by Douglas Page©, 1999

At one a.m. on April 26, 1986, Chernobyl nuclear power plant No. 4 exploded with such force it lifted a 1,000 t cover off the top of the reactor, showering the environment with burning chunks of radioactive graphite and spewing 10.9 pBq of radioactive debris into the atmosphere, dusting an area larger than California. University of Georgia environmental toxicologist Cham Dallas, one of the few Western scientists conducting research there, is trying to understand the environmental effects of the world's worst nuclear accident.

On an autumn afternoon, on a dirt road lining the shore of one of the idyllic ponds that freckle the lush, rolling region surrounding the Chernobyl sarcophagus, five men in white environmental suits, cinched booties and gloves, wearing respirators and carrying dosimeters, stand in peculiar contrast to the barefoot boy on a bicycle carrying a creel.

The men in white, scientists from America on an expedition to find the details in the damage done by the 1986 detonation of the Chernobyl nuclear power plant, have just pulled a catfish from the same contaminated channel as the Ukrainian youngster. When the men run their Geiger counter over the top of their fish, the machine jumps to life, registering so much radioactivity it sounds like they're vacuuming sand. They will take this fish back to their nearby lab and prepare samples of its tissue for shipment to more sophisticated laboratories in the U.S., where its DNA will be analyzed. The boy's fish, which registers the same amount of radioactivity, is headed to the boy's home, to be prepared for dinner.

The scientists are part of a Ukrainian expedition led by University of Georgia environmental toxicologist Cham Dallas. "Here we are in our protective suits and respirators, and along comes this kid on a bike with a fish sticking out of his basket looking like a Norman Rockwell painting," Dallas says. "We get him to stop and when we scan his fish the counter just roars. We run it over his bare feet and it roars some more. Then he smiles that toothless grin of an 8 year old and off he goes." The men in white just look at each other, in disbelief.

The Abandoned City of Pripyat

There are many such surreal scenes in the Exclusion Zone, the area inside a 30 km radius of ground zero of the destroyed nuclear power plant. "The most eerie place is downtown in the abandoned city of Pripyat," says Dallas, of the town the size of Alexandria, Virginia, built to house the elite of the former southern Soviet Union's nuclear power industry. The Soviets had four operating reactors here before the accident, with two more nearing completion, and plans for six others. It was to be the largest reactor complex in the world. Within a month of the explosion, Soviet authorities shut down the entire compound and relocated 116,000 people living and working in Pripyat and the surrounding area.

"This is is a modern, high-rise metropolis and now it's a shell. Empty. You can be out in the country and be lulled into thinking there's nothing wrong around here," says Dallas, who describes the region as resembling southern Georgia, with lush, rolling woodlands embellishing a low, swampy terrain. "But downtown Pripyat is different. It's deserted. And it was vacated in a hurry. There are dolls lying in the street."

Pripyat is where Dallas has stationed his makeshift laboratory - refrigerator, centrifuge and computer, placed in what was once a kindergarten classroom appropriated from an abandoned elementary school in an abandoned city in the most radioactively contaminated region on earth. "We picked this particular school because it was relatively uncontaminated," he says. "There are jungle gyms and swings outside the door, but the electricity is on." Dallas and his team of specialists and graduate students occupy the lab for about three weeks twice a year, attempting to determine the effects of high levels of radiation on the genetic material of living organisms.

Getting the proper permits to even get in the country is never easy, given the unsettled nature of regional politics in the republics born out of the former Soviet Union. "It took me two years to get in the first time," Dallas recalls. "They treated me like I was radioactive. Sometimes I get that treatment on this side, as well. It's inherent in toxicology work. We're troublemakers, always looking for problems. It's still not a smooth process, taking an expedition in over there. Every time we go it seems like we're dealing with a new set of administrators."

Once they get in the country, their first priority, they feel, is to protect themselves. In the lab, for example, they unroll plastic sheets, covering the floor. "You still have to watch where you sit and where you lay things," says Dallas, who has made 10 such expeditions to Chernobyl since 1989. "Working in an environment like this, you have to be thinking all the time, because if you sit down you can contaminate yourself. The contamination doesn't go away. It stays on your clothing. You have to think whether you've contaminated your hands all the time. If you do, you have to re-glove."

At times, Dallas has an armed escort. "On the Belarus side of the border there is a lot of anarchy," he says. "Some of these zones are violent, male-only cultures, existing like the Wild West, outside the rule of law. On one of my first excursions into Belarus territory we had this officer, this sheriff-looking guy, who escorted us. Sure enough, just a few miles from the site of the explosion, we encountered a group of men stealing tiles from the roofs of abandoned houses to sell in Kiev - tiles that are highly contaminated. The thieves fled when the 'sheriff' confronted them. He told us later one of the men had once killed another in a brawl with a broken whiskey bottle."

According to the escort, these outlaws are attracted to the region because building materials are extremely expensive, and because of the food left behind by the fleeing residents 12 years ago.

"It creates an interesting bond between those of us that go on these trips because of the hazards," Dallas says. "Yet all the while, our Ukrainian escorts, who have a cavalier attitude about the radioactivity, are sitting around, hand-rolling cigarettes, laughing at us."

One of the reasons the locals may be so passive about the risk of radioactivity is the apparent lack of any environmental or genetic damage. They seem to know what Dallas is just finding out: there are no defects and deformities in the local human and animal populations. None. None of the feared mutations or birth deformities have appeared as the result of the radiation discharged by the world's worst nuclear accident.

Fears for the Worst

In the aftermath of the Chernobyl explosion, the worst was feared. The greatest contamination covered several regions in Ukraine, Belarus and Russia, often in the form of 'islands' tens and hundreds of km from Chernobyl. Within a week, over 200,000 children and pregnant women were evacuated from Kiev. Contamination with Cesium-137 (137Cs) above 185 kBq/m2 covered 14,290 km2 in these areas, levels comparable to an average lifetime dose; 137Cs levels reached 104 kBq/m2 in Norway, 200 kBq/m2 in Sweden and 102 kBq/m2 in Greece, Romania, Austria, Switzerland and parts of Germany.

Soviet nuclear power workers were allowed 5 rems/year. Everyone who lived in Kiev, 160 km south and downwind of the explosion, got 7 rems in the first three days. (The average radiation dose received by a person in the United States is about 180 millirems/year.) Up to 800,000 workers, using bucket and shovel technology, assisted in mitigation activities to clean up the burning graphite and chunks of reactor core in the 30 km Exclusion Zone. All of them were exposed to extremely high levels of radioactivity. "The people in Pripyat weren't even informed for three days," says Dallas, shaking his head. "Most of them stood on their balconies and watched the reactor burn, inhaling clouds of plutonium and uranium."

A form of nuclear hysteria spread behind the winds. More than 100,000 European women, for instance, chose to abort pregnancies after Chernobyl, for fear of giving birth to nuclear mutants. Yet, 12 years later, no mutant rodents or fish have been found, much less mutant human babies. Dallas is trying to understand what he's not seeing. What he's not seeing are the expected mutations.

"These are the most radioactively contaminated living organisms in the wild we've ever found," a baffled Dallas says. "To be honest, these animals has so much radiation in them it defies the ability to understand how they survive. We have animals where the amount of radiation is over 80,000 Bq/g of tissue. Some of them are getting 2, 3 and 4 rems of radiation each day. Yet, they're apparently thriving on the most radioactive land on earth. We don't have an explanation."

It doesn't seem to be costing the animals anything, he says, shaking his head again. "We would have expected to see more deleterious effects in these species, given the enormous radiation loads we're seeing. So far we've investigated several species of fish and several species of rodents, all of which were chosen because of the high radioactivity in them. Yet we aren't finding mutations of any kind."

Dallas finds this lack of genetic damage in the Chernobyl animal populations disconcerting. They're finding genetic changes in these animals, but no apparent damage. "I use the word 'change' and not damage," he says, "because the implications remain unclear."

The catfish, carp and other fish species examined near Chernobyl show levels of radioactive contamination three to five times higher than anything found in the U.S. Rodents such as voles show even higher levels, 10 times the levels found in U.S. rodents. "No one has seen levels like this before," Dallas says.

"My biggest fear," he continues, "is that we're doing all this research, all this ecosystem risk assessment over there, wandering around this radioactive wilderness and we're missing it, that something is going on out there and we're getting a false negative." He's afraid something is there - long-term genetic changes in the form of a mutation time bomb, perhaps - but because of a lack of creativity or because there aren't enough researchers in the field they're missing it. Dallas is practically the only one looking. "I was expecting to see hoards of scientists descending here from all over the planet," he says. "There are some investigators from Western Europe who are mostly interested in radiation measurements, not the biological effects. There's almost no one here from the U.S.

"It would be nice to know why these organisms can handle the radiation so well. With increasing concern over the threat of a nuclear terrorist attack in this country, we may need this information."

Theodore Rockwell, former technical director, Naval Reactors, for the U.S. Atomic Energy Commission and the U.S. Navy, thinks the clue is in the numbers.

"The human body has about 100 trillion cells, and each of these cells routinely undergoes about 200,000 DNA alterations per day - just from the action of free radicals created in the normal process of cellular metabolism. That's 70 million alterations per day per cell. In addition, there are 60,000 different kinds of genes in the body and each gene is in each cell. Each gene undergoes about 400,000 replication mutations each day - a total of 24 billion gene mutations every day. Now, if any single mutation in the DNA could cause cancer, we wouldn't live very long."

What saves us? "We know that one rad of radiation causes about 20 DNA alterations in a cell. Even a lethal dose of radiation, say 1,000 rad, would cause only 20,000 alterations - 0.02 percent of the natural background change. It is not through additional DNA alterations that high-level radiation injures us; the critical factor in determining whether we get cancer from these billions of mutations is the cellular repair and removal process. Like many other toxins, high level radiation degrades these processes, but low-level radiation actually stimulates them. This is why high-level radiation may hurt us but low-level radiation may help us."

Be that as it may, the researchers in the Exclusion Zone prefer to error on the side of personal safety. No one is absolutely sure what the long-term effects of radiation are. Dallas would just as soon not inhale radioactive particles of plutonium or cesium. "I feel compelled to protect myself," he says. "If you ingest or inhale these particles they're going to permanently reside in your body. So we wear the gleaming white space suits to keep the particles off. Because we have good funding, from the U.S. Department of Energy, we put on new protective suits every day. At the end of the day we discard them. We carry good electronic dosimeters, with backups, to give immediate digital readouts."

Like ground fog, radiation in the region is patchy. "There can be a very pristine area with little radioactivity in it," he says, "and then right next to it, just a few yards away, is an extremely contaminated area. You can be 160 km from the reactor and hit an hot pocket, or you can be only 8 km from the reactor and see an area where there's no radioactivity at all. You just have to be careful. When we get in an area with suspected dust particles we put on the respirators."

Maps of the radioactive pockets have evolved from government efforts, but Dallas finds them unreliable. "They were done by Soviet soldiers, walking around with Geiger counters - uncalibrated in many instances. In Belarus you can get a moderate dose of radiation just sitting on a public bus. We found at some of the bus stops in the area, where people are getting on and off, carrying out the business of their lives, we were getting readings on our dosimeters 10,000 times radiation background."

-----------------------------------------------

Suggested Reading

Dallas, C.E., et. al. "Evaluation of genotoxicity in wild organisms due to the Chernobyl Nuclear Disaster", Ecology of Industrial Regions 1:44-54 (1995).

Dallas, C.E., et. al. "Flow cytometric analysis of leukocyte and erythrocyte DNA in fish from Chernobyl-contaminated ponds in the Ukraine." Ecotoxicology (in press, 1998).

Lingenfelser, S.K., et. al. "Variation in blood cell DNA content in Carassius carrassius from ponds near Chernobyl, Ukraine," Ecotoxicology 6:187-203 (1997).

Sugg, D.W., et. al. "DNA damage and sadiocesium in channel catfish from Chernobyl," Environmental Toxicology and Chemistry 15:1057-1063 (1996).

-end-

This feature appeared in Science Spectra (No. 15, 1999).