you so now that we can quantify radiation we need to actually see what it will do to a person remember we have of the unit of a sievert that's a lot of radiation we also have the unit of a millirem but the chart I'm about to show you is in sieverts so let's just put up the 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 there could be lots of reasons but from a radiation point of view it's not do you get dose sure some of the gamma rays from their potassium get you 0.05 microsieverts 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 point one micro sieverts a hundredth of the millirem bananas are loaded with potassium they're good for you don't despair just because there is a noticeable or at least measurable radiation dose living next to a coal power plant why would you get radiation dose from a coal power plant or remember inside coal is just about everything including probably a little uranium and thorium it goes up in the smoke an x-ray so finally you get your arm x-rayed it's a micro sievert a micro sievert is a tenth of a milligram 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 milligram nothing whatsoever to worry about your natural dose is mmm 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 microsieverts a day that will add up to something like this 40 50 micro millirem extra per year just because you have less atmosphere protecting you from the cosmic rays let's go to a little bit higher levels of dose a dental x-ray half of a milligram your normal background dose about one milligram per day and then here at the bottom is if you fly on an airplane you go across the US from New York to LA at six hours up in the air you're at 33,000 feet remember Denver was giving you extra millirem because it was at 1,000 feet now you're five miles up much less shielding from the cosmic rays from outer space and you get a whole four millirems from flying across the country don't panic much more dangerous is the part about the plane maybe not landing the four millirems nothing to worry about let's look a little further now we'll take all those blue charts and they will turn into B just one of these green ones you see an x-ray of your chest is 20 micro sieverts about two millirem and if you actually were in Tokyo during the Fukushima accident you may have at most gotten an extra four millirem not the same as flying across the country once if you live in a stone building a uranium thorium in the stone that's part of that natural background that's at least just an extra seven millirem a year compared to a wood building Three Mile Island the worst nuclear accident in the u.s. tiny amounts of dose within 10 miles 8 mil around we keep going down here we get the amount that you might have been in the Fukushima pawn 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 milligrams 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 one hundred milligrams extra per year here is the amount of dose that anyone possibly could have gotten from Three Mile Island equal to the normal public safety limit of a hundred milligrams 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 millisieverts that's 200 milligram not equal to the amount of radon exposure on average for a given year and finally here is that somewhere around three hundred and twenty or so milligrams in this case they say four hundred milligrams from a normal yearly background dose so all of these things we've talked about Fukushima Three Mile Island Act 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 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 any complete unmitigated disaster in terms of radiation and radioactive substances this for an hour two Nobel in 2010 many years later compares to say one CT scan all 700 milligrams of 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 and this is uniform across the world is five REM per year right 50 milli sieverts now they actually limit it per quarter so you can't like hey last day of the year I get my five REM the next day I get my whole next five REM they say 1.25 per calendar quarter you still see we haven't talked about health effects that be is because that even if you're a worker and you get five REM and you go to the doctor and say doctor doctor I think I've I've hit my limit for exposure as a radiation worker test me test me I want to see 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 10 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 multiplied pretty quickly by here if you get 10 REM you do not feel sick in fact if you didn't have a blood test you never even know if you get four times that if you get 40 room you can start having radiation sickness hair loss redness nausea and if you go up here to two sieverts which is 200 REM you're definitely in this range of radiation sickness and radiation poisoning you're gonna need medical care there's a a interesting number called the ld50 30 sounds like a motor oil but it's the lethal dose for 50% of the population to die in 30 days that's the number down here for sieverts 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 10 REM level there is not a noticeable effect to your body and then 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 10 minutes next to the core after the meltdown or an explosion nothing comparable to the radiation loss in doses at Fukushima so what we've been talking about our acute doses doses you get all at once there's always the question about cancer what type of dose do you need that would increase your chance of getting cancer let's talk about that next at what radiation dose level do you start having an increased risk of and cancer clearly we know it's not in the tens of million 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 who are 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 an 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 oh I died of old age chances are though something wore out something went on a rampant growth 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 than that number there were excess deaths that happened earlier and maybe that's because that population had some sort of chemical some carcinogen in their environment or maybe it's because they had a radiation dose if you take these cases you can make some cases Chernobyl ocean or some other things and you can put data points and there's air bars on them 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 now if I take the slope of this line a 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 times 10 to the minus 6 excess deaths per Rev per year what does that mean well let's say we have here the number of people okay and here is the dose they each get so if I had 500 people each getting 10 REM I multiplied 500 times 200 times 10 to the minus 6 times 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 not have normally developed 1 out of 4 people are going to develop cancer at some point during their lifetimes but in this case the extra radiation dose gives you an extra one out of 500 chance of getting it of course this is linear meaning that if there are 50 people each getting 100 rim 100 REM you've certainly experiencing radiation sickness you will have a chance of 1 out of 50 of developing and excess cancer every year goes the other direction too right I could say this is 5,000 people each getting one rim of those 5000 people one person is likely 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 mil around or 500,000 people each getting 10 mil around remember when we're at this scale of ten extra millirem this is like living at 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 about logical effects at 10 REM maybe at 1 REM there still is some excess cancer but certainly in these lower levels the hundred mil around the 10 Miller room the one millirem five 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 a 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 one millirem a day that everybody gets from natural causes that's been happening since the earth was here all 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 or maybe from other carcinogens in our environment as well there been some very famous examples of radiation exposure and one of the most interesting stories is the women in World War two who were painting radium dial watches actually have one of those watches as you can see here and this watch has very fine lines printed on the second hand 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 didn't 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 down watch why do you need to see what time it is in the dark well let's say you were 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 gonna do it by iFly at this range for this length of time at this speed you look at your speed you look at your compass you look at are you very precisely time and then you know that you are 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 anti-aircraft Gunners down load on the ground are going to look up and they'll see oh look there's an airplane probably hear it they don't know where it is where to shoot as soon as you turn a light on you're advertising where you are and you 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 u.s. 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 has to be a very steady fine hand and you need to have your paintbrush come to a very fine tip best way to do that put 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 are 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 to kind of do a model to figure out every time someone how often would they put them up 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 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 Radian was first concentrated my grandfather was a dentist well more than that he was a back then in the 1920s it was a dentist and orthodontist and oral surgeon and x-ray machines were available and x-rays for teeth are extremely important right you have 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 ha kwanghoon hurt right while he's holding his film in there I remember my grandfather extremely fondly wonderful man and it was always interesting that you never actually did the game pull my finger because it might come off little gross sorry about that but he did have kind of a constant festering bit of a store 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 did that dying 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 act up getting some cancer of the mouth or the esophagus of course as you ingested in 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 to 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 that that's what you need to know about radiation exposure you [Music]
