KIEV, Ukraine — With every cough and sore throat, every ache and pain, Valentyna Stanyuk feels Chernobyl stalking her.
"It's only a matter of time," she said as she waited for a thyroid test at a mobile Red Cross clinic in her village of Bystrichy, 150 miles west of Chernobyl.
The tests came back clean, but that's little reassurance to this 54-year-old or to millions of others who live in parts of Ukraine, Belarus and Russia that were heavily irradiated when the nuclear reactor exploded 20 years ago, spewing radioactive clouds over Ukraine and much of Europe for 10 days.
The April 26, 1986, disaster forced the evacuation of large swaths of some of the Soviet Union's best farmland and forests. The radiation spread far enough to be detected in reindeer meat in Norway and rainfall in the U.S. Pacific Northwest. It shocked most European countries into a generation-long freeze on building nuclear plants. In so starkly exposing the failings of the communist system, the world's worst nuclear accident may even have hastened the collapse of the Soviet Union five years later.
And the effect on the health of the people exposed to its invisible poisons? That is the most heatedly debated legacy of Chernobyl.
"There is so much that we still don't know," said Dr. Volodymyr Sert, head of a team of Red Cross doctors who canvass Ukraine's rural Zhytomyr region in search of thyroid abnormalities _ one of the few health problems that all scientists agree is linked to Chernobyl's fallout.
"The most important thing we can do is reassure people that they aren't being forgotten," he said.
After the explosion about 116,000 residents were evacuated from a 20-mile zone around the plant. Some 5 million others in areas that got significant fallout were not evacuated.
Over the years, reports and rumors have spoken of thousands of these especially vulnerable people dying from radiation. But a September report by a group of United Nations agencies concluded that the accident wasn't nearly as deadly as feared.
Fewer than 50 deaths have been directly linked to radiation exposure as of mid-2005, the report said. A total of 4,000 of the 600,000 "liquidators" _ workers who were hastily mobilized to clean up the accident site _ are likely to die from radiation-related cancers and leukemia, it predicted. That's far below the tens of thousands many claimed were fatally stricken.
The researchers found that thyroid cancer rates have skyrocketed among people who were under 18 at the time of the accident, but noted more than 99 percent survive after treatment.
It said there was no convincing evidence of birth defects or reduced fertility, and most of the general population suffered such low radiation doses that the scientists decided not to make predictions about deaths, except to say that some increase _ less than 1 percent or about 5,000 _ might be expected.
Venyamin Khudolei, director of the Center for Independent Ecological Expertise at the government-founded Russian Academy of Science, disagrees with the findings.
In the part of Russia most heavily hit by the fallout, mortality rates have risen nearly 4 percent since the explosion, indicating the Chernobyl toll in Russia alone could be calculated at 67,000 people, he said. His findings are cited by the environmental watchdog group Greenpeace, which on Tuesday (April 18) is to issue a report on Chernobyl's consequences.
A spokesman for Greenpeace International's main office in Amsterdam, Omer ElNaiem, said the report will use data from various sources, some hitherto unpublished, which "will indicate a rise" over the U.N. report's casualty estimates.
Other experts point to studies which show increases in everything from schizophrenia among the traumatized liquidators to breast cancer.
The U.N. report suggested that people in heavily affected areas were gripped by "paralyzing fatalism" that induced them to see themselves as victims and blame Chernobyl for every ailment, even those caused by smoking or drinking.
That outraged Ukrainian officials.
"I am speechless that we can allow this blasphemy in front of the graves of those who died," said lawmaker Borys Oliynyk.
Researchers trying to determine death tolls _ and predict deaths still to come _ don't have an easy task. Soviet-era attempts to cover up the chaotic and often inhumane response made it difficult to track down victims. Lists were incomplete, and Soviet authorities later forbade doctors to cite "radiation" on death certificates.
The rural regions affected are impoverished and unemployment is high. Alcohol abuse is rampant, diets poor. It's hard to distinguish Chernobyl-related health problems from a more general post-Soviet malaise, scientists said.
"I'm sure we'll see claims of thousands, tens of thousands, hundreds of thousands, millions of deaths, but again we checked, we checked all the research, all the files," Didier Louvat, a radiation waste expert with the International Atomic Energy Agency, said by telephone from Vienna.
"The explosion was very concentrated around the facility and the fallout was spread in great plumes that went high into the atmosphere and crossed Europe, diffusing the concentration ... It could have been much worse."
About 1,000 people _ plant personnel, military conscripts, firefighters from the Kiev region, emergency workers _ bore the brunt of the inferno, and 134 were officially confirmed as suffering from acute radiation syndrome.
One person died during the explosion and his body has never been recovered. The U.N. report says that another 28 died from radiation sickness in 1986, and 19 of those suffering from radiation syndrome died between 1987-2004 but not all the deaths were necessarily caused by radiation. The rest remain alive.
Wearing no masks or protective suits, dozens of firefighters were deployed. While the bosses sheltered underground, plant workers recall, people stood around awaiting instructions, breathing poisoned air as they watched smoke burst from the reactor's exposed core.
The disregard for human life persisted. Natalya Lopatyuk, the widow of a plant worker, said that as she was being evacuated, she saw groups of young conscripts sunbathing while waiting for orders.
Radiation burns "tear at the skin and look something like a volcano erupting on the body," said Oleksandr Zelentsov, head of the Kiev-based International Organization for People with Radiation Disease. The victims' bodies were considered so radioactive that family members were told not to touch them and they were buried in double-layered lead coffins.
Such high radiation doses, however, were short-lived. The last people diagnosed with acute radiation syndrome _ three firefighters extinguishing a cable fire _ fell ill at the end May 1986, Zelentsov said. One is dead, one suffered a heart attack and is in serious condition and the third is healthy, Zelentsov said.
The Chernobyl plant now is a cracked hulk in the eerie "dead zone." The last of its four reactors was taken out of service in 2000 and the main activity is to shore up the concrete-and-steel "sarcophagus" that covers the destroyed reactor.
But radiation infects a vast stretch of Ukraine, Belarus and Russia _ in the soil, in the berries and mushrooms, in the firewood needed to heat homes.
Oleksandr Nabok, 21, has never been near the nuclear station, some 60 miles from his village, but he was recently diagnosed with thyroid cancer. "I never thought about Chernobyl until I got this news," he said in a Kiev hospital as he awaited surgery.
He is one of more than 5 million people who live in areas deemed contaminated but habitable, far removed from the villages circling the plant that were considered so irradiated that they were bulldozed under grave-like mounds of dirt. There, isotopes with half-lives of 24,390 years came to rest.
In Nabok's village, experts say, the biggest concern was radioactive iodine.
People suffer from a lack of iodine in this region, so when the radioactive iodine was released, their thyroids gobbled it up; children's thyroid glands work most actively, putting them at greatest risk. Many ingested the iodine in milk from cows that had grazed on radiated fields.
Accounts vary, but experts agree that between 4,000 and 5,000 people, children when the explosion happened, have been diagnosed with thyroid cancer in Ukraine and Belarus _ making it the single biggest Chernobyl-related medical problem. At least nine have died. Before the accident, the illness was so rare that in most years only about 10 children were diagnosed with it.
The numbers keep growing. The main spurt was expected to come around this time, but no one knows whether this is the beginning of the peak or its end.
"We cannot tell a patient that after a certain time, cancer will not appear," said Halyna Terehova, an endocrinologist with the Kiev Institute of Endocrinology.
The U.N. report found that the high anxiety levels persist and even appear to be growing among people such as Stanyuk who live in zones affected by contamination. "It is scary, you try not to worry about it," said Valentyna Yanduk, whose face brightened into a smile after the Red Cross doctors gave her 12-year-old son Ihor's thyroid the all-clear. Technically he's not considered part of the risk group _ he wasn't even born at the time of the explosion _ but his mother worries.
"For 20 years, these people have been living as victims instead of survivors," Louvat, the IAEA radiation expert, said. "We need to be telling them: 'Look, you survived this.'"