explain the different bilogical effect of nuclear radation on human matablosum.
The unit used to measure radiation dosage is the rem, which stands for roentgen equivalent in man. It represents the amount of radiation needed to produce a particular amount of damage to living tissue. The total dose of rems determines how much harm a person suffers. At Hiroshima and Nagasaki, people received a dose of rems at the instant of the explosions, then more from the surroundings and, in limited areas, from fallout. Fallout is composed of radioactive particles that are carried into the upper atmosphere by a nuclear explosion and that eventually fall back to the earth's surface.
Effects of Radiation Exposure on Human Health
Although a dose of just 25 rems causes some detectable changes in blood, doses to near 100 rems usually have no immediate harmful effects. Doses above 100 rems cause the first signs of radiation sickness including: + nausea + vomiting + headache + some loss of white blood cells
Doses of 300 rems or more cause temporary hair loss, but also more significant internal harm, including damage to nerve cells and the cells that line the digestive tract. Severe loss of white blood cells, which are the body's main defense against infection, makes radiation victims highly vulnerable to disease. Radiation also reduces production of blood platelets, which aid blood clotting, so victims of radiation sickness are also vulnerable to hemorrhaging. Half of all people exposed to 450 rems die, and doses of 800 rems or more are always fatal. Besides the symptoms mentioned above, these people also suffer from fever and diarrhea. As of yet, there is no effective treatment--so death occurs within two to fourteen days.
In time, for survivors, diseases such as leukemia (cancer of the blood), lung cancer, thyroid cancer, breast cancer, and cancers of other organs can appear due to the radiation received.
Major Radiation Exposure in Real Life Events Hiroshima and Nagasaki
For more information on what happened at Hiroshima and Nagasaki, consult the nuclear past page and the nuclear warfare page.
Many people at Hiroshima and Nagasaki died not directly from the actual explosion, but from the radiation released as a result of the explosion. For example, a fourteen-year-old boy was admitted to a Hiroshima hospital two days after the explosion, suffering from a high fever and nausea. Nine days later his hair began to fall out. His supply of white blood cells dropped lower and lower. On the seventeenth day he began to bleed from his nose, and on the twenty-first day he died.
At Hiroshima and Nagasaki, the few surviving doctors observed symptoms of radiation sickness for the first time. In his book Nagasaki 1945, Dr. Tatsuichiro Akizuki wrote of the puzzling, unknown disease, of symptoms that "suddenly appeared in certain patients with no apparent injuries." Several days after the bombs exploded, doctors learned that they were treating the effects of radiation exposure. "We were now able to label our unknown adversary 'atomic disease' or 'radioactive contamination' among other names. But they were only labels: we knew nothing about its cause or cure... Within seven to ten days after the A-bomb explosion, people began to die in swift succession. They died of the burns that covered their bodies and of acute atomic disease. Innumerable people who had been burnt turned a mulberry color, like worms, and died... The disease," wrote Dr. Akizuki, "destroyed them little by little. As a doctor, I was forced to face the slow and certain deaths of my patients."
Doctors and nurses had no idea of how their own bodies had been affected by radioactivity. Dr. Akizuki wrote, "All of us suffered from diarrhea and a discharge of blood from the gums, but we kept this to ourselves. Each of us thought: tomorrow it might be me... We became stricken with fear of the future." Dr. Akizuki survived, as did several hundred thousand others in or near Hiroshima and Nagasaki. In fact, at least ten people who had fled from Hiroshima to Nagasaki survived both bombs.
The survivors have suffered physically from cataracts, leukemia and other cancers, malformed offspring, and premature aging, and also emotionally, from social discrimination. Within a few months of the nuclear explosions, leukemia began to appear among the survivors at an abnormally high rate. Some leukemia victims were fetuses within their mothers' wombs when exposed to radiation. One child who was born two days after the Hiroshima explosion eventually died of acute leukemia at the age of eighteen. The number of leukemia cases has declined with time, but the incidence of lung cancer, thyroid cancer, breast cancer, and cancers of other organs has increased among the survivors. Three Mile Island
For more information on what happened at Three Mile Island, consult the nuclear past page.
On a Wednesday morning, maintenance workers cleaning sludge from a small pipe blocked the flow of water in the main feedwater system of a reactor at Three Mile Island near Harrisburg, Pennsylvania. The sift foreman heard "loud, thunderous noises, like a couple of freight trains," coming. Since the reactor was still producing heat, it heated the blocked cooling water around its core hot enough to create enough pressure to have popped a relief valve. Some 220 gallons of water per minute began flowing out of the reactor vessel. Within five minutes after the main feedwater system failed, the reactor, deprived of all normal and emergency sources of cooling water, and no longer able to use its enormous energy to generate electricity, gradually started to tear itself apart.
The loss of coolant at the reactor continued for some 16 hours. Abort a third of the core melted down. Radioactive water flowed through the stuck relief valve into an auxiliary building, where it pooled on the floor. Radioactive gas was released into the atmosphere. An estimated 140,000 people were evacuated from the area. It took a month to stabilize the malfunctioning unit and safely shut it down. The reactor was a total loss and the cleanup required years of repair and hundreds of millions of dollars.
No one was reported injured and the little radiation that leaked out was quickly dispersed. Although this accident did cost lots of money and time, no one was hurt. Chernobyl
For more information on what happened at Chernobyl, consult the nuclear past page.
A far more serious accident occured at Chernobyl, in what was then still the Soviet Union. At the time of the accident, the Chernobyl nuclear power station consisted of four operating 1,000 megawatt power reactors. Without question, the accident at Chernobyl was the result of a fatal combination of ignorance and complacency. "As members of a select scientific panel convened immediately after the... accident," writes Nobel laureate Hans Bethe, "my colleagues and I established that the Chernobyl disaster tells us about the deficiencies of the Soviet political and administrative system rather than about problems with nuclear power."
Although the problem at Chernobyl was relatively complex, it can basically be summarized as a mismanaged electrical engineering experiment which resulted in the reactor exploding. The explosion was chemical, driven by gases and steam generated by the core runaway, not by nuclear reactions. Flames, sparks, and chunks of burning material were flying into the air above the unit. These were red-hot pieces of nuclear fuel and graphite. About 50 tons of nuclear fuel evaporated and were released by the explosion into the atmosphere. In addition, about 70 tons were ejected sideways from the periphery of the core. Some 50 tons of nuclear fuel and 800 tons of reactor graphite remained in the reactor vault, where it formed a pit reminiscent of a volcanic crater as the graphite still in the reactor had turned up completely in a few days after the explosion.
The resulting radioactive release was equivalent to ten Hiroshimas. In fact, since the Hiroshima bomb was air-burst--no part of the fireball touched the ground--the Chernobyl release polluted the countryside much more than ten Hiroshimas would have done. Many people died from the explosion and even more from the effects of the radiation later. Still today, people are dying from the radiation caused by the Chernobyl accident. The estimated total number of deaths will be 16,000.
For a more in-depth view of current medical technologies available to the treatment of radiation, go to the medical imaging page.
There is currently no effective medical treatment available for potentially fatal radiation doses. The case of the Japanese boy mentioned above illustrates an important fact about radiation sickness. The boy had probably received a dose of 450 rems or more, yet his symptoms were about the same as those of a person who received about 300 rems. Medical science has no way of telling the difference between people who have received fatal doses and will die despite all efforts and others who received less radiation and can be saved. Treatment for the ones that can be saved includes blood transfusions and bone-marrow transplants. Bone-marrow transplants rejuvenate the supply of white blood cells which was affected by the radiation.