211Disasters and Public Health: Planning and ResponseCopyright 2009 by Academic Press. Inc. All rights of reproduction in any form reserved.
Nuclear and Radiological Disasters
Objectives of This ChapterExplain the difference between ionizing and nonionizing energy.Recognize the primary units of measurement for radiation.Describe the differences in risk among types of radiation.Explain the various stages and effects of acute radiation syndrome.List the effects of a nuclear detonation.Describe the difference between an improvised nuclear device and a dirty bomb.List the factors that determine the morbidity and mortality of a dirty bomb.Explain what can be done to reduce the threat of nuclear and radiological weapons.Describe the three most important protective factors when dealing with radiation.List the key issues that hospitals must consider when planning for radiological disasters.
Introduction (Case Study: Chernobyl Nuclear Accident)In April 1986, a small city in Ukraine became the focus of international concern and the site of the largest technological disaster in history. The Chernobyl Nuclear Power Station was constructed in the 1970s and consisted of four reactors. The first reactor, Reactor Number 4, started generating power in 1983. Others were in various stages of construction in 1986 when a terrible catastrophe occurred. A routine test was under way to determine whether Reactor Number 4 could keep cooling pumps operating during a power outage until the backup generators could trigger. A power surge during the test led to a massive explosion in the reactor that sets a meltdown in motion (See Figure 91) (United States Nuclear Regulatory Commission, 2006). The fuel rods and the graphite reactor cover melted through the floor and a huge cloud of radiation was released. The amount released has been described as 3040 times the amount of radiation released from the detonation of the Hiroshima and Nagasaki atomic bombs (Library of Congress, 1996).
The groups at risk from Chernobyl radiation exposures have been studied by dividing them into several groups including liquidators or those who responded and did on-site response and clean-up, evacuees from the highly contaminated zone, resi-dents of the strict-control zones, and residents of other contaminated areas beyond the control zones. These areas span across Ukraine, Belarus, and Russia. However,
212 DISASTERS AND PUBLIC HEALTH: PLANNINg AND RESPONSE
measurable contamination from Chernobyl was detected in nearly every nation in the Northern Hemisphere (United Nations, 1988b).
The first populations exposed were plant personnel and first responders. They received whole body gamma irradiation, substantial skin exposure to beta radiation, and inhalation of a variety of nuclides including radioiodine and cesium. Just over 200 workers were involved in the initial response and over half of them suffered from Acute Radiation Syndrome (ARS). Over the next 3 weeks 19 died (United Nations, 1988a). In the 4 months following the accident, a total of 28 facility workers and responders died from their exposures (United States Nuclear Regulatory Commission, 2006).
Hundreds of thousands were recruited to carry out clean-up operations. To limit the exposure of individual workers, each one would work a shift of several minutes and quickly move out as the next crew came in to work several minutes. As individuals reached their limit for allowable exposures, more workers would be brought in to replace them. Besides the initial workers and responders who were present during and immediately after the explosion, these liquidators received the most significant radiation exposures. Most were 2045 years old at the time of the accident. There are ongoing debates over the health impact among these workers. While some claim that tens of thousands have died from illnesses related to their exposures, the International Atomic Energy Agency claims that the morbidity and mortality studies carried out among the liquidators show no correlation between their exposures at Chernobyl and their cancer and death rates (International Atomic Energy Agency, 2005).
The other groups that have been observed for radiological health effects include evacuees from the area immediately surrounding the facility and those who reside in potentially contaminated areas. Besides the direct exposure to the initial radioactive plume that was emitted from the facility, area residents have received additional expo-sure from contaminated food, water, and air over the years following the disaster. Eating food grown in contaminated soil and drinking milk from cows grazing on contaminated grass have increased the exposure of those living throughout the region but not sig-
FIGURE 91 (a) Chernobyl Nuclear Power Station following the April 1986 explosion and (b) the sarcophagus built to entomb Reactor Number 4 and the radioactive remains.
Source: New York State Education Department and Nuclear Regulatory Commission. Image of damage on left available at: http://www.emsc.nysed.gov/ciai/images/chernobyl.jpg. Image of sarcophagus on right available at: http://www.nrc.gov/about-nrc/emerg- preparedness/images/chernobyl.jpg.
Chapter 9NuclearandRadiologicalDisasters 213
nificantly (See Table 91). While there are reports of increased thyroid cancers among children exposed, others claim that the increases are the result of enhanced surveillance activities and do not represent a true increase. The United Nations Scientific Committee on the Effects of Atomic Radiation comprises a staff of 15, a committee of 146, and 21 national delegations (Jaworowski, 20002001). It is considered by many to be the most knowledgeable and objective collection of nuclear experts in the world. With the pos-sible exception of increased thyroid cancers among exposed children, they have not seen compelling evidence of any serious health problems resulting from Chernobyl. However, there are still many who disagree .
Chronic doses of radiation are cumulative over each persons lifetime and are known to cause thyroid cancer, leukemia, solid cancers, circulatory disease, cataracts, and birth defects. There are several possible reasons why these problems are not being observed in the exposed population as dramatically as many public health experts pre-dicted. First, there still may be changes in health status among the exposed that has yet to occur. Several of these conditions develop over many years and the differences between those exposed and those not exposed may not become apparent for several more years. Second, there is ongoing mistrust of authorities and some doubt if results showing sub-stantial increases in latent radiological morbidity and mortality will be shared with the international community. Finally, there may not be the long-term morbidity and mortality that many predicted. If this is the case, there will still be many conspiracy theorists and others steeped in their own dogma that will never believe it.
Table 91 Average Accumulated Dose of Chernobyl-Affected Populations Compared to Natural and Medical Radiation Sources (The Chernobyl forum, 2005; Health Physics Society, Health Physics Fact Sheet, Radiation exposure from medical diagnostic imaging procedures, http://www.hps.org/documents/meddiagimaging.pdf)
Population Number Exposed Exposure Timeframe Average Dose (mSv)
600,000 19861989 ~100
116,000 1986 >33
Residents of strict control
270,000 19862005 >50
Residents of other
5,000,000 19862005 1020
All 19862005 48
Medicalchest X-ray N/A Per procedure 0.08
Medicalmammogram N/A Per procedure 0.13
Medicalhead CT scan N/A Per procedure 2
N/A Per procedure 10
N/A Per procedure 757
CT, computed tomography.
214 DISASTERS AND PUBLIC HEALTH: PLANNINg AND RESPONSE
Nuclear and Radiological Disaster DefinitionsAbsorbed dose: The amount of energy deposited by ionizing radiation in a mass of tissue
expressed in units of joule per kilogram (J/kg) and called gray (gy).Acute exposure: Exposure to radiation that occurs in a matter of minutes.Alpha radiation (alpha particle): A positively charged particle consisting of two neutrons and
two protons. It is the least penetrating but most ionizing of the three common forms of radiation. It can be stopped by a sheet of paper but can cause significant long-term dam-age if inhaled or ingested. It carries more energy than beta or gamma radiation.
ARS: An often fatal illness caused by receiving a high dose of penetrating radiation to the body in a short time (usually minutes).
Background radiation: Radiation from the natural environment originating primarily from the natural elements in rock and soil of the earth and from the cosmic rays.
Becquerel (Bq): Amount of a radioactive material that will undergo one decay (disintegra-tion) per second.
Beta radiation (beta particle, beta ray): An electron of either positive or negative charge has been ejected by an atom in the process of a transformation. Beta particles are more pen-etrating than alpha radiation but less than gamma. They can cause serious skin burns with high exposures.
Cumulative dose: The total dose that accumulates from repeated or continuous exposures of the same part of the body, or of the whole body, to ionizing radiation.
Curie (Ci): The traditional measure of radiation that was based on the observed decay rate of 1 g of radium.
Cutaneous Radiation Syndrome: A complex syndrome resulting