Gresham College Lectures

Reducing harms after Nuclear, Radiological and Chemical Incidents

December 08, 2023 Gresham College
Gresham College Lectures
Reducing harms after Nuclear, Radiological and Chemical Incidents
Show Notes Transcript

Nuclear, radiological and chemical incidents have the potential to cause major harm.

The risk of nuclear and radiological events causing health effects can usually be significantly reduced by relatively simple measures, which are based on the properties of the chemicals released, especially at a distance from the incident.

Chemicals that can cause harm, such as organophosphate and mustard chemicals, need to be understood to mitigate the risks and establish medical countermeasures.

This lecture was recorded by Sir Chris Whitty on 28 November 2023 at Barnard's Inn Hall, London.

The transcript and downloadable versions of the lecture are available from the Gresham College website:

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This year, I'm going to be doing a series of lectures on, uh, medical and healthcare issues after disasters and major accidents. And in the first one, I'm gonna talk about reducing harms after radiological nuclear and chemical emergencies. Now, uh, these are broadly defined, defined as, uh, radiological incidents, uh, where you don't have a blast or explosion from a nuclear event, uh, a nuclear incident, uh, where there is a blast or explo or exposure, uh, due to nuclear fission, uh, and then chemical, which can be deliberate. So, chemical warfare, for example, poisonings, uh, or accidental. Now I'm in the chemicals. I'm really gonna talk, uh, just as about the, uh, agents that are used in, uh, military, uh, uses throughout this. The key thing to understand with both radiological and, uh, with chemical issues is an old, uh, saying from Paracelsus, uh, in the 16th century that the dose makes the poison. Very low doses of either radiation, uh, or of even quite dangerous chemicals, uh, are usually harmless or you recover from them, uh, really quite quickly. Uh, high doses, of course, are what cause significant problems. Radiological, uh, nuclear and chemical incidents tend to cause widespread and very understandable concern. They tend to dominate, uh, the news agenda, uh, and they are indeed, um, uh, dramatic, uh, and, uh, are turned quite frequently into dramas, including, uh, two very, uh, well, uh, regarded, uh, ones I've put up here. Um, this talk, however, is going to talk, uh, to think much more about the science of these events, uh, and also what we can do in health terms to minimize the risk to, uh, individuals, to families, uh, after the event, Radiological incidents from civil, mainly from civil, uh, um, uh, nuclear ins, uh, installations are the, um, the are the most common of these, although even these are very rare. Um, some important, uh, large scale events include, uh, the Fukushima and the au, uh, disasters we shall talk about, uh, in more detail. But there have also been, uh, leaks from nuclear, uh, inst, uh, installations, uh, in the USA three Mile Island, for example. Uh, and in the uk in Windscale mainly, uh, very, uh, small and with, uh, limited health impacts. And there have been several smaller incidents along the way. The Gresham College lecture that you're listening to right now is giving you knowledge and insight from one of the world's leading academic experts, making it takes a lot of time. But because we want to encourage a love of learning, we think it's well worth it. We never make you pay for lectures, although donations are needed, all we ask in return is this. Send a link to this lecture to someone you think would benefit. And if you haven't already, click the follow or subscribe button from wherever you are listening right now. Now, let's get back to the lecture. Now, it's important when thinking about this to recognize that, uh, power generation, at least by conventional sources, has always had a risk to health. Uh, and most conventional power generation, uh, causes substantial air pollution. And this causes, uh, very significant harm. Uh, coal, uh, burning, uh, for production of power in particular, is extremely damaging to human health, uh, and through air pollution can cause increases in heart disease, stroke, lung cancer, uh, and, uh, many other, uh, potential diseases, uh, and nuclear, uh, power needs to be seen, uh, in that context. Uh, I have given a talk previously at Gresham College, uh, on the risks of air pollution. Uh, and here's a graphical way, uh, of really demonstrating this, uh, and showing that deaths from, uh, air pollution and other accidents, uh, are much higher actually, in terms of numbers, particularly from the most polluting form of coal, uh, called lignite. Uh, but coal in general has, uh, and to lesser extent, oil ha burning have very significant potential health impacts due to, uh, pollution. Moving on to, um, uh, radiological incidents, accidents tend to be either due to, uh, the human error or to natural disasters, and they can be some combination of those, uh, to novel. In 1986 is the best known, uh, the best studied, uh, and the largest of these, uh, the causes for it, uh, were complex, and a whole series of things essentially lined up. Uh, combination of poor design of the reactor and human error, uh, led a test shutdown to lead to an energy surge. And then there was a, an explosion. It's caused by steam, uh, and then a secondary explosion, which breached, uh, the, the call. Um, and then there was a reactor fire, and that led to, uh, radioactive material being carried, carried a long way up 'cause of the heat of the fire into the atmosphere. And then, uh, it, uh, tracked around, uh, over Europe, uh, for quite some time. I'm not gonna go into the details of this. Those who are interested can look at the IAEA report on this, which is really the definitive, uh, version. Fukushima, um, uh, in 2011 in Japan, uh, was, uh, largely caused by a natural, uh, disaster. An earthquake, uh, led, uh, to the, uh, reactor shutting down as it was designed to do. But then there was a sub, sub subsequent tsunami wave, uh, which damaged, uh, the cooling, uh, system, and then the reactors overheated, and there was a partial meltdown. And then there were subsequent explosions, mainly due to hydrogen buildup. To be clear, this is hydrogen. The gas, this isn't a hydrogen, uh, like a hydrogen bomb. This is actually just buildup of hydrogen gas, uh, which, uh, exploded and breached the core. Again, the, the, uh, there is an official report of this for those who are interested in the details. Now, after there's been an accident, there are broadly four kinds of effects on health. The first of these, um, uh, the first two of these are really only going to occur for people in the immediate vicinity. Generally, people who are actually nuclear workers or emergency workers on the site at the time of the emergency. There's physical trauma, um, if there are explosions, and there were explosions in both those two, uh, cases. And then there is acute radiation sickness, uh, which I'll go on to describe, uh, in the next few slides for those not actually on the site, um, there is a risk, uh, but it's massively lower. Uh, and the longer term, uh, effects, which can occur for people who are exposed usually to a radioactive plume, downwind are cancers. But the rate, the rates of those as I show, are low in fact. And then psychological effects. And the studies of, uh, hun, uh, nuclear disaster survivors showed that these psychological effects were often the most, both the most common and in many ways, the most severe. So people worry about it, uh, after the event, for understandable reasons, To understand the risks, um, and how to, uh, reduce them significantly after an event. It's important that we have, uh, a basic understanding of radiation. So the next few slides are really going to just run through some key bits of understanding of radiation. There are broadly three types of, uh, radioactive material or radioactive exposure, uh, which are important after a radiological, uh, and indeed a nuclear incident. Uh, alpha particles, um, these are, are, these can travel just a few centimeters in air, uh, and they can be stopped by a variety of relatively small barriers. Then there are beta particles more important. Um, and these can travel tens of centimeters in the air, but not huge distances. Uh, and again, they can be stopped by slightly larger barriers. And then finally, um, there are gamma rays. These are not particles. These are, uh, wave forms, uh, and they can travel many meters to some kilometers, but not indefinitely. But the further they travel, the more their energy will be attenuated, reduced. Um, so, uh, the effects will weaken over distance. And just, you know, to reiterate this point, alpha particles are stopped by things as as limited as paper, uh, and the out outer, therefore dead, uh, layer of the skin. So really, if it's only if, uh, significant amounts are ingested, they tend to cause, uh, any significant harm. Beta particles, uh, again, more important, uh, are stopped by glass, aluminum and other relatively small, uh, barriers, uh, or at least very significantly reduced. And gamma rays can penetrate those, uh, but they are significantly attenuated by, uh, walls, uh, uh, and brick made of brick, concrete or stone. And essentially, the larger, the mass between you and the gamma ray source, the lower the amount, the dose of radiation that you are going to get. Repeating my constant refrain through this talk. The dose equals the poison. If you can reduce the po the dose, then uh, the effects will be much smaller. The human body, uh, is remarkable in its ability to handle and to recover from large numbers, uh, of, uh, uh, assaults on it. And radiation is one of these. Radiation is actually occurring in the background every day as radiation in, in, uh, almost, uh, all, uh, environments. Um, some buildings are, have, have higher levels of radiation. Quite a lot of very healthy foods, uh, have traces of radiation. Tobacco has radiation, um, and so you are being exposed to radiation the whole time. Now, come on in a second to kind of the doses we're talking about at a higher dose. Um, uh, in medicine, we use radiation in two, broadly, two ways. Uh, it's used diagnostically using X-rays. And people who have an X-ray have a CT scan are exposed to very small amounts of radiation, which really have, uh, for practical purposes, uh, with the exception of fetuses, um, uh, from, for women who are pregnant, but for practical purposes, have, uh, no increase in risk, uh, under ordinary circumstances if people just have a single x-ray. Uh, and then the, at a much, much higher dose, uh, radiotherapy, which is based on the fact that, uh, healthy cells exposed to radiation may be damaged, but they will then recover, uh, from the radiation dose. So the body can both handle small amounts and recover from, uh, larger amounts. Now, I talked about cancer treatment in a, uh, a series, uh, a previous series at Gresham Cottage. I'm not gonna go through this in detail, but I think it's just useful to understand this background for understanding the, uh, wider risk. So the way in which, uh, radiotherapy occurs, uh, in a variety of ways of achieving it. But, um, the most common thing is to, uh, fire external radiation at the body from, uh, multiple angles so that there's only one, only the area with a cancer in it has a very, very high level of radiation. The other areas of the body that the radiation passes through has a much lower level, and those cells will recover. So again, this is just a demonstration of the fact that normal cells will recover from radiation, uh, in the great majority of cases, and the right of ways of doing it on the right, I've shown, uh, how, um, uh, both, uh, x-ray type and proton beam therapies can be used for this concentration of x-rays. Where a, uh, cancer is found, there are quite, there are the way in which you measure the, uh, amount of radiation can get quite confusing. Uh, gray's, seaberts, a variety of ways of, of thinking about it. Uh, one way that people have thought about it is the, uh, number of, um, bananas you'd need, uh, to eat to achieve the same amount of radiation exposure, because even bananas, very healthy, uh, uh, food, like many other foods, have a very small, very small amount of, uh, radiation in them. And on the left here, uh, you can see, um, uh, the, and essentially the banana equivalent. This is a slightly crude scale, so, but it's just to give a sort of sense of relative scale, uh, of, um, the amount of radiation you get. So your normal background dose would be around about a hundred. A dental X-ray would be lower than that, so it's less than a day's worth. Uh, a, an X-ray of the chest, uh, might be somewhere between twice and five times that. So five days worth of background radiation. Uh, and, and the, the, by, by the time, by the time, you know, by the time you get up to ct, slightly higher than that, but really a, a very substantially greater amount of radiation for radiotherapy, um, and a massively higher dose, uh, if you are to have a fatal dose. These are the kinds of, uh, levels of radiation, which actually are going to cause really substantial harm. So, low doses we handle, uh, as bodies, uh, really well. So the first of the major causes of, uh, illness after exposure to radiation, um, is acute radiation sickness. This is by far the most severe end of the spectrum, uh, and a relatively or very small number of people, uh, will be affected. But for them, uh, this, uh, is a serious, uh, risk to their health for this. And these, as I say, will be people really just on the site of an emergency. Generally, there are four, uh, sub syndromes with right of ways of describing this. Uh, but they, they're all, uh, caused by the fact that radiation has its biggest impact on the cells in the body that are rapidly dividing. Uh, and the, for the hemopoietic system, this is the thing that makes blood, uh, makes red cells, makes platelets, which stop bleeding. Uh, and importantly, it makes white cells which fight infection. And if the bone marrow is temporarily essentially switched off because of the damage from the radiation as it recovers, uh, you can have a period of time when people have anemia, uh, there. Uh, but more importantly, uh, they are very susceptible to infection until their white cells recover. Then there's, uh, the gastro tonal system. The gut, gut rapidly, uh, turns over, uh, with diarrhea and a variety of other, uh, gut problems, uh, the cutaneous system, the skin system, including, uh, hair, uh, and then the neurovascular system, which really only tends to be affected by very high doses. Indeed, all of these, uh, are in the great majority of people temporary, so they will recover, but, um, for a period, they will be at significant risk because of, uh, radiation sickness. And for those who get radiation sickness, there are four stages, and not everybody, uh, goes through all of them. The first of them, which happens commonly, including people who actually go on to have no further issues, is a prodrome. People feel really very rapidly. They have vomiting or a nausea, headaches, loss of appetite, diarrhea, fever, and this is a short term effect. Uh, and it then, uh, improves. Then there's a period for days, uh, to weeks. Um, the shorter the, uh, those, the bigger the dose, the shorter the period where people make an apparent recovery. They, in more severe cases, they may have some hair loss, but otherwise they appear to get better. And then weeks to months later, uh, there is a period of illness, manifest illness where people have diarrhea, infection, anemia, um, uh, and during this period, they are very vulnerable, particularly, as I say, to, uh, infections. And then, except in people who have the heaviest dose, there will be recovery and people will recover, uh, largely or completely from their radiation dose to give some sense of scale. Remembering that, uh, VO was the, uh, largest, um, civil nuclear, uh, sorry, civil, civil radiological event. Um, uh, that, that had probably about 134 acute radiation sickness in total, uh, and around 28 deaths. Uh, Fukushima, uh, had no, um, deaths from acute radiation sickness recorded at all. So these are rare, but these are obviously serious when they occur. And what will happen depends on the dose. So, uh, at a relatively low dose, um, this is, uh, uh, measured in grays on this particular thing. These, these da these data are, again, open source. Uh, people will have the prodrome, they may have the nausea, vomiting, and anemia, and they may, uh, subsequently have a slightly increased risk of infection and of fever, but the recovery will be relatively quick. Uh, there isn't severe disease, and there will be no mortality, uh, in people who've had this kind of very low dose, uh, overall, Uh, at a high, uh, dose, but not a completely lethal dose for most people. Here's, um, a, uh, someone who's been exposed to, uh, three to five grays, uh, which is a much higher dose. They'll have a much wider range of symptoms, uh, much longer and more severe, uh, fever, infection, diarrhea, uh, weakness. Uh, and the mortality rate of this kind of dose would be somewhere between five and 50%. So still the majority of people will recover, but, uh, they will be very sick for, um, a period of time and need, uh, very careful medical care. And then at very, very high doses, uh, the effect will be lethal, but that's exceptionally high. So that's acute radiation sickness, very small numbers, very, uh, heavy, uh, exposure to radiation. The other thing that people, uh, understandably worry about is cancer. And, uh, this has been studied, uh, uh, both in, uh, tanavo and in, um, uh, Fukushima. And I think it's worth looking at some of the data, and I've chosen Fukushima to do this. It was, there was a really heavy study by the World Health Organization, WHO, uh, looking at this, the first thing I want you to look at is the map, uh, on, on, on Fukushima, which is on, on the right of this slide. And, uh, in red, that red streak is where people had a high dose, uh, potentially exposure from the plume of radioactive material that moved downwind, uh, away from the radia. The, uh, the, the, the reactor, uh, after it had been breached, uh, in blue, um, a much lower, uh, exposure, uh, and other areas outside that really no exposure for practical purposes at all. And I wanted to show, uh, really, uh, two things, um, uh, with the graph, uh, on the left of this slide. The first is that, um, the, uh, risk of a subsequent cancer is very much dependent on the dose. So in the risk of people in absolutely the middle of the red area, the highest exposure in the plume nearest to the reactor have unsurprisingly, a higher risk of cancers than those, uh, than they're the ones on, uh, location one, uh, than those in location h which is much further away from the plume, but still affected. The second thing to note is that, um, this varies by age. So if children under one are exposed, they have a higher risk, not a massively higher risk, but a slightly higher risk than those, uh, who are older children, uh, and higher, again, than young adults. So, age does have some implication here, but, and I think this is where it's important not to get things, uh, see things in a, in the wrong perspective, if you compare the risks as a result of this exposure to someone's lifetime risks, overall, The actual proportionate increase caused by having been exposed to this nuclear, this radiological accident from a nuclear power station, uh, are actually extremely small. And the, uh, very, the dark blue or the blue bars at the top of these, uh, are the actual risk. And then the gray bar below it is the, uh, lifetime risk, not caused by, uh, the radiological events, but by everything else that someone goes through in life. And as you can see, uh, really even in this, uh, very, uh, uh, this relatively heavy exposure compared to others, the actual increase in risk over a, a lifetime, uh, is small, uh, still larger in someone who's a child than, uh, someone who's an adult. But still, uh, in both of those, uh, small, and I've, uh, what we have shown on this is, uh, solid cancers, uh, on the left and leukemia, uh, bone, uh, bone marrow cancer. Uh, on the right there is, however, one particular cancer, which is, uh, made more likely by exposure, uh, and where the effects are attributable. It's a very rare cancer. It's made more common by, uh, radiological exposure. Uh, but it's still very rare in absolute terms, and that is thyroid cancer. And again, uh, worth looking at, uh, really two, two things. Firstly, on the right, this is really to demonstrate again, this effect that, um, uh, small children are at a higher risk than, uh, adults. And secondly, um, that, uh, women are at higher risk of thyroid cancer than men. And that is also true after radiological exposure. And you can see this in terms of the lifetime attributable risk. Again, uh, on the, uh, on the bit of the graph on the left, what you can see in the gray bars is what people would've had had they not had the exposure. The blue bars are the additional, um, risk as a result of exposure. And this is in area one. This is the people who are most exposed, immediately downwind of the, um, uh, the, the reactor. But the numbers involved are very small. Um, and, uh, it's important to stress that, uh, thyroid cancer, the great majority of people will not get thyroid cancer. And of those who do, uh, the great majority will in fact survive. So looking at, um, uh, the snuggle risk, uh, after 30 years, so this is after a long follow-up, the total number of, um, people who had thyroid cancer at all. This is all causes. This isn't just caused by radiation. In the three most affected cancer, uh, countries, was about 11,000. Um, but only a fraction of those will have been due to radioactive iodine, and most, uh, would make a full recovery, even of those who've got cancer. Very modest increases in other cancers, uh, for those who were exposed, um, uh, to long-term radiation. And there was probably a small, but not, not, not substantial, but, but small, but real risk of increased of cardiovascular risk, uh, and also of cataracts, uh, of the eyes. All of these are dose related. So if you can reduce the dose, you substantially reduce the risk that any of these will occur. But to make a point I made earlier, by far the most common, uh, imp implications were mental health issues, where people were very worried that they or their families, uh, will, would be suffering as a result of being, having exposed to radiation. And it was actually this concern, there was probably the bigger, uh, risk than the actual risk of cancers and other physical harms. So, since the body can deal with very small amounts of radiation and recover well from, uh, low to moderate ones, the key thing is to reduce the dose of radiation and the, after an event, there are three ways to minimize exposure, uh, reduce time, so the amount of time you are, uh, subject to radiation, uh, increased distance from you and the source, and shielding, putting a barrier between you and the radiation source. So if you assume a fixed concentration, the risk is broadly proportional to the time exposed. So the less time you have exposed, uh, the better. And, uh, nuclear, uh, workers are trained very heavily in this distance is very important. So at a distance of a few kilometers from a radiation source, there will be no alpha or beta radiation, and gamma will be minimal. So keeping away from sources, either the, um, uh, the actual accident or a plume, uh, if you can put distance between you and them, uh, the impact will be extremely small. The plume of radioactive material, if there is one, uh, as it moves, is likely to get larger physically, but also to dilute. So a larger number will be of people may be exposed to a much lower amount of radiation, But, uh, it is important to track the plume and to make sure people who are likely to be under it are aware of what to do to minimize their risk. And finally, uh, shielding, uh, is a very effective way of preventing alpha and beta radiation, putting you a barrier between yourself and the radiation source, and significantly effective, but not completely effective against gamma, uh, radiation. I'll go onto that in slightly more detail. But to summarize, to reduce your radiation exposure, limiting time, increasing distance and using shielding will significantly reduce the dose. And the dose is what predicts how bad the possible outcomes will be, both short term and long term. If there is a nuclear event. Um, uh, and this is just one of, uh, this is just an example, uh, of, um, plume modeling. Uh, there will be, um, expert groups will, uh, be providing a maps of and predictions of where this is gonna go based on weather conditions. And this will depend on several factors, how far up it goes, uh, into the atmosphere. So much, uh, higher, uh, temperatures will much, uh, any kind of explosion may, uh, loft things much higher than, um, if that doesn't happen. And the wind will go in different directions depending on, uh, which, uh, height it is. The wind speed and direction is obviously important. Uh, things like precipitation, rain, rain, and other events, uh, will, um, have big implications for how quickly it's washed out. And also, local factors on the ground will have, uh, big implications for exactly how much concentration occurs. So the Met office and others will model it, model any kind of plume, and be able to predict, uh, in which direction it's likely to go next. So apart from the people immediately on the site, the plume is the major risk, and this is what will affect, um, uh, anybody who is affected, who isn't immediately on the site. And I think that the key thing here is to understand, uh, the, the advice and the reasons for it after an event. And the first bit of advice is get inside and then stay inside, don't, uh, venture out. Uh, and finally, uh, stay tuned to try and get advice as to when it is going to be safe for you and your family to move. The reason for this advice is really, uh, flows from what I said earlier on, uh, about the way in which radiation works, houses, offices, and schools built usually of, uh, brick or concrete or stone, um, provide very good short-term protection. We're talking one to three days against alpha and beta radiation. They may land on the, uh, on the walls, they may land on the roof, but they will, uh, not be able, the radiation will not penetrate them, uh, and from other elements of radioactive dust. But it is important that you then close windows, block off any holes, turn off the air conditioning, so that air is not coming in, uh, from the outside. They will also substantially reduce gamma radiation. Um, but you want to get as many walls, uh, between you and the outside as possible, because the greater the mass between you and the gamma at the radiation, the smaller the dose you are going to, uh, actually receive due to atte attenuation. Cars, on the other hand, are much less safe. And this is one of the reasons that, uh, the advice is not to immediately jump in your car, uh, pick up, um, the family and, uh, drive. Firstly, other people may well have had the same idea. So you maybe be stuck, uh, on the roads. And secondly, uh, you will have much less protection in a car than if you are in a building. But if there is time to evacuate, uh, do so, but with advice. And the reason for that is plumes may not be where you think they are, you can't see them. Uh, it's the mapping of them that will tell you where the risk is, where it's going to be, uh, in the next, uh, few hours and days. So just to, uh, give some idea of this, um, uh, any house will provide protection, but again, the more walls there are between you and the outside, um, the better. Uh, and this is just kind of graphic to give you some idea about where you want to go. You want to go essentially into the center of the building, uh, down, uh, down into a cellar, if there is one 'cause that puts more, uh, distance between you and the, uh, roof. Um, a typical brick house will reduce this down by about to about point, uh, oh one five. So essentially 85% reduction, uh, and a multi-story building will reduce it even further 'cause there's more concrete, uh, and brick involved. The next thing you can do and should do is decontamination. If you've been outside during a radiological, uh, or indeed nuclear emergency. And, um, for radiation, I'll come onto chemicals, which are slightly different, but for radiation, important to understand that a, that minutes don't matter here. The key thing is that you do this, uh, effectively. So if you've been outside, remove your outer clothes. And ideally, if you're on the right kind of environment where you can do this, remove all your clothes, put in, put on clothes that are, uh, are, um, clean and, uh, haven't been contaminated. This substantially reduces the risk. So any kind of be remitters, are all remitters on those clothes are then off you. They're not gonna penetrate. Uh, they're going to be, um, some distance away from you. Double bag them, put them, uh, somewhere away from where you are. Then, uh, shower, uh, using soap, um, uh, lots of water. Uh, but don't put in conditioner 'cause that can lead to, uh, things sticking to your hair. So just soap and water. Mild soap and water, uh, will just get rid of further amounts. And this will generally remove more than 90% of the, the radiation on you. So this is an effective way, again, of reducing the dose. Remembering the dose makes the poison. Then it's worth thinking about what other things you can do, particularly the of, from the risks of, uh, radioactive material that's been ingested. And the novel accident really provides the model, uh, for which isotopes are important. So, quite a lot of radioactive isotopes, um, occurred actually on the site of the, uh, the reactor. But, um, uh, only really two became important, uh, in for medical, in medical terms, uh, outside, uh, radioactive iodine and, uh, radioactive cesium. And they provided more than 90% of the radioactive material in the plume. So they were really, uh, the big risks. And they have slightly different, um, uh, properties. Radioactive iodine has a, uh, relatively short half-life just over a week. So that means that the dose is going to be dropping very rapidly over the first two or three weeks, uh, and or decay way in months to a point where for practical purposes, it's not adding much risk. Seizing, on the other hand, has a much longer half-life. So this will, this will survive in the environment for, uh, a much longer period of time. But they do actually have different medical, uh, properties. Um, iodine, uh, generally iodine one three. One is a product of uranium and plutonium, uh, both of which may be used or either or both of which may be in the reactor. It's also used, uh, medical treatment. Uh, most of its radiation is beta, so it's quite short, uh, range. And therefore, the risk is if you ingest it, uh, in some way, there's a small amount, a much smaller amount of gamma radiation. The reason it's important, uh, however, is that it's taken up by and concentrated by the thyroid gland. And that is because the main, uh, thyroid hormone is based on iodine. So the thyroid gland, uh, seizes iodine that's passing and concentrates it in the gland, uh, to make, uh, thyroid, uh, hormones. And the problem with this, therefore, is you get a very heavy concentration of the iodine, which might, at the very low levels in the rest of the body, really has minimal effects. Because it's highly concentrated in this area, it is, uh, therefore, and producing beta emissions, it therefore can cause local damage to the thyroid, uh, gland. And this can do, uh, two things. Uh, it can damage the thyroid glands so it doesn't continue to produce its, uh, hormone. Now, that is a nuisance, but it is an entirely, uh, manageable process. Lots of people have to have thyroid, uh, replacement therapy. Uh, it's really then means people have to have thyroid replacement therapy subsequently, uh, with, uh, just oral, oral drugs. Uh, but there is this increased risk, which I talked about earlier of thyroid cancer. Important to note that radioactive, uh, iodine of different forms, uh, is used also for treatment, sometimes for an overactive thyroid, uh, and sometimes in fact, for treatment of cancers themselves. Uh, so it is given, but obviously that's in a environment where you're trying to treat a disease. So this issue about radioactive iodine in the thyroid, uh, means that it is worth, if you are, know, you're about to be exposed, taking iodine to reduce the risk of thyroid cancer. And the reason this works is by flooding the body with iodine just before the event, uh, the, uh, thyroid is then taken up a huge amount of iodine, uh, and, um, is, uh, much less likely to grab radioactive iodine, uh, as it goes past, reduces the risk of it being concentrated in thyroid subsequently. So for people exposed to significant risks from inhaling iodine, uh, from the plume, uh, the recommendation is to have stable iodine, uh, given between 24 hours before and two hours after. If you give it later than that, it actually can do more harm than good. So you definitely want to do it before the event. Uh, and then longer term risks can occur from, uh, milk products, uh, and food. Uh, but these can be picked up by people detecting the radiation and essentially taking them out of, uh, production. So that side of things, uh, will be dealt with by, um, safety, uh, measures on food subsequently. So it's really that initial risk under the radioactive plume, those who are not under the plume and not at risk from radioactive iodine. Cesium, uh, 1 3 7, uh, is, as I say, longer lasting. Um, it's also water soluble and potentially stable, so it can spread through the environment. It is taken up by humans, but it's, uh, very rapidly, um, excreted in the same way the potassium is excreted. So it's actually quite rare that people will get significant amounts of cesium concentrating in the body, remembering that the body is extremely good at dealing with low levels of radiation and recovering from moderate levels. So, uh, the biggest problem from caesium really is the fact that it has a relatively long half-life. Uh, and, uh, you can see, uh, on this map, uh, where caesium was deposited in Europe. Uh, and these, this has implications for subsequent agriculture in those areas, potentially where red is, uh, high amounts, It is very unlikely that tap water will be contaminated to a significant degree. So that's not a worry that people should have. They can still drink tap water unless told otherwise. Um, and anything that's indoors in your house, indeed, in a supermarket before the accident is safe to consume, it won't have been contaminated. The only real risk is vegetables outside when contamination occurred. So if you've got a kind of plot outside, then, uh, don't start digging up your, um, uh, your, uh, lettuce or whatever it is, uh, straight afterwards. Seems an obvious point. Uh, and, um, remembering that over 90% of radiation from food is naturally occurring and at very, very low levels. Uh, what what will happen then is there'll be a safety assessment of all the different food stuffs, and where there's a risk, it'll be removed from the food chain. So, um, the risk really in, in, from this point of view is likely to be very small. So that's the, um, uh, the what to do after a radiological event. And this is, uh, the majority of the talk. But I wanted now just to talk about some, uh, events, which we hope will never happen again, but it is worth understanding a bit about the medicine around these. And the first of these is a nuclear device explosion, a nuclear bomb. Uh, this will cause, um, death and destruction and disability, our three roots. The first is blast straight, blast. It, it is an explosion. It's a very large explosion, uh, and people will be killed by that explosion. The second is thermal flash where people, uh, get burns. And the third, uh, is radiation. Radiation, of course, is the one that's specific to, uh, nuclear devices. The great majority of the death will in fact be from, uh, blast and the fast storm, uh, that goes with it. So, um, those two, uh, are the, uh, what will will kill the great majority of people. And did so, uh, in, uh, in, uh, the, um, uh, second World War, Depending on the nuclear device size and variety of other things, there may be a zone where people survive the blast, but have a lethal, severe or moderate amount of radiation sickness For many nuclear devices that won't actually happen. The, the blast, uh, will essentially kill everyone who's going to be killed, uh, anyway, uh, unfortunately. But, um, the, some devices that may be a sort of outer layer where radiation sickness is important. And then the radioactive plume principles are exactly the same as for a civil, um, uh, radiological event. Uh, you get indoors and you stay indoors, uh, until you're given advice, um, to move, because it's become safer to do so. One slight difference is that radioactive iodine is much less important in, uh, in plumes provided, uh, which are created this way. And therefore, getting stable iodine is of practically much less importance. Now, the physics of this, I'm not gonna go through, but just to say that, um, the size of the nuclear device will determine whether there is a zone of people who get acute radiation sickness, but who were not killed in the initial, um, blast and fire in general. What this, this, this, uh, graph is demonstrating is that, um, the, uh, the dark blue line, uh, is the radiation injuries at a high enough level to cause very significant harm. And as you can see in small nuclear devices, there may be a group of, uh, quite a significant group of people who have, uh, radiation injury beyond the blast radius for very large, uh, blast, um, very large nuclear devices. Uh, essentially everybody would've been killed in the blast and fire, uh, unfortunately, but, uh, let us hope that this never occurs again. Um, uh, in the future within this, there's a lot of ra vari variation, um, uh, buildings, terrain, what's hills variety of build. All, all, all these kind of environments will have implications for both the effects of the blast injury, uh, and, uh, burns and radiation in due course, uh, and how high up the, uh, the, um, devices when it explodes, uh, will also have invocations. Uh, but I think probably the details of this are, are, are unnecessary at this point. The point is, uh, unfortunately, with a large event, most people will die in the blast. Um, So now to move on to, uh, chemicals, uh, and I'm really just gonna talk here about chemical warfare agents, but some of the points that I'm making in general are applied to all contamination with dangerous chemicals at high enough doses. Uh, many chemicals and drugs given quite perfectly appropriately by, uh, doctors, uh, can be toxic. And some are indeed occasionally used as poisons where people deliberately give someone, uh, a much higher dose than is safe. Uh, but, um, uh, in general, uh, if you keep within the, the recommended dose, uh, they will do, uh, much more good than harm. A much smaller number of chemicals have been designed deliberately to kill and maim humans. And there are three classes in particular. There are some others, but three in particular have been used, uh, unfortunately, uh, over, over, uh, our recent history. The first group are the blistering agents of which mustard gas is the best known. The second are the choking agents, um, uh, of which chlorine and sine, uh, are best known. And, uh, all of these, unfortunately, were used in the first World War. I'll go through them in a bit more detail. And then the third group are the nerve agents, especially the organophosphates, Start with the blistering agents. Um, there are several of them, but the three probably best known sulfur mustard, I'll say mustard gas, uh, cyte and nitrogen mustard, uh, are the ones that, uh, were used. And you can see, uh, on, on the right of this. Um, some of the studies of, uh, these agents, uh, on people at different concentrations, uh, on the effects on people's skin. Um, sulfur mustard is a gas or an oily liquid. So the actual, it's not just a gas. You actually can have it, uh, as a li in liquid form, and therefore people touch it and get bl blistering from that. And it causes its damage by, uh, skin contact, uh, eye contact and inhalation, and all of these, it causes severe burns and blisters eye damage and lung da damage. It's not, uh, often not immediate. It can be delayed by up to 24 hours as it's heavier than air. And this is important if you want me to get outta an environment where this is, uh, there. So it sinks to low lying areas. It's one of the reasons it was used as a military agent, 'cause it's sunk down into trenches and foxholes and so on. Uh, and, and, and normal weather conditions, it lasts about one to two days. It can, uh, be slightly longer in cold weather. The key, if someone is exposed to this, is get them out into fresh air and remove all their clothes immediately. So, unlike radiation where speed is much less important, uh, speed really is absolutely essential. You've just got to do it immediately and then go on to do decontamination, which I'll come onto. There are no antidotes to these agents, but the great majority of people will survive them. But it's exceptionally painful for the period, uh, over the, uh, next few weeks. Um, and it may cause some scarring, so extremely unpleasant. Uh, agents Subsequently, uh, master gas agents, however, were then used, um, because of their damage to cells. Um, uh, they were then, uh, studied for their effects, um, in medicines. And from them, several drugs were in fact developed, which are, some of which are still in use, um, because they cause damage to, to rapidly dividing cells, that's really where they cause the most damage. Um, this can lead, uh, it was seen that this led to a drop in white cells. And as a result of that, uh, doctors initially in the States, um, uh, started trying to see if this could be used. Uh, these drugs could be used to treat, uh, the cancers of the blood cells. Uh, and the first patient who had this was someone with lymphoma. And the drug significantly improved their lymphoma, uh, with repeated doses, uh, but eventually they relapse. But this was really the start of, um, chemotherapy. So chemotherapy actually derives in part from these, uh, appalling, uh, military agents. Uh, then, um, various, uh, pharmacologists, uh, use use those principles and found mechanisms to make them much less toxic to the general inter individuals. Uh, and this led to a se a series of drugs, which are still used, uh, today in chemotherapy, uh, probably the most widely used is a drug called Chlorambacil, uh, which, um, is essentially derived from this by several removes, still uses a chemotherapy agent, uh, and also used for severe immune diseases. So, uh, this has gone into medicine from, uh, military agent, um, over, over many years. The second groups of agents are the choking or pulmonary agents that affect the lungs, uh, of which the best known are chlorine, gas and sine very extensively used in World War I. Um, uh, but they're also dual use. They're used a lot in chemical processes. So these are drugs which were known in industry, uh, for other reasons. Uh, a very high dose is, again, a very low dose. Uh, it's entirely manageable, very high doses. They cause burning sensations, the lungs, eyes, uh, coughing in very high doses. You get fluid on the lungs. Pulmonary edema and phosgene, uh, can additionally cause heart problems. Uh, like with the, um, the mustard, uh, group, the blistering group, the key thing is getaway and get clothes off as fast as possible. Most people will make a, a full recovery in between seven and 14 days, but, um, extremely unpleasant in the intervening period. Uh, phosgene has a higher mortality rate, but still the majority recovered. But Phosgene, in fact, was the chemical agent, which killed the most people, uh, in World War I. The third big group, um, not, uh, used, uh, in this way in in World War I. Um, but subsequently developed are the organophosphates and the carbonates. These are the nerve agents. Um, that's how they're popularly referred. These were originally developed, um, uh, by a as, uh, and insecticides and pesticides, and we still use 'em, this class of drugs in very different doses and different formulations for that purpose. Sheep dips, for example, which have organ, organ phosphates to help kill ticks, uh, if, uh, you treat, uh, yourself or children. Uh, with Malian, it's an incredibly low organ. Organ phosphate used to treat headly and scabies a very effective drug. Doesn't, uh, have, uh, good any problems, uh, uh, of, of a significant sort, uh, with toxicity, um, uh, if used as, as intended. So it was actually developed for medical and agricultural use. Um, the way they work is via the acetylcholine system. And, um, a, an enzyme that breaks down acetylcholine, uh, called ttyl cone esterase. Um, AST acetylcholine is used by lots of different species, uh, human, but also insects, um, as a neurotransmitter, uh, in multiple parts of the body. It's, it's, it's really widely used across, um, uh, all, all of, uh, biology in neuromuscular junctions. It causes muscles to contract. It's also affects the brain, uh, can affect the, as used in the brain sympathetic and parasympathetic nervous system. So it's got large numbers of effects. And what normally happens is the, uh, ACON is released, it then binds the receptor, it leads to the action, and then the asoc conone esterase breaks it down in nanoseconds. So the system turns on and then immediately turns off. And s more AOL coline is re released. These agents, uh, stop the breaking down of the AOL coline, uh, acetylcholine. And because of that, the system is then always on. It's not in the kind of balance, it's always on. And this is what causes, uh, the damage. Uh, these agents at high doses, and the doses used to actually damage humans deliberately, rather than as a, an insecticide or to treat, um, conditions can be delivered in a variety of ways. They can be delivered as gases, uh, which the most well known is sarin, and they can also be delivered as liquids. In military terms, this is a area denial agent, uh, uh, of which the best known, uh, was, uh, vx. But in the UK unfortunately, we've also, uh, had, uh, due to deliberate, uh, use, uh, Novi shock, uh, which is another of these gon phosphate, um, agents. The symptoms of phosphate poisoning are twitching, shortness of breath, diarrhea, involuntary tearing, uh, pinpoint pupils in a moderate dose and in higher doses, uh, still convulsions, coma, cardiac arrest, respiratory arrest, and death. So, as with all of these things, dose makes the poison very, very small. Exposure will be dealt with by the body relatively, uh, quickly. Uh, if you've got, uh, very high doses, uh, potentially lethal amounts, there are treatments for this, um, of which the most, uh, widely used is atropin, uh, which blocks some of the receptors. So it reduces some of the effect of this. So it, it blocks some of the acetylcholine receptors that this acetylcholine is, uh, is going to affect. Um, but, uh, the treatment is only moderately effective. Um, and you have to wait until, uh, the system, uh, has recovered, which can take a very long time if people do make a full recovery For all of these chemical agents. And the same is true if you're talking about industrial chemicals that people are exposed to. Uh, decontamination is absolutely critical, and there is a real need for speed in decontamination with chemical agents. In contrast to, uh, the, um, uh, radiological in, uh, incidents where, uh, its speed is less essential. You need to remove all clothes possible. Uh, don't pull things over the head. If you've got scissors, just cut them off to avoid them being smeared over the face, the eyes, and so on. Then they should be double backed and put a long way away from anywhere where, uh, an a anyone is. If it's an oily substance, then dab it off quickly initially. Uh, this is to avoid it being spread more widely. So, um, using kitchen towels, for example, would be, uh, a, a good way of doing that. And then go onto wash shower, ideally with copious amounts of water, uh, and potentially mild soap that basically is decontamination. Uh, and then remove contact lenses, which could be, uh, could have concentrated some of the chemicals inside them. So, um, removing all clothes, removing excess oily material, and then, uh, lots and lots of water. And mild soap really is the way to reduce the dose as much as possible. So this is, that's really an overview, uh, of the major radiological nuclear and chemical deliberate chemical incidents and accidents throughout all of this. The point I was trying to emphasize is the dose makes the poison. And therefore, since the body is so good at dealing with very low doses, if you can minimize the amount of dose, the chance of harm are substantially reduced. And may well, for practical purposes, for long-term harm, be close to zero. Whereas if there's very high dose, then the risks obviously are much greater. So reducing the doses are the key expect, except for those in the immediate vicinity of radiological nuclear or chemical incidents. It's possible, uh, very substantially to reduce the dose by taking relatively simple measures, generally at very low doses. The health effects are small and, uh, temporary. Uh, and even for, um, moderate doses, the body is remarkably good at recovering from things. It's, it's got extraordinary regenerative, uh, capacity for radiation. Uh, get inside, stay inside and decontaminate if you are outside in the, uh, under the plume. And for chemicals, rapid removal of contaminated clothes, further decontamination with copious showering, and then seeking medical care, uh, are the best ways to minimize the risk. This is gonna cause any long-term, uh, medical harm. Thank you very much.