Countermeasures to Cope With Radioactive Exposure

The threat posed by an intentional manmade explosion from a radiation dispersal device, a nuclear detonation, or an accidental failure of a nuclear power plant persists. Recent events have brought these threats into focus over the past couple years – e.g., the Iranian plans for nuclear development and the earthquake/tsunami/nuclear radiation event in Fukushima.

Emergency managers have not lost sight of radiological/nuclear threats in their planning processes and are aware of the public perception that some of these events may be existentially threatening and perhaps not survivable. However, considerable progress in coping with such events has been made and emergency managers can now more affirmatively ensure that future responses and post-event recovery will be more effective.

Radioactive Threats Posed by Terrorists 

In 2009, the Obama Administration announced several changes in the U.S. nuclear posture, with the primary intent of reducing the nuclear threat to domestic and global well-being. President Barack Obama highlighted the threat posed by state actors, armed with nuclear weapons, who may pose a global threat. As part of the revised policy, there was prominent acknowledgment of the threat from non-state actors, an observation that instigated a new focus on prevention of a terrorist-delivered nuclear detonation. The timeliness of this policy change was significant, as were the subsequent efforts to ensure that such catastrophes never occur.

The intent and capability of al Qaeda and/or other terrorist organizations to obtain and use weapons of mass destruction is well documented – even in the stream of unified information available to the general public. Intelligence officials and scientific experts have testified that, despite the death of Osama Bin Laden, there is still a significant chance of a similar event occurring within the next five years. However, prevention capabilities may have limits, and the 2009 policy statement did not publicly address the most serious issues of response and recovery should such an event actually occur.

Various credible and respected groups have analyzed not only the threat potential but also the preparedness status of local, state, and federal agencies to cope with such threats, and have consistently reported that most Americans are unprepared to deal with these events. Currently, there are simply not enough medical facilities, trained personnel, or medical supplies in place to treat all of those who could potentially be injured from the detonation’s blast and burn effects.

In addition, there are no proven medical countermeasures available to prevent or lessen the severity of the toxic effects of what is termed Acute Radiation Syndrome (ARS) – i.e., reduction in the human body’s blood-producing and infection-fighting capacity at even relatively low levels of exposure, and/or the more harmful effects on the gastrointestinal tract and the brain at higher levels.

Nuclear Power Accidents 

The 2011 Fukushima disaster in Japan exposed another significant vulnerability in the threat posed by radiation disasters – more specifically, nuclear power generation. In Fukushima, the multiple failed attempts to prevent the release of radiation materials from the core of a reactor led to the widespread exposure of citizens in the vicinity to radioactive iodine, cesium, and other heavy metals. The global social impact of that event raised greater safety concerns about nuclear reactors being used as an energy source. Nonetheless, nuclear power generation will almost assuredly continue for the foreseeable future as a viable use of nuclear technologies, thus presenting a persistent challenge to responders.

Fukushima also revealed a significant lack of the technological tools needed to address the public health and medical impacts of radiation exposure, particularly one caused by the breakdown of a nuclear power plant. Although potassium iodide was pre-staged, there were few other intervention possibilities available. That failure in preparedness created a panic environment – as citizens realized there were few alternatives available to prevent and treat exposure-related diseases, it was difficult to quell the anxiety. Political decision makers around the world now realize that much more must be done to create a sense of survivability and resilience in the populations at risk.

Although the scope and nature of the radiation exposure from a deliberate terrorist detonation differ somewhat from the effects of an accidental nuclear explosion, both scenarios have a common element: namely, the historical lack of the tools needed to prevent and treat exposures to ionizing radiation. Intensive ionizing radiation wave energy, which is released during a nuclear blast of any type, causes immediate damage to human body cells. In a nuclear facility accident, the exposure is more commonly associated with the radioactive elements that are being inhaled, ingested, or otherwise absorbed, thus continuing to emit radiation either on or inside the body.

Both types of incidents can cause ARS. Exposure to ionizing radiation during an event, particularly a nuclear detonation, can be mitigated to some extent by certain shelter-in-place approaches. However, there is little available to treat those who have been exposed to quantities of ionizing radiation large enough to cause various forms of ARS.

Current Approaches Available 

The severity and scope of illnesses associated with exposure to ionizing radiation depend primarily on the total level of radiation absorbed over a short period of time. The initial ARS effects may be as simple as fatigue, nausea, and vomiting, but can progress to an increased risk of bleeding, an inability to fight infections, and ultimately neurological and respiratory damage leading to death. Long-term, low-level exposures also can cause cancer and/or other diseases, whereas short-term, high-level exposures also lead to severe life-threatening illnesses.

In medical terms, radiation exposure is usually measured in what are called “grays” – i.e., the amount of radiation actually absorbed, as opposed to the ambient radiation in the environment. The short-term exposure to levels above 1 gray causes changes in: (a) the bone marrow; and (b) the ability of the body to produce blood cells. This lowers not only the number and capability of the red cells that carry oxygen, but also the platelets necessary for clot formation and the body’s infection-fighting white cells. In Fukushima, all of the patients examined were reported to be below this level of exposure.

When the exposure/absorption rises to 3-6 grays, the gastrointestinal system is affected. In essence, the cells lining the stomach and intestine are killed and slough off, causing bleeding and the inability to digest nutrients. Moreover, as exposure continues to climb, the lungs, skin, and brain also are affected, thus causing a simultaneous failure of many of the body’s vital systems. Anyone within one mile of a 10-kiloton nuclear detonation is likely to receive this level of exposure/absorption. The risks are progressively lower (depending on the fallout cloud pattern) as the distance from the detonation increases. In nuclear facility accidents, however, it is unlikely that many, if any, people in the area would absorb a level of radiation that high.

Because exposures related to nuclear power plants are more frequently associated with the ingestion of radioactive materials, one strategy recommended for preventing illness, and/or reducing the exposure over time, is to speed the elimination of radioactive materials from the body. This can be accomplished through the use of chemicals that bind the radioactive material and move it through and out of the body before it can attach itself to any vital cells. The chemicals used in this process are generally described as “chelating” agents – i.e., agents that bind to the materials through a chemical process and are swiftly eliminated through the kidneys (or gastrointestinal tract).

Potassium Iodide is the best known agent used in radiation exposure protection, but is not a chelating agent per se. Instead, it simply saturates the body with stable iodine and, by doing so, prevents radioactive iodine from being absorbed. Among the best known of the true chelating agents are such drugs as Prussian Blue (which binds cesium) and CaDTPA (which is effective in binding platinum, americanum, and curium). These chelating agents are not useful as treatments for ARS, but: (1) they can reduce ongoing radiation exposure; and (2) are widely available for use. Although they present certain challenges in administration and have potential side effects, they would still have a clear role to play in certain types of radiation exposure events.

Exposures to waves of ionizing energy cause immediate changes in cells that can quickly lead to cell death. One strategic approach used in drug development for ARS focuses on interrupting the cell-death process. Fortunately, scientific research in the late 20th century led to an improved understanding of the pathways that lead to cell death stimulated by radiation exposure. Capitalizing on these theoretical and laboratory-developed insights, drug developers have conducted animal studies using various compounds that may inhibit or halt the cell-death process. These compounds hold promise for preventing the development of ARS despite a significant absorption of radiation.

Advanced development research in mice and non-human primates (i.e., monkeys and apes) also has shown great promise. In some studies where large numbers of non-human primates were exposed to >7 grays (a level that usually would be expected to kill 60 to 70 percent of hosts), the compounds saved more than 70 percent of the animals when used within 24-48 hours of exposure. Many additional studies on the human-safety aspects of such products are still required to ensure that the drugs do not cause unacceptable side effects in humans, but those products seem to be quite promising in providing protection, particularly when administered in a single dose within a short time after exposure. There also seems to be less need for medical monitoring and/or clinical service support, which could reduce surge on the medical delivery system. Of course, more studies must be completed to demonstrate the most appropriate use of these compounds as well as the safety implications, but some of the compounds may be available for use as early as in the next 2-3 years.

Other & Better Drugs Now Being Evaluated 

Another approach currently being explored involves the study of drugs that may stimulate a quicker recovery of the blood-forming elements of the body after their destruction by radiation. It is known that some drugs currently in use for cancer therapies can stimulate the development of white and/or red cells after the destruction of the body’s own capability to do so. One of drugs being studied closely for use in radiation-exposure situations is called Granulocyte-Clone Stimulating Factors (G-CSF), which has been used for many years to restore the body’s own immune-system capabilities following the use of cancer or transplant therapies.

Other studies also are being planned to assess the use of these drugs as therapeutic tools in the wake of a nuclear or radiation event. The advantages provided by the use of G-CSFs are that: (a) they have been in use for many years; (b) their side effects are well understood; (c) the medical management protocols needed already have been established; and (d) the daily use of these drugs will reduce the need for a separate stockpile supply. The disadvantages discovered thus far include: (a) multiple doses are needed for them to work; (b) they require frequent medical evaluation and supportive medical care; (c) they address only the radiation effects associated with the blood-forming functions of the body; and (d) they may be able to provide only supportive care for people exposed to more than 1-2 grays.

Significant Progress – But Several Questions Remain 

After a nuclear event, hundreds of thousands of people may be exposed to radiation levels high enough to cause ARS, which can be quite lethal. The number exposed after a nuclear plant accident may be smaller, but still significant. The chelating agents described above can play a major role in reducing the overall number of deaths and serious illnesses. However, there are at present not enough medical facilities and/or staff that would be needed for full management of the health effects of a widespread population exposure to significant doses of radiation.

One approach for managing this problem is toentify or develop other drugs that may reduce the total number of deaths and illnesses caused by radiation.eally, these drugs: (a) could be given post-exposure; (b) would require fewer doses; and (c) would need little in the way of medical follow-up. Such drugs are currently in the research stage, but have not yet received full safety and efficacy approval. However, advanced development is underway for other promising compounds that also may be effective in countering radiation. Moreover, some drugs that are already available for other uses may be able to address certain aspects of the ARS syndrome.

These ongoing developments are a significant cause for optimism about the survivability of those exposed to radiation in a future nuclear attack or accident. In addition to their current public information strategies and sheltering approaches, emergency management personnel should closely monitor the progress achieved in developing countermeasures. After all, a belief in survival is, in itself, frequently a significant factor in both response and recovery.

W. Craig Vanderwagen

Rear Admiral W. Craig Vanderwagen, M.D., was appointed the Department of Health and Human Services (HHS) Assistant Secretary for Public Health Emergency Preparedness and promoted to the rank of Rear Admiral, Upper Half, U.S. Public Health Service (USPHS) in July 2006. He now serves as the Deputy Assistant Secretary for Preparedness and Response and Chief Preparedness Officer. In this position, he is the HHS Secretary's principal advisor on matters related to bioterrorism and other public health emergencies. The mission of his office is to lead the nation in preventing, responding to, and reducing the adverse health effects of public health emergencies and disasters. Admiral Vanderwagen has significant public health emergency and disaster-response experience. Most recently, he was the deputy secretary's special assistant for preparedness and led the teams that implemented the changes at HHS recommended in the White House Report Katrina Lessons Learned. He also: was the senior federal health official in the response to Hurricanes Katrina and Rita in Louisiana; led the public health team deployed on the hospital ship USNS Mercy to Indonesia to assist in the 2005 tsunami recovery; served as chief of public health for the Coalition Provisional Authority and Ministry of Health in Iraq; and directed some of the health care operations initiated to help Kosovar refugees during the 1999 Balkans conflict.



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