EXPOSED: Temporary exposure to radiation levels many times above safety limits is not necessarily dangerous.
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The developing crisis at the Fukushima Daiichi nuclear power plant in the wake of the March 11 earthquake and tsunami has raised concerns over the health effects of radiation exposure: What is a "dangerous" level of radiation? How does radiation damage health? What are the consequences of acute and long-term low-dose radiation?
Though radioactive steam has been released to reduce pressure within the wrecked complex's reactors and there has been additional radiation leakage from the three explosions there, the resulting spikes in radiation levels have not been sustained. The highest radiation level reported thus far was a pulse of 400 millisieverts per hour at reactor No. 3, measured at 10:22 A.M. local time March 15. (A sievert is a unit of ionizing radiation equal to 100 rems; a rem is a dosage unit of x-ray and gamma-ray radiation exposure.) The level of radiation decreases dramatically as distance from the site increases. Radiation levels in Tokyo, about 220 kilometers to the southwest, have been reported to be only slightly above normal.
"We are nowhere near levels where people should be worried," says Susan M. Langhorst, a health physicist and the radiation safety officer at Washington University in Saint Louis.
According to Abel Gonzalez, vice chairman of the International Commission on Radiological Protection who studied the 1986 Chernobyl disaster, current information coming from Japan about levels of radiation leakage are incomplete at best and speculations about "worst-case scenarios" are as of yet irrelevant.
The health effects caused by radiation exposure depend on its level, type and duration.
Radiation level:
The average person is exposed to 2 to 3 millisieverts of background radiation per year from a combination of cosmic radiation and emissions from building materials and natural radioactive substances in the environment.
The U.S. Nuclear Regulatory Commission recommends that beyond this background level, the public limit their exposure to less than an additional one millisievert per year. The U.S. limit for radiation workers is 50 millisieverts annually, although few workers are exposed to anything approaching that amount. For patients undergoing medical radiation there is no strict exposure limit—it is the responsibility of medical professionals to weigh the risks and benefits of radiation used in diagnostics and treatment, according to Langhorst. A single CT scan, for example, can expose a patient to more than one millisievert.
Radiation sickness (or acute radiation syndrome) usually sets in after a whole-body dose of three sieverts—3,000 times the recommended public dose limit per year, Langhorst says. The first symptoms of radiation sickness—nausea, vomiting, and diarrhea— can appear within minutes or in days, according to the U.S. Centers for Disease Control and Prevention. A period of serious illness, including appetite loss, fatigue, fever, gastrointestinal problems, and possible seizures or coma, may follow and last from hours to months.
Radiation type:
Of concern in the current situation is ionizing radiation, which is produced by spontaneously decaying heavy isotopes, such as iodine 131 and cesium 137. (Isotopes are species of the same element, albeit with different numbers of neutrons and hence different atomic masses.) This type of radiation has sufficient energy to ionize atoms (usually creating a positive charge by knocking out electrons), thereby giving them the chemical potential to react deleteriously with the atoms and molecules of living tissues.
Ionizing radiation takes different forms: In gamma and x-ray radiation atoms release energetic light particles that are powerful enough to penetrate the body. Alpha and beta particle radiation is lower energy and can often be blocked by just a sheet of paper. If radioactive material is ingested or inhaled into the body, however, it is actually the lower energy alpha and beta radiation that becomes the more dangerous. That's because a large portion of gamma and x-ray radiation will pass directly through the body without interacting with the tissue (considering that at the atomic level, the body is mostly empty space), whereas alpha and beta radiation, unable to penetrate tissue, will expend all their energy by colliding with the atoms in the body and likely cause more damage.
In the Fukushima situation, the radioactive isotopes detected, iodine 131 and cesium 137, emit both gamma and beta radiation. These radioactive elements are by-products of the fission reaction that generates power in the nuclear plants.
The Japanese government has evacuated 180,000 people from within a 20-kilometer radius of the Fukushima Daiichi complex. They are urging people within 30 kilometers of the plant to remain indoors, close all windows, and to change clothes and wash exposed skin after going outside. These measures are mainly aimed at reducing the potential for inhaling or ingesting beta-emitting radioactive material.
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15 Comments
Add Comment"The average person is exposed to 0.2 to 0.3 microsieverts of background radiation per year"
Reply | Report Abuse | Link to thisNot to be pedantic, but there appears to be a unit conversion error here. I think it should be 0.2 to 0.3 millisieverts per year (or 200-300 microsieverts per year).
Not pedantic at all. You are correct and the change has been made. m and µ are just so similar...
Reply | Report Abuse | Link to thisSoldiers of Soviet army used primitive integral dose meters. They there the size of a pen and had a charged wire, a needle and a lens. Each soldier could watch the needle and find out the dose of radiation he was exposed to. The scale was 0-50rem (0-0.5 sieverts). If needle was close to maximum (wire discharged) his job was over and he had to be replaced. However the meter could be recharged and used again with the next soldier.
Reply | Report Abuse | Link to thisA highly concern its about Pacific Sea radiation level, like we know, Japan are trying to cool the reactor with sea water, so the sea water are returning to the sea or evaporating, if the contaminated water is returning to the pacific there is radiation that will contaminated the ecologic sea life, so our marine pacific food has the potential contamination in course. Is necessary monitor the sea radiation level in each station avalaible.
Reply | Report Abuse | Link to this"as-of-yet" is not an expression. It is "as yet" and i expect better from SA. Thanks for the article and comments.
Reply | Report Abuse | Link to thisA professional radiation epidemiologist should have vetted this article. There are a number of errors. For example, the effect of deposited Chernobyl radioisotopes on the health of children was primarily due to I-131 (radioiodine) which was deposited on plants, eaten by cows and passed into milk products. This is thought to have been the main cause of the increased incidence of thyroid cancer observed in children from the affected areas. Cesium-137 does not accumulate (as does radioiodine) in the thyroid tissue and is unlikely to have been a significant contributor to the thyroid dose.
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Thanks, Dr Jagadeesh, you post good stuff.
Reply | Report Abuse | Link to this"The average person is exposed to 0.2 to 0.3 millisieverts of background radiation per year"
Reply | Report Abuse | Link to thisI think the numbers here are still not correct. According to World Nuclear Association, people receive 2.4 millisieverts of background radiation per year in average. Check http://www.world-nuclear.org/info/inf05.html
Fujia is correct--the "The average person is exposed to 0.2 to 0.3 millisieverts of background radiation per year" figure quoted in the article is still off by an order of magnitude.
Reply | Report Abuse | Link to thisSecond point, whenever quoting radiation dosage levels present in the environment, a unit time must be provided to make the value meaningful.
"The highest radiation level reported thus far was a pulse of 400 millisieverts at reactor No. 3..." would appear, on the face of it to represent a radiation level 167x normal background dose (400/2.4). It was reported that the radiation level at the plant was measured at 400 millisieverts *per hour* (eg. http://www.bbc.co.uk/news/world-12740843).
This is obviously a much, much higher figure (by 8,760x--24 * 365). Anyone exposed to radiation is receiving a dose at a rate of of 3.5kSv/a, which is 1.4 million times normal background dose, or an annual dosage of radiation every 22 seconds. These levels are very harmful to human health, and thus the outpouring of concern for the Fukushima workers.
Thank you for the article. It would be great to see more rigor in the reporting of technical figures though, particularly from Scientific American.
-Brad
I'm sorry, I'm not trying to be picky. In the article, you write:
Reply | Report Abuse | Link to this"The thousands of children who became sick in the aftermath of the Chernobyl disaster were not harmed from direct radiation or even from inhalation of radioactive particles, but from drinking milk contaminated with cesium 137."
While the Chernobyl disaster did release large quantities of cesium-137, the body cannot distinguish the cesium from potassium, and it tends to concentrate in muscle tissue, irradiating organs. Most of the children sickened by Chernobyl had thyroid issues which was caused from iodine (-131 and, to a lesser degree, -133), which is readily taken up by the thyroid gland. See more at:
http://www.who.int/mediacentre/factsheets/fs303/en/index.html
Perhaps, to correct inaccuracies around dosages, as well as the agents of sickness for the children at Chernobyl, another edit of the article might be warranted?
Thanks, mikeq, Fujia, and bradleygibson for pointing out my mistakes. Corrections have been made.
Reply | Report Abuse | Link to this"Anyone exposed to radiation is receiving a dose at a rate of of 3.5kSv/a, ... These levels are very harmful to human health, and thus the outpouring of concern for the Fukushima workers."
Reply | Report Abuse | Link to thisTo get that level of radiation dosage, you have to stand on the blown Fukushima nuclear reactor for one year. Actually you'll get a lot less than that bec. the nuclear fuel rod would ran out and the half-life of radioiodine is only 8 days.
The reported radiation level at Fukushima of 40 rem/hr. was less than the hazardous dosage of 100 rem even if you stand there for one hour unprotected by radiation suit.
I've read there are four groups of 50 workers not including the firemen working at the site. In one of the letters to their families, one said, "Have a good life." After it's calmer, I hope they are retired at full pay and have a long and healthy life.
Reply | Report Abuse | Link to thisTEPCO is not known for compliance with safety regulations nor openness.
Nuclear radiation is still being detected leaking out of the Fukushima Facility in Japan. There are plutonium and other poisons entering our environment wherever we are. The effects of radiation include cancer, DNA damage, reproductive damage, hormonal damage, and thyroid damage (that's why they want you to take potassium iodine, another dangerous toxin) but I wouldn't. There is a much safer substances like <a href="http://thehealingfrequency.com/zeolite/">Zeolit</a>.
Reply | Report Abuse | Link to thisInstead you can use natural substances. There is one that is strong enough to protect against radiation. A good article on radiation sickness protection that shows what you need do to test radiation levels and protect yourself is here:
<a href="http://thehealingfrequency.com/japan-reactor-fukushima-nuclear-radiation-protection/">Radiation Sickness</a>
And to make sure the water you drink is safe, look at the following article:
<a href="http://thehealingfrequency.com/nuclear-radiation-and-water-purification-tablet-adya-clarity-minerals/">Water Purification Tablet</a>