Exposure time:
A very high single dose of radiation (acquired within minutes can be more harmful than the same dosage accumulated over time. According to the World Nuclear Association, a single one-sievert dose is likely to cause temporary radiation sickness and lower white blood cell count, but is not fatal. One five-sievert dose would likely kill half of those exposed within a month. At 10 sieverts, death occurs within a few weeks.
The effects of long-term, low-dose radiation are much more difficult to gauge. DNA damage from ionizing radiation can cause mutations that lead to cancer, especially in tissues with high rates of cell division, such as the gastrointestinal tract, reproductive cells and bone marrow. But the increase in cancer risk is so small as to be difficult to determine without studying a very large exposed population of people. As an example, according to Langhorst, 10,000 people exposed to a 0.01-sievert whole-body dose of radiation would potentially increase the total number of cancers in that population by eight. The normal prevalence of cancer, however, would predict 2,000 to 3,300 cancer cases in a population of 10,000, so "how do you see eight excess cancers?" Langhorst asks.
Chernobyl's lessons:
According to Gonzalez, some of the emergency workers at Chernobyl received several sieverts of radiation, and many were working "basically naked" due to the heat, allowing contaminated powder to be absorbed through their skin. In comparison, the Japanese workers are most likely very well-equipped and protected at least from direct skin doses.
The Tokyo Electric Power Co. (TEPCO), the plant's owners, has evacuated most of its workers, but 50 remain at the site to pump cooling seawater into the reactors and prevent more explosions. These workers are likely exposing themselves to high levels of radiation and braving significant health risks. "As a matter of precaution, I would limit the workers' exposure to 0.1 sievert and I would rotate them," Gonzalez says. The workers should be wearing personal detectors that calculate both the rate and total dose of radiation and that set off alarms when maximum doses are reached. "If the dose of the workers start to approach one sievert then the situation is serious," he says.
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 iodine 131. The isotope, released by the Chernobyl explosion, had contaminated the grass on which cows fed, and the radioactive substance accumulated in cows' milk. Parents, unaware of the danger, served contaminated milk to their children. "Certainly this will not happen in Japan," Gonzalez says.
When it comes to radiation exposure, professionals who frequently work with radioactive materials, whether in a hospital or a nuclear power plant, abide by the ALARA principle: "as low as reasonably achievable". Radiation exposure limits are conservatively set well below the levels known to induce radiation sickness or suspected of causing long-term health effects. Temporary exposure to dosages many times these limits, however, is not necessarily dangerous.
News of the U.S. Navy repositioning its warships upwind of the reactor site, the distribution of potassium iodide pills by the Japanese government, and images of officials in hazmat suits using Geiger counters to measure radiation levels among babies may stoke the public's fears—but, for now, these measures are ALARA in action, or "good extra precautions," Gonzalez says. The idea here is to always err on the side of caution.
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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 ยต 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.
Reply | Report Abuse | Link to thisThanks for showing up such fabulous information. I like this post, keep writing and give informative post...
Reply | Report Abuse | Link to this<a href=" http://www.seobaba.com/seo-services-india/seo-services-india.html"> Seo Company India</a>
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>