Talk:Carbon-14

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Elements / Isotopes  (Rated B-class, Low-importance)
WikiProject icon This article is supported by WikiProject Elements, which gives a central approach to the chemical elements and their isotopes on Wikipedia. Please participate by editing this article, or visit the project page for more details.
B-Class article B  This article has been rated as B-Class on the quality scale.
 Low  This article has been rated as Low-importance on the importance scale.
Taskforce icon
This article is also supported by the Isotope Taskforce.
 

I think this article, though short, is complete as the radiocarbon dating article covers the magority of important facts about this. Hence I remove the stub label.--LukeSurl 14:09, 26 Mar 2005 (UTC)


I agree that it doesn't need to be called a stub, but I would like it if someone would add some information about how C14 is industrially produced. I don't know the answer myself (that's what I went to Wiki for) other wise I would add it. --Road Not Taken 09:41, 21 Jan 2006

See the article radionuclide Jclerman 17:48, 21 January 2006 (UTC)

The production of C-14 by O-17(n,alpha)C-14 is a major source in the CANDU industry. Perhaps it should be included?--209.167.53.3 (talk) 16:57, 25 February 2010 (UTC)


C14 Controversy[edit]

This article lacks information about the controversy surrounding C14 dating as already published on other websites and in reference books. See, for example, http://www.answersingenesis.org/articles/nab/does-c14-disprove-the-bible . — Preceding unsigned comment added by 114.30.102.170 (talk) 14:07, 2 November 2012 (UTC)

Controversy? What controversy? answersingenesis.org has its own page here. The page you link, however, is controversial. But it's not mentioned on the Carbon-14 Wikipedia page so there's not problem with it.--83.208.175.71 (talk) 17:04, 19 February 2013 (UTC)

carbon 14 half-life[edit]

I have read from different sources in the internet that the half-life for C14 is 5715 years. Yet, here in wikipedia it appears as 5730 years. Does somebody know which the correct answer is?

See [1] for the best value as determined some years ago. As far as radiocarbon dating, the difference is not relevant since raw (Libby) dates are calibrated into calendar dates as described here [2] Jclerman 03:27, 26 January 2006 (UTC)

box[edit]

COMMENTED OUT UNTIL AN EXPLANATORY CAPTION (clarifying the meaning and relationship of each one of the entries) IS WRITTEN FOR THIS BOX:


Lighter:
Carbon-13
Carbon-14 is an
[[Isotopes of Carbon|isotope]] of [[Carbon]]
Heavier:
Carbon-15
Decay product of:
Nitrogen-18
Boron-14
Decay chain
of carbon-14
Decays to:
Nitrogen-14

Age/dating calculations[edit]

I removed the calculations as the Radiocarbon dating article is the place for them and already contains adiquate discussion of correct and accepted calculations. --Vsmith 01:05, 26 June 2006 (UTC)

User:Pce3@ij.net has previously tried to insert his/her simplified calculations improperly in Half life as well as creating a fork article which has been deleted per AFD, see Wikipedia:Articles for deletion/Half-life computation. Vsmith 01:12, 26 June 2006 (UTC)

deletions for benefit of authors and not readers - think about this...[edit]

When the wants of authors are placed above the needs of readers then other wikis such as the Urban dictionary will begin to take the Wikipedia's place along with the potential of financial contributions. ...IMHO (Talk) 01:17, 26 June 2006 (UTC)

It has been noted[edit]

Could a reference for this statement be included?

"It has been noted that Carbon-14 levels in oil deposits appears to be positively correlated with radioactivity in rocks surrounding the oil deposit."

Dan Watts 18:10, 5 March 2007 (UTC)

Activity[edit]

The activity of modern standard radiocarbon is about 14 disintegrations per minute (dpm) per gram carbon (ca. 230 mBq/g).

I first thought that this means that if you have one gram of Carbon-14, then 14 atoms will disintegrate per minute, but I didn't like the phrase "per gram carbon". Then I played with the numbers and clearly this is not what the statement means. Rather, it appears if you take one gram of modern standard carbon (where is that defined?), then 14 of the contained Carbon-14 atoms will disintegrate per minute. With this interpretation, the phrase "activity of modern standard radiocarbon" seems misleading. It is not really the radiocarbon that is modern standard, it is the proportion of radiocarbon in carbon that is modern standard. I'm struggling to find a better formulation. AxelBoldt 16:17, 15 April 2007 (UTC)

The relevant standard(s) is(are) defined in [3]. Please refer to them with the NIST language. If it appears incorrect to you, contact the NIST and propose your nomenclature. Jclerman 17:18, 15 April 2007 (UTC)
Well, looking at the link the phrase "modern standard radiocarbon" does not appear to be NIST nomenclature.
I have a hard time making sense of that link though; maybe our article can explain it better. Among several others, they seem to speak of "principal modern radiocarbon standard", "International Radiocarbon Dating Standard", "absolute radiocarbon standard", "Oxalic acid standard", "Oxalic acid II standard", and I don't know which, if any, of these are synonyms, and which of these our article refers to when it says "mondern radiocarbon standard". In fact, I'm even unclear what these standards are - just certain well-defined substances? Also I don't see the number 14 dpm anywhere.
Here's my current best guess: NIST prepares a certain batch of oxalic acid and declares it "standard", mainly to fix the proportion of C-14 atoms. Now if you took an amount of this oxalic acid that contains precisely 1 gram of carbon, and waited for a minute, then 14 of the C-14 atoms would have disintegrated. Is that the intended meaning of the sentence in the article? AxelBoldt 19:38, 15 April 2007 (UTC)
Yes. The wiki article is not a lab manual. Readers who want to do their own measurements can read the details in the NIST site. Also, this article doesn't need to overlap with info in the radiocarbon dating article. Jclerman 22:37, 15 April 2007 (UTC)
I agree, it's not a lab manual, but it must be self-contained and the meaning of all statements must be clear without having to guess or read obscure external sources; or else the statements are better removed. (Especially if they are unsourced, as the 14 dpm number currently is.) AxelBoldt 04:41, 18 April 2007 (UTC)

The article as it is now states the activity of the modern radiocarbon standard, but does not define it; the standard is not discussed in the radiocarbon dating article either. Jclerman, is the definition of the modern radiocarbon standard outside the scope of both this article and the radiocarbon dating article? Whosasking (talk) 05:10, 22 February 2008 (UTC)

In my opinion details about the sample used as standard and the standard activity belong to the lab and not to a general encyclopedia. For the sake of completion the one would have to describe and discuss the backround sample used as blank, the C13 graph9ite and belemnite standards, etc. Jclerman (talk) 18:52, 22 February 2008 (UTC)
If you do this calculation
dN/dt = -λN
λ = ln2 / t1/2
= ln2/(5730*365.25*24*60) = 2.3e-10
per mole: 2.3e-10 * 6.022e23 = 1.38e14
C14 is 1ppb: 1.385e14 / 1e12 = 138.5
per gram: 138.5/12 = 11.5 disintegrations per minute
why is there a discrepancy with the "standard" answer? 129.31.72.52 17:10, 13 May 2007 (UTC)
You are asuming that the natural abundance of C-14 is 1.000 parts per trillion. Is that figure correct or it should be approx 1 pp-trillion? Jclerman 19:28, 13 May 2007 (UTC)

elevated C-14 in oil deposits[edit]

It has been noted that carbon-14 levels in oil deposits appears to be positively correlated with radioactivity in rocks surrounding the oil deposit.

I've removed this sentence form the article until it can be verified. Whosasking 20:18, 3 June 2007 (UTC)

It is worth noting that instrumental background levels of 14C are often in the 40,000 year range, so in such systems carbon older than that will have that apparent age. —Preceding unsigned comment added by Cwmagee (talkcontribs) 10:21, 24 March 2010 (UTC) Cwmagee (talk) 10:23, 24 March 2010 (UTC)

i'd like to see a descritption of the decay reaction from C14 to N14.[edit]

thanks Wikiskimmer 07:13, 30 June 2007 (UTC)

See: http://en.wikipedia.org/wiki/Radiocarbon_dating#Basic_physics. Jclerman 08:14, 30 June 2007 (UTC)
Hmm.. that's odd. should there be two separate articles? confusing! Wikiskimmer 17:40, 30 June 2007 (UTC)
One is about dating. Jclerman 19:44, 30 June 2007 (UTC)
still, there is alot of overlap, and in the carbon 14 page the decay equation:
\mathrm{~^{14}_{6}C}\rightarrow\mathrm{~^{14}_{7}N}+ e^- + \bar{\nu}_e
is not present. when i looked for it, it did not occur to me to look for it in the article on RADIOCARBON DATING! i still say it's confusing. Wikiskimmer 06:21, 1 July 2007 (UTC)
Sectionized the article and added a Radiocarbon dating blank section with a See main tag to make the link more obvious. A brief summary could be added to the empty section, but it's all just a click away. Vsmith 14:39, 4 July 2007 (UTC)

C-14 and DNA[edit]

I would like to know if C14 present in DNA molecules could affect in some way the behaviour of this complex system of reproduction, to say, mutations.--Jorgeluismireles 01:43, 13 May 2006 (UTC)

A paragraph citing "Williams, C.P. Recycling greenhouse gas fossil fuel emissions into low radiocarbon food products to reduce human genetic damage. Environmental Chemistry Letters. 2007 May 23 (online). DOI: 10.1007/s10311-007-0100-7". Retrieved 2007-06-28. , was contributed by Biochem92. The paper proposes that

...human genetic damage can be significantly reduced using low radiocarbon foods produced by growing plants in CO2 recycled from ordinary industrial greenhouse gas fossil fuel emissions...

Since the paper is recent (and hasn't had time to be reviewed by the community), and since the author of this "proposal" is in the business of selling isotopically-enriched nutritional supplements, I've moved the claims here for discussion. Does a "proposal", written by an interested party, published in Environmental Chemistry Letters, qualify for inclusion in an encyclopedia? Whosasking 01:21, 5 July 2007 (UTC)
Well, technically it looks like it has been peer-reviewed by the community (= 2+ reviewers). After all, it is published in a proper scientific journal from a reputable publisher - and that's no mean feat. It's probably fairer to say that there hasn't been time for the wider community to comment on its findings (which might take the form of comment by omission - that is, no citations for the paper). But, as far as I can tell, it has been through the peer-review mill, so it shouldn't be saying anything that's too questionable. That said, I'd have thought that other sources of radiation (ultraviolet, cosmic rays) were at least as significant (if not more so) than ingested 14C - which, after all, isn't terribly radioactive (c.f. 32P). And some of the conclusions of the paper (e.g. regarding terrorism) are fairly bizarre. Anyway, while I must admit that my eyebrows raised when I read the section on 14C in food, I don't think your criticism of it as a "proposal" entirely holds up. It is a proper scientific paper. Still, until this subject is written about more widely (the paper's reference list doesn't appear to contain any similar works), I concur about removing it from the article. The idea simply hasn't established itself as notable. Cheers, --Plumbago 09:15, 5 July 2007 (UTC)

Wrong nuclear reactions[edit]

[Thoughtless and stupid comment removed by the author.] 147.231.12.9 14:31, 16 August 2007 (UTC)

Hi 147.231.12.9. I've responded to this back over at Radiocarbon dating. I thought I'd better leave a note here to direct any discussion to the one place. Cheers, --Plumbago 14:33, 16 August 2007 (UTC)

A note on C14 production in geologic strata[edit]

I thought it would be best for me to provide here some relevant information regarding my edit to the "Carbon-14 and fossil fuels" section, where I changed edited the last part of it to read "Presence of carbon-14 in the isotopic signature of a sample of carbonaceous material therefore indicates its possible contamination by biogenic sources or the decay of radioactive material in related geologic strata." C14 is produced in the ground by the radioactive decay of uranium and thorium. I'm sure more digging around would provide many additional references, but here are just three:

Excess carbon-14 abundances in uranium ores: Possible evidence for emission from uranium-series isotopes by D. Barker, A. J. T. Jull, and D. J. Donahue (Geophysical Research Letters, Volume 12, Issue 10, p. 737-740 [1985]) http://adsabs.harvard.edu/abs/1985GeoRL..12..737B

Carbon-14 Abundances in Uranium Ores and Possible Spontaneous Exotic Emission from U-Series Nuclides by A. J. T. Jull, D. Barker, and D. J. Donahue (Meteoritics, Vol. 20, p.676 [Dec. 1985]) http://adsabs.harvard.edu/abs/1985Metic..20..676J

14C in uranium and thorium minerals: a signature of cluster radioactivity? by R. Bonetti, et al (European Physical Journal A, Vol. 5, No. 2, 235-238 [Jun. 1999])

As you can see, geophysicist and physicists working in this particular area of study have been aware of this underground production of C14 for some time. —Preceding unsigned comment added by Greeneto (talkcontribs) 07:08, 17 October 2007 (UTC)

Just to clear up a little problem that some can have with Uranium and Thorium in coal.
Since most coal comes from old peatbogs AND since Uranium and Thorium have higher solubility in oxidicing water than in reducing water and since Uranium and Thorium is disolved from the rock if present and since groundwater changes from oxidicing to reducing in the peatbog, coal DO concentrate Uranium and Thorium together with other heavy metals with the same reaction! In fact some peatashes are that radioactive from Uranium and Thorium that they could be classed as radioactive waste!Seniorsag (talk) 14:34, 6 February 2012 (UTC)

It is good to see that work is being done on this. At the current measurable ratio of 14C/C (~10-15) (from Carbon-14 Abundances in Uranium Ores and Possible Spontaneous Exotic Emission from U-Series Nuclides by A. J. T. Jull, D. Barker, and D. J. Donahue(Meteoritics, Vol. 20, p.676 [Dec. 1985])http://adsabs.harvard.edu/abs/1985Metic..20..676J above) this implies that there is roughly an equal amount of uranium to carbon in the deposits (2X10-15 14C/U). The reactor community should be ecstatic over this news. Also, bacteria in situ couldn't reasonably affect 14C/C ratios unless there were weekend trips to the earth's surface. If these are the best references on the subject, it appears to me that labelling it an open question is more accurate. Dan Watts (talk) 18:27, 9 January 2008 (UTC)

All this is interesting, inasmuch as it's worth emphasizing that the "exotic" process being discussed in these papers is the so-called cluster decay emission of C-14 nuclei from certain nuclides of Rn and Ra. This is not the same process as spontaneous fission or induced fission, and in natural ores of U produces a good deal more C-14 than would be predicted from those other fission mechamisms. Some of these uranium daughter isotopes selectively emit C-14 nuclei as though they were alpha particles! But not C-12 or C-13. C-12 is emitted by a few other isotopes, but C-13 not by anything.

BTW, I don't understand the comment about the "reactor community" above. SBHarris 18:53, 9 January 2008 (UTC)

Considering that the referenced paper measured total 14C/U concentrations, then according to this logic, there must be ~ the same number of uranium atoms as carbon in the oil (or coal) deposits for this proposed mechanism to be the cause of the measured 14C. Dan Watts (talk) 23:12, 9 January 2008 (UTC)
I see your point, but all that supposes that C-14 stays in place, and there's no more reason to think it does, than the helium from alphas from U and Th does. A naked C-14 nucleus is going to go to gas: it will react chemically with just about anything, and I suppose will probably end up stripping O off silicate in the crust (O is the most common crustal atom) gassing out as CO. From there it may wind up in carbon deposits by whatever mechanism it is that helium winds up in natural gas at concentrations of up to 7%. And yes, almost all that He is retired alphas, because it's depleted of primordial He-3 by a factor of 100 or so. Of course, since C-14 isn't immortal but has a half life of < 6000 y, the CO carrying it will not show up as anything like 7%... SBHarris 06:59, 12 January 2008 (UTC)
It appears your understanding differs from the authors of http://adsabs.harvard.edu/abs/1985GeoRL..12..737B since the decay branching ratios of 14C they are discussing are based upon their measurement of in situ 14C. Dan Watts (talk) 22:48, 12 January 2008 (UTC)
Well, not my fault if they missed the obvious inference that the same thing will happen to C-14 nuclei created in U deposits, as happens to C-14 nuclei created in the atmosphere. Q: Which seems more likely to you: that the authors missed a mechanism, or that there really is as much uranium as carbon-12 in the average carbon deposit? You've pointed out a calculation YOU did which is inconsistant with a published paper, and contradicts known data. Okay, I pointed out a mechanism I know of, which is missed in the paper, and would tend to explain known data. Which of us is more likely to be right? If you're right, there's a mechanism missing for getting C-14 out of U deposits and into C deposits, since there surely isn't that much U in C deposits. You don't like my mechanism, even though it is strictly analogous to the way He is known to get from U deposits into C deposits. Okay, then, where's yours? SBHarris 17:41, 24 January 2008 (UTC)
I don't like your method because there is no good reason for 14C to behave like He. C is not a noble gas. It has valence electrons which can (and will) form covalent bonds. And (to answer the Q:) it seems more likely to me that there hasn't been enough time for earth's primordial 14C to disappear. I still believe that the most charitable thing to say concerning 14C in fossil fuel is that there are theories and no concensus.Dan Watts (talk) 19:31, 24 January 2008 (UTC)
C-14 produced in the atmosphere rapidly oxidizes to CO2, a fairly inert gas (as seen by its presense in natural gas, which is typically 1% CO2 or so). There's no use arguing that CO2 will react with something else in the deep earth, because it's typically present in natural gas, and that's a simple fact that you can't get away from. In U ores, you'd expect that oxygen in silicate would be the first thing C12+ would react with. So, helium production in U ores should mirror 14-CO2 production in them, and 14-CO2 in petroleum deposits should stay there with the rest of the CO2.

As for primordial C-14 still being around, you're kidding, right? How old are you assuming the Solar system is?? 4.5 B years is 775,000 half lives, and 2 raised to that power is 10^234,000, a number so gigantic it's inconceivable. If all the atoms in the universe (10^80) were C-14 that long ago, there wouldn't be a single one left by now. SBHarris 20:05, 24 January 2008 (UTC)

SBharris--so why don't you include this theory of yours in the Wikipedia article?207.81.62.86 (talk) 07:54, 5 May 2010 (UTC)
So, how many 14C are likely to be generated per radioactive atom, and what is the ratio of radioactive atoms to fossil fuel C atoms in the same geologic deposit? (And, yes, 14C in the oil doesn't give the earth a long history.) Dan Watts (talk) 20:40, 24 January 2008 (UTC)
Dan Watts is a young earth creationist. He assumes on the basis of Genesis in the Bible that the earth has not been in existence more than several thousand years. So here's the deal, editors, right now we have a young earth creationist systematically contaminating the Carbon-14 page with misinformation, as motivated by his belief in a religious dogma. Every edit by Watts needs to be examined thoroughly, and either corrected or removed. I would do it myself but at the time right now that I'm writing this (where I've just discovered what Watts has been doing) I don't have the time to dig into this (though I'll be coming back later on to do some further investigation). As one example of the misinformation he's put in the article is where he wrote, "measured amounts of 14C/U in uranium-bearing ores imply vast quantities of uranium, roughly half as much as the carbon in the deposits, to supply the 10-15 14C/C measured" and then gives a citation. But the citation doesn't actually back up what he wrote. Todd Greene
Todd--just visiting, and I do hope you're not committing the Fallacy of Poisoning the Well. After all, Science doesn't care if a Wikipedian is a a Wife Beater or a 'UFO nut' or even a CSICOPophile :) Asides from putting in false info, that is. That said, one thing that I'm very curious aboot the possible explanation for the C-14/uranium connection is shouldn't that mean that shouldn't there be some symmetry there? Where abundant C-14 is found in coal, then abundant uranium is found as well? If so, is that the case? I'm just asking because the 'possible explanations' in that particular section of the wikipedia article seems rather theoretical to me...207.81.62.86 (talk) 07:54, 5 May 2010 (UTC)
Paul Giem is a Seventh Day Adventist who teaches *medicine* at Loma Linda University (a Seventh Day Adventist school). Giem has never published a single research article in a professional science publication on carbon-14, radiophysics, radiometric dating, geology, or geophysics in his life. Why is Giem being cited as substantiating anything in this article? Answer: A young earth creationist has been corrupting this article with misinformation. We have some editing to do. Todd Greene —Preceding comment was added at 17:51, 25 February 2008 (UTC)
I forgot about the four tildes (I have not actively edited here in quite awhile), so I'll get that right this time. Dan Watts had added the following phrase: "although measured amounts of 14C/U in uranium-bearing ores imply vast quantities of uranium, roughly half as much as the carbon in the deposits, to supply the 10-15 14C/C measured." He put in this citation in support of that: "Abundances in Uranium Ores and Possible Spontaneous Exotic Emission from U-Series Nuclides" by A. J. T. Jull, D. Barker, and D. J. Donahue (Meteorics, vol. 20, Dec. 1985, p. 676). Of course, in that brief note written by them - please go read it - they clearly state that "we are left with the interpretation that 14C decay of a nuclide in the U-decay series is responsible for most of the observed 14C." Additionally, they do not say anything about the measured amounts implying any "vast quantities of uranium." As seen in discussion above, that idea is merely being imposed on the article without justification by Dan Watts. When a scientist tells you one thing, and a young earth creationist tells you something quite different yet pretends that the scientist backs up what the young earth creationist has told you, then you know that the scientist is being misrepresented. That is the case here. Greeneto (talk) 21:03, 25 February 2008 (UTC)

<outdent> Okay. Yes, we have some cleaning to do. The oldest moon rocks have been dated to 4.5 B years by 4 different methods, all giving the same answer. This either requires a malicious god to screw up the isotope ratios (for no single mechanism will make 4 processes with 4 different rates, all pop out the same number), OR else the Earth is 6 thousand years old and the moon is 4.5 billion years old. Boy, that's some set-design. Anyway, direct C-14 dating of cave deposits goes back 40,000 y at least, and tree ring data far longer than 6,000 years. You can see hundreds of thousands of snow deposit yearly-rings in ice from antarctica. A young Earth dating to a few thousand years in the face of such obvious stuff, is madness.

And look what kind of arguments I'm getting in return, by people who don't like the ideas. CO2 is not an inert case but He is? Sure, but CO2 is inert ENOUGH. It's going to difuse through dry or hot rock. It's already in natural gas, showing that this is so. I think that's pretty much the end of that argument. SBHarris 21:22, 25 February 2008 (UTC)

I haven't seen any numbers being proposed for the number of 14C nuclides/radioactive atoms or the number of radioactive atoms per C. You don't like the numbers calculated from the Jull reference, are there any quantitative values with which to replace them? Dan Watts (talk) 02:32, 3 March 2008 (UTC)

[Removed comment; article was correct after all]

Peer Review[edit]

[peer review template removed; duplicated at top of page. Dr pda (talk) 10:37, 18 January 2009 (UTC)] --CyclePat (talk) 21:53, 20 October 2008 (UTC)

humm! I just noticed a potential fork Carbon 14 dating. --CyclePat (talk) 22:35, 20 October 2008 (UTC)

Did Chernobyl disaster produced this isotope?[edit]

Did the Chernobyl disaster produced this isotope?RBMK reactors used graphite as their moderator.Does graphite became full of this isotope in a nuclear reactor?Agre22 (talk) 22:54, 21 February 2009 (UTC)agre22

That depends heavily on the amount of neutron radiation absorbed. I was under the impression that it was mostly electrons, neutrons, and photons. In other words: Beta, thermal neutron, and (low nanometers) Gamma radiation. Most of that would have been turned into heat and atoms like C-13. Can someone more familiar with this such as a physicist or environmentalist tell us how much of the carbon actually absorbed alpha rays, beta rays, and neutrons? C-14 was measured in fallout.71.196.246.113 (talk) 00:50, 9 May 2012 (UTC)

first passage[edit]

The first passage of this article talks about the history of carbon-14. I think that this should be in a history section. the first passage should concentrate on introducing carbon-14 to the reader. Lea phys (talk) 12:05, 21 January 2010 (UTC)—Preceding unsigned comment added by Lea phys (talkcontribs) 15:22, 19 January 2010 (UTC)

I see what you're getting at, but the history portion is only the tail end of the opening sentence. It's not as if it dominates the lead to the article, in fact it's probably a bit short for a history section. Perhaps the lead could be shuffled somewhat so the history does not appear in the very first sentence? --PLUMBAGO 12:34, 21 January 2010 (UTC)

Is ionizing radiation, including that resulting from beta emissions from carbon-14 an under-acknowledged primary cause of human cancers[edit]

Tim doe (talk) 02:22, 12 April 2010 (UTC)Is ionizing radiation, including that resulting from beta emissions from carbon-14 an under-acknowledged primary cause of human cancers?


There is no doubt that ionizing radiation can and does cause cancer in humans. Radioactive atoms produce ionizing radiation when they decay and most carcinogens contain some radioactive atoms. This paper presents the case that many cancers are ultimately caused by the ionizing radiation resulting from radioactive decay. This proposition is supported by the observation that the histology of cancers known to be caused by radiation are indistinguishable from the histology of cancers currently not considered to be related to radiation.

Some elements exist naturally as a mixture of stable isotopes and unstable radioactive isotopes (see Appendix). These radioactive isotopes are referred to as radioisotopes or radionuclides. When a material contains one or more of these elements it will contain a (small) proportion of radionuclides which emit radiation. If this material is ingested by an organism the radionuclides may become incorporated into the cells of the organism along with the stable isotope.

Radionuclides may release alpha particles (which are the nuclei of helium), beta particles (which are quickly moving electrons or positrons) and/or gamma rays. All these particles and waves that are released may be ionizing. Ionizing radiation consists of highly energetic particles or waves that can detach (ionize) at least one electron from an atom or molecule. Alpha and beta particles can be ionizing and cause most damage to humans when they are emitted inside the body. An ionization event normally produces a positive atomic ion and an electron. The negatively-charged electrons and positively charged ions created by ionizing radiation can cause damage in living tissue. If the dose is sufficient, the effect may be seen almost immediately, in the form of radiation poisoning. Lower doses can cause cancer (1). Gamma rays are less ionizing than either alpha or beta particles, but they are more penetrating. The damage gamma rays produce is similar to that caused by X-rays and this damage includes burns and also cancers.

“Ionizing ability depends on the energy of individual particles or photons, and not on their number. The ability of photons to ionize an atom or molecule varies across the electromagnetic spectrum. X-rays and gamma rays can ionize almost any molecule or atom; far ultraviolet light can ionize many atoms and molecules; near UV, visible light, infra-red, microwaves and radio waves are non-ionizing radiation….. There are significant biological effects of ionization where the most critical target is the DNA (strand breaks and chromosomal aberrations). Such DNA damage may lead to mutations and therefore cancer induction.” (2)

There are three naturally occurring isotopes of carbon in and on Earth. Carbon-12 makes up 99% of this carbon. The remaining1% is mostly carbon-13, but carbon-14 is also present in very small amounts making up around 1 part per trillion (0.0000000001%). As already indicated, carbon-14 is a radioactive isotope. Its nucleus contains 6 protons and 8 neutrons whereas carbon-12 has a nucleus containing 6 protons and 6 neutrons. The half-life of carbon-14 is 5,730±40 years. The radioactivity of carbon-14 is about 14 disintegrations per minute per gram of carbon (3). It decays into nitrogen-14 through beta-decay. Nitrogen is changed back into carbon-14 in the Earth's upper atmosphere as it is bombarded by cosmic radiation.

Plants convert atmospheric carbon into tissue by the process of photosynthesis. Since essentially all sources of human food are derived from plants, the carbon that comprises our bodies also contains carbon-14 at the same concentration as the atmosphere (1 part per trillion). The beta-decays from this internal carbon-14 contribute approx 0.01 millisieverts (mSv) /year to each person's dose of ionizing radiation. The beta particles resulting from the decay of carbon-14 may produce secondary electrons when passing through matter and these electrons may then in turn ionize other atoms.

Approximately one in every trillion carbon atoms that are part of every DNA strand in our bodies is carbon-14 and each atom of carbon-14 has a 50% chance of emitting a beta particle within 5730 years. The chance that this may happen before cell death depends on the life span of the cell containing this particular strand DNA.

If ionizations occur in a biological system it can be destructive by causing DNA damage in individual cells. For example, radioactive iodine is treated as normal iodine by the body and used by the thyroid; its accumulation there leads to thyroid cancer. Ionizing radiation can also result in the mutations that affect future generations. Evolution driven by the “survival of the fittest” depends on such mutations. Mutation can be resisted by cells by either correcting the changes in the DNA or by the cells inducing cell death in the mutated cell.

The average exposure of each human to radiation is about 3.66 mSv per year, 81% of which comes from natural sources of radiation. Almost all of the remaining 19% results from exposure to human-made radiation sources such as medical X-rays. Medical procedures, such as diagnostic X-rays, nuclear medicine, and radiation therapy are by far the most significant source of human-made radiation that the general public are exposed to. The public also is exposed to minor amounts of radiation from consumer products, such as luminous watches and dials (tritium), smoke detectors (americium) and tobacco (polonium-210). Long term close contact between tobacco tar (containing polonium-210) and the tissue in the lungs of smokers could result in the ionizing event that creates the first malignant cell of a cancer.

Cosmic rays contribute about 20-30% of the background radiation we are exposed to every day. A recent paper published in The International Journal of Astrobiology looked at data for cancer deaths from around the world for the past 140 years, and found a strong correlation between rises in cancer deaths and the amount of cosmic rays emitted by the sun. In a paper titled, Correlation of a 140-year global time signature in cancer mortality birth cohorts with galactic cosmic ray variation by Dr. David A. Juckett from the Barros Research Institute at Michigan State University, he showed that the amount of deaths due to cancer on a global scale was higher when the cosmic rays coming from the sun were more numerous. Dr. Juckett showed that as the amount of cosmic ray activity increased, the number of people who died from cancer was also higher. There is a 28-year lag between the increased presence of cosmic rays and the increase in cancer deaths.

There are two historical peaks in cosmic ray activity, around 1800 and 1900, and a low point around 1860. The total deaths due to cancer were highest, though, around 1830 and 1930, and lowest in the 1890's. Also, because nitrogen is changed into carbon-14 in the Earth's upper atmosphere as it is bombarded by cosmic radiation, these cosmic ray peake could be expected to also result in increased availability of carbon-14 in the atmosphere..


“The biological effects of radiation on living cells may result in a variety of outcomes, including: 1. Cells experience DNA damage and are able to detect and repair the damage. 2. Cells experience DNA damage and are unable to repair the damage. These cells may go through the process of programmed cell death, or apoptosis, thus eliminating the potential damage to the larger tissue. 3. Cells may experience a nonlethal DNA mutation that is passed on to subsequent cell divisions. This mutation may cause the formation of a cancer.” (4) Acute radiation exposure is an exposure to high levels of ionizing radiation which occurs during a short period of time.

“Extreme examples include

• Instantaneous flashes from nuclear explosions. • Exposures of minutes to hours during handling of highly radioactive sources. • Intentional and accidental high medical doses.” (4)

The associations between ionizing radiation exposure and the development of cancer are mostly based on populations exposed to relatively high levels of ionizing radiation, such as Japanese atomic bomb survivors, and recipients of selected diagnostic or therapeutic medical procedures, however, it is important to note that cancers that develop as a result of acute radiation exposure can be indistinguishable from those that are thought to be caused by from lower level exposure to ionizing radiation (below about 10 mSv). Studies of occupational workers exposed to low levels of radiation, above normal background, have provided mixed evidence regarding cancer and transgenerational effects, however, the linear dose-response model suggests that any increase in dose, no matter how small, results in an incremental increase in risk.

The following table includes some short-term dosages for comparison purposes. (5) Level (mSv) Duration Description 0.001-0.01 Hourly Cosmic ray dose on high-altitude flight 0.1 Annual Average dose from consumer products 0.27 Annual Dose from natural cosmic radiation 0.28 Annual Dose from natural terrestrial sources 0.39 Annual Level of human internal radiation due to radioactive potassium varies varies Human internal radiation from radon, varies with radon gas levels 0.66 Annual Average dose from all human-made sources including medical diagnostic radiation 3.0 Annual Average dose from all natural sources 3.66 Annual Average from all sources

The term carcinogen refers to any substance that is an agent directly involved in the promotion of cancer or in the facilitation of its propagation. This may be due to ability the to damage the genome or to its disruption of cellular metabolic processes. Several radioactive substances are carcinogens and their carcinogenic activity is attributed to their radiation. (6)

Cancer is a disease where damaged cells of the patient's body do not undergo programmed cell death, and their growth is no longer controlled. Carcinogens may increase the risk of getting cancer by altering cellular metabolism or damaging DNA directly in cells, which interferes with biological processes, and induces uncontrolled, malignant division, ultimately leading to the formation of tumours. Usually DNA damage, if too severe to repair, leads to programmed cell death, but if the programmed cell death does not occur, then the cell may become a cancer cell. (6). It probably only requires a single cell to become malignant to begin the formation of a cancer.

The literature identifies all radionuclides as carcinogens, although the nature of the emitted radiation (alpha, beta, or gamma), its capacity to cause ionization in tissues, and the magnitude of radiation exposure, determine the potential hazard. Carcinogenity of radiation depends of the type of radiation, type of exposure and penetration. Marie Curie, one of the pioneers of radioactivity, died of cancer caused by radiation exposure during her experiments and workers licking the brushes used to apply the luminous numbers to watch dials died from cancer of the tongue so there is little dispute that radiation can cause cancer. There is also a lot of research concerning cancer resulting from causes other than radiation, however, although the resulting tumors can be identical, the way in which these carcinogens produce aberrant cell division is not thought to be caused by emissions from radioisotopes. Could these carcinogens also be causing cancer because of their contained radioisotopes and because they are in an intimate relationship with DNA in cells that are relatively long lived, that is to say, in tissue where cell life is relatively long? It is worth noting that the likelyhood of an individual being diagnosed with cancer increases as the individual gets older. It is probable that this relationship is not between cancer and the person’s age but between cancer and the age of the person’s cells.

What about the carcinogens that are not composed party of radioactive isotopes, for example arsenic. The ingestion of arsenic can lead to cancer, however Pradosh Roy and Anupama Saha consider that “the genotoxic effects of arsenic compounds may be connected with an inhibition of DNA repair” (7). That is to say, could ionizing radiation still be the primary cause of the cancer but arsenic inhibits the cells ability to repair itself?

Asbestos fibers lodge in the lungs and due to the chemical and physical stability of these fibers as well as their minute diameter they remain is intimate contact with the cells of the lungs for very long periods of time. It would be useful to determine if small amounts of radioactive isotopes are naturally associated with asbestos.

I have had recent personal reason to consider the cause of one particular type of cancer. My wife was diagnosed with an advanced melanoma on the sole of her foot. The melanoma was surgically removed. The skin on her foot has never been exposed to significant sunlight or to any other obvious source of radiation, however the histology of the cancer was indistinguishable from melanomas caused by excessive exposure to sunlight (far ultraviolet light), that is to say, caused by ionizing radiation. If most melanomas are caused by ionizing radiation (sunlight) then is it a reasonable proposition that an identical melanoma in the tissue on the sole of the foot could.be caused by ionizing radiation resulting from the radioactive decay of radionuclides in the human tissue.

John Gofman (1919 – 2007) was Professor Emeritus of Molecular and Cell Biology at the University of California at Berkeley and his work led to the view that “ionizing radiation may turn out to be the most important single carcinogen to which huge numbers of humans are actually exposed (environmentally, occupationally, and medically” Radiation-Induced Cancer from Low-Dose Exposure (1990) (8)


APPENDIX Naturally Occurring Radionuclides: Isotope Name Half-life / Natural occur. Principle Decay Mode Maximum Energy Product of: Uranium-238 4.5 billion years 2 : 1million alpha 4.267 MeV

Radium-226 1599.0 y 1 : 1trillion alpha 4.78450 Mev Natural Source 238U Radon-222 3.82351 d alpha 5.48966 Mev Same Polonium-210 138.3763 d 1 : 1millionth of a trillionth alpha 5.30451 Mev daughter 210Bi in radium decay Artificially Produced Radionuclides which also exist Naturally:

Tritium 12.346 y beta 0.018610 Mev 6Li Carbon-14 5730 y 1 : 1trillion beta 0.155 Mev 14N Krypton-85 10.701 y beta 0.672 Mev 84Kr


Table above from: Biologically Significant Radionuclides www.davistownmuseum.org/cbm/Rad2.html


References

1. Camphausen KA, Lawrence RC. "Principles of Radiation Therapy" in Pazdur R, Wagman LD, Camphausen KA, Hoskins WJ (Eds) Cancer Management: A Multidisciplinary Approach. 11 ed. 2008.

2. SCENIHR (Scientific Committee on Emerging and Newly-Identified

          Health Risks), Scientific opinion on light sensitivity, 23 September 2008.


3. "Class notes for Isotope Hydrology EESC W 4886: Radiocarbon 14C". Martin Stute's homepage at Columbia. http://www.ldeo.columbia.edu/~martins/isohydro/c_14.html

4. en.wikipedia.org/wiki/Ionizing radiation

5. Agency for Toxic Substances and Disease Registry and National Center for Environmental Health (Content Partners); Sidney Draggan (Topic Editor). 2008. "Public Health Statement for Ionizing Radiation." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth October 1, 2007; Last revised April 23, 2008; Retrieved July 29, 2009]. http://www.eoearth.org/article/Public_Health_Statement_for_Ionizing_Radiation

6. www.newworldencyclopedia.org/entry/Carcinogen

7. Department of Microbiology, Bose Institute, P-1/12, C.I.T. Scheme VII-M, Kolkata 700 054, India Metabolism and toxicity of arsenic: A human carcinogen Pradosh Roy* and Anupama Saha


8. Radiation-Induced Cancer from Low-Dose Exposure (1990)

Tim Doe

Tim doe (talk) 02:22, 12 April 2010 (UTC)

Formation during nuclear tests: lens crystallins[edit]

The wiki article states that "the primary restrictions on the technology are that the person has to have been born after 1950, the lens must be removed while the subject is alive or within three days after death before it decays too much, and the individual cannot have subsisted primarily on seafood". However, the cited research paper only mentions the diet restriction. Either citation in support of the two outstanding claims (i.e. "born after 1950" and "three days after death") should be added, or the claims should be removed. AndrewGarber (talk) 11:48, 3 January 2011 (UTC)

External Link Broken[edit]

The external link seems to be broken for me. Should it be removed? — Preceding unsigned comment added by Wikiuser523 (talkcontribs) 21:16, 25 March 2012 (UTC)

Fixed. Vsmith (talk) 23:34, 25 March 2012 (UTC)

Mysterious radiation burst recorded in tree rings[edit]

Want to add something from http://www.nature.com/news/mysterious-radiation-burst-recorded-in-tree-rings-1.10768

The radiation burst, which seems to have hit between ad 774 and ad 775, was detected by looking at the amounts of the radioactive isotope carbon-14 in tree rings that formed during the ad 775 growing season in the Northern Hemisphere. The increase in 14C levels is so clear that the scientists, led by Fusa Miyake, a cosmic-ray physicist from Nagoya University in Japan, conclude that the atmospheric level of 14C must have jumped by 1.2% over the course of no longer than a year, about 20 times more than the normal rate of variation.

But where and how? FX (talk) 20:51, 4 June 2012 (UTC)

How are the neutrons generated?[edit]

It is said that uranium and thorium in the surrounding rock and even in the coal itself can give rise to C14 but I don't see a proper explanation for it. U238 can spontaneously split and give off neutrons but this is a rare event. Is it possible that the alpha particles reacts with C12 like this : C12 + alpha -> O15 + n and C13 can react like this : C13 + alpha -> O16 + n and the neutron might then be captured by a C13 : C13 + n -> C14 + gamma. I have not been able to track down a proper explanation for how the neutrons are generated. Vmelkon (talk) 17:38, 12 October 2012 (UTC)

See the note on C14 production above. Some of the references are on cluster decay which is emission of whole C-14 nuclei from uranium atoms in one step. Read the article on the process. SBHarris 22:21, 19 February 2013 (UTC)

14C Origin Section and 14C Production by Decay[edit]

Of the various emissions from radioactive decay (alpha particles, beta particles, etc.), I think that an entire 14C atom (6P, 8N, 6E) can be emitted as a unit in a single step from a particular decay chain. If so, even if this is only a negligible source of 14C, perhaps this can be added in the Other carbon-14 sources section. Thoughts? --Bob Enyart, Denver radio host at KGOV (talk) 19:28, 14 March 2013 (UTC)