Posted on 06/29/2005 4:09:18 PM PDT by NormsRevenge
WASHINGTON – Even very low doses of radiation pose a risk of cancer over a person's lifetime, a National Academy of Sciences panel concluded Wednesday. It rejected some scientists' arguments that tiny doses are harmless or may in fact be beneficial. The findings could influence the maximum radiation levels that are allowed at abandoned reactors and other nuclear sites. The conclusions also raise warnings about excessive exposure to radiation for medical purposes such as repeated whole-body CT scans.
"It is unlikely that there is a threshold (of radiation exposure) below which cancers are not induced," scientists said in the report.
While at low doses "the number of radiation-induced cancers will be small ... as the overall lifetime exposure increases, so does the risk," the experts said.
Scientists for years have debated how extremely low doses of radiation affect human health.
Pro-nuclear advocates, as well as some independent scientists, have maintained that the current risk models for low-level radiation has produced more stringent requirements than is necessary to protect public health.
It is an issue in determining decontamination requirements at abandoned reactors and at federal weapons sites.
The academy's panel stood by the "linear, no threshold" model that generally is the acceptable approach to radiation risk assessment. This approach assumes that the health risks from radiation exposure decline as the dose levels drop, but that each unit of radiation – no matter how small – is assumed to cause cancer.
"The scientific research base shows that there is no threshold of exposure below which low levels of ionized radiation can be demonstrated to be harmless or beneficial," said Richard R. Monson, the panel's chairman. He is a professor of epidemiology at Harvard's School of Public Health.
The panel said new and more extensive data developed over the past 15 years only strengthen the conclusions of the panel's last report, in 1990, on low-level radiation risks.
The scientists estimated that one out of 100 people exposed to 100 millisievert of radiation over a lifetime probably would develop solid cancer or leukemia, and that half of those cases would be fatal.
It also said that 42 additional cancers can be expected in the same group from other than low-level radiation sources.
A millisievert is a measurement of radiation energy deposited in a living tissue. People absorb about 3 millisievent of radiation annually from natural sources and 0.1 millisivert every time they get a chest X-ray.
The report noted that exposure from a whole body CT scan is about 10 millisievert, much higher than a normal X-ray. That raised concerns about the frequency of such medical diagnostics.
The report should not scare people away from nuclear medicine, said Dr. Henry Royal, a professor of radiology at Washington University in St. Louis. He said most often the benefits of such tests and treatments outweigh the risks.
But Royal also said that procedures such as CT scans should be used to deal with a specific medical problems and not part of annual medical screenings. "You should not be exposed to radiation for superficial reasons," Royal said in a telephone interview.
Some anti-nuclear advocates said the study reaffirms that stringent regulations are needed when cleaning up abandoned nuclear sites or considering health risks near nuclear power plants.
"The NAS panel puts to rest once and for all claims that low doses of radiation aren't dangerous ... nuclear advocates have been making this claim for years" said Daniel Hirsch, president of Committee to Bridge the Gap, a Los Angeles-based nuclear watchdog group.
Mitchell Singer, a spokesman for the Nuclear Energy Institute, the industry's lobbying arm, said the report "is a positive finding. It shows there is very little risk of exposure from low levels of radiation."
The academy is a private organization chartered by Congress to advise the government of scientific matters.
Living in the material universe in a physical body.....hazardous!
"When life appeared in the geological record, it incorporated potassium which gave it a radiation dose almost 7 times higher than typical contemporary lifeforms endure. This would both argue for a higher mutation rate, but also constrain the complexity by rendering a long genome with low redundancy too unreliable in such a high radiation environment.From: www.fourmilab.ch/documents/k40.htmlCould it be that the long delay between the emergence of protists and metazoans -- about 2.5 billion years, was due to the need for endogenous K-40 radiation to abate to a level compatible with the vastly greater complexity of eukaryotic metazoans? "
They still have a reputation. Probably because they stay out of politics as much as possible.
Trajan88
Reading this post will cause cancer.
They still have a reputation.OH yeah ...
"A Closer Look at Global Warming" www4.nationalacademies.org
So, now that the US is poised on a nuclear comeback, these stories start coming out AGAIN! The same crap as was being put out by the anti-nuclear crowd in the '70's and '80's. Let's see some articles and truly serious discussions on hormesis. The LNT crowd screams and threatens anyone who tries to discuss this 'heretical' notion.
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