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March 25, 2011

Radiation Effects

Due to the recent devastation of the Fukushima Daiichi nuclear plant in Japan, more and more people around the world start worrying about what levels of radiation effects may have fatal impact on the human body.

Radiation is usually measured in rem, millisievert (msv), millirem (mrem), or microsievert (µsv). The following is a brief list and conversion for these measurement units:

  1 rem            =            10          millisievert           (msv)
  1 msv            =            100        millirem               (mrem)
  1 mrem         =            10          microsievert         (µsv)
  1 rem            =            10,000   microsievert         (µsv)

According to the Environmental Protection Agency in the United States, our body chemistry would be changed if we were exposed to the radiation levels of 50,000 to 100,000 microsievert (µsv). If the levels of radiation exposure increased to 550,000 µsv, we would start feeling nausea and fatigue. Furthermore, we would experience vomiting if the levels of radiation exposure reached to 700,000 µsv. Also, our hair would start falling if the levels of radiation exposure rose to 750,000 µsv. When exposing to 4,000,000 µsv, people would possibly die in 2 months. The much higher levels of radiation exposure will speed up the rapidity of death.

Generally, radioactive materials are composed of unstable atoms. Radiation is the product of these unstable atoms produced when they become stable. These unstable atoms release excess energy during the processes of becoming stable, and the excess energy released is so called radiation. In fact, many things surrounding us produce radiation. For instance, smoke detectors, luminous watches, and TVs can give off small amounts of radiation. Even in foods such as bananas and carrots or beer may also content natural radioactive materials.

According to the U.S. Nuclear Regulatory Commission (NRC), an American will averagely receive an annual radiation level of about 6,200 µsv, and this level of radiation is not dangerous to human health. About 50% of this level of radiation exposure is caused by natural radioactivity, such as those radioactive materials found in soil, rocks, cosmic rays, and other natural sources. The other 50% of radiation exposure comes from human sources mostly caused by diagnostic medical procedures. For example, a full set of dental X-rays and computer tomography scans usually give off about 400 and 1,500 µsv of radiation, respectively.

Doctors have proved that significant radiation exposure will increase the risk of cancer. Human body’s natural control processes will be interrupted by the radioactive damages at cellular and molecular. As a result, cancer, the uncontrolled growth of cells, will be facilitated by the overexposure of radiation. Peter Caracappa, a clinical professor of nuclear engineering at Rensselaer Polytechnic Institute in Troy, N.Y., believes that every increased dose of radiation consumption will amplify a certain rate of cancer risk. He estimated that the increasing rate of cancer risk caused by ingested radiation is about 4% per sievert (1 sievert = 100 rem). In other words, ingesting a radiation level of 1,000,000 µsv will increase the probability of the occurrence of cancer by 4%.

However, according to NRC, there is no significant evidence can prove that cancer will occur when exposing to a radiation level of below 100,000 µsv. The levels of radiation recorded around the Fukushima Daiichi nuclear power plant by the Tokyo Electric Power Company, Incorporated (TEPCO) at 14:00 on March 19 was 3,443 µsv, and it reduced to 2,758 µsv by March 20 at 15:40. Japanese government currently restrains the sales of some agricultural products from those devastative regions and requires further precaution of radiation exposure. It hopes people can understand the radiation effects, so that they will not be panic and overreacted by the fears of radiation exposure.