on the following guidelines:
The overall morbidity and mortality of trauma patients is exacerbated when there has been acute exposure to ionizing radiation or contamination with radioactive materials. Trauma can be in the form of lacerations, puncture wounds, abrasions, gunshot wounds, blunt force injuries, crush injuries, and burn injuries (Chapter 7, Blast Terrorism).
The initial step in the management of victims with combined injuries, i.e., radiation and trauma, should be the immediate stabilization of the most life-threatening injury as well as addressing airway, breathing, and circulation problems. After stabilization, radiation injury can be assessed and further managed. The fundamental concept to appreciate is that radiation injuries are not acutely life threatening.
Thermal burn injuries may be complicated by the fact that the wounds may become contaminated with radioactive particles that need to be removed. Tissue that is irradiated may not respond in the normal physiological manner afterward. This may affect surgical success. Animal studies have indicated that performing initial surgery within 36-48 hours is optimal. Surgery beyond that time puts the patient at risk of life-threatening sepsis due to profound neutropenia with the acute radiation syndrome.
Radioactive material embedded in wounds should be removed if possible. Otherwise, a victim is at risk of both infection and local radiation injury. Surgeons should never touch the radioactive particles (even with a gloved hand) due to the high probability of direct permanent damage to the fingers. Particles should be touched only with forceps.
Depleted uranium (DU) munitions may be encountered because they are a critical component of U.S. weaponry. DU has <50% of the radioactivity found in natural uranium. DU is not a radiation risk, but it is a heavy metal risk. Prime concern is its effect on the kidneys as a heavy metal if it is absorbed. However, DU has also been demonstrated to have potential tumorigenic effects in animal studies. Therefore, DU fragments should be removed from wounds if possible, the victim should be kept hydrated, and renal function should be monitored. Sodium bicarbonate helps bind DU and reduce renal toxicity. DU may also be absorbed via inhalation from a DU fire or ingestion.
Children are particularly susceptible to the transforming effects of ionizing radiation. This is true for children exposed to radioactive fallout, release of radioactive materials from nuclear power plants, and external beam radiation therapy for medical conditions. External beam radiation therapy, used for example in the treatment of Hodgkin's disease or CNS tumors, is associated with an increased risk of second malignancies, particularly solid tumors arising in the radiation field. In contrast, children exposed to high levels of radioactive fallout from nuclear weapons at Hiroshima, Nagasaki, or the Marshall Islands testing site have increased risks of leukemia, benign and malignant thyroid neoplasms, and breast cancer (as young women). Those exposed to lower levels of radiation or possibly a more limited number of isotopes, such as from the Chernobyl nuclear accident, have an increased risk of thyroid neoplasms.
Thyroid nodules and cancers are one of the most frequent late complications of ionizing radiation. Although generally uncommon in children, they are very frequent 10-20 years after radiation exposure. Four of the 39 children (10%) exposed after the Bravo nuclear test in the Marshall Islands developed thyroid cancer, and the incidence of thyroid cancers increased by 193-fold in areas contaminated by the Chernobyl nuclear accident. In contrast, only 1 of 39 children (2.5%) developed leukemia after the Marshall Islands nuclear test (compared with 10% incidence of thyroid cancer), and the incidence of leukemia did not increase after the Chernobyl nuclear accident (compared with 193-fold increase in the incidence of thyroid cancer). From these data, it is clear that children are very susceptible to radiation-induced thyroid neoplasia. Indeed, children were found to be 10-fold more likely than adults to develop thyroid neoplasms after exposure to similar doses of ionizing radiation. It is also clear that thyroid neoplasms are a more common late effect from radiation exposure than are leukemias.
Although there may be quantitative differences in the risk of thyroid neoplasia after both of these accidents (Marshall Islands Bravo test and the Chernobyl accident), this could relate to differences in the types of radionuclides released or the doses absorbed. Exact quantification of the doses to which these children were exposed has been difficult to determine because many ingested contaminated milk, which would be a leading source. Quantification of the level of contamination and the quantity of milk consumed has proved difficult. Current studies are underway to better define the individual levels of exposure.
These data underscore the particular susceptibility of the thyroid that arises from unique genetic changes known as recombinant ret proto-oncogene in papillary thyroid cancer (ret/PTC) rearrangements. These rearrangements can be induced by ionizing radiation and are sufficient to cause thyroid cancer in experimental animals. Once induced, ret/PTC gene rearrangements generate a chimeric gene that places the tyrosine kinase portion of the ret proto-oncogene under the control of different gene promoters, leading to increased and uncontrolled ret tyrosine kinase activity.
Stable iodine prophylaxis can reduce the risks of thyroid cancer after nuclear disasters or accidents but has no effect against external beam radiation therapy because the latter does not involve radioactive iodine. The World Health Organization and the U.S. Food and Drug Administration recommend stable iodine prophylaxis for exposed populations stratified according to age. Thyroid function tests should be monitored in infants to allow early recognition and treatment of hypothyroidism.
In general, radiation-induced thyroid cancers appear to be more aggressive than "spontaneous" thyroid cancers and are frequently multifocal. Exposed children should be monitored by serial ultrasound examinations, and suspicious lesions should be removed by total thyroidectomy to eliminate other microscopic foci of disease.
Most children who develop thyroid cancer present with a thyroid nodule. Malignancy must be considered in any child with a thyroid nodule because the risk of malignant disease is much higher in children (30-50%) than in adults (10-14%), and it is even higher after radiation exposure. Routine serum thyroid function tests are not helpful in making a diagnosis of malignant disease because they are usually normal even in the presence of malignancy.
Suspicious lesions can be evaluated by ultrasound, which may reveal features highly suggestive of malignancy (such as microcalcifications, heterogeneous echo-density, and central blood flow), in addition to identifying other unsuspected lesions that may also require surgical removal. Radionuclide scans generally cannot distinguish benign from malignant disease and should not be routinely ordered for this purpose. Determination of serum calcitonin levels should be reserved for patients with a family history suggestive of multiple endocrine neoplasia (MEN) because medullary thyroid carcinoma, which is the form associated with MEN and elevated serum calcitonin, is not induced by radiation exposure. Also, there is some risk of false-positive calcitonin levels in patients with any thyroid nodule. Fine needle aspiration cytology is the best single test to distinguish benign from malignant disease but may have a higher false-negative rate in children than in adults unless combined with clinical risk assessment. Due to the high risk of malignant disease, some have recommended removing all thyroid nodules from children, especially those with a history of radiation exposure. Thyroid hormone has been prescribed to reduce the size of benign nodules. Only a few respond, but those that increase in size must be removed.
A logical sequence to evaluate a thyroid nodule would involve ultrasound to define the architectural features and the presence of other unsuspected disease, fine needle aspiration to determine benign or malignant cytology, and then removal if the overall clinical picture is suspicious of malignant disease. Most centers do not rely entirely on the results of a single test such as a fine needle aspirate but would remove the entire thyroid gland due to the increased risk of developing another malignant lesion in any remaining thyroid tissue that was exposed to radiation.
Thyroid cancer is most frequently treated in children with total thyroidectomy, cervical lymph node dissection, and radioactive iodine ablation (RIA). This approach has induced remission in 70% of children but with a significant risk of disease recurrence (19%) and complications (5-25%). Disease-specific mortality is low (1-2%), but this could be artificial because followup in almost all studies has been brief. After surgery and RIA, thyroid hormone is prescribed to suppress thyrotropin (thyroid stimulating hormone [TSH]) without inducing hyperthyroidism. Routine surveillance for recurrence has generally included 131iodine whole body scans and serum thyroglobulin (Tg) levels performed after thyroid hormone withdrawal. After total thyroidectomy and RIA, undetectable serum Tg when the patient is off thyroid hormone is predictive of complete remission, whereas Tg levels >10 ng/mL off thyroid hormone suppression or TSH-stimulated Tg levels >2 ng/mL indicate residual disease. Despite favorable survival, recurrence is three times as likely in children as in adults.
Due to the increased incidence of leukemia in children exposed to high doses of radiation, close followup with regular physical examinations and complete blood counts is warranted. The incidence of breast cancer is also increased in young women who had been either pubertal or lactating at the time of exposure to the Hiroshima device. Cancers began to appear as early as ages 25 to 30 years, which was earlier than in sibling controls. For that reason, regular breast examinations should be emphasized, and abnormalities should be evaluated with a high level of suspicion. Enrollment in a high-risk breast clinic may be indicated. The latency period (i.e., the time interval between irradiation and appearance of a malignancy) is shortest for leukemia (5-7 years) but can extend to 45 years or more for solid tumors.
The environmental damage from a terrorist incident involving radiation has many potential consequences for children. These effects can be minimized by a better understanding of the types of incidents that involve radioactive material and the environmental exposure pathways involved. Response planning involves actions that may be taken to minimize exposure both immediately after and during recovery from a terrorist incident.
The environmental damage and effects on children differ significantly depending on the type of terrorist incident.
More specifically, whether the incident involves a/an:
An RDD is any device that causes the spread of radioactive material across an area, typically to contaminate people and buildings in an urban environment. RDDs can also be used to contaminate water, livestock, fish, and food crops. The radioactive material acts as a toxic chemical that is harmful or fatal. RDDs use an explosive device to scatter the radioactive material over a general but fairly confined area. Simple RDDs spread radioactive material without the use of explosives, typically by the covert placement of radioactive material in a high traffic area. The radioactive material is then spread when it is disturbed, e.g., by people walking through material spread on the ground or spread on the wheels of vehicles that drive over the material.
Sources1 of radioactive material for construction of an RDD include medical facilities, military, industrial and waste storage facilities, the black market, and orphaned sources. The vast majority of sources contain only one radioactive element, such as cesium-137, strontium-90, cobalt-60, or iridium-192.2 Cesium chloride is of particular concern because of the fine powder form in which it is normally used. However, any nuclear material, including nuclear power plant fuel rods (uranium-235) or spent fuel rods (contains a mixture of radioactive components), could be used for dispersal.
The health effects of RDD weapons can vary sharply. The time required to accumulate significant doses of radiation can vary. Harmful effects often require either inhalation or ingestion. Although exposure does not require actual contact with radioactive material, health effects are further reduced as the radioactive material spreads. In most cases, it is extremely unlikely that an RDD can spread enough radioactive material to the air and ground to pose an immediate health hazard to people near the event.
1 Medical facilities contain high activity irradiators, teletherapy machines and brachytherapy sources, as well as radionuclides which are vulnerable to malevolent use. Military and industrial sources include: radioisotopic thermoelectric generators (RTGs), high activity irradiators, gamma radiography equipment, high activity gauges and well logging equipment, used in drilling or oil, gas and water exploration. Vulnerability to theft or malevolent intent, including sale on the black market, of these sources is increased by factors such as bankruptcy, abandonment, long-term storage, transport, or change in expert personnel. An orphan source is defined by the International Atomic Energy Agency (IAEA) as a radioactive source that poses sufficient radiological hazard to warrant regulatory control but which is not under regulatory control because it has never been so or because it has been abandoned, lost, misplaced, stolen, or otherwise transferred without proper authorization. See International Atomic Energy Agency, IAEA-TECDOC-1388, dated February 2004.
2 Each radioactive element has its own decay scheme by which it becomes a stable element. Most sources have short decay schemes, with few radioactive intermediates.
INDs (improvised nuclear devices) use fissile material, either uranium or plutonium, and produce a nuclear yield. The fission process produces tremendous, potentially catastrophic damage from an initial intense radiation, intense heat, and blast effects over a large area. A plume of radioactive fallout is usually produced, composed of large quantities of a variety of radioactive products. Although fallout is carried by atmospheric conditions and potentially may circle the earth, the heaviest dispersal pattern—and the area of greatest concern for health effects—is the area close to the blast zone. Health effects from an IND include injuries from the blast and heat effects, as well as acute radiation syndrome symptoms from the high doses of radiation released from the nuclear weapons explosion. Depending on the population density, an IND is capable of killing tens to hundreds of thousands of people.
A terrorist attack at a nuclear power plant could release radioactive material into the environment. Nuclear power plants produce energy through the controlled release of energy from a critical mass of nuclear material by the fission process. Many safety and security features have been designed into U.S. reactors. For example, U.S. reactors use containment structures designed to contain release of radioactive material in an accident. The most serious U.S. nuclear power plant accident occurred at Three Mile Island Unit 2 (TMI) in 1979. The accident at TMI was the worst case scenario of a nuclear power plant accident, namely, a loss of coolant, resulting in the partial meltdown of the reactor core and release of radioactive material into the atmosphere. Although the reactor core at TMI was damaged by excessive heat, the mishap resulted in only very small releases of radioactivity into the surrounding environment. Environmental samples of air, water, milk, vegetation, soil, and foodstuffs at TMI showed that most of the radiation was contained, and that those isotopes released had no physical or health effects on individuals or the environment.
More extensive releases at TMI did not occur primarily because of the containment structure. Containment structures have been included in U.S. reactor designs since the early stages of commercial power plants. They are meant to prevent the release of radioactive material to the area surrounding the power plant if an accident occurs. In contrast, in the reactor accident at Chernobyl in 1986, which was the costliest industrial and environmental accident ever, there was no containment structure. The reactor core at Chernobyl continued to release radioactive material—mainly xenon-133, iodine-131, and, to a lesser extent, cesium-137, strontium-90, and plutonium-239—into the atmosphere for 2 weeks after the accident occurred due to graphite fires that could not be extinguished.
There are three main routes of exposure by which the health of people are affected by radioactive material:
Figure 6.2 illustrates one way in which children could be harmed by radiation in the aftermath of a terrorist attack involving radioactive material. In this example, I-131 is used because it is the isotope for which there is the most evidence of its environmental exposure pathway—namely, the grass-cow-milk pathway—and because it is one of the few isotopes for which there is a specific radioprotective agent. However, the likelihood of an RDD using I-131 is extremely low because of its short half-life (a few weeks). I-131 will be released if there is a nuclear yield after an attack using an IND, and it may be released after a terrorist attack on a nuclear power plant if the attack results in an environmental release of radioactive material.
In contrast, strontium-90, which also follows the grass-cow-milk pathway, is of lesser concern because it does not become airborne as easily as the iodines and thus is less likely to travel as far as the radioiodines. However, strontium-90 has a much longer half-life (30 years), and although there is less concern, it will last for decades.
In contrast to radioiodine, most radioisotopes do not have a stable isotopic form that is biologically important and for which the radioactive form can cause biological damage via normal metabolic pathways. The element of each isotope has different biological, chemical, and physical properties that would result in different health effects. Most of the effects of the radiation from radioiodine are on the thyroid. Radioiodine is also one of the few radioisotopes for which there is a targeted organ and specific method of prevention and treatment, namely, administration of stable potassium iodide.
The Chernobyl nuclear power plant accident in 1986 provides the best documented example of a massive radionuclide release in which large numbers of people across a broad geographical area were exposed to radionuclides released into the atmosphere. Chernobyl also most closely mimics the worst-case scenario of a successful terrorist attack on a nuclear power plant. At Chernobyl, radioiodine was released from a graphite and nuclear fuel fire that burned for 2 weeks after the initial core meltdown.
The medical effects on children from an environmental radioiodine release have been extensively studied. The U.S. Food and Drug Administration did a comprehensive review of the data relating radioiodine exposure to thyroid cancer risk after the Chernobyl reactor accident in 1998. Hundreds of thousands of measurements were made from some of the millions of people exposed in the most heavily contaminated regions of the former Soviet Union: Belarus, Ukraine, and the Russian Federation.
Thyroid radiation exposures after Chernobyl were virtually all internal, either through ingestion or inhalation of radioiodines. Starting 4 years after the accident, thyroid cancer increases of 30- to 100-fold were observed (compared with pre-Chernobyl rates), with estimated doses of <30 cGy (30 rads) to the thyroid. Consistent with the short half-life of iodine-131, children born more than 9 months after the accident have not shown an incidence of thyroid cancer above the levels seen prior to the Chernobyl accident. The Food and Drug Administration (FDA) concluded from the Chernobyl data that there is a significant increase in the risk of childhood thyroid cancer at exposures of >5 cGy (5 rads) or greater. In contrast, there was no perceived increase in thyroid cancer in adults from the exposure to radioiodine during the accident.
Stable KI protects the thyroid by preventing the uptake of radioactive iodine. Stable KI was distributed throughout Poland after the Chernobyl accident to more than 10.5 million children younger than 16 years of age. Although there is no evidence on the degree of protection provided by the KI distribution throughout Poland compared with other regions around Chernobyl, the widespread distribution does provide valuable data on the safety and tolerability of KI in the general population. Twelve of 3,214 neonates treated with KI in Poland after Chernobyl showed a transient hypothyroidism. The FDA concluded that the benefits of KI treatment are especially important to children and neonates to reduce the risk of thyroid cancer and outweigh the risks of transient hypothyroidism. In contrast, the recommendation for adults older than 40 years is to administer stable KI only in the case of a projected dose of radiation to the thyroid greater than 500 cGy (rads), 100 times the exposure level for children.
Other measures may be taken to reduce exposures. For example, bans on the sale of milk products from contaminated areas prevent internal contamination during the first few weeks after an emergency where radioiodines are released. Due to the short half-life of I-131, canned milk or other milk products that can be stored for a few months will not have any residual radioactive iodine and may be consumed.
Decisions and actions to prevent radiation exposure must "do more good than harm." In other words, the benefit to health effects from dose reduction by using protective actions should more than offset the socioeconomic disadvantages of the protective actions.
Evacuation is an effective countermeasure to the presence of radiation and may prevent exposure to children. The decision to evacuate should take into account the potential disruption and actual risk. Area evacuations can result in increased risk of exposure if a plume already exists or if evacuation is to a location with a higher risk of exposure. Also, casualties can result from the evacuation process, and negative psychological effects can occur. Ideally, the evacuation would begin before the passage of any radioactive material carried in a dispersal cloud. Evacuation is almost always indicated if the projected average effective dose is likely to be >0.5 Sv (50 rem) within a day.
Variables affecting the pattern of radioactive material distribution include the time of day and year, the elapsed time since the accident, the size of the accident, and meteorological data to include wind patterns. Again, when deciding whether to evacuate or shelter in place, it is not recommended that predetermined levels alone be used for the decision. Basing the decision on these levels alone might lead to socioeconomic, physical, and psychological hardships that outweigh the benefits of lower exposure. For example, during the TMI accident, the Governor of Pennsylvania recommended that those members of society most vulnerable to radiation—namely, pregnant women and pre-school-age children within a 5-mile radius of the plant—leave the area. Studies done more than 10 years after the TMI accident found that many residents still showed psychological symptoms of stress. Most vulnerable to stress were the mothers of young children and those who had been evacuated. Symptoms included somatic complaints, anxiety, and depression, posttraumatic stress disorder symptoms and physiological symptoms, hypertension, and higher levels of norepinephrine, epinephrine, and cortisol. Persistent fears and anxiety were found that centered on the fact that the residents had been living close (within 5 miles) to the source of such potentially catastrophic danger years earlier.
The evacuation after the Chernobyl accident was poorly planned and chaotic. The 45,000 residents of Pripyat, the city closest to the power plant, were evacuated during a 3-hour period 36 hours after the accident occurred and were not allowed to return to their homes. Ninety thousand more people were evacuated over the next few days, clearing a 30-km zone around the power plant. Thousands of farm animals were slaughtered because there was no longer anyone to tend to them. The evacuees often were relocated to areas that were openly unreceptive and even hostile to them. Preliminary reports suggest that women pregnant at the time of the accident were more likely to have stress symptoms than others evacuated during the accident. Children evacuated to Kiev were more likely to report frequent headaches, chronic illness, and poorer overall health.
Additional factors must be considered when deciding whether to advise evacuation or sheltering in place in response to a radiological terrorist incident. Earlier recommendations by the EPA for evacuation were written for a nuclear power plant accident in which the release of radioactive material would occur hours after the initial accident, allowing the population to be evacuated in a plume-free environment. However, a terrorist attack is more likely to release a plume within minutes rather than hours of the initiation of the event. Therefore, sheltering is likely to be more protective in response to a radiological terrorist event. Sheltering should be performed whenever it is more protective than evacuation.
Sheltering in place for protection from radioactive fallout is also an effective countermeasure with little negative impact for short periods of time (hours) and may be done in a fallout shelter, an underground area, or in the middle of a large building. Any roofed structure would be of some benefit and would protect people from alpha and beta radiation, because the structure would keep radioactive particles from falling on the skin and further reduce the chance of inhalation. The degree of protection from gamma radiation increases with the type of material used in constructing the shelter, from wood, to masonry, to metal, metal being the most effective. Glass is not very effective in preventing the penetration of gamma radiation, and windows should be avoided because of the risk of lacerations from broken glass due to pressure changes or other consequences of the accident. Sheltering generally reduce exposures to external and internal contamination by 5 to 10 times. Sheltering is almost always justified if it will prevent exposures of 0.050 Sv (5 rem). At exposures <0.005 Sv (500 mrem), sheltering is not warranted. Sheltering provides protection from the falling radioactive material by absorbing the radiation (shielding) and keeping the radiation outside of the shelter (distance) while the radioactive material decays (time).
Table 6.11 shows the shielding factors from gamma radiation in a radioactive cloud plume. After the plume has passed and local authorities have announced that it is permissible or advisable to leave indoor protection, there will still be some radioactive material spread by the plume that is contaminating tree leaves, automobiles, and outdoor playground areas. Care should be taken to ensure that when children go outside they are in an area that has not been contaminated. Also, after leaving the shelter, it may still be necessary to relocate the population surrounding the region if the levels of contamination cannot be reduced quickly. It is also important to remember that family pets are not allowed in government shelters. Families should make plans and arrangements for the family pets ahead of time to keep them safe during the crisis.
Water and food may be scarce. They should be used prudently, but severe rationing of water should not be imposed, especially for children because they are more susceptible to dehydration than adults.
Parents should check with school officials to determine the school's plans for an emergency and discuss with their children what procedures will be followed to reunite children with parents and caregivers. It may not be possible to reach children away from home immediately after the incident. A prearranged plan of where the children should go, if not in school, should be discussed and agreed on ahead of time.
The decision whether to remain long-term in an area or to abandon the area will depend on the levels of radiation remaining, the decay properties of the material, and the ability to physically remove the contaminated material. The decision should be reached in coordination with qualified health physicists because of complicating factors.
Response organizations (local, State, and Federal) will need to prepare a site remediation plan. The clean-up process is lengthy and depends on the type of contamination and the site contaminated. There are temporary measures to fix radioactive material in place that will stop the spread of contamination. For example, flour and water mixtures, road oil, and water can be used to wet ground surfaces and prevent resuspension of the radioactive material.
Rehabilitation of contaminated areas, equipment, and facilities depends on the physical removal of contaminated particles. Usually, this will be done by trained personnel. It is important to determine whether or not water sources have been contaminated.
Hard surfaces are easier to rehabilitate than porous ones. Walls will generally be less contaminated than top and ground surfaces. Washing clothes and blankets in home washing machines can remove most contamination. It may not be possible to remove all contaminated material, however. Some articles can no longer be safely used (e.g., toys that have been left outside).
RDDs can also be used to contaminate livestock, fish, and food crops. However, huge quantities of radioactive material would be required to effectively contaminate food or water, and most radioactive material is not soluble in water. The U.S. Food and Drug Administration has guidance for accidental radioactive contamination of human food and animal feed.
Water may also be contaminated as an aftereffect of an explosion involving an RDD or IND. The safety of water sources should be evaluated after the attack. Water filtration in the home can reduce levels of radiation by removing many of the radioactive particles, but boiling or chlorination is not beneficial. Until the water supply has been determined to be safe, only bottled water should be used for drinking and cooking.
Water of questionable quality can be used for cleaning contaminated skin. This is because radiation exposure follows the principles of time, distance, and shielding. Radioactive material left on the skin will cause a higher level of exposure to an individual than exposure to water or the exposure from washing with contaminated water. Cleaning and washing the hands and face are especially important to prevent internal contamination when eating and drinking.
Women who are breastfeeding should be especially concerned about the products they are ingesting. Fruit may be eaten if thoroughly washed or after the skin has been removed. Many types of fallout can become more concentrated in breast milk. For example, commercial milk can become contaminated with radioactive fallout if the milk was produced by cows grazing in the contaminated area. Contamination is further concentrated in human breast milk. Commercial formula reconstituted with bottled water is a safe alternative to breastfeeding until the mother's milk is demonstrated to be safe.
Bottled water and canned food products or foodstuffs imported from noncontaminated areas or produced before the radiological incident occurred should be free of radioactive contamination.
Pets may bring radioactive material into the house on the bottoms of their paws and should be kept indoors. Wiping or washing the pet's paws can be helpful to reduce the spread of contamination into the house.
The body retains radioactive materials after death. The body itself provides adequate shielding for alpha and beta-emitters. For gamma emitters (e.g., cesium-137), which are more penetrating radiation sources, radiation levels will be emitted by a contaminated corpse. Cremation should be avoided to prevent the radioactive material from vaporizing and becoming airborne. Guidance should be sought from local health physicists or city or State radiation safety experts or health departments. Concerns about burying the victims of radiation accidents have, in the past, raised fears in a community; specifically, the radiation accident in Goiania, Brazil, in 1987, and this possibility will need to be considered.