[Date Prev][Date Next]
[cdn-nucl-l] It's the Dose that Makes the Poison: The Importance of Numbers
Ted really has a remarkable ability to communicate.
----- Original Message -----
From: "Ted Rockwell" <firstname.lastname@example.org>
To: "Rod Adams" <email@example.com>; "Cuttler, Jerry"
Sent: Saturday, January 30, 2010 8:47 PM
Subject: Re: Tritium in Vermont
I just posted the following blog on my site, learningaboutenergy.com
It's the Dose that Makes the Poison: The Importance of Numbers
http://www.learningaboutenergy.com/2010/01/its-the-dose-that-makes-the-poison-the-importance-of-numbers.htmlSometimes people claim that nuclear radiation is uniquely scary because youcan't see it, or smell it, or detect it with any of the human senses,implying that "ordinary hazards" are not so sneaky. We're even told that asingle gamma ray can kill us--a statement that affronts both science andcommon sense. Like all such claims, we need to examine this one in light ofreal-world experience, not by the exchange of uncheckable rumors.Let's look first at other, non-nuclear, hazards that surround us daily. Howabout germs that fill the air when people around us sneeze, cough, or justbreathe? How good are we at detecting germs? From birth to death, we arecontinuously immersed in germs, but healthy bodies protect us from harm. Wedon't need to see them. Similarly, we are continuously irradiated by cosmicrays and the natural radiation of the soil, water, air, and the flesh of ourbod!
ies. Life first arose in a prehistoric earth many times more radioactivethan today's.We minimize our chances of getting disease, not by trying to developgerm-free bodies (not compatible with life), but by trying to maintain ahealthy immune system. Similarly, the natural radiation levels we encounterjust by living, are not a danger, and that presumably is why humans havedeveloped no organs to detect radiation. It is not a danger. Of course,there are levels of germs, and levels of radiation, that are harmful, but wedon't normally encounter them in the natural world.(Aha! But how about the unnatural world of nuclear reactors?) I won't tacklethe theological issue of whether we can properly exclude humankind and itsproducts from the natural world. Let's just look at the numbers. Theproto-scientist, Paracelsus, said in 1540 that nothing is poison but theDOSE makes it so. That is the basis for vaccination. That is why ancientking-poisoners knew they could safely swallow a small m!
outhful of poisonedfood, which in larger amounts could kill. It's a fu
ndamental principle ofbiology that assaults that don't kill you make you stronger.So the relevant numbers here are that the average natural radiation levelwhere people live is hundreds of times the radiation levels permitted forexposure to the public from nuclear reactors and other sources of human-maderadiation. Natural radiation levels on this radioactive earth varyhundreds-fold from one place to another. And the measured fact is, thehigher the background radiation, the LOWER the cancer rate. So if we had noradiation whatsoever from nuclear power plants, we could hardly measure thedifference in human exposure, because the nuclear contribution to our totalradiation dose is trivial.A further irony is that our dose from increased use of medical irradiationin life-saving procedures is now commensurate with high natural backgrounds,further invalidating concern over the negligible doses from nuclearfacilities.The facts just stated show how we should respond to occasional reports!
ofleakage or other incidental exposure of radioactivity. The phrase "exposedto radiation" tells us nothing about hazard. It's the dose that makes thehazard (if any). The anti-nuclear activist, Sheldon Novick, correctly notedthat "nuclear waste" is no more hazardous than many other industrial wastes,so if we hear of a spill of radioactivity, we should judge its hazard as wewould a spill of oil or any other biologically harmful chemical: What's thetoxic dose?While we're talking numbers, let me divert for a moment to talk units. Theunit of radioactivity used to be the Curie, which was about one gram ofradium. A gram is one-twenty-eighth of an ounce, so that's a reasonableunit. When the metric system came in, the unit of radioactivity became theBecquerel, named after another radiation research pioneer. The Becquerel(Bq) is a single atomic disintegration per second. There are 37,000,000,000Bq in a curie. So levels of radioactivity that are entirely harmless are nowmeasured in m!
illions or billions of Bq, instead of a few milliCuries.What does all
this mean in the real world? One example is the case oftritium, which is an isotope of hydrogen that usually shows up as water. Itis used widely to light exit signs without electricity. It doesn't stay inthe body long, and its radiation is low-energy. So its biological impact ifingested is low, and the US permissible limit in drinking water is 20,000picoCuries (millionths of a millionth of a Curie) per liter, which isestimated to give the body a 4 mrem dose. This is about 1% of the averagedose we receive from natural radiation background.Recently, some tritium was detected in the soil near the Vermont Yankeenuclear plant, leading quickly to demands that the nuclear industry be shutdown. Previous minor leaks elsewhere led to industry promises to make allplants "zero leakage." I've always avoided, as a matter of principle,promising there will be no more accidents. One cannot be sure to deliver onsuch promises. What we should promise, is that we will ensure that accidentswill n!
ot cause significant harm to people or the environment. And that isthe situation here. If we look at the potential dose (i.e. toxicity) fromsuch a leak, we find that it is considerably LESS than from numerous smallleaks of oil and other chemicals that occur from time to time.In these more hazardous cases of non-radioactive spills, we devote a modesteffort to cleaning up the area, leaving earth or concrete permanentlystained and contaminated to the degree that, if you tried to eat it, youmight suffer some deleterious effects. And we rightly conclude, that's areasonable course. (Maybe we should post OSHA warning signs: DO NOT EAT THEDIRT.) There is no realistic justification for requiring that the ground bedecontaminated to hospital or "clean room" standards.Radioactivity is not unnatural, nor uniquely hazardous per se. Many of thenew chemicals we use in abundance, such as pesticides and other organicsdesigned to interfere with natural functions, more nearly fit thatcharacter!
ization. Radioactivity does not multiply, like germs; instead itdecrea
ses in toxicity. We should stop viewing radiation as demonic andrecognize its place in the natural world, and its special role in healing.Even after large spills of oil (and there are many), we don't demand thatthe oil industry be shut down. Let us base our judgments of danger onmeasured toxicity, not some panic-driven demand for a radiation-free planet.---------------------Ted and Jerry:I do not know if you have been paying attention to the controversy over thediscovery of tritium in the ground water on the site of the Vermont Yankeeplant. I have put up a post on Atomic Insights aimed at showing just howtiny the number "28,000 picocuries" really is and how small the mass of thatquantity is. (A trillion picocuries of tritium has just 0.1 milligrams ofmass. You would have to cut a 385 mg aspirin tablet into 3,850 pieces to beable to isolate a piece of a common substance with that mass.) http://atomicinsights.blogspot.com/2010/01/comparing-leak-of-tritium-that-causes.htmlAs an!
example of your common refrain of finding the enemy in our own group,here is a link to an article where the press contacted nuclear engineeringprofessors who expressed a desire to "find the leak". http://sentinelsource.com/articles/2010/01/29/news/local/free/doc4b63b551bae05352756969.txt I thought I might be able to interest you both in getting involved in thepublic discussion.Best regards,Rod Adams