Nuclear Weapon Testing Effect On The Existing Pollution Crisis?
Voice of Biotecnika | Episode No: 46
“The world has been gradually reducing its nuclear arsenals. Testing must stop so that progress on the destruction of nuclear weapons may begin.”
Hello and welcome everyone to yet another interesting episode of Voice of Biotecnika podcast. I am Deepa Sharma and today we are going to unveil the different effects of nuclear weapon testing on existing pollution.
Cessation of World War II marked the commencement of the atomic age when a number of states launched the nuclear arms race. During the period of 1945-1964, countries like the United States, the United Kingdom, the USSR, China, and France became nuclear powers, steering a large number of nuclear tests in all global environments (atmosphere, underground, and underwater). These nuclear tests cause rigorous environmental damage, the most powerful ever to be conducted in the atmosphere, as well as the general context of global nuclear weapons tests, have created the grounds of the first illustration of large-scale international cooperation to abolish nuclear weapons testing. The National Resources Defense Council assessed the total yield of 510 megatons (Mt) from all nuclear tests conducted between 1945 and 1980. Atmospheric tests on its own accounted for 428 mt, which is equivalent to over 29,000 bombs of Hiroshima size. Depending upon a number of factors, the amount of radioactivity generated by a nuclear explosion can vary significantly. These embrace the size of the weapon as well as the location of the burst. In comparison to an airburst, a ground-level explosion may be likely to generate more dust and other radioactive particulate matters. The dispersion of radioactive material is also reliant on weather conditions.
Nuclear explosions can be categorized into two chief categories: atmospheric and underground. In case of atmospheric tests, placing of the device on a boat or in a tower is done, or it is dropped from a balloon or from an airplane, or, maybe fired by a missile or detonated on the ground. All of these tests lead to the dispersion of radioactive debris in the upper atmospheric layers, which further falls to the ground, often over very wide areas. Underground tests have been run in tunnels or deep shafts. A hole is bored into the bedrock, and the measuring instruments and nuclear devices are positioned in the bottom. The complete shaft is refilled to avoid any leakage of radioactive material. The monitoring instruments register the explosion on the container microseconds prior to their destruction. The heat of the explosion melts and vaporizes the substratum, and the pressure creates a fissure and causes vibrations in the ground. Usually, a crater is formed, its size depending on the kind of rock and the yield of the explosion. Sometimes underground tests also lead to the discharge of radioactivity.
A key moment in the efforts to end the nuclear arms race and, indirectly, nuclear weapons testing was the entry into force of the Non-Proliferation Treaty (NPT) in 1968, banning nuclear arming of all states of the world, with the exception of the five existing nuclear powers. A different category of nuclear states had emerged outside the scope of the NPT, including India, South Africa, Pakistan, North Korea, and apparently Israel (unconfirmed nuclear status), with a few of these countries conducting nuclear weapons tests of their own. In terms of energy released in nuclear explosions, which is expressed in megatonnes (Mt), two different procedures are involved, namely fission (of 235U and 239Pu isotopes in a chain reaction) and fusion (of the hydrogen isotopes, deuterium, and tritium, in a thermonuclear process). In terms of radioactivity, the fusion process generally only produces tritium (3H), while, the fission process produces a whole range of radionuclides. However, the fusion process can also generate other radioactive materials which are accountable for large amounts of radioactive debris, especially because of the intrinsic fission process of particular stages of thermonuclear reactions.
Atmospheric nuclear weapons testing involves the liberation of substantial amounts of radioactive materials directly into the environment and causes the largest collective dose from man-made sources of radiation. Among the most relevant studies on the total collective dose to the world population, the UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) reports stand out, especially those drawn up in 1982 and 1993, which are considered to be complete and valid even to this day. According to the report of UNSCEAR, following atmospheric nuclear testing, the main contributor to the total effective dose commitment to the world’s population is 14C, contribution of which is 70 % over the course of thousands of years. It is further estimated that not counting radionuclide 14C, most of the other radionuclides will have delivered almost their entire dose over the next two centuries. The radionuclide 14C is created by nitrogen (14N), which is naturally present in the atmosphere—capturing the neutrons released in surplus during nuclear tests. After being formed, it is rapidly oxidized to 14CO and then to 14CO2, and then it is transferred to the global carbon reservoirs (the atmosphere, the ocean, and the terrestrial biosphere), from where it is very difficult to remove, because of its extremely long half-life, i.e., 5730 years.
Since the dawning of the atomic age in July 1945, nuclear weapons have been tested on more than 2,000 occasions – in the atmosphere, underground and underwater. The toll on human health as well as on the environment has been shocking. Today many of us in our bodies carry radioactive substances from the upshot of nuclear testing, thus increasing our risk of advancing cancer. Much of the Earth’s surface at some point has been contaminated with radioactive particles.
All the way through nuclear test explosions, the testing nations have been able to proof-test new missile designs and thus create increasingly sophisticated nuclear weapons. However, most of the test sites are in the lands of indigenous people and are far from the capitals of the testing governments. A hefty number of the early tests were detonated in the atmosphere, which spread radioactive materials through the atmosphere. Further, many underground nuclear booms have also expelled radioactive material into the atmosphere and thereby left radioactive contamination in the soil.
Over the last five decades, radionuclide 14C has been continuously transferred from the atmosphere into the ocean, but there are differences in terms of its assimilation by the marine environment. Even though the terrestrial biosphere has played a significant role in assimilating radionuclide 14C from the atmosphere via the process of photosynthesis, the ocean is, however, the largest storage reservoir of this radionuclide. Hence, in respect of environmental effects, the marine environment has played a crucial role in limiting these effects by means of its prodigious assimilation capacity, although there are some negative aspects concerning the radionuclide buildup in the aquatic organisms. Or else, there would have been a key menace that the radionuclide 14C be assimilated in massive quantities in the biosphere, especially by forest ecosystems, and subsequently assimilated in the food chain, too, including in the human body.
An additional radionuclide of supreme importance in residual global contamination from atmospheric nuclear testing is 137Cs, with its 30-year half-life. During atmospheric testing, it is released in enormous quantities and thus continues to be a chief source of anthropogenic radioactivity. As more than 70 % of the Earth’s surface is covered by water, the substantial amounts of 137Cs radioactive debris are built up in oceans and seas. At present, it is assessed that radionuclide 137Cs is the principal source of anthropogenic marine radioactivity, along with other important radionuclides (mainly 90Sr, 239–240Pu, 3H, and 14C), released in copious quantities during nuclear tests.
According to the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), the United States has conducted the highest number of nuclear weapons tests, a number of them conducted especially on the North American soil. The Nevada desert is the major region where 44 % of all the nuclear tests worldwide were conducted. The environmental consequences are related to atmospheric contamination with radioactive isotopes (especially 14C and 137Cs) following the atmospheric nuclear tests conducted during 1951–1963. Other negative effects reported were in relation to atmospheric contamination with the radionuclides, 131I and 133I, which were later transferred to the biosphere mainly through rainfalls. As the radionuclide 131I was released in large quantities mainly during atmospheric nuclear tests (especially during 1951–1958), it was one of the key causes of increased thyroid cancer occurrence in the United States. Presently, there is a high risk of groundwater contamination with several radioactive isotopes in the Nevada Test Site region. Among the most critical isotopes, there are the 239–240Pu isotopes, since it was observed that they can be involved in groundwater’s hydrodynamic processes with the risk of reaching the surface. An added setback of underground tests is linked to accidental atmospheric contamination with certain radioactive isotopes, corresponding to venting.
With regards to India and Pakistan, due to the very low number of nuclear tests conducted, it can be concluded that there are no significant instances of environmental contamination. One of the biggest environmental catastrophes from the nuclear tests was caused by the USA in the North Pacific, causing radioactive contamination in the wake of the Castle Bravo nuclear test on the Bikini atoll, in 1954. The negative consequences of this most serious chapter of radioactive contamination in the history of nuclear weapons testing is the pollution of marine ecosystems in the region, and particularly the impact on the local population in terms of the radical increase of thyroid cancer incidence as a result of the population’s exposure to tremendously high doses of radiation.
The 23 atmospheric nuclear tests conducted by the United States in the Pacific region have steered to the contamination of soil and marine ecosystems, particularly with radionuclides such as 137Cs (found in lagoon sediment, marine water, and fish), 90Sr (in coral soils), and 239,240Pu. At present, radioactive pollution of the two atolls is mainly due to radionuclides 238,239,240Pu released in enormous quantities and, to a lesser extent, due to radionuclides 3H, 90Sr 137Cs and 125Sb. From the ecological point of view, at this point, there are a few critically contaminated test sites both on land and in the marine environment. In terms of having caused a major impact on the environment and irradiation of the human body, 137Cs, 90Sr, 239–240Pu and 131I stand out among the radioactive isotopes released during nuclear tests. These isotopes were primarily found in most of the nuclear test sites worldwide. A substantial portion of these radionuclides has been transferred into the marine environment since approximately two-thirds of the Globe’s surface is covered by water.
The implied transfer of radionuclides into the geospheres and their buildup in living cells, by way of the food chain, was yet another form of radioactive contamination of the marine and terrestrial ecosystems. One of the most typical examples is the isotope 14C, which is released into the atmosphere during nuclear tests and is later integrated into the CO2, and then reaches the marine environment, as a result of the ocean-atmosphere gas exchange, or the biosphere owing to the process of photosynthesis.
Over the past century, there has been a steady accrual of knowledge about the vulnerabilities of radioactivity. It was recognized early that exposure to an adequate radiation dosage could cause injuries to internal organs, as well as to the eyes and the skin. Radiation exposure can cause damage to living cells while killing some and modifying others. The destruction of an adequate number of cells will impose conspicuous harm on organs which may result in death. If repairing of altered cells is not done, the resulting modification will be passed on to further cells and may sooner or later lead to cancer. The exposed individual with modified cells that transmit hereditary information to the offspring might cause hereditary disorders. Vegetation can also be contaminated when fallout is directly deposited on external surfaces of plants and absorbed through the roots. Furthermore, people can be exposed to radiation when they consume meat and milk from animals grazing on contaminated vegetation.
It has always been clear that any use of nuclear weapons would have catastrophic humanitarian consequences. The human and environmental devastation caused by nuclear weapons – whether by testing, mistake or malice – is the very reason we need to eliminate them altogether.
Thank you all for listening. Keep tuning with Biotecnika Podcast to learn more about the latest updates of the scientific world.