Dr. Raabe

I'd like to start right off with the slides, please. This one has the title of my talk. I am professor at the University of California in Davis and I have a PhD in radiation biology and biophysics from the School of Medicine at the University of Rochester, in Rochester, New York. I've worked in the radiation field for about 40 years. I put down at the very bottom here a quick thumbnail summary of my talk. Basically what you're going to find is that the significant difference between protracted radiation exposure which is extended over perhaps a whole lifetime and the kind of instantaneous exposure that occurred for the atomic bomb survivors and occurs in medicine when people are exposed to X-rays or [fluoroscopes?] or something like that, and the difference is about a factor of 100--that the radiation's about 100 times less effective at producing cancer when that exposure is protracted. This is a very important from the point of view of environmental exposures and exposures in industry.

I'm also the immediate past president of the Health Physics Society. The Health Physics Society is not a dupe of the nuclear industry as Helen suggested this morning, but in fact it's a society of professionals who specialize in radiation safety. Our job is safeguarding the health and the environment from potential hazardous exposure to radiation. We're the people who worry about workers being exposed and how much they're exposed and measure carefully how much internal ah, emitter's they're exposed to, and so forth. And we have, ah, a, ah, program for certifying professionals in this field. I have CHP after my name. It stands for Certified Health Physicist. There are about one thousand board certified Health Physicists who go through a rigorous program to insure their professional competence. If you really want to know the truth about radiation, ah, call the Health Physics Society, the American Board of Health Physics, get the names of board certified health physicists. There are plenty in every area of the United States.

Now all of us, of course, are exposed to ionizing radiation all the time. Actually we're getting a higher exposure in this room because of these ah, nice granite walls that we're s--we're sitting near. They're filled with thorium and radium and all kinds of radioactive material and we're being irradiated and we know that ah, for example, that ah, this pie chart shows how the distribution of--of exposures occur. Ah, most of the exposures that we get from natural sources are alpha particle exposures, those, ah, high LET alpha particles that some people like to say are so dangerous. Fifty-five percent of our exposure from n--from all different sources comes from alpha particles from radon'd decay products.

Of course, there's cosmic neutrons--we're all exposed to neutrons and protons from cosmic space and gamma rays and ch--of course the g--the earth has radioactive material every--every spec of--of soil on the earth has radioactive material in it, radium and thorium. And we have ah, potassium [floating?] in our bodies from our food and other radio-neucleids, and then of course the extra radiation exposure we get--almost all of that comes from medicine. Now, compared to the nuclear industry and fallout, medicine beats exposures every time, and it doesn't make any difference what kind of exposure you want to talk about, the big thyroid exposures are not from fallout of iodine 131, their from medical uses of X-rays from 1920 to 1950. Most extra exposure that the average person gets comes from medicine. And then, after medicine, fallout, fuel cycle and so forth are down here in the roundoff error.

Now we might wonder, are these ah, background exposures hazardous. So, scientists have been studying background exposures throughout the world and have looked at places where background exposures are much higher than they are in--in average place in the United States. Now, I just chose to pick out Denver because someone might say, what would happen if I got an extra exposure equal to background exposure which is about 360 millirem per year. What if I got twice that much from some source? Would that be a problem? Well, people living in Denver are getting more than twice that much. They're getting twice that much from [caldic?] rays, natural minerals, internal radioactivity, and they're getting from radon up to four times as much exposure to alpha particles because radon gas is in much higher concentrations in Colorado. A lot more uranium and radium in the soil there.

So, you might ask, well, these people are getting twice as much exposure as the average person in the United States. What's this doing to their health? Well, when look first at lung cancer they've got this gigantic dose of almost 9 rem per year of alpha particle radiation to the lung--9 per year, 634 a lifetime, perhaps, rem. What ah,--what's this doing to their--to their lung cancer rate? Well, Colorado has got one of the lowest cancer rates in the United States. Only Utah--with the Mormon's that don't smoke--have a lower rate.

I think hot air is a problem, because I notice that DC always ends up being high on the list of ah--of cancer.

Ah, ah, yes. Radon. Ah, study by ah, Dr. [Colin?] of University of Pittsburgh, ah, has actually looked at radon in ah, most of the counties in the United States and he finds that the cancer rate--lung cancer rate for ah--associated with radon is actually ah, inversely proportional to the exposure--those hou--homes that have higher radon actually--[or those?] counties with higher radon tend to have lower lung cancer rates.

So, at least at the levels that we find in our homes [...?...] would be major problem, now for overall cancer in Colorado we've got--there are 48th out of 51 and again, ah, Washington DC has the highest cancer rates in the United States.

Now where does--where do cancer come from? Well, we know a lot about risk factors. The CDC has published and American Cancer Society has published risk factors. We know that, ah, tobacco is a big source. We see ah--a epidemiological study where they say that lung cancer is a--is caused by radiation. Well, if they haven't done a rigorous control for--for cigarette smoking, they really don't have information that's very useful. Diet is a major source. Infection. Intake of alcohol is a source. All these things have to be considered. What is causing cancer in radiation workers? Primarily it's being caused by the same sources and risk factors that ah, we're all exposed to. In addition, ah, radiation workers are exposed to organic solvents and ah, asbestos and all kinds of other materials s--very careful rigorous control of these is necessary for good studies.

Now, we always ah, ah, look at the--look at the atomic bomb survivor data, and this is just some of the ah, raw data from the atomic bomb survivor studies. Atomic bomb survivors, you know, were instantaneously exposed to penetrating radiation--primarily gamma rays and some neutrons. And what we find is that for doses below about .15 ceverts or 15 rem, there's no observed effects, actually, although people like to fit sometimes linear models and in fact all of our recent standards have been based very conservatively on calculations of risk based on linear models. A study in this month's health physics journal by David [Hole?], a very prominent ah, bio-mathematician, shows that these data can be equally well described with an--with a model that involves a threshold, where there's really no effect below, in this case, .05 ceverts or 5 rem.

And Geoffry [Howe?] ah, did a study of peo--people who's ah, lungs were irradiated with X-rays ah, repeatedly ah--case of tuberculosis patients and what he found was that with this protracted exposure that there was no effect at a dose of 1 cevert, even though the atomic bomb survivor data would suggest that there should be a 60% increase. Now, one cevert is a gigantic dose compared to what you heard about this morning in these occupational exposures and there's no lung cancer effect.

So, are risks different for acute vs. chronic exposures. They definitely are. We know that for sure in some of the new information that's available today. The risks are definitely different. There's a much lower risk associated with cancer induction when the radiation exposure is protracted.

And a very good st--probably the best study of the radiation workers is a gigantic study, ah, that was published in Lanti--[Lancet?] and this was a study of the International Agency for Research on Cancer, also, ah, the [Carda?] study, sometimes called, and it showed very clearly that for U.S. workers there really is no indication of any radiation induced cancer for workers exposed below the current standards.

Now, I've--I've been doing epidemiology of a different type. I've been working on data that's been collected in studies with la--with laboratory animals--namely the beagle. And here we have an opportunity, with the laboratory animal, to control all these factors that we can't control in people. We can control the diet, we can take very good care of their health, ah, we can ah, be very careful that we know everything about them, and even we can control their genetics to some extent.

And my interest has been internal emitters. The first study I want to review very quickly is a study that involves radium 226. Radium 226 is a radioactive material to which many people have been exposed, and you know, we did this study on beagles and all the other studies on beagles not because we were interested in the effects of radiation on beagles. We're only interested in finding out how we can predict more accurately the potential risk to people from exposure to radiation. So the whole purpose of the beagle study is not to figure out what happens to a beagle. So, we started off with radium because we have a lot of data on humans exposed to radium. And we can [therefore] figure out what the relationship is between the risk to beagles and the risk to people. This is a big study involves about 400 dogs, six different dose groups varying from very low to very high and ah, these--this is what we call a lifetime study that exposures were done early in the life. The beagles are irradiated then. Ah, their skeletons are irradiated by the bone-seeking radium, by alpha particles for the rest of their lives and we take care of them and give them ah, ah, best possible medical care and find out what their long term health effects are.

These studies are all over. They're done and the data is in the computer and now it's ah, up to us to rep--to report the results. I plotted all the data together on one slide here--every beagle in the study. Ah, as a function of average dose rate to the skeleton, this is alpha radiation exposure of the skeleton vs. time to death. This is actually a two dimensional plot of three dimensional phenomenon. And this is where I get into the three dimensional model story, because you really can't understand what's happening with regard to ah, radiation effects from protracted exposures such as increased background exposures or internal emitters without looking at it in three dimensions. And what are the three dimensions? Well first that the dose--given here is dose rate, the time to and effect, and then the clustering of the data points represents the probability density function describing the various effects. And at very high doses there were early deaths associated with direct injury to the skeleton. All the bone cancer cases occur in this distribution along the narrow line, and of course, these are controls here and ah, other deaths that occurred.

The--the--the s--the bone cancer cases are very interesting because they sh--they proceed in a way that quite remarkable. They are tightly distributed around a--a single line on this [log-log?] plot. And this distribution around the line has a coefficient of variation of only--only 20% and for those of you who are biologists or statisticians, you have to realize that this is a remarkable tight distribution--tightest I've every seen in any biological experiment.

So, in order for the beagles to build cancer time has to pass until they get to this line, and lower dose rates ah, result in lower total cumulative dose leading to cancer, but as the dose rate goes down, the time required to develop cancer gets longer and longer and eventually that time required to develop cancer exceeds the natural life span of the beagle colony. And the beagles die of causes that we associate with natural aging and we don't get bone cancer.

So this is the distribution that I say is the three dimension--so now we're going to put on your gla--three dimensional glasses. We're going to jump into three dimensions. I'm going to replot this in three dimensions. This is what it looks like in three dimensions. Here we have the three dimensions. The dose rate to the skeleton from the alpha particles in grey per day, the time to death and then the probability density function. And at high dose rates we have early deaths from--from radiation injury, intermediate dose rates of lung cancer and f--low dose rates while there's no effect except deaths associated with natural life span.

Now to get the risk we have to integrate this and to integrate this we, ah, we end up with the risk of dying from 0 to 1. All of the beagles in our studies died. We had no immortal beagles. So that means that they all died and they all make it to the top of the plot here where the risk is 1. Eventually everybody dies. So, what's the story about the radiation? Well, the radiation exposure cause premature death at high dose from radiation injury. At intermediate dose rates, from bone cancer, and at low dose rates there was no change in natural life span.

Now we can break this into it's complement parts. What's the risk of developing radiation injury death in the beagles from radium in the skeleton. Well, it's--it occurs only at the high dose rates. And what's the chance of dying from natural causes? Well, there it is, it occurs at the low dose rates and what's the risk of developing bone cancer from radium in the skeleton? Well, it's kind of a mountain coming out of this plain. Very non-linear and at dose rates that were--are quite low, there's no effect.

Now, you know, if you were being paid to produce bone tumors in beagles from radium, you'd like to have this plot. Because without it you could make some very big mistakes. If you gave too much radium, you get no bone tumors because the beagles die of direct injury. And if you give too little radium, you get no bone tumors because the beagles die of natural life span.

OK. This brings us to the people. Primarily the--the radium [doll?] painters who earlier in this century swallowed large quantities of radium 226 and also 228, but I'm--I'm talking about radium 226, by tipping the brushes on their tongue as they painted luminous dials on clocks and watches. There are other people who've been exposed to radium. In medicine it was very popular. In medicine again, to give ah--you can always find medical exposures that top everything else, but [...?...] said it was--ah, was people giving injections of radium thinking there were some healthful benefits ah, earlier in this century. And there are chemists who were exposed to radium. Now, these data have all been collected and studied for most of this century.

And I plot here the data we have for the beagles, ah, data on mice that from [Argon?] Laboratory, and data on the people, and the first thing I observed--I published it in 1980 in Science Magazine, and the first thing I observe--observed was that there was a correlation to life span. Now, if you non-dimensionalize this di--these data, and just ah, convert it to fraction of life span, you can plot all of the data for mice and beagles and people on exactly the same plot. Here we have the skeletal dose now is in grey per fraction of life span and the time death is in fraction of life span, and all the data, the m--human data and the beagle data, the mouse data are on the same plot.

So now we know the relationship. It's life scan nor--life span normalization, so I can take the beagle data and predict the risk to people. So I did this. And this line here--these lines represent the risk to people that I predicted from the beagle data alone, and then here are the beagle--the human data plotted on the--on the illustration. So, basically, you can see that the line I calculated from the beagle data fits the human data extremely well. It turns out that the--besides bone tumors in humans, we also get head carcinomas because the beagle has a better nose than--than people. And it doesn't happen. It sounds like a silly statement to make, but beagles have better noses and they don't have these sinus--sinuses in their head that which--which gases are trapped and radium 226 decays to form radon gas which is trapped in the head and sinuses in about half the people who develop cancer ah, who are exposed to radium--or not quite half--ah, actually died of carcinoma's of the sinus region in the head.

So those are two--there are two parts of that. Then we can plot that in three dimensions. Basically, here's what the ah, bone cancer ah, risk distribution looks like. It's a function of dose rate. You know, I sent--I sent the paper, in 1979 to Science Magazine describing these phenomenon and it seemed like only a day or two went by and I got a call from the editor of Science. And he said I've got your paper here, and I've read it but you've made a big mistake. And I said, Oh, what was that? And he said, well, the doses that you're describing for these people go from 20,000 rem to 120,000 rem. No one could have a dose--a skeletal dose that large. I said, no--tho--those are the correct doses. We know now after studying 3,000 people in the United States exposed to radium that the lowest dose in any of those people--the lowest dose to skeleton that resulted in bone cancer was 10 grey for alpha particles that's 200 ceverts--20,000 rem. No person in the U.S. radium studies who's skeletal dose was less than 20,000 rem developed bone cancer. Quite remarkable. Especially when you start talking about worrying about a few millirem.

Well, this, of course is not new information. Ah, this was published in the Health Physics Journal 25 years ago by Robley Evans, ah, and he s--pointed out this threshold effect which I like to call the effective threshold, he calls the--he calls the ah, [p--practical?] threshold below 1,000 rads which for alpha particles is tw--is twent--is 20,000 rem or 200 ceverts. There were no cases. And it's 25 years later, after all the data that ev--will ever be analyzed--have been analyzed, there's no change in this.

OK. Let's look at plutonium. We also--we note that--studies not at my laboratory, but at [Battel?] Northwest Laboratory, ah, beagles were exposed to plutonium dioxide by inhalation and then they were studied for a life time. Very similar results occurred. There were lung cancers in this case. Ah, direct injury deaths by ah, injury to the lung, and when you're plotting this in--in three dimensions, this is the way it looks at high dose rates--lung injury and immediate dose rates--lung cancer, ah, low dose rates--natural life span.

The ah, jumping to the bottom line on this, the ah, occurrence ah, at P&L, Pacific Northwest Laboratory of beagle deaths with lung cancer [plutonium t--39?] dioxide has this shape, this again, ah, quite ah, non-linear with the effective threshold associates with long dose--low dose rates.

I tried to take these data and now since I know about life span normalization, I can predict the risk to people from inhaling plutonium dioxide. Now, you know, I don't have any data up there on people, and the reason is we have no documented cases of any person in the United States who inhaled plutonium or developed bone--ah, ah, lung cancer because of that exposure. Although thousands of--of workers have--have inhaled plutonium.

The--they told me when I first did this that the Russians would provide the data and actually it turned out to be true. Because the Russians were nowhere near as careful as we have been in the United States. We're very careful about our standards. They haven't really changed much in 50 years. But here's the prediction and the result here, and I plotted thi--this one in terms of initial lung burn [kilobeckerels?] of plutonium dioxide in the lung and [...?...] for people. This is the prediction by life span normalization. And you can see that ah, where ah, initial lung burns below one, which is way above the maximum permissible, ah, allowed in industry, we don't expect any lung cancers and there are none.

Ah, the Russians did supply the data, and they found also there was a threshold. They found a threshold at 8/10ths of a [grey?] very close to the one I predicted. Fact they said that below 3/10ths of a grey there was a protector effect--the lung cancer incidence was lower.

[With their?] exposure level [leading?] to zero risk, certainly is. Ah, [Casini?] is one that was popular in the news last year, and I was on the radio several times with Michio Kaku doing debating on the TV program. You probably know about [Casini?]--it ah, contains plutonium batteries that uses plutonium as a heat source for batteries [Casini's] going out to Saturn and in order to get out to Saturn, ah, it was ah, launched last October and it goes around the sun twice and passed Venus to pick up speed. Ah, it passed Venus this spring and then along about August next year it will, ah, go past ah, th--the earth. Now there are some people who are worried that ah, if--if the one in a million chance occurs that ah, Casini will hit the atmosphere at 40,000 ah, miles per hour that all the plutonium will burn up and then we'll all be poisoned. Of course we've all got plutonium in our body at all already and in fact we've already done this experiment. Almost that amount of plutonium has already been burned up in the atmosphere ah, for the nuclear weapons tests and so we each have a tiny amount of plutonium in our bodies, but the dose is--is--is really quite negligible--less than 1/10th of a percent and if Casini does burn up in the atmosphere the dose will be negligible--no one ah, will notice it.

We did a study with Strontium 90 and I just quickly go through that very non-linear dose response. Strontium 90 in bone ah, required at least a dose of 22.5 [grey?], actually, that works out to be 2,250 rem before there are any observed biological effects and in fact I've gone through and will skip through that one because my time's almost up. I've looked at all the radionucleids for which ah, studies have been done and they all have the same characteristic that as the dose rate goes down, the time required to develop cancer goes up and the consequence is that there is an effective threshold and ah, there are no cases at low dose. I've got this published in numerous publications. Here's my next slide.

Ah, the last thing I wanted to put up here was the Health Physics Society ah, information. The Health Physics Society has a position statement. I encourage you to look at our web site at www.hps.org and the position statement basically says there's no--there's no scientific basis for attempting to calculate ah, risks for exposures that are less than 5 rem in a--in a year, or 10 rem in a lifetime. There are know known expec--or expected risks at these exposure levels. Thank you for your attention.

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