Environmental Impact of Radiation
–Background of Radiation
–Radiation Scales and Impact
–Atomic Bomb Testing on Islands
–Lessons From Chernobyl
The following students contributed to this section of the paper:
Background of Radiation:
Since radiation exists for a long time, it has the capacity to inflict damage upon anything exposed to it. Before getting into the dangerous effects of radiation, a brief explanation of what it is may help. Radiation is energy traveling in the form of particles or waves in bundles of energy called photons (http://www.umich.edu/~radinfo). Alpha rays, beta rays, gamma rays, X rays, and neutrons are all types of radiation that are evaluated for radiation protection. Spontaneous decay of specific radioactive atoms, such as radium, plutonium, uranium, and radon, are what causes Alpha rays. It can only pass a short distance in water. Actually, a single piece of paper can stop an alpha ray. Internal exposure is really the only way health effects occur from this form of radiation. The next form of radiation is beta ray. They are produced through spontaneous decay of certain radioactive materials, such as tritium, carbon-14, phosphorus-32, and strontium-90. The distance that beta rays travel depends on its energy. Like alpha rays, concern for health effects is after their ingestion. Third, which are gamma rays, are similar to ordinary visible light except in its energy and wavelength. A gamma ray is much shorter compared to ultraviolet and is higher in energy. They are produced like beta rays. The types of radioactive materials that cause gamma rays are cobalt-60 and cesium-137. X rays are much like gamma rays except that they are produced differently. They are produced when electrons at high speeds hit metal atoms; these stop the electrons and release energy in the form of an electromagnetic wave. Lastly, neutrons are released after an atomic nucleus splits and produces large amounts of energy; this is called a nuclear fission. Nuclear fission generally occurs with plutonium and uranium. They hardly damage cells; however, because the biological cells do not carry electrical charges. However, we do have large amounts of hydrogen in our bodies and if a neutron hits the nucleus of hydrogen it causes ionization in the body. This leads to various types of damage to the body. (http://www.rerf.or.jp).
Radiation Scales and Impact:
Radiation is a quantifiable unit of energy given off by atomic particles. There are several various units of measure for radiation. The two often used are the rem and the sievert. Scientists estimate that the average person in the United States receives a dose of about 360 millirem of radiation per year. Eighty percent of that exposure come from natural sources: radon gas, the human body, outer space, and rocks and soil. The remaining 20 percent come from man-made radiation sources, primarily medical x-rays (http://www.epa.gov/radiation/rrpage/rrpage1.html). One sievert is approximately 100 rem.
Most doses are relatively small and so measured in the millirem or millisievert. This table from the book Environmental Science: A Study of Interrelationships is a relative value of various levels of radiation (175):
| Sources | Dose | Biological Effect |
| Nuclear bomb blast or exposure in a nuclear facility. | 100,000 rems/incident | Immediate death |
| 10,000 rems/incident | Coma, death within 1 day | |
| X-rays for cancer patients | 1000 rems/incident | Nausea, lining of intestine damaged, death in 1-2 weeks |
| 100 rems/incident | Increased probability of leukemia. | |
| 10 rems/incident | Early embryos may show abnormalities | |
| Upper limit for occupationally exposed people | 5 rems/year | Effects difficult to show. |
| X-ray of the intestine | 1 rem/procedure | Effects difficult to show |
| Upper limit for release from nuclear installations (except nuclear power plants) | 0.5 rem/year | Effects difficult to show |
| Natural background radiation | 0.2-0.3 rem/year | Effects difficult to show. |
| Upper limit for release by nuclear power plants. | 0.005 rem/year | Effects difficult to show. |
Atomic Bomb Testing on Islands:
U.S. post-WWII nuclear testing was initiated in 1946 with several detonations conducted in the Pacific Ocean. Between 1946 and 1962, the U.S. would conduct 100 tests on the Bikini and Enewetak Atolls. In addition, extensive testing was also conducted on Christmas and Johnston Islands. The tests in the Pacific were conducted to test the yields produced by various design and fuel variations, as well as the applicability of nuclear weapons to various tactical situations, and included the first “true” hydrogen bomb detonation and the largest blast of U.S. testing program, in 1952 and 1954 respectively. The majority of the 64 detonations conducted during and before 1958 were atmospheric tests conducted primarily on the two atolls, with the exception of two blasts which were conducted underwater. The U.S. concluded its testing in the Pacific in 1962, with a series of 36 blasts conducted on Johnston and Christmas Islands. This series was conducted underground, and because of this had dramatically reduced; therefore, the environmental impacts were dramatically less than those of the atmospheric tests conducted before 1962. More detailed information on this topic can be found at http://www.warewulf.com/nuke/Usa/Tests/.
The U.S. elected to test nuclear bombs on the island of Bikini Atoll. Bikini Atoll is one of the twenty-three islands that compose the Republic of the Marshall Islands (http://bikiniatoll.com/facts.html). The total land area of the atoll is a mere 3.4 square miles; the island is 586 acres (http://bikiniatoll.com/facts.html). In an effort to make the U.S. into a world power, it exploited the island, the natives, and especially the environment. Three of the islands were, in fact, “vaporized during the nuclear tests” (http://bikiniatoll.com/facts.html). As a result of the nuclear tests, “the soil [was] removed to a depth of about 15 inches. The removal of the topsoil would severely damage the environment, turning it into a virtual wasteland of wind-swept sand” (http://bikiniatoll.com/radclean.html). With hopes of preserving the island for future generations, the Bikini Atoll Council proposed a scrape of the island; however, the islanders do not like this plan too much. Instead, they proposed a plan to build a causeway between the islands of Bikini and Venue. A compromise is in the works between scientists and the islanders. This compromise is being given serious consideration in light of a new finding by the International Atomic Energy Agency. Their plan is to scrape only the living area of the island. Nonetheless, environmental damage has been done to this island, which was pronounced habitable once again in the end of 1995 (http://bikiniatoll.com/radclean.html). The environmental damage inflicted on this small island has certainly left a big scar.
Lessons from Chernobyl:
In 1986 the Chernobyl nuclear reactor meltdown occurred, forever changing our impressions of the effects of radiation on the environment. Following this nuclear meltdown, scientists were able to monitor the surrounding ecosystems and develop an understanding of the impact of ionizing radiation on the environment. Apparently, some plant and animals species are more resistant to the damaging effects of radiation than others. The variability in plant and animal sensitivity to radiation can disrupt ecosystems by eliminating a food source for one animal or creating an opening for another species to flourish in exponential numbers. Pine trees were the first type of trees to die from radiation poisoning from Chernobyl. Birch, oak and other leafy species were reported to have survived the first year of radiation exposure. Rodent populations and sensitive plants were eliminated almost immediately. The fallout of radiation from Chernobyl severely contaminated the environment, affecting the agriculture and food supplies of much of N. Europe and the Nordic countries following the Chernobyl disaster. In 1996 a meeting of international scientists met in Vienna, Austria to report on the Chernobyl incident 10 years after the accident. They concluded that most of the severe environmental impacts were short-term, and that full recovery of the ecosystems would occur given ample time.
Cesium is the element that clearly dominates the long-term radiological situation after the Chernobyl accident. Due to its penetrating radiation, Cesium deposited on the ground may give an external dose. It may also enter the food chain and give an internal dose. It is eliminated metabolically in a matter of months. Cesium is relatively easy to measure.
Plutonium and strontium, on the other hand, present difficulties in measurement; but there is relatively little strontium in the fallout and it does not give a dose unless ingested or inhaled. Very little plutonium traveled far from the reactor site, and because of its chemical stability, it does not find its way easily into food chains.
Measurements and assessments carried out under the project provided general corroboration of the level of surface contamination for Cesium reported in the official maps that were made available to the project in the USSR. Analytical results from a limited set of soil samples obtained by the project teams near the evacuated zone corresponded to the surface contamination estimates for plutonium. However, project results were lower in the case of strontium. The concentration of radio-nuclides measured in drinking water and, in most cases, in food from the areas investigated, were significantly below guideline levels for radio-nuclide contamination in food moving in international trade and in many cases were actually below the limit of detection.
The analytical capabilities of Soviet laboratories appeared to be adequate. The range of performance of the Soviet laboratories that participated in the inter-comparison exercise was broad, but similar to that found in previous international comparison exercises. The few problems identified, including the tendency to overestimate strontium, did not significantly affect the use of data for purposes of making conservative dose assessments. The extensive surface water sampling programs in the USSR are adequate.
It should be noted that certain problems during the sampling and analytical procedures could result in the overestimation of the concentration of radio-nuclides in water. In addition, the insufficient information available was used to evaluate air sampling equipment and procedures. Although the relative contribution to radiation doses of some re-suspension of radioactive materials in the air (as dust) is believed to be minor, it should be noted that the occurrence of such airborne re-suspension, particularly during agricultural activities or dry periods, cannot be excluded.
Rapid screening and sophisticated techniques used locally for monitoring commercially available food from production to consumption also appeared to be satisfactory; however, the relevant instrument calibration technique could not be evaluated sufficiently by the project, owing to the lack of detailed technical information. The radioactive contamination of food samples was found to be, in most cases, below the levels established by the responsible authorities for specific countermeasures in the settlements surveyed. In some settlements, milk from individual farms and food collected in contravention of official recommendations could be contaminated above these levels. Some technical recommendations about analytical methods used by Soviet scientists were made and, in particular, it was felt by the Committee that there should be fuller participation in the future with international inter-comparison programs and inter-calibration exercises.
As an effect of the Chernobyl accident, 125,000 km2 of land in Belarus, Ukraine and Russia were exposed to radiation, with radioactive levels sometimes greater than 37 kBq/m2. Among the land affected was 73,000 km2 of forest, water bodies, and urban centers. To the south and west of the accident site lays a wasteland dubbed the “Red Forest,” where once stood acres upon acres of pines. The forest was subjected to up to 100 Gray of radiation, and subsequently, the first 10-15 inches of topsoil and all dead trees had to be removed (http://www.nea.fr/html/rp/chernobyl/c06.html). The contamination of water bodies resulted directly from deposition from the air, discharge as affluent, and indirectly as washout from the catchment basin. The image at this address, http://www.nea.fr/html/rp/chernobyl/chern8.gif illustrates the rivers Pripyat, Uzh, and Dniepr, which flow into the river Kiev and then into the Kanev and Kremenchug reservoirs. As the rivers drained, contamination levels fell dramatically, and have not posed any significant threat to human, plant, or animal life. However, outside the former Soviet Union, fish in many lakes have been contaminated above acceptable levels for sale. In addition, contamination of groundwater in the area of the accident may lead to future problems in the catchment basins downstream of Chernobyl as radioactive sediments collect (http://www.nea.fr/html/rp/chernobyl/c06.html).
