[MUSIC] So now that we can quantify radiation, we need to actually see what it will do to a person. Now remember, we have the unit of a sievert because that's a lot of radiation. We also have the unit of millirem, but the chart I'm about to show you is in sieverts. So let's just put up a little conversion on the side so that you're ready for it as we come along. So, if we want to look at health effects of radiation, there's a really convenient chart. This chart is going to compare lots of different radiation doses and what their effects are. So, let's zoom in to the top left corner. Sleeping next to somebody. Why is it dangerous? Well, it could be lots of reasons, but from a radiation point of view, it's not. Do you get those? Sure, some of the gamma rays from their potassium get you. 0.5 mSv, not much at all. Living next to a nuclear power plant for a year, tiny amount of dose, why? Because nuclear power plants emit no radiation, okay? Eating a banana, 0.1 mSv, a hundredth of a milligram. Bananas are loaded with potassium, they're good for you. Don't despair just because there is a noticable, or at least measurable, radiation dose. Living next to a coal power plant. Why would you get radiation dose from a coal power plant? Well remember, inside coal is just about everything including probably a little uranium-thorium, goes up in the smoke. An x-ray. So finally you get your arm x-rayed, it's a microsievert. A microsievert is a tenth of a millirem and that's what you get. Or if you use a CRT, the old fashioned television, the kind that's actually wide, or a computer screen. Use that for a year, you get a whole tenth of a mRem. Nothing whatsoever to worry about. Your natural dose is mRem a day just from nature. So the last one on here is spending an extra day at some place that's in higher elevation. I talked about living in Colorado, 1.2 mSv a day, that will add up to something like this 40, 50 micro mRem extra per year, just because you have less atmosphere protecting you from the cosmic rays. Let's go a little bit higher levels of dose. A dental x-ray, half of a mRem. Your normal background dose about 1 mRem per day. And then your here at the bottom is if you fly on an airplane. You go across the US from New York to LA that's six hours up in the air, your at 33,000 feet. Remember Denver was giving you extra mRems because it was at 1,000 feet. Now, you're 5 miles up, much less shielding from the cosmic rays from outer space and you get a whole 4 mRems from flying across the country. Don't panic, a much more dangerous is the part about the plane maybe not landing. The 4 mRems, nothing to worry about. Let's look a little further. Now we'll take all those blue charts, and they will turn in to be just one of these green ones. You see, an x-ray of your chest is 20 uSv, about 2 mRem. And if you actually were in Tokyo during the Fukushima accident, you may have, at most, gotten an extra 4 uSv, about the same as flying across the country once. If you live in a stone building, hey uranium thorium in the stone, that's part of that natural background. That's at least just an extra 7 mRem a year, compared to a wood building. Three Mile Island, the worse nuclear accident in the US, tiny amounts of dose within 10 miles 8 mRem. We keep going down here. We get the amount that you might have been in the Fukushima Town Hall. And here is the amount the EPA says you could get from a nuclear reactor. Of course, you do get much much less than that. This is the potassium in your body and this is what you get from a mammogram. A mammogram, of course, can be extremely important because it can detect breast cancer early. Just because you get a whole 40 mRems from it is nothing to worry about. Compared to the potassium in your body, or the mammogram, this is the amount of radiation that you're allowed to get for the public. 100 mRems extra per year. Here the amount of dose that anyone possibly could've gotten from Three Mile Island, equal to the normal public safety limit of 100 mRems per year. Here we have the same thing if you were about two weeks right at the edge of the Exclusion Zone. And a CT Scan of your head to 2 mSv, that's 200 mRem about equal to the amount of radon exposure on average for a given year. And finally here is that somewhere around 320 or so mRem in this cases like 400 mRem from a normal yearly background those. So all of this things we talked about Fukushima, Three Mile Island, medical procedures, these are all still much smaller than the normal background dose you get in a year. No health effects at this point. All right so let's go back to the power plant, that's how much the EPA says they want and of course power plants usually do much less than that. Here is Chernobyl, for an hour. The scale between the radiation exposure at Fukushima and Chernobyl are not even comparable. Chernobyl was a complete, unmitigated disaster in terms of radiation, radioactive substances. This for an hour at Chernobyl in 2010 many years later compares to one CT scan or 700 mRems radiation. Still though these numbers are below the limit imposed for workers who work in radiation. In fact, it's a lot larger than this looks. Let's go ahead and blow that up to the full size. The limit for a radiation worker in the United States, this is uniform across the world, is 5 rem per year, 50 mSv. They actually limit it per quarter, so you can't hey, last day of the year, I get my 5 rem. The next day, I get my next 5 rem. They say 1.25 per calendar quarter. And you still see, we haven't talked about health effects. That is because that even if you're a worker and you get 5 rem and you go to the doctor. And say doctor, doctor, I think I've hit my limit for exposure as a radiation worker. Test me, test me, I want to see how sick I've become. They can't tell. This chart, right up here, this is the five Rem. This is the dose per a radiation worker in normal situations. Of course, if you have to go save property or if you have to go save lives, those dose limits can go up. Here are the limits for property, here's the limits to save people. And interestingly, this amount was the amount the radiation workers at Fukushima got. This is medically noticeable, the first health effect of radiation we have here, the first detectable changes in your blood happen at 10 Rem. This chart right here, ten Rem. There, you can see some changes in your blood cells, some potential that you may, someday, get cancer at a higher rate than somebody else who's not been exposed. The health effects multiply pretty quickly by here, if you get ten Rem, you do not feel sick. In fact, if you didn't have a blood test you'd never even know. If you get four times that, if you get 40 Rem, you can start having radiation sickness, hair loss, redness, nausea. And, if you go up here to 2 Sv, which is 200 Rem. You are definitely in this range of radiation sickness and radiation poisoning, you are going to need medical care. There's a interesting number called the LD 5030, sounds like a motor oil. But, it's the lethal dose for 50% of population to die in 30 days. That's the number down here, four Sv, 400 Rem. And, if you get 800 Rem, even with medical care, not instantly, but you are likely, very likely to die. Those are the medical effects of radiation, until you get to this ten Rem level, not a noticeable effect to your body, and an acute dose. The worst nuclear disaster, of course, ever was at Chernobyl, and if we take that entire chart and we turn into one of these yellow boxes, this was ten minutes next to the core after the meltdown or explosion. Nothing comparable to the radiation loss and doses at Fukushima. So, what we've been talking about are acute doses, doses you get all at once. There's always a question about cancer, what type of dose do you need that would increase your chance of getting cancer? Let us talk about that next. At what radiation dose level do you start having an increased risk of having cancer? Clearly, we know it is not in the 10s of mRem. People in Denver are not dying faster of cancer than people of the same economic-social class in New York City. But if you were having hundreds of Rem, in many cases, we have documented cases where the people that were exposed, the people were exposed at Chernobyl, have documented how much exposure. And there are certainly increases in cancers, in certain types of cancers, and in certain populations. So, taking not intentional disasters, but accidental disasters that happen over time, you can draw a chart where you have excess deaths, I'll get back to what I mean by excess deaths, versus radiation dose. Now what is excess death? It's unfortunate but everybody dies, eventually. One out of four, approximately, will die of cancer. That doesn't mean they were all exposed to radiation, it's just you die of something. You'd love to be able to say, I died with old age, chances are that something wore out, something went out the rampant growths streak, something happens. So you have to compare populations and say, the number of people that should have died of cancer was this but hey, there were actually more then that number there were excess death that happened earlier. And maybe that's because that population had some sort of chemical, some carcinogen in their environment, or maybe its cause they had a radiation dose. If you take these cases, you can make some cases, Chernobyl, Hiroshima, some other things, and you can put data points. And there's error bars on them, all right? And you can draw these, and then you notice that this is linear, okay? And it goes through zero, and you get some chart. And you can take a slope from this chart, and this is called the linear hypothesis. And it says that any amount of excess dose is going to give you cancers at an excess number. And if I take the slope of this line the convenient unit of that slope Is 200 times 10 to the minus 6. That's 200 per million, excess deaths, excess deaths per Rem of radiation, per year. All right so the slope of this line. Is this 200 x 10 to the minus 6 excess deaths, per Rem, per year. What does that mean? Let's say we have here, the number of people, and here is the dose they each get. So if I had 500 people each getting 10 Rem, I multiply 500 x 200 x 10 to the -6 x 10. And by the way, that number turns out to be 1. So this will be a chart here of what it takes to make one excess death from cancer. So you get exposed for 10 Rem. This theory based on data will say that you have a 1 in 500 chance. Each year of developing a cancer that you would have not normally developed. One out of four people are going to develop cancer at some point in their lifetimes. In this case, the extra radiation dose, gives you an extra one out of 500 chance of getting it. Meaning that if there are 50 people, each getting 100 Rem. 100 Rem, you're certainly experiencing radiation sickness. You will have a chance of one out of 50 of developing an excess cancer every year It goes the other direction too, right? I could say, this is 5,000 people each getting 1 Rem. Of those 5,000 people, one person slightly to die from cancer from this excess radiation. Maybe. Let's go a little further. What if it was 50,000 people each getting 100 millirem? Or 500,000 people, each getting 10 milligram. Remember, when we're at this scale of 10 extra milligram, this is like living in a little bit higher elevation of a couple thousand feet above sea level. And we don't have statistical evidence that says these small levels of dose follow this. In fact, the data we have says these small levels of dose actually don't give you excess deaths and excess cancers. The curve doesn't look like this. It looks something like this, where there is a threshold. Exactly what the threshold is, we don't know. But we do know we can see logical effects at 10 Rem. Maybe at one Rem, there still is some excess cancers. But certainly in these lower levels, the 100 millirem, the 10 millirem, the 1 millirem, 5 million people exposed to it, will one of those develop cancer that would not otherwise? I think the answer here is clearly, not. This is the difference between the threshold and the linear theory of radiation exposure. The data supports the threshold theory. And there's probably good reason for that from an evolutionary point of view. That 1 millirem a day, that everybody gets from natural causes, that's been happening since the Earth was here. All of the evolution of life has been exposed to that. And that level of radiation exposure, our bodies are equipped to make certain repairs. Probably not just from radiation damage, but maybe from other carcinogens in our environment as well. There have been some very famous examples of radiation exposure. One of the most interesting stories is that women in World War II who were painting radium dial watches, I actually have one of those watches. So you can see here, in this watch has very fine lines printed on the second hands that was using radium paint. Why? A radium glows. Radium is radioactive. The alphas and betas coming out of it, if you put a little phosphorous essence with it, will actually create light. In the 1940s, we did not have fancy little LED lights, or other types of liquid crystals with a nice visual display. If you wanted to see what time it was, you needed to turn a light on or have a radium dial watch. Why do you need to see what time it is in the dark? But let's say, you're going on a bombing run over Germany taking off from the United Kingdom. Bombing was very imprecise, there's no GPS, there's no laser guided bombs. You want to basically know am I over the industrial section of that city? So I can bomb the factories that are making tank parts. If I try to find that city, I'm going to do it by I fly at this range, for this length of time, at this speed. You look at your speed, you look at your compass. You look at it, you very precisely time, and then you know that you're going to, hopefully, be over your target. So you've got to know time to a very precise degree. To measure that time to a precise degree, if you suddenly turn on the light in your cockpit, all of a sudden, the antiaircraft gunners down on the ground are going to look up, and they'll see, look, there's an airplane. Probably hear it, they don't know where it is, where to shoot. Soon as you turn a light on, you're advertising where you are, and you get shot down. So you needed to have a timepiece you could read in the dark. And that's where radium paint came in. So the US allied bomber pilots needed a radium dial watch. Well, how do you make it? There are no fancy laser engraving tools, or wonderful assembly lines. What you do is you get somebody to paint it. It has to be a very steady fine hand, and you need to have your paint brush come to a very fine thick. The best way to that, let the paint brush tip in your mouth. Dip it into the radium paint, and then very carefully go over each second hand. Pretty soon, the tip of your paintbrush starts getting dull. So it goes back into your mouth to make the tip sharp again, back into the paint, and back on the watch. These were the radium girls. These were the people whose job was to paint these watches. There are records, how many watches someone produced? Or at least how many hours they worked in the factory? How many months they worked in the factory? There is, of course, the ability kind of do a model to figure out every time someone. How often would they put the brush in their mouth? How much radium did they likely ingest? Therefore, what type of dose did they receive? And indeed, the women who did this the most, not all of the them but the ones who did it the most hours had a higher incidence of getting cancer. In fact, some of those initial cancers, were cancers of the mouth and of the esophagus itself, because that's where the most of the dose, that's where the radium was first concentrated. My grandfather was a dentist, well, more than that. It was back then in the 1920s, there was a dentist, an orthodontist, an oral surgeon. And X-ray machines were available. And X-rays for teeth are extremely important, right? You had to be able to see where the root of the tooth is, and what the problem is. There was no lead curtains over people, there were no fancy holders, right? He would hold the X-ray film in the person's mouth [INAUDIBLE] right while he's holding the film in there. I remember my grandfather, extremely fondly, wonderful man. And it was always interesting that he never actually did the game, pull my finger, because it might come off. I'm sorry about that. He did have kind of a constant festering bit of a sore and final falling off flesh on his one finger. The finger he held the film with. For all of those years for the radiation exposure. He didn't die of cancer. He died of a stroke. Fairly old age especially for the time. But this ability of saying, hey, the radiation goes through my finger. I can get a much larger dose. There are no critical organs in your finger. The same thing in your mouth and teeth, of course. There could end up getting cancer of the mouth or the esophagus. Of course, as you ingested and that radium goes through you, you can have some systemic cancer from your whole body. Not all the people, by any means, got cancer. But it's one of those data points on the linear hypothesis. Understanding the health effects of radiation is very important, because you don't want to just be in fear of someone saying, it's radioactive. After all, you're radioactive and almost everything around you is too. What you have to be able to do is quantify it, and be able to say how radioactive? How does it compare to background? How does it compare to the point where my body could repair the damage I'd have from it? That's what you need to know about radiation exposure. [MUSIC]
