Scientific Jigsaw Puzzle: Fitting the Pieces of the Low-Level Radiation Debate

New submitter Lasrick writes "Skip past the dry abstract to Jan Beyea's main article for a thorough exploration of what's wrong with current 'safe' levels of low-level radiation exposure. The Bulletin is just releasing its 'Radiation Issue,' which is available for free for two weeks. It explores how the NRC may be changing recommended safe dosages, and how the studies for prolonged exposure have, until recently, been based on one-time exposures (Hiroshima, etc.). New epidemiological studies on prolonged exposure (medical exposures, worker exposures, etc.) are more accurate and tell a different tale. This is a long article, but reads well." Here's the free, downloadable PDF version, too.

Comments

Short summary

[Anonymous Coward]

Ionizing radiation causes cancer. More ionizing radiation causes more cancer. There is no "safe dose", though there is a certain unavoidable dose. So we're all at risk of cancer if we live long enough.

Re:Short summary

[MozeeToby]

Exposure is always expressed in amounts over the background rate. So "Lower than background level" effectively means exposure to up to 2x the background level (background level + artificial); there's nothing illogical about being worried about it (though I wouldn't personally be concerned about a ~.0025 Sv per year exposure rate).

As for the rest of your comment, if you read the paper the summary links to, you'll see that all the evidence is pointing toward all exposure (presumably below radiation poisoning levels) carrying approximately the same relative risk. It doesn't matter high or low energy, it doesn't matter if you're exposed in 10 minutes or 10 years. Your total exposure level linearly maps to your risk of cancer (and, new information to me at least, heart attack and stroke).

Re:Short summary

[History's Coming To]

Your best bet is to read a high-school level introduction. Concisely, there are three types of radiation from radioactive atoms, alpha, beta and gamma. Alpha is a He nucleus, two protons and two neutrons - it can do a huge amount of damage to living cells, but is easily stopped by, eg, a sheet of paper. Beta is a high speed electron, less damaging but will penetrate clothing etc. Gamma is nasty - it can travel through a reasonable thickness of lead and still do harm.

If we look at the Uranium example, it gives off alpha, so you'd probably be quite safe with it on the other side of the room. Handling it, on the other hand, is an easy way to accidentally ingest some, which would probably be more harmful because it's then inside the body (this goes for any ionizing radiation source). When you see people being showered off after radiation exposure it doesn't stop any harm thats already been done, just reduces the chances that they are still in contact with a source.

This all ignores the fact that Uranium decays into several other isotopes which give off their own idiosyncratic radiation in turn, and a bunch of other things.

protracted exposure

[sl4shd0rk]

Like fallout from nuclear testing and nuclear disasters.

Re:protracted exposure

[Volante3192]

And emissions from coal fired plants...and living in a concrete building...

Re:Low level radiation

[InterGuru]

There might be a level at which radiation is beneficial. This is called hormesis

From Wikipedia

Hormesis (from Greek hórmsis ...) is the term for generally favorable biological responses to low exposures to toxins and other stressors. A pollutant or toxin showing hormesis thus has the opposite effect in small doses as in large doses

The concept is vigorously debated, but has been shown to work in some animal experiments. In humans, small doses of alcohol, a toxin, seems to improve heart health.

Humans, as all life, have evolved under low level background radiation. We may be adapted to it.

Anti-nuclear publication

[bradley13]

Do note that the "Bulletin of the Atomic Scientists" is a generally an anti-nuclear, scare-mongering publication. These are the people whose count-down to nuclear disaster has been just a few minutes before midnight for decades. Whatever they publish should be viewed with this in mind.

Scanning RFTA, in the end, it says basically nothing at all. They did no studies themselves, but just looked around at ones already done. The key points seem to be:

• The same total exposure in the form of long-term exposure may be slightly (20%) more dangerous than the same dosage in a short, high-intensity form.
• They desperately search for something to say about low-level, long-term exposure. They spend pages talking about the competing theories, from "Supralinear response" (really dangerous) to "Adaptive response" (a little radiation is healthy). In the end, they find no convincing evidence one way or the other, because the uncertainty bounds at such low levels include essentially all possibilities.
• Based on this lack of evidence, they conclude that low levels of radiation are really dangerous, and that all Western populations are "primed for radiation-induced, delayed cancers from releases from nuclear reactors".

In the end, given the publication, the conclusion was obvious.

Re:Extended exposure is riskier, and no superpower

[vlm]

The standard /. car analogy breaks down in that running my car engine up to 80% of redline RPM for a half hour a day is a pretty stupid idea that will only wear it out faster. Yet daily aerobic exercise seems to be a brilliant idea for long term cardiovascular health.

You can also have hilarious fun making vaccine analogies. "You mean, you'd intentionally inject small amounts of possibly fatal microbes into a healthy body? Madness I tell you! Madness!" Sadly there are highly educated actresses and pr0n models who pretty much use this argument when providing their valuable medical advice, along with the usual folks doing the FUD-for-profit thing.

Re:Bad article, little information [Re:Short summa

[AdamHaun]

Of course. The question is, how much more cancer is caused by a given dose of radiation?

Unfortunately, this is a question that the paper in question does not answer, because it completely neglects to mention actual numbers. (The pretty colored graphs have units of "excess relative risk." How do you convert that to deaths? You can't. What are the units-- per year? Per lifetime? they don't say. Relative to what? They don't say.) I'd like to see a number, like "excess cancers per year per sievert of exposure," but they don't give one. They compare different studies, but never discuss whether the differences are statistically significant.

As the article states, the graph is taken from another study, Preston et al (2007) Solid Cancer Incidence in Atomic Bomb Survivors: 1958–1998. You can find many tables with actual numbers there. The caption on the graph also answers some of your questions:

FIG. 3. Solid cancer dose–response function. The thick solid line is
the fitted linear gender-averaged excess relative risk (ERR) dose response
at age 70 after exposure at age 30 based on data in the 0- to 2-Gy dose
range. The points are non-parametric estimates of the ERR in dose categories.
The thick dashed line is a nonparametric smooth of the categoryspecific
estimates and the thin dashed lines are one standard error above
and below this smooth.

Re:Low level radiation

[girlintraining]

I know that hormesis sounds like a crackpot theory along with holistic super-diluted medicinal honey therapy, but some of the greatest minds in Medical Physics believe it exists.

Extraordinary claims demand extraordinary evidence. Wikipedia is not evidence of any variety. It is commonly held, and backed by numerous studies, that ionizing radiation is harmful. non-ionizing radiation may be harmful, in cases where it causes heating of the tissue (especially eyes), or electrical discharge. Hearing that the "greatest minds" in medicine believe something is disappointing; In their field, I would hope they don't practice medicine based on belief... I would hope they do it based on facts, evidence, working theories, etc.

Altitude [Re:Bad article, little information]

[Geoffrey.landis]

Well, it would correlate with latitude as well.

That is, if cosmic radiation were in fact the main location-dependent factor that caused cancer.

But since cosmic radiation dose is something on the order of 0.5 millisievert per year, it's probably not significant enough to see the signal over the noise, assuming that there are other sources of cancer.

Berkely Lab study suggests LNT is wrong

[JSBiff]

From what I understand, this is not absolutely definitive, but cancer researchers at Lawrence Berkeley Lab published a paper where they used imaging of cellular responses to radiation damage to show that at low levels, it appears that cells repair DNA damage due to radiation very effectively.

Seriously, follow that link, and learn.