Wednesday, July 1, 2015

The Health Risks Of Radiation


Non-Ionizing Versus Ionizing Radiation: Ionizing radiation is the greater concern; the World Health Organization writes: “Epidemiological studies on populations exposed to  radiation (for example atomic bomb survivors or radiotherapy patients) showed a significant increase of cancer risk at doses above 100 mSv.” It, however, adds: “If the dose is low or  delivered over a long period of time (low dose rate), there is greater likelihood for damaged cells to successfully repair themselves. However, long-term effects may still occur if the cell damage is repaired but incorporates errors, transforming an irradiated cell that still retains its capacity for cell division. This transformation may lead to cancer after years or even decades have passed. Effects of this type will not always occur, but their likelihood is proportional to  the radiation dose. This risk is higher for children and adolescents, as they are significantly more sensitive to radiation exposure than adults.”
Source: Teraphysics

An article, by Sarah Laskow, in Foreign Policy gives a comprehensive review on humanity’s use of radiation, with the intent of answering a couple of important question. What do we really know about the harmful effects to humans of ionizing radiation like gamma rays (γ) and medical x-rays? The question to ask is what is considered a safe dose?

In “The Mushroom Cloud and the X-Ray Machine” (March 26, 2015), Laskow writes about the history of determining safe radiation exposure, beginning with the United States testing of nuclear weapons on Ailuk Atoll in the Marshall Islands on March 1, 1954 (It detonated a thermonuclear bomb of 15 megatons, 1,000 times greater than was dropped over Hiroshima.) There was fallout:
In the 1950s, the U.S. government may have had the best of intentions when it told the residents of Ailuk that they were safe, but technically speaking, authorities weren’t in a position to offer those assurances. What U.S. government scientists said at the time was that below 25 roentgens, they could not see any effects on a person’s body. But they allowed for the possibility that, over time, small amounts of radiation exposure might cause genetic damage. In other words, the most reliable science of the era could not measure the effects of the relatively low levels of radiation that reached Ailuk.
Today, despite the 2,053 nuclear weapons tested around the world during the Cold War, the more than 430 nuclear power plants currently operating in 31 countries, and the skyrocketing use of radiation in medicine—annually, there are 20 million nuclear-medicine procedures in the United States alone—scientists are still uncertain about those risks. The estimated total levels of radiation that reached Ailuk were ultimately determined to be less than 10 roentgens. By today’s safety standards, such levels would be less than what is referred to as “low dose,” which is anything below 100 millisieverts (mSv), the metric measure now used, or roughly equal to 10 roentgens.
Over the past 17 years, the U.S. Energy Department has invested in more than 240 projects, at a cost of over $130 million, to discover the effects of low-dose radiation on humans and the environment, to no avail. This January, the House of Representatives passed a bill calling for a new road map for low-dose research to find a science-backed reason to end what are—in the words of House Science Committee Chairman Lamar Smith, a Texas Republican—“overly restrictive regulations” on nuclear industries.
Although the bill appears on its face benign, calling for coordinated efforts by scientists to finally get to the bottom of low-dose exposure risks, its goal is to discredit the so-called “linear no-threshold” (LNT) model, which has formed the basis for radiation safety policy for decades. This model assumes that radiation at any dose is harmful—an approach used by regulatory bodies, both in the United States and internationally. While most scientists agree that the LNT model offers a reasonably conservative guide for establishing standards, they know it’s based on an estimate—and they understand that, eventually, studies will pinpoint the exact effects of radiation at low doses.
This last point is particularly important to me, because in 1980 I worked as a summer engineering student at a research nuclear reactor; and like all employees who worked around or near the reactor, I received doses of radiation. Before the summer ended, I was given a whole-body scan in a machine similar to a CT scanner to see if I suffered any ill effects during my short four-month internship. None was detected; equally important, my radiation monitor (a thermoluminescent dosimeter, or TLD) registered a low dose. I think it was 17 millirems), which is equivalent to 0.17 mSv, well within safety standards. So I was “safe.” (Today, for example, the Canadian Nuclear Safety Commission lists the annual dose limit as 50 mSv).

But was I? To be sure, I was certainly within government and industry regulations. But, is this sufficient? Is it a surprise that I was diagnosed with colorectal cancer in 2012? Or was this a random non-correlating event? A mere coincidence? family history? the misfortune of a bad genes? I have no proof of any connection, nor am I willing or have any desire to look for any. The only question that concerns me today is what I can do to limit my exposure to ionizing radiation to only what is medically necessary.

Tomorrow, for example, I am going for a CT scan of my lungs and abdomen (expected dose of radiation: 102 mSv, a not-insignificant dose, but much lower than what an individual undergoing radiation treatment for cancer typically receives). This will be my sixth CT scan in less than three years. It is important to remember that there is an cumulative effect to exposure to radiation.

There are important questions and concerns that many of us today face, One being that science has not yet obtained sufficient understanding of radiation and its effects to humans to know what is really a safe amount of radiation. Then there are the non-medical cases. As is the case with newer technologies, radiation has the ability to do both good and bad, the trick it seems is to determine and thus know the boundary lines between the two. This is important, because if we regularly use a technology like radiation for good purposes (like X-rays, cancer diagnosis and cancer treatment), we ought to know its full effects on the human body, including its risks to well-being and health.

For more, go to [FP]

Today is Canada Day, a celebration and recognition of our nation’s birth on July 1, 1867, a national holiday with the usual and expected fireworks and festivities. To all my fellow Canadians, Happy Canada Day.

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