HEALTH EFFECTS OF THE CHERNOBYL ACCIDENT

Ten years ago this April, massive explosions rocked unit 4 at the Chernobyl nuclear power plant in Ukraine, then part of the Soviet Union. It was the worst accident in the history of commercial nuclear energy.

The cause of the accident was twofold: operator error and a flawed reactor design. In an ill-advised and uncoordinated test, operators were running the plant outside its design parameters at very low power. The test got out of control, and the reactor's design flaw caused a sudden, rapid surge in power that led to a chemical explosion.

The explosion vaporized some of the nuclear fuel and propelled radioactivity high into the early morning sky. It fell to earth over large areas of Ukraine and its neighboring republics, Belarus and Russia. It was also detected in many countries of Western Europe - and beyond.

In the years since, Chernobyl has become a catchword for disaster. Any Soviet designed reactor is deemed unsafe-and regardless of its design type- is called a Chernobyl-type nuclear reactor. Any disease or death that cannot be satisfactorily explained is blamed on Chernobyl.

Reports of thousands, tens of thousands and even hundreds of thousands of Chernobyl-induced deaths are not uncommon. (There is even a report that Chernobyl caused 40,000 deaths in the United States). They are also untrue.

In fact, 31 people died as a result of the accident, most of acute radiation sickness. They were either workers at the plant or firemen called in to tame the blazes. The accident is also most certainly responsible for more than 500 cases of childhood thyroid cancer. And the mass evacuation of people from affected areas - not to mention the official secrecy and mishandling of the accident's aftermath- caused tremendous stress, which has resulted in a number of psychological disorders. But other than the thyroid cancer in children, no study to date has shown an increase in leukemia or solid cancers that can be caused by radiation.

The long term health effect of the Chernobyl accident may never be clear. But it's in everyone's interest to continue studying the affected population. Major strides have been made in the past decade n the treatment of children with thyroid cancer, in the quality of cancer registries, health studies and research infrastructures, and in the training of epidemiologists and medical personnel. In addition, Russia and Ukraine - with the support of countries like the United States- have done much to improve safety and reliability of their nuclear power plants. This special report examines what we know - and what we don't - 10 years after the Chernobyl accident.

TRUTHS AND CONSEQUENCES:

It was nearly 1:30 in the morning on Saturday, April 26 1986, and Andrei Glukhov was still awake in his apartment in the town of Pripyat, two miles from the Chernobyl nuclear power plant, when he heard the sound.

There were two explosions, followed by a momentary interruption of the electricity supply. The sound was similar to that made by the special relief valves in the plant turbines. When they shut down, there was a boom and sometimes a power interruption says Glukhov, who was an employee of the plant.

I assumed that one of the units had gone off line.

Five hours later, a friend telephoned. He said that something had happened at the plant, and he asked me to call the control room and get some information, says Glukhov.

But when Glukhov telephoned Unit No. 4 no one answered. So he called Unit 2 and talked to one of the reactor operators.

I asked him about the status of Unit 4. There was silence. Then he said "Look out your window " . Units 3 and 4 were housed in the same building, which was painted white. But that morning, says Glukhov, the part of the building containing Unit 3 was white, while the part containing unit 4 was black. I saw smoke coming out of unit 4 , and I knew that something serious had happened.

"I don't like to remember that time" says Glukhov. But the memory of the accident haunts him still. I can t escape it.

The explosion of Chernobyl unit 4 reactor released large amounts of radioactive iodine, cesium and other isotopes. They were carried on the wind and washed out of the skies by rain to contaminate significant areas of Ukraine- where Chernobyl is located- Belarus and Russia.

It would be days before the full extent of the accident was known. The local security apparatus immediately drew a veil of secrecy across the plant. Even plant employees , like Glukhov, who had been a reactor operator and was working at Chernobyl 's nuclear safety division at the time, were told nothing. The coverup extended to Pripyat, where plant employees and their families lived. Special troops were sent to the town to carry out initial decontamination. but the official explanation was that they were on a training exercise says Glukhov. Meanwhile, the wind - which had been blown away from Pripyat at the time of the accident- changed direction. The authorities said nothing, and life went on normally that Saturday. Children played outside. There were even several outdoor weddings says Glukhov.

That evening, volunteers from the young communist league were sent round to distribute potassium iodine pills to Pripyat residents. But it was a hit-or -miss operation. No one came to our apartment building at all says Glukhov.

Then early Sunday morning came the announcement: The town was being evacuated. Residents were told to take only their documentation, plus some pillows, sheets and blankets for a few day s stay in the countryside. The authorities lied. They said that families would be relocated for only three or four days. So people left everything behind says Glukhov.

Today Pripyat is a ghost town. Pictures decorate apartment walls, cabinets are stocked with dishes and cutlery, children's toys are scattered about.

Pripyat is a legacy of the accident. So too are the more than 550 cases of thyroid cancer diagnosed to date in children below the age of 15- about 330 in Belarus , 200 in Ukraine and 25 in Russia. The incidence of the tumors has risen sharply, especially in Belarus. For the country as a whole , the number of cases between 1990 and 1995 is abut 50 times that in the United Kingdom, says professor Dilwyn Williams, who specializes in thyroid studies at Addenbrokes Hospital in Cambridge, England. And in the Gomel region of Belarus the incidence rate is close to 200 times that found in the United Kingdom.

CONTAMINATED MILK:

Some of the radioactive iodine that spewed out of the damaged reactor ended up in the food chain. It fell onto plants, the plants were eaten by cows, and the milk from those cows was drunk by children. The authorities could have broken the link by simply prohibiting the consumption of milk.

"That's a high crime", says Marvin Goldman, professor emeritus at the University of California at Davis. The cases of childhood thyroid cancer could have been largely prevented if the authorities had supplied powdered milk, for instance. If detected sufficiently early, thyroid cancer can be treated with surgery, followed by iodine 131 therapy and then thyroid hormone replacement. About 15 percent - or roughly one in seven- of all cases of childhood thyroid cancer will result in complications, says Cristoph Reiners, director of the nuclear medicine clinic at the University of Wurzburg in Germany. If the complications aren't treated in time they could result in death at a later date. Reiners has treated 99 children from Belarus at the clinic, using funding from German utilities. He says," We've completed treatment for 58 percent, and they were cured. The remainder are sill being treated, but I would estimate that 10 percent of them won't respond well to radioactive treatment."

Those children who were among the first to be diagnosed with thyroid cancer in the former soviet union didn't receive optimal treatment, says Reiners. Surgeons didn't have the right instruments, radioiodine treatment wasn't available, at last in Belarus, and imported thyroid hormone was of poor quality. According to an expert at the World Health Organization, at least five children have died of the disease, two in Russia, two in Ukraine and one in Belarus.

But treatment is better now, and the long term prognosis for children with the disease is quite good , says Reiners.

That the accident was responsible for the dramatic increase in childhood thyroid cancer is generally accepted. I have seen about half of the post-Chernobyl tumors personally , says Williams. I have no doubt that they are in general accurately diagnosed, and that they are related to the Chernobyl accident and almost certainly to the uptake of radioactive iodine. Several studies have suggested a casual relationship. But a small case-control study in Belarus involving 321 children -107 with thyroid cancer and 214 in the unaffected control group- provides the strongest evidence to date that the cancers are the result of the Chernobyl accident, says Gilbert. Beebe, an epidemiologist at the US national cancer institutes radiation epidemiology branch.

MISSING INFORMATION:

What about the accidents other health effects ? That's a much tougher question. Key pieces of information are often missing, such as dosimetric data on the amount and type of radiation people were exposed to. Records of the incidence of disease and causes of death for people in the affected areas - both before and after the accident- often aren't available. The latency period for solid-tumor cancers is at least 10 years.

The people affected by the accident fall into two major groups- the cleanup workers called liquidators and the general population.

Included in the cleanup worker category are the firemen who tried to contain the blazes and the plant workers who aided their colleagues - a group numbering several hundred. They were exposed to very high levels of radiation, and more than 200 suffered from acute radiation sickness as a result. Within a four-month period, 31 of them died. In addition hundreds of thousands of people from military and civilian walks of life helped clean up in the weeks and months after the accident. They worked at the plant site and within the 30-kilometer (18 mile) restricted zone around Chernobyl. Estimates of the number of these workers range wildly from 300,000 to 800,000 and information on the doses they received is incomplete and often unreliable.

More than 400,000 people living in areas affected by the accident were evacuated . Their displacement was a wrenching experience. It severed community ties and forced people to cope with unfamiliar surroundings. This uprooting also feeds people's fear. "They re worried ", says Williams. The stress of knowing that you and your children were exposed to an unknown amount of radiation that you can't see, touch or smell is understandable. And this stress has created a significant he health problem for Ukraine, Belarus and Russia.

RADIOPHOBIA:

There is an epidemic of radiophobia, says Goodman. Scientists may pooh-pooh it. But it s had a hell of an effect on people.

The result has been an increase in such stress-induced disorders as high blood pressure and ulcers. But the appearance of cancer- to be expected in any population group- also is being laid at the door of Chernobyl.

When a disease occurs, there s a natural tendency to try to find out t he cause of it, says NCI's Beebe. It s common to blame some different experience that you had for your present difficulties. Chernobyl comes in for an awful lot of blame for illness that is probably unrelated to it.

"The claims that every childhood malfunction has been caused by Chernobyl are just not true", says Williams. But without accurate data, how can you say they are not true?

What's needed is some honesty, says Goldman. Someone needs to say: This is how bad it was. But to do that, he adds , "we need credible dose reconstruction, so we can say: You were in an area with such and such a dose." That entails identifying the type and amount of radioactivity that fell to earth, where it was deposited, who was in the area at the time, for how long, and what they were doing. Even today, some of the pieces of that puzzle are missing. Until we can identify precisely what the liquidators were doing, for example, we won't know if they received significant doses , says Colin Muirhead, head of the epidemiology group at Britain's National Radiological Protection Board (NRPB). John Harrison, who's responsible for the NRPB s medical division, believes that retrieving good data may be difficult because of the stranglehold that the security services had on the release of information at the time of the accident. Hopefully this information will now be made available.

Tracking down people who were living or working in the areas affected by Chernobyl is a problem too. In most cases ,says the NCI's Beebe, we know where they were at the time of the accident but we're not sure where they are now A number have emigrated, some to Israel and some to the United States. For example Glukhov, the former Chernobyl employee, lives with his wife and children in Washington State.

Assessing the accident's health effects depends not only on dose reconstruction, but on epidemiological studies, which look at the connection between hazard - in this case radiation- and disease . These studies are difficult to mount in any country. says the NRPB's Harrison. That's because they depend on a system of public health identification of diseases, registration of cancers and registration of deaths . That information isn't as complete or as accurate as western epidemiologists would like.

The caliber of historical diagnosis and the accurate identification of the cancer type are critical, says Williams. If a cancer registry is reporting twice as many cases of a particular tumor, we need to know whether it is related to Chernobyl, and that depends in part on any change in the diagnostic criteria and the screening frequency.

You're not just taking raw data. You're checking diagnoses and creating a good baseline for epidemiological studies, says Williams. Adds Goodman: if you don't know what the baseline is, how will you know if there are small increases in the incidence of cancer ?

The infrastructure in the former Soviet Union is not designed for such studies . "In the west", says NCI's Beebe, "we estimate the risk of disease in terms of the hazards or the environmental influences". But that whole area of study was quite neglected by soviet medicine.

For example, says Beebe, they don't often think in terms of bias. So they may not reach the conclusion they should draw from the experience of two groups because they haven t ensured that there s only one factor of interest , say radiation, involved in the difference between them. Dietary differences or smoking, for instance, could confuse the results. Inconclusive studies benefit no one . If we don't have information that is verified , says Williams, that will allow for people who wish to overplay or underplay the consequences of an accident

Funding is another obstacle. Belarus, Ukraine and Russia don t have the money for epidemiological studies says Goodman. They have immediate public health problems to take care of. But if the rest of the world is willing to underwrite such studies, they'll certainly cooperate .

INTENSIVE TRAINING:

One way of underwriting epidemiological studies is to transfer the knowledge needed to carry them out. Organizations in several major industrialized countries have initiated training programs. While generally modest in scale , they seem be working says the NRPB s Harrison. We gave two weeks of intensive training in epidemiology to six traineed last year and they found it of immense value.

Two young physicians from Ukraine have attended the summer training course in epidemiology offered by John Hopkins University's school of public health, says the NCI s Beebe. After that they were with a contractor for a week, watching how we collect data - interviewing, getting death certificates, abstracting, setting up files, then they spent five or six weeks in the epidemiology research group at Oak Ridge, Tenn. NCI also has trained Ukrainian endocrinologists, hematologists and pathologists, and shown a Belarussian the computer techniques used to run studies that rely on a data coordinating center.

The European union is about to launch a larger training effort, says Williams. The two year program will train about 60 physicians, surgeons, technologists and nurses from Belarus, Ukraine and Russia.

Japan too, is providing training - especially in population screening techniques- to support its work in measuring radiation doses of people in the affected countries.

The training efforts are admirable, and though they're not always coordinated among the various national and international organizations, the're still effective.

When it comes to epidemiological studies themselves however, lack of coordination can doom the outcome. There have already been overlapping studies, says Williams. You don't want different groups to attempt to study the same patients for different purposes. In addition, if many organizations study pieces of the same sample, you may find different changes in samples from the same patient.

Despite the desire to help, says Goldman, we haven't been able to develop a central focus, where all cooperated, decided who did what and stuck to it. All we do is pilot studies. Nothing ever gets finished.

The challenge may be too much even for the leaders of the countries involved. "We probably need a God," says the NRPB's Harrison. Goldman thinks the answer lies in an independent foundation to which interested countries could contribute. But the affected countries must call the shots, he says.

Williams says that nothing will happen until the three big players in terms of funding - the European union, Japan and the United States- reach agreement on how their money is to be spent. A meeting in Minsk, Belarus in march may provide an opportunity for representatives of the three to discuss a joint approach, he says.

IMPERPFECT ANSWERS:

Ten years after the Chernobyl accident , experts like Williams say they know of no studies showing a significant increase in the incidence of any type of cancer other than childhood thyroid cancer. But it's far too early to draw any conclusions . There may well be a very large absolute increase in thyroid cancers in adults in the future .

Some of those living in areas that were contaminated by the accident will develop cancer in their lifetime. Some of the cleanup workers will too. That is to be expected.

Even if dose reconstruction is successful and sound epidemiological studies are carried out, the results may not tell people whether their cancer was the result of Chernobyl or something else. It may well not be possible to detect increases in cancer other than thyroid , says Williams, but we have to be cautious .

We're dealing with a whole generation says Goldman. It won't happen in a few months. It will take a generation .And there may never be perfect answers, he says.