Environmental and Biological Studies on the Long-Term Effects of the Chernobyl Incident

Posted on February 5, 2019

Environmental and Biological Studies on the Long-Term Effects of the Chernobyl Incident


Norman Klieman, PhD is the Director of the MS Degree Program in Radiological Sciences and Toxicology at Columbia University’s Mailman School of Public Health in New York. He and his colleagues, at Columbia and other institutions, have been conducting environmental and biological studies on the long-term health effects of the 1986 Chernobyl disaster in and around the region.

Chris Thomas: Hi, this is Chris Thomas with S.E. International. How are you doing today?

Norman Kleiman: Good. Hang on just one second.

CT: Sure

NK: I’m glad we finally connected! I really like your Ranger.

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CT: That’s great. Do y’all use the Ranger Wipe Test Plate for wipe sample counting?

NK: No. I have a variety of different sources that we use with it and then we do a little bit of investigation. You know, hide some check sources and ask them to find them. I’m always open to new suggestions. But, we usually do scintillation counting for wipe testing. We kind of set up scenarios where you hunt for different sources as part of the RSO course.

CT: Sound like fun. Cool. Do you just generally hide sources or do you try and do some kind of surface contamination that they have to hunt down or…..

NK: No no no. I wouldn’t want to do it that way in the classroom. There are cross contamination issues.

CT: That’s understandable. So, you’re going over to a Pripyat and Chernobyl as part of a program you’re working on?

NK: Yes, I’m on the faculty here in the Department of Environmental Health Sciences in the School of Public Health at Columbia. I have expertise in health effects of radiation exposure and general radiation biology, but also trained in ophthalmology. What I’m probably best known for is radiation effects on the eyes. My research portfolio has expanded quite a bit in recent years.

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We do a variety of things. For example, DARPA and BARDA funded work on biodosimetry in case of accidental or terrorist radiation exposure. Another area of interest is heavy metal exposures and potential ocular effects. The Chernobyl work in particular is geared to look at health effects of long-term radioactive low-dose exposure in both human and animal populations. I work with Tim Mosseau, at the University of South Carolina, who has graciously hosted my visits to the exclusion zone. My primary interests are in long term ocular and other health effects in the Liquidators, the folks who went in and cleaned up after the accident in Chernobyl from 1986 to 1989 and in various exposed animal populations such as mice, voles and feral dog populations. During my most recent trip, our primary goal was to examine the eyes of these dogs, but secondary goals included collection of hair samples to look for heavy metal exposure as well as blood, fecal and saliva collection.  By the way, we also collected, and stored in ethanol, any ticks we removed from these dogs!

We did gamma counting on the dogs to determine their baseline radioactive contamination. We use the Ranger to get background levels in the surrounding areas where we trap the dogs, but we also use it for a variety of other purposes. We’re trying to correlate environmental low-dose radiation exposure with health effects in animal and human populations. That’s the one sentence overview of what we do.

CT: I can’t imagine there being a large human population.

NK: Interesting question. We could talk for hours about this. I first started talking about Chernobyl in the early 90’s with my Columbia mentor, teacher and friend Basil Worgul, who passed away over a decade ago. He first started work with Chernobyl Liquidators only a few years after the accident. Initially, within the 30 km exclusion zone, no one was allowed to live there, back when it was kind of a radioactive wasteland. Since then, and after extensive cleanup and the passage of time, the area has changed quite a bit. For example, the first time I went over to Chernobyl, I wanted to see the so-called Red Forest, named that because the all trees died from radiation exposure and turned red.  You can clearly see that in pictures from the late 1980s.

So, the first time I go over and we’re near the power plant I say, okay, well let’s go to the Red Forest. And I’m told, “you’re in it”. And I replied, “But it’s not red”?!. And they’re saying, “Well, that’s because the Ukrainian Forestry Service bulldozed all the trees, buried them, and planted thousands of new saplings!”

CT: I didn’t know that.

NK: Most people don’t know that. It’s still quite hot in certain areas there, upwards of 70 micro-Sieverts per hour in some places. You saw my picture of the mushroom, one of my favorite pictures, showing much higher radioactivity in the mushroom compared to the surrounding soil. (Yes, mushrooms really do concentrate 137Cs!) We always hear cesium in the soil can make mushrooms particularly hot and they really are!

So, part of the story is that at the reactor site there’s quite a bit of activity. There’s actually a nuclear fuel reprocessing plant that’s been built there and there are hundreds of workers that come in and out every day that work there. Trains arrive in the morning that come from a city about 50 kilometers away. Every morning they come in and every evening trains leave, bringing workers in and out. And if you walk around, although there is a lot of rusting buildings and industrial debris, there are also office buildings and work spaces and people with briefcases and suits and you’re like, “Wait a minute, Chernobyl was the worst nuclear disaster in history-no one is supposed to be here”. No, it’s not what people expect. The reactor that was damaged is now enclosed by a shield or dome and there are office buildings and workers literally, 500 yards away, and plenty of people working well around there. The dose rate around the reactor site where workers are is generally far less than 1 micro-Sievert per hour.

CT: Amazing.

NK: The site around the reactor has been extensively remediated. One of the ways that initially they shielded the reactor was by dropping greater than 2,500 tons of lead, sand and concrete onto the exposed reactor core  to shield workers building a steel and concrete containment structure from lethal doses of radiation.  When completed, this structure  was called the sarcophagus, and over time, exposure to the elements has degraded it somewhat, which is why they built a new protective cover, a dome, to protect it from the elements.  For comparison, the picture I sent you of the Ranger dose at 35,000 feet in an airplane is in the same order of magnitude as on the ground at the reactor site. No-one thinks twice about flying overseas, right? So, when I show them this picture, people are like, “but wait a minute, that’s the same dose you receive at Chernobyl!”

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But if you go out into the forest where those mushroom pictures were taken, there are hot spots it can be quite radioactive in some areas in the forest. I wouldn’t want to live there, but there are plenty of animals that do. Wild populations of all kinds and you’ve probably read reports about animal populations that have expanded now, because the people have left and there was no one hunting them. There’s no one getting in their way. So, the populations are expanding and there is surprisingly little evidence for long-term health effects in these animals. Most animals in the wild, however, don’t live very long, certainly not 70 years like a human does. So, they don’t exhibit the same kinds of things you would see from long-term radiation exposures in humans. In the wild, mice and the voles on average, even without radiation, may only live two to six months before being eaten or dying from other causes.

Initially when I went out there and looked at the eyes of the mice and voles I was particularly looking for radiation cataract, as the dose levels were certainly high enough in some regions to cause this effect. I didn’t see near the level of severity I was expecting, however, until I realized these were all pretty young animals. And then, fortuitously, I found out there was a captive population back in Kiev that had been trapped in the red forest and brought back to Kiev when they were young but were  now as much as 18 months old. When I looked at the eyes of these animals, sure enough, I saw the kinds of radiation-induced changes I would have expected to see, because they were much older than the wild populations.  You see, radiation cataract is a long-term effect of radiation exposure and the animals caught in the red forest and examined while young had not had time for this pathology to develop. Just like in the mice and voles, we are also looking at radiation cataract in the human Liquidators, those at-the-time young soldiers who helped clean up at the plant 32 years ago, who received an average dose of 100 millisieverts.

Their individual exposure range is quite wide, from zero to over a gray, but on average this population got about 100 millisieverts to the eye.  Sure enough, they have a statistically significant increases in the kinds of changes in their lenses you’d expect to see with that level of radiation exposure. We’re currently doing follow up in this population to track continued changes in their eyes. Colleagues have done studies on other health effects as well. Surprisingly, as you may or may not have heard, the primary human health concern is really mental health; the fear and anxiety and stress that people feel because they’re concerned that they’d been exposed to radiation and that they may develop cancer or they’re going to pass on genetic defects to their children.  These concerns and fears lead to things like excessive smoking and drinking and unsafe sex and all the other bad things that people do when they’re convinced they have received an eventual, a death sentence. These indirect health effects are potentially much more profound than any direct health effects of radiation exposure.

The name Chernobyl actually refers to the nearest major village, about 10 kilometers from the power plant. Today, despite being within the 30 km exclusion zone, it has an active population of several hundred people living there on a semi-permanent basis, which people don’t realize. Most of them workers, but not all. The town has also been extensively remediated and currently has a dose rate of far less than 1 micro Sievert per hour. And you know, there are some restaurants, there’s a couple of hotels, a bar; ecotourism is now quite popular at Chernobyl.  Buses come in with people dressed in silly “protective” bodysuits going around and tourists visit nearly every day to see the reactor site, the countryside and the former city of Pripyat.


Pripyat was a city two kilometers from the plant where the workers and their families lived. It was a very modern, highly desirable, exclusive place that had all the best of everything the Soviet Union had to offer. It was evacuated 24 hours after the accident with the residents never to return again. My incorrect initial understanding of the disaster was that the city that was abandoned and left undisturbed for the next 30 years because of the high radiation levels. And when you get there, it’s like where is everything? There’s virtually nothing here other than the shells of the buildings. Little furniture, belongings, architectural details. The story is that over the intervening decades, it’s been looted and much of value removed No wiring, no electrical boxes, all gone. Even the window frames in some cases! So, there is some concern about radioactive stuff all over the former Soviet Union now. Today, the touristy areas of Pripyat are not particularly hot except for some limited areas. There is a famous amusement park that was been built in the center of town that was scheduled to open the day after the accident. I took some measurements there and they were some of the more radioactive areas of the city actually.

CT: Do you have any pictures with the Ranger taking readings around the Ferris Wheel?

NK: Yeah, I think I do actually.

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CT: That’d be great.

NK: I think I do. I’m trying to remember what my reading was. It was higher than expected. There also seemed to be a lot of manhole covers in that regions. Generally, around the sewer system, the radioactivity levels tend to be higher.

CT: Oh, that makes sense.

NK: Yeah, it does make sense. But again, by and large, the whole area, while certainly more radioactive than background, is not particularly hot, as compared to the red forest. Curiously, the area in Belarus, just on the other side of the Pripyat River across from the power plant is a different story. It’s actually environmentally different and has not been remediated the same was as on the Ukrainian side. It’s much swampier there as well and there’s no one working or living there as compared to the 30+ villages on the Ukrainian side that were abandoned, The Ukrainian territory appears to have been more agricultural and more settled than the Belarussian side.

And there’s also persuasive evidence that the way the winds blew and rain fell after the accident, that there was more deposition on the Belorussian side.  There is a train that goes through this area every day to reach Slavutych, the Ukrainian city that the workers now live in some 50 km away and where I stayed for part of my visit, I had my Ranger out and took some readings during the 45 min trip. There’s a spike in dose about five kilometers from the power plant, in the middle of heavy foliage but no one lives there, so it’s probably not a major human health concern.

The overall “take home” message for me from Chernobyl is that this is not just a radiological disaster but also an ecological one because of the overall disruption of the biome during remediation and because of the debris and dumping of industrial and cleanup waste material.  It was not just a nuclear power plant. There were factories, plants, various industrial activity, all abandoned…. trashed.

They had years of trucks and equipment and chemicals going in and out to remediate. There are exposed waste dumps. Furthermore, when they bulldozed and removed the contaminated soil, the whole ecosystem was disturbed. The fact that you don’t see the kind of wildlife you might expect in the red forest, for example, (the forest is kind of very quiet) is likely because this is a disturbed ecosystem. It’s not because the radiation had killed everything. It’s because the top soil is gone, new trees were planted, the ecosystem was greatly disturbed. The insect populations were displaced. It’s going to take years for that to rebuild into a more normal ecosystem.

CT: You said that the insect population was removed?

NK: Well, if you remove the soil and remove all the trees where the insects live…… So, one of the things you noticed about the red forest, it’s kind of quiet. You don’t see a lot of birds. I didn’t see a lot of insects. And I think that’s likely because the system is greatly disturbed

CT: How does that affect the decomposition of say, the trees?

NK: I don’t know the answer to that but I suspect it’s going to take some, time for that biome to rebuild itself. That’s my gut feeling. I’m not an expert on that topic. But that’s my gut feeling. That appears to me to be a better explanation than the radiation has simply killed everything.  Curiously, there are lots of birds and lots of insects in Pripyat. But the city wasn’t remediated the same way. They didn’t bulldoze Pripyat and replace it.

The whole story is just fascinating from many different perspectives and has lots of lessons to teach us about the environment and its capacity for renewal. It’s a captivating area of study and actually quite beautiful country.

About feral dogs. There are large populations in the area and, among other, things, we retrieved hair samples during a program to spay, neuter and vaccinate these animals. Right after the accident many thousands of tons of lead were dumped from the air by helicopter to help shield workers from the radiation in the destroyed reactor core. Some of that found its way into the soil, air and water and we hypothesize that feral dog populations are exposed to this toxic metal, and others, every day.

CT: Wow.

NK: We have a core metal analysis lab in my department and our preliminary data suggests, as I suspected, that the lead and other heavy metal concentrations are much higher in hair from these feral dogs than in an unexposed population They’re running around in the woods and in the abandoned industrial areas inhaling and ingesting it. Quite possibly this could be a human health issue as well with all people are working there.

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During our next visit, we plan to take blood samples from other dogs for genetic testing for potential radiation exposure biomarkers. We also put dosimeters on the dogs we captured during our last visit to better measure their radiation exposure. By the way, there is a very practical and understandable reason the Ukrainian authorities are concerned about the explosion in populations of these wild dogs, who are somewhat accustomed to human activity. Often, the workers leave food out for them, and even have names for some of these dogs wandering around. They don’t act like true feral dogs. They’ll come close to you. They’ll take a piece of bread out of your hand and run away. So, the authorities are very interested in programs to spay, neuter and vaccinate them to better control populations and the potential spread of disease. So, SPCA International initiated a vaccination and spay and neuter program and we tagged along to help and, at the same time, accomplish some scientific goals, for example to take fecal, saliva, blood or hair samples. With respect to radiation cataract, I also examined the eyes of the dogs for the kinds of lens changes associated with radiation exposure A parallel spay and neuter program was also initiated in Slavutych, the city about 50 km away, and we were able to get some samples from there as unexposed controls, which was useful.

CT: Okay. And is there a local animal organization that SPCA is working with over there?

NK: SPCA International is who did it. They’re an international organization. If you actually google “Dogs of Chernobyl”, you’ll come up with some on this. I don’t have any affiliation with them other than we were the scientific team that worked alongside them with their  authority’s approval of human health relevant science. There was also an adoption program which made the news, made People Magazine, where 12 dogs were adopted abroad from Chernobyl. Some folks were like, “Oh my goodness. they’re adopting radioactive dogs!” but in actuality these dogs are not radioactive!

CT: And how do you use The Ranger in this program?

NK: We used it extensively. We use The Ranger, and before that, your Inspector quite a bit.  And then SPCAi used another of your products to check the dogs as they were brought in.

CT: Which one?

NK: Oh, the Frisker. I’d love to have one of those to use in our RSO training course. I think that would be useful for the students.

CT: I will get you one!

NK: So overall, that’s kind of a summary of what we do and how we use the Ranger and other dosimeters.

CT: That is really fascinating. Did you do any plant studies or is it all just animal? You had mentioned that they had kind of bulldozed and buried the red forest and replanted trees. Are they seeing any large amounts of uptake in the newer plants that are coming up?

NK: Yes. Excellent question. There is a growing problem related to that; there have been forest fires.

CT: Oh no. Wow.

NK: Actually, we were told we might need to evacuate the plant area at one point because the fire was literally a couple of hundred yards from the power plant. I mean I have pictures of big black plumes of smoke and you can see the helicopter flying overhead with a giant sodium iodide detector trailing behind it. The authorities are aware and concerned about the problem and trying to address it. There’ve been a couple of scientific papers reporting the dispersion of radio-cesium after these forest fires. So, the short answer is that when the forest burns radio-isotopes get re-disbursed and potentially aerosolized, primarily cesium with some strontium. That is definitely an area of current concern.

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CT: Wow. You mentioned that there is a workforce and industrial zone that seems to be flourishing. Where are they getting their consumables? I mean, for example, in the U.S., there’s a huge push for local everything. So, you know, I just wonder how exactly are they feeding and hydrating a population and how far do they have to go to, to find soil and livestock that are suitable for growing and consumption.

NK: That’s a good question. I am told that the Ukrainian authorities are pretty watchful for radioactive contamination of any food and products and have an active surveillance program. Actually, from time to time we’ve taken our Ranger out to scan various items, but I’ve never noticed anything amiss. Within the town of Chernobyl, there are apartment complexes where folks live, private houses, etc. Many of them have gardens and a few of them even have animals in the yard.  I don’t know what is the actual dose rate might be but it is likely very low. I suspect that consumption of contaminated food is probably not a big issue. I haven’t noticed, honestly, anything of concern and am not personally worried about my own exposure. So, yeah, I’m not too concerned about that.

CT: The people who grow their own backyard gardens, are you able to see a cataract without much test equipment?

NK: No, to detect these changes you need to do a more comprehensive eye exam. I have portable equipment that I bring with me but again, I suspect that these folks have little to no exposure.

CT: Oh yeah, I imagine so. I couldn’t imagine that not being the case. I was just wondering for the populations that aren’t necessarily being tested, you know, with a simple hello, are you able to see a cataract in their eyes?

NK: Well one example might be to measure background radiation levels in an area where we trapped a vole or captured a dog. I might put the Ranger next to it, just show what the average dose is at that location and I use my phone to give me a GPS coordinate.

CT: Oh, that’s great. We’re in development here. It’s a few months out, but we have an android app out now. We’re trying to get the iOS version finished up, but at that point you’ll be able to just append all of your GPS data, notes, and comments and stuff to your survey and email it or text it. Any way you want to send or save a survey. Time counts, everything. We just finished up the Android and integrated the RadResponder Network into it and now we’re trying to pump out an iOS version.

NK: So useful. Yeah, I’m an iOS guy, so that would be great.

CT: I will definitely let you know as soon as we have it there.

NK: Another way a colleague has used it is in conjunction with what are called camera traps. Do you know what a camera trap is?

CT: No.

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NK: It’s essentially a digital camera that you mount on a tree or a post with an infrared motion detector.

CT: Oh yeah, we call them hunting cameras down here in Tennessee.

NK: The Ranger is used by the scientific team to survey the forested areas surrounding where each camera trap is located to get a sense of background radiation exposure levels at each trap location. It provides supplemental data about the relationships, if any, between animal population counts and the environmental radiation exposure surrounding each site as well as providing the researchers and assistants guidance as to potential radiation hazards at each site.

CT: Oh Wow. This is really fascinating. Um, I, I got to say I’m, I’m a, a little bit overwhelmed. We’re all very excited about having some pictures of the Ranger over there.  Everyone here at the office is really excited about that. So, I can’t imagine how much it takes to shield out the background over there. Do you use a lead pellet shield or….

NK: Lead sheets for whole body gamma counting in dogs.

CT: Oh, wow. That must be fun to carry around. We came up with this very small pig with a one-inch thick shielding. It looks like a big lead Marinelli pretty much.

NK: The shielding we used for whole body gamma counting in mice and voles was actually built one out of lead brick. It kind of looks like a kiln and then with a hole at the top where the sodium iodide detector drops down. And we put the rodents at the bottom of the cylinder and then drop the detector on top of them. So that’s a much more substantial shielding for this work. Some of these mice had whole body counts as high as 10,000 cpm!

CT: Wow.

NK: Yeah. Really hot. Remember, these animals live in the ground in soil that may be heavily contaminated, especially if they’re from the red forest.

CT: So, you were saying earlier that there isn’t really a big bird population in the Red Forest because there are no bugs for them to eat?

NK: Possibly. My colleague in South Carolina is the bird expert and has worked with barn swallows, As he explained to me, the swallows like to live and breed near people and livestock. So, when the people left, the bird populations also decline. Contrary to belief, it’s probably not because of radiation exposure, they need human activity and barns where there are cows and goats and such to use straw and waste matter in their nest building.

CT: Wow. This is all just so fascinating. Thank you so much and have a great day!

NK: You too!


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