Episode 144      30 min 40 sec
Waiter, there's cesium in my soup: The health implications of radioactivity

Associate Professor Tilman Ruff explains how radiation from nuclear energy sources can affect the human body and our health. With science host Dr Shane Huntington.

"Cells tend to be affected in relation to how rapidly dividing they are, so the more rapidly dividing the cell generally the more vulnerable it is to radiation damage." -- Associate Professor Tilman Ruff





           



Assoc Prof Tilman Ruff
Associate Professor Tilman Ruff

Tilman Ruff is an infectious diseases and public health physician, committed to the urgent public health imperative to abolish nuclear weapons, and to realising the potential of immunisation. He is Associate Professor in the Nossal Institute for Global Health, University of Melbourne.
Tilman chairs the International Campaign to Abolish Nuclear Weapons (ICAN). He has been active in the Medical Association for Prevention of War (Australia) since 1982 and a past national President; and is South-east Asia Pacific vice-president of International Physicians for the Prevention of Nuclear War (Nobel Peace Prize 1985). In 2008-10 he was an NGO Advisor to the Co-chairs, International Commission on Nuclear Non-proliferation and Disarmament, and in 2008 and 09 a civil society representative on the Australian delegation to the NPT PrepComs. 
Tilman contributed to the development of travel medicine; worked on hepatitis B control, immunisation and maternal and child health in Indonesia and Pacific island countries; and documented the link between nuclear testing and outbreaks of ciguatera fish poisoning in the Pacific. He is Australian Red Cross international medical advisor; provides immunisation advice to WHO, UNICEF, AusAID and vaccine manufacturers; and is a member of the WHO Western Pacific Hepatitis B Expert Resource Panel. 

Credits

Host: Dr Shane Huntington
Producers: Kelvin Param, Eric van Bemmel
Audio Engineer: Gavin Nebauer
Episode Research: Dr Dyani Lewis
Voiceover: Dr Nerissa Hannink
Series Creators: Eric van Bemmel and Kelvin Param

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VOICEOVER
Welcome to Up Close, the research, opinion and analysis podcast from the University of Melbourne, Australia.

SHANE HUNTINGTON
I’m Dr Shane Huntington.  Thanks for joining us.  When we heard the word radiation it is hard for most people to avoid thinking about catastrophic events such as the use of the atomic bomb in World War II or the destruction of the nuclear power plant in Chernobyl.  Radiation comes in numerous forms, each damaging in its own way and often misunderstood.  The March 2011 earthquakes and tsunami in Japan have caused significant problems with the reactors of the Fukushima power plant, resulting in an incredible level of misinformation about radiation levels and public safety.  On Up Close today, Associate Professor Tilman Ruff joins us to provide some clarity around the risks and effects of radiation on the human body in light of the recent events in Japan.  Associate Professor Ruff is from the Nossal Institute for Global Health here at the University of Melbourne, Australia.  Welcome to Up Close, Tilman.

TILMAN RUFF
Thank you, Shane.

SHANE HUNTINGTON
Why don’t we start with a description of what radiation actually is and how go about characterising the different types that we experience?

TILMAN RUFF
There are lots of different kinds of radiation and essentially it either comes in the form of electrical and magnetic energy, the electromagnetic spectrum, so part of that is normal light that we used to see, at the far end in terms of wavelengths, it’s radio waves, infrared and microwave and then ultraviolet, getting shorter and more energetic, and then X and gamma rays at the far end of the spectrum of the most high energy short wavelength radiation.  When we’re talking about radiation in a nuclear context, it’s usually in relation to what’s called ionising radiation and the ionising bit refers to the fact that it’s got enough energy in the little packets that it comes in to actually knock the electrons off atoms and therefore is chemically reactive.  Now it basically comes in two ways: either as part of that electromagnetic spectrum, as X and gamma rays up at the high energy end; or in the form of subatomic particles, neutrons, electrons, different bits of atoms, sometimes bits of the whole nucleus of an atom rather than just a single particle.  But they’re all called ionising radiation because they all do the same kinds of damage to human tissue.

SHANE HUNTINGTON
What natural sources of radiation do we experience?

TILMAN RUFF
We’re all immersed in a radioactive environment, it’s impossible to avoid.  We all get of the order of between two and three millisieverts of radiation, is the units that it’s typically measured in, every year.  Much of it come from background sources which can be from the rocks, from the ground, from uranium and it’s decayed products that are widely dispersed in granite containing rocks and ubiquitous in soil and water, more in some areas than others.  We get cosmic radiation from the sun and other space objects that filter through the atmosphere.  We get radiation from some daily appliances - electrical and electronic appliances - very small amounts.  We get some obviously from past nuclear weapons tests, the fallout from 2000-odd nuclear weapons that were exploded, many of them in the atmosphere that dispersed global fallout.  Importantly, and a very rapidly increasing source of radiation for much of the population is from medical x-rays and it’s now estimated that in many countries those exposures from medical diagnostic purposes are actually now exceeding, in some cases, the background levels that we’re exposed to.  About half of the background radiation, the other main source I want to mention, is radon gas and that’s one of the main decay products of uranium which is widely dispersed in the Earth’s crust.  Uranium itself, the different isotopes have half lives of billions of years, so they’re basically around forever.  Radon has a much shorter half life and much of the radioactivity that’s of concern for nuclear industry workers, particularly in the uranium mining industry but also for all of us generally, is radon.  It accounts for about half of the natural background radiation and it’s estimated to account for a substantial proportion, probably about 40 per cent, of the lung cancer that’s not related to smoking.

SHANE HUNTINGTON
When we speak about that broader exposure to all of these types of radiation, is this low level constant exposure that we experience a problem?

TILMAN RUFF
It is a problem, in the sense that every little bit of extra radiation can do you harm.  It’s thought now that - really the strong consensus of evidence and scientific opinion and the basis for all of the regulatory standards around the world about protecting workers and the general population from excessive exposure to radiation - all of those are based on the idea of so-called linear no-threshold modelling of radiation risk which says that there’s no level below which there isn't some harm to health; the more you get the worse it is but that, particularly in relation to the long term effects and especially related to cancer, there’s no level below which there isn't an increase the risk of cancer, just the more you get the worse it is.  So it’s thought that the overall risk related to radiation at a population level for every millisievert of exposure that there’s about a 1:10,000 extra risk of cancer induction and about half of those are fatal roughly.  So the couple of extra millisieverts that the population get on average from medical causes, each little bit poses some health risk - it’s just that the more there is, the greater the risk.

SHANE HUNTINGTON
When you speak about millisieverts as a measure, is that a measure of the radioactivity that is coming out of a particular atom or is it the measure of the exposure and affect overall that it has on the body, I guess on average.

TILMAN RUFF
Yeah, you're opening up a really important subject, Shane, and that’s how radiation is measured and how we understand its effects.  This can be looked at in different ways.  There are units for the amount of radioactivity - it used to be curies mainly, now it’s becquerels and its multiples - which is based on the number of atomic disintegrations, the number of actual decay steps that happen.  So that defines the level of activity, if you like: how radioactive is something; how rapidly is it decaying - per second, per unit mass; how intensely radioactive is it.  But then the level of that results in energy that’s absorbed, and how it’s absorbed in the body depends on how you're exposed, whether it’s externally from material the atmosphere that’s in dust - it’s deposited on the soil from rocks from the stars - or whether it’s from material that’s taken into the body, either through wounds and breaks in the skin or through inhalation, it can be stuck in the lung, or taken in through food and water in the mouth.  So there are many different radioactive isotopes and they behave differently and exposes us to radiation in different ways.  If they get into the body some of them stay there for a long time, some of them are eliminated reasonably quickly.  Then there’s the type of radiation that they emit; gamma rays and so forth - what’s called low linear energy transfer radiation, so it doesn't transfer or deposit a lot of energy per unit of distance travelled.  So x-rays are useful medically because they’ll go right through things, a significant proportion of them, so you can get nice pictures on the other side.  At the other end of the spectrum you've heavy particles like neutrons, like alpha particles which are helium nuclei, which are heavy which don’t travel long distance but which are intensely biologically active because they have a lot of energy and the punch they pack is delivered over a very short distance - inside a cell or over a couple of cell’s distance, a couple of microns - very short.  Then different tissues are susceptible to radiation to different extents and different people are susceptible to radiation to different extents.  So, for example, we know that in general children are at least three to four times more sensitive to the harmful effects of radiation than adults are.  In general, the risk for women and females overall is higher; they’re at somewhat lower risk of leukaemia than males but they’re about 50 per cent higher risk of other solid tumours.  So, overall, because solid tumours are more common than leukaemia, it’s thought that the risk of radiation health effects for women is about 40 per cent higher than for men.  So there are many factors.  And then you're looking at how the different isotopes are dispersed in different people at different times through different exposure pathways, and then trying to look at how damaging that radiation in that site is biologically, and all of this is sort of weighed up in sort of complicated estimates and evidence.  So transferring from an amount of radiation in terms of how fast a radioactive material is decaying, how many atoms are disintegrating over any unit of time, to the biological effect at the other end is a long and complicated process, and there’s contested science and not always strong evidence at various of those steps.  So the gray’s the unit of dose, the amount of energy that’s delivered to the tissue by a given amount of radiation, and then that adjusted for its biological effect is what is converted into sieverts and a millisievert is just a thousandth of a sievert.  So typically we get a couple of millisieverts from background radiation.  From x-rays you might get, you know, a CT scan might involve 10 or even 20 millisieverts; if it’s not a well-calibrated machine you might even get 30 or 40 or 50 millisieverts, which is not a minor dose.  People who get radiotherapy for cancer might get sieverts or tens of sieverts delivered to very targeted tissues and organs to try and kill cancer cells.

SHANE HUNTINGTON
This is Up Close coming to you from the University of Melbourne, Australia.  I’m Shane Huntington.  Our guest today is Associate Professor Tilman Ruff and we’re talking about radiation and its effects on the human body.  Tilman, what’s actually happening to the body when it gets exposed to radiation?

TILMAN RUFF
The radiation can act indirectly or directly.  So the acute effects, many of these sort of have a threshold: so you don’t get a cataract, you don’t lose your hair, your white blood cell count doesn't drop, your skin doesn't burn unless you get a certain dose, generally a pretty high dose.  So these effects related to high dose exposure, such as happened in the victims of the people that lived in Hiroshima and Nagasaki when the atomic bombs were dropped, the people who have been subject to fallout from nuclear weapons tests, people who have been exposed in industrial accidents and nuclear disasters like Chernobyl and now Fukushima, they can get big doses that will cause acute damage and they generally kick in around the sort of 100 millisieverts and above, particularly above sort of 500 millisieverts.  Then you start to get effects on depressing the white blood cells and cells tend to be affected in relation to how rapidly dividing they are, so the more rapidly dividing the cell generally the more vulnerable it is to radiation damage.  The cells that are most rapidly dividing in our bodies are the blood cells, the bone marrow, the blood forming organs - they’re working overtime pretty much all the time; the cells that line the gut, the intestines, the stomach and so forth; the reproductive cells that produce eggs and sperm.  Those are really the most important fast-dividing cells so they’re particularly vulnerable to high doses of radiation acutely.  So invest you get a couple of sieverts the lining of your stomach and intestine will become ulcerated, will bleed, will allow bacteria to enter and cause infection.  The depression of the blood forming elements will cause anaemia, a drop in white cells causing susceptibility to infection.  A drop in the little things called platelets that help your blood to clot when you cut yourself, so people bleeding spontaneously internally and so forth.  So those syndromes have a significant mortality and they’re dose related and those occur over days and weeks.  There are also dose related longer term effects like cataracts, like infertility, like burns on the skin but they generally occur at higher doses related to widespread direct tissue damage from radiation.  But the main story, I think really here, is in relation to cancer and genetic effects and, in a sense, cancer is a genetic effect.  There the radiation is working in two ways.  One is direct damage; these large, complex, double-helix chain of DNA molecules packaged in various complicated ways into chromosomes, you know, those are big complex macromolecules.  They are our most precious inheritance: the most important thing we get from our parents and the most important thing you leave for your kids is your genes, you know, that defines and makes essentially who we are.  They can be damaged directly, bonds can be broken, atoms can be ionised so that the DNA can be directly damaged.  It can kill the cell, it can cause damage which can be repaired - the body has repair mechanisms.  If it’s not repaired it may be significant or not.  If it’s significant it could cause a genetic defect that could be inherited or it might go on to later on increase the risk of the cell dividing uncontrollably and becoming a cancer.  Radiation can also probably damage those big complex molecules indirectly by creating reactive chemical species - super oxide irons, hydrogen peroxide radicals - things that are highly chemically reactive; you produce them inside cells and they can indirectly damage the DNA as well.  So that’s thought to be the mechanism.  Now, recent science has shown a couple of sort of additional mechanisms that are not widely understood and the significance of which hasn't yet kind of worked through into the practical radiation protection world very much.  But there are clearly effects, one called genomic instability, so that not just the cell that’s hit by radiation can be damaged but its progeny sometime in the future can also be more susceptible to genetic damage, and so-called bystander effects where there, presumably if there was some kind of chemical mediation of reactive intermediates, not just cells that are directly hit by radiation can be harmed but adjacent cells as well.  Then there are additional concerns about possible damage to particular regions of the chromosome that might cause more effects than others.  So the mechanisms here are quite complex and not fully understood but they’re many and diverse and the bottom line is that damage to the large complex molecules, particularly DNA, seems to be the main mechanism.

SHANE HUNTINGTON
Tilman, in our daily lives, as we mentioned we are exposed to many forms of radiation - dental x‑rays, CT scans, airline travel.  How does the various levels we experience here sort of compare overall?  I mean, what it the comparison between taking a long haul flight and getting a dental x‑ray, for example?

TILMAN RUFF
Yeah.  Many of those exposures certainly involve radiation but quite small.  Many x-rays - chest x‑rays, dental x-rays, most ordinary kinds of x-rays, the x-rays that you would have for a fracture - those involve tiny fractions, you know, tenths or hundredths of a millisievert.  Certainly, for airline crews who are flying pretty much all day everyday working days, they are exposed to more cosmic radiation because they’re flying eight or ten kilometres up.  They will get an extra couple of millisieverts a year in general and that could be an issue for, for example, somebody who was pregnant who gets a couple of millisieverts a year.  We know that in the old days when x-rays were more commonly done in pregnancy to assess the pelvis for delivery - medically quite inappropriate but they used to be widely done.  There are very good studies, particularly from the UK from the National Childhood Cancer Registry studies that were done by remarkable pioneers in this field, particularly Alice Stewart, that showed that even one x-ray during pregnancy, that at that time could involve 10 or 20 millisieverts, produced a measurable increase in cancer in the kids, up to about a 40 per cent increase in cancer incidence in the children from just one x-ray in pregnancy.  So there is, I think, now much more consciousness about the need to reduce doses of all forms of radiation that are unnecessary.  If you can get medical information in a way that doesn't involve ionising radiation exposure that’s as good, or nearly as good, then you should always err on the side of something that doesn't involve radiation exposure.  But in general we’re talking about levels that are way under a millisievert for most of these, but some medical interventions, particularly CT scans, you know, 10-20 millisieverts is quite possible.  Now, the recommended maximum permissible limits of additional non-medical radiation exposure that are set by the International Commission on Radiological Protection adopted in most countries, including Australia, Japan, the United States and most of Europe, is that extra doses without medical cause for members of the public should be kept below one millisievert per year.  For workers in the nuclear industry where the risks are clearly higher but it’s an intrinsic part of the job - they’re usually healthy youngish males who have lower risk of harm from radiation than children or pregnant women - in most countries the maximum recommended occupational level is 20 millisieverts per year averaged over five years, so no more than 100 over five years and no more than 50 in any one year.  Now, in emergency situations it may be a compromise to increase those levels and in Japan following the Fukushima disaster, for example, the levels allowed for workers were increased to 100 and then 250 millisieverts.  That’s a substantial dose; that’s a couple of lifetimes’ worth of background radiation.  In Chernobyl, which is I think probably one of the most instructive precedents here, there were a total of well over 600,000, some estimates up to 800,000, what were called liquidators - emergency service personnel, mainly fit young men who were drawn from all over the former Soviet Union, the Baltic States, not experienced radiation workers but who were brought in as part of the emergency effort to try and plug the reactor and cap it with large amounts of concrete.  They needed so many to distribute the substantial radiation risk over lots of people and to keep their radiation exposures reasonably limited but, you know, 600,000+ people involved in that immediate control effort is substantial.  In Fukushima one of the particular social dimensions of this is that TEPCO, the Tokyo Electric Power Company, has about 1100 workers in the Fukushima Daiichi plant, regular workers.  But it had about 10 times that many of essentially itinerant labourers, day labourers, who are mainly pretty marginalised and poor people who are not well monitored and protected and for whom there will be the incentive of higher level of pay to put themselves at risk and who already, there is a history that typically in the nuclear industry, these people will work in one place until they accumulate the maximum permissible dose and then they’ll go and work somewhere else and do the same again and perhaps again.  So there are potentially large numbers of people at risk occupationally here.  Beyond that there’s a current major controversy in Japan because the government has decreed that the maximum permissible limit for children in Fukushima will be not one millisievert, which is the normal standard internationally and in Japan, but 20 millisieverts.  Now that involves significant risks.  That means that if you say that there are two million people living within 80 kilometres of Fukushima, if you say roughly half a million of them might be under 20 then you're talking about potentially 3000 or 4000 additional cancers per year in those from 20 millisieverts.  So that’s currently under intense controversy, as it should be, in Japan.  This is a still evolving and unstable situation so things could still happen, but it’s clearly a very significant event with potentially and actually substantial exposures that would put hundreds of thousands, if not millions of people at increased risk.

SHANE HUNTINGTON
I’m Shane Huntington and my guest today is Associate Professor Tilman Ruff.  We’re talking about radiation and its effects on the human body here on Up Close, coming to you from the University of Melbourne, Australia.  Tilman, it’s very hard for people when they hear reports in the media to determine just how bad the situation is.  For example, often they will refer to a tripling of the radiation levels and, as you stated earlier, in terms of medical x-rays that could be the difference between one x-ray machine and another and is not necessarily a significant problem for a particular patient.  We’re hearing about radioactive material being detected in food in and around Japan.  What sort of problem are we actually seeing there?  Is it at a level that people should be showing concern, especially for example in North America, or are these levels that are so insignificant that it is really just a bit of a media beat up?

TILMAN RUFF
I think the answer to that question is rather complex.  There’s no doubt that exposure pathways to radiation that are internal through breathing contaminated material, particularly for plutonium, for example, alpha emitter, a nasty, highly biologically injurious if inhaled in the lung, doesn’t do anything if it’s on your skin, the radiation won't penetrate your skin.  But radiation in foodstuffs is long term a significant hazard from nuclear fallout from either nuclear weapons or from accidents involving nuclear reactors or spent fuel.  That’s complicated and exacerbated by the fact that a number of important isotopes behave a mimic important biological constituents that are normally part of our bodies and how they work.  So, for example, iodine 131 - one of the important particularly early radioactive contaminants released in Fukushima and Chernobyl - has a half life of eight days, it’s pretty short.  Your body can't tell whether that iodine is radioactive or not, it treats it just as iodine which your body uses to make thyroid hormone - the hormone that’s basically the accelerator pedal on your metabolism; it sort of revs you up or slows you down.  Now the uptake and the risk from iodine, which is a major cause of thyroid cancer, and this major rise - about 7000 cases of thyroid cases in the vicinity of Chernobyl so far, and increase that’s likely to continue for some decades - is directly related to exposure to iodine because there were not appropriate constraints on eating iodine-contaminated green leafy vegetables or dairy products, where the iodine contaminates the soil and the grass, the cows eat, it gets concentrated in the milk and cheese and then people eat.  Now that would have been relatively easily avoided by properly monitoring the foodstuffs, informing people about what not to eat when and, for milk products, using it for powdered or milk products that can sit there for a few months before they get used, by which case the iodine will have decayed away to insignificant levels.  Cesium, another important isotope, behaves chemically like potassium, so your body puts it inside cells, treats it like potassium so it’s widely dispersed in the body.  Strontium 90, another important nuclear fallout contaminant also with a half life of 28 years, so around for a long time, behaves chemically like calcium, so it’s concentrated in bones and teeth.  Plutonium is also concentrated biologically.  So because these sort of mimic important substances that our bodies use, these can be concentrated in plants and animals and up the food chain so that the levels that may be present in fish or crustaceans or in lichen that reindeer eat in Sweden following Chernobyl may be hundreds or thousands of times higher than in the environment.  So there may be particular foodstuffs, particularly at the top of the food chain - meat and so forth - that may have significant levels of radiation that may constitute a real hazard if it’s something that people are eating regularly and those are exposure that we can monitor, that we can minimise.  Certainly radioactivity can move through wind, through ocean currents, through fish, for example.  So there is an issue, no question, but a lot of it can be used as a way of helping to minimise people’s exposures in ways that make good public health sense and informing people about the risks.  Particularly protecting the most vulnerable, who are children and pregnant women, who take up more radiation for example because their thyroids are relatively more active, who are more susceptible to the effects and who may have, in fact, accumulate higher levels in their bodies.  So, simply things like avoiding milk in the weeks and months after a release of iodine will avoid the risk of thyroid cancer very substantially.  So there are significant risks but certainly exposures that would involve small fractions of a millisievert of additional risk are relatively insignificant.  But it’s also important, I think, to say that what might be an insignificant risk at an individual level - if an individual is exposed to one millisievert extra radiation increases their lifetime risk of cancer by 1:10,000, it doesn't sound like a bit deal.  But if you apply a 1:10,000 risk to a million or 10 million or 100 million people then you're talking about thousands or tens of thousands of additional cancer cases.  So it’s about how that burden is shared as well as the dose itself.

SHANE HUNTINGTON
We’ve heard a fair bit about the fact that radiation causes cancer, but we also use radiation in actually dealing with cancer in patients.  Tilman, can you clarify how what is one of the primary causes of cancer is also used in effectively eliminating cancer?

TILMAN RUFF
Sure.  Radiation can be a very useful part of treatments of cancers and that's because of its capacity to kill and injure cells at high doses.  Because cancers are typically fairly rapidly dividing they are often relatively sensitive to radiation damage because they’re dividing fast.  The problem, of course - and this is the problem of anti-cancer drugs as well as with radiation therapy - is that you can't localise the effect.  We don’t have many very clever ways of targeting the radiation only to the cancer cells, particularly if it’s dispersed.  So radiation therapy is a very sophisticated art of delivering as high a dose as you safely can in as localised and circumscribed as possible a way to the cancer, but exposing normal organs to as little additional radiation as possible.  That’s based on the fact that if you give enough radiation to any tissue you will kill it, to some extent, in proportion to how rapidly its dividing.  So that can be through external beam therapy, most often as basically a big x-ray machine that focuses x-rays on a very carefully mapped target area in the body.  It can be through the implantation, for example with prostate cancer, this is sometimes used as a local source of radioactivity that delivers a high dose in a small area just around it, can be inserted into a tumour to kill the tumour.  These can all be very useful parts of treatment.  Those exposures, however, are associated with a longer term risk of second cancers but, on balance, clearly it’s a major benefit where, you know, it adds value in terms of the treatment and cure rates of cancer, but it’s always that double-edged sword.  When we use radiation in diagnostic purposes it’s a controlled dose for a very specific benefit for an individual using, if it’s a nuclear medicine procedure, usually quite short-lived isotopes that don’t hang around for very long.  If it’s x-rays then there’s no residual radioactivity left in the person.  But it always needs to be weighed up with the risks and benefits and I don't think we’ve done that well enough, particularly with CT scans.  Nowadays there’s quite a move, particularly in the paediatric community, before children have CT scans the best practice radiology now would say that you really should inform the parents about the risk of cancer induction for the children related to a CT scan.  So informed consent and careful risk-benefit evaluations are fundamental principles of medicine that apply in this area, as in everything else.
SHANE HUNTINGTON
Associate Professor Tilman Ruff from the Nossal Institute for Global Health here at the University of Australia, thank you for being our guest on Up Close today and giving us a great understanding of radiation and the risks it poses to human health.

TILMAN RUFF
My pleasure, Shane.

SHANE HUNTINGTON
Relevant links, a full transcript and more info on this episode can be found at our website at upclose.unimelb.edu.au.  Up Close is a production of the University of Melbourne, Australia.  This episode was recorded on Thursday 5 May 2011.  Our producers for this episode were Kelvin Param and Eric van Bemmel.  Audio engineering by Gavin Nebauer.  Background research by Dyani Lewis.  Up Close is created by Eric van Bemmel and Kelvin Param.  I'm Shane Huntington, until next time, goodbye.

VOICEOVER
You've been listening to Up Close.  For more information visit upclose.unimelb.edu.au.  Copyright 2011, the University of Melbourne.


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