- More than 2 million people in Belarus were affected by the Chernobyl disaster
- About 5 million people in Belarus, Ukraine and Russia received whole-body radiation
- Several groups provide relief to kids who live in areas that received radioactive fallout
- It is not possible to say that any particular illness was caused by Chernobyl radiation
Yulia Gorelik describes her 8-year-old son, Daniel, as "a very clever boy." He plays "Fur Elise" with elegant ease on the piano and enjoys eating McDonald's chicken nuggets.
Mother and son arrived in the United States this summer through an organization called Hope for Chernobyl's Child. Gorelik had faith that American doctors could fix Daniel's headaches, weakness and vertigo during their six-week stay.
"I have the hope that we can do something here to make him stronger, because he is intelligent, he is nice, but his body is weak," Gorelik, 34, said in July.
The Goreliks live in a region called Gomel, Belarus, which was heavily hit with radioactive fallout from the worst nuclear accident the world has ever seen.
On April 26, 1986, explosions at a reactor at Chernobyl in Ukraine produced radiation effects almost 14 times greater than the 2011 Fukushima Daiichi disaster in Japan and 400 times more powerful than the 1945 atomic bomb dropped on Hiroshima.
More than 2 million people in Belarus were affected by the Chernobyl disaster, according to the World Bank. Two-thirds of the contamination from the accident fell in Belarus, diminishing the quality of life in the region.
Hope for Chernobyl's Child helps 10 to 15 children living in Belarus find host families and dental and medical care in Washington state every summer. The organization also helps families on the ground in Belarus by delivering humanitarian aid.
Medical and dental care are lacking in areas affected by the disaster, Hope for Chernobyl's Child says. Families there often earn little money and have limited job opportunities, making it difficult to provide food, clothing and medications for their children.
Ask Gorelik whether her son's health problems are caused by radiation, and she says, "Yes, of course."
But the reality is much more complex.
What does radiation really cause?
People who lived in the areas that received significant contamination from Chernobyl in 1986 have been the subject of many scientific studies. But researchers haven't looked much at health problems in the region's children who weren't yet born at the time of the disaster, said Scott Davis, epidemiologist at the Fred Hutchinson Cancer Research Center at the University of Washington.
The lack of hard evidence doesn't mean that lingering radiation isn't causing harm in some ways, Davis said, but it would be difficult to establish that anyone's particular disease or condition stems from low-dose radiation exposure over a long period in that area.
"This is a major problem in talking with people who, either themselves or someone close to them, (are) sick," he said. "To say, 'Well, we don't see any risk' -- people just can't get their head around that."
The issue is complicated because cancer, for example, caused by radiation looks exactly like cancer that developed for other reasons, experts say. There's no "Chernobyl" name tag on tumors in people who suffered radiation exposure.
Scientists know radioactive iodine-131 got into the human body when people drank milk from cows that ate contaminated grass, said Dr. Fred Mettler, professor emeritus of the Department of Radiology at the University of New Mexico. This led to higher incidences of thyroid cancer in people who were children at that time -- such as Yulia Gorelik, who underwent treatment at age 12.
More than 4,000 such cases were diagnosed from 1992 to 2002, but it's impossible to say which ones were caused by Chernobyl radiation. Mettler said the iodine is unlikely to have caused cancer in anyone born later -- especially because iodine-131 has a half-life of eight days, so in about two months, it's almost undetectable.
Another radioactive chemical from the reactor explosion, Cesium-137, has a half-life of about 30 years, so it stays around a lot longer than iodine-131 and can still be measured in some soils and foods in several areas of Europe. Still, the dose to which people in the area have been exposed isn't very high, Mettler said.
The doses from cesium contamination "are low and insufficient to cause effects, had there been any," said John Boice, professor of medicine at Vanderbilt University School of Medicine and president nominee of the National Council on Radiation Protection and Measurements.
"A lot of the issues become: Are the health things really due to Chernobyl, or are they things which would have occurred anyhow?" Mettler said.
Zones of uncertainty
For Jennifer Henning, president of Hope for Chernobyl's Child, there's no question that the ailments the children in the program suffer are the result of radiation exposure.
"I've seen the health effects firsthand," Henning said. "I know that it's there."
A physical education teacher in one of the schools that the organization works with told her that children there are getting weaker and weaker, Henning said.
That there are serious health problems among many youths in Belarus is not in dispute.
In 2008, nearly 22% of adolescents in Belarus had chronic diseases and disabilities, according to a 2010 UNICEF report. Risk factors, according to this report, included smoking and using alcohol and drugs.
Experts say that what organizations such as Hope for Chenobyl's Child are doing to help children with medical problems -- providing assistance in Belarus and flying them to the United States for medical respite -- is great. Several other organizations also operate in regions devastated by the Chernobyl accident, such as Chernobyl Children International, the Chernobyl Children's Project and Chernobyl Children's Trust.
But rather than radiation-related illness, according to the 2005 Chernobyl Forum report, "The most pressing health concerns for the affected areas thus lie in poor diet and lifestyle factors such as alcohol and tobacco use, as well as poverty and limited access to health care."
The cause of Chernobyl evokes greater sympathy from the public than some other causes might, Mettler said.
"It's a very unique, scary accident," he said. "Everybody in the world knows about it. But, if you were to say, 'I've got children starving in the Sudan,' people would go, 'huh, whatever.' It wouldn't get their attention."
Henning points to a 2009 report, published by the Annals of the New York Academy of Sciences, rounding up evidence that radiation has had a lasting effect on the health of the population in contaminated areas. In Belarus, for instance, cancer morbidity increased 40% from 1990 to 2000, the report said, and girls age 10 to 14 born to irradiated parents had an increase in malignant and beni