A traffic sign at the entrance of Chornobyl two years after the nuclear accident / Photo from UNIAN

"The total death toll from cancer from the accident is projected to reach 4,000 for people exposed to high doses of radiation, and another 5,000 deaths among those who had less radiation exposure, according to the International Atomic Energy Agency, the United Nations and the World Health Organization," U.K.-based journalist for USA Today Kim Hjelmgaard writes in an article titled "30 years later: Chernobyl disaster could trigger more cancer, deaths," published on April 25.

At the same time, those organizations say there is no evidence of higher rates of death or illness for the 5 million people still living on contaminated lands in Belarus, Russia and Ukraine.

Some doctors, scientists and health workers who live and work in the region insist the death toll will be far higher — up to 1 million under a worst-case scenario study published by the New York Academy of Sciences in 2011. They acknowledge it's difficult to separate natural rates of cancer and illness in the general population from cases that could be attributed to Chernobyl, but they say the clinical evidence on the ground is overwhelming.

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"The government in Ukraine speaks very openly about the fact that it thinks the problem of Chernobyl is firmly in the past — that the majority of deaths have already been accounted for, and that with each passing anniversary things will only get better," said Liudmyla Zakrevska, president of Children of Chernobyl, a group based in Kiev, Ukraine, that raises money to treat children connected to the accident. "We are constantly trying to show the authorities that in reality this problem is not going anywhere."

Not all experts consider the current situation so dire.

"The biggest health danger from Chernobyl is from panic and stress caused by very inaccurate reporting by the news media," said Michael Fox, a radiation biologist at Colorado State University.  "We are constantly exposed to both internal and external sources of radiation with no problem unless it is very high."

Fox said the consensus of "the mainstream scientific community is that Chernobyl was not as bad as we feared."

Yury Bandazhevsky, a scientist from Belarus who specializes in Chernobyl’s impact on children, was jailed for his criticism of the country's public health policies after the disaster. He said there are no healthy children in some areas of Ukraine, where he now works, and illness rates have increased for all age groups.

"I don't like the term 'low dose' (radiation) because it is made up by advocates of nuclear energy," Bandazhevsky said. "If any amount of radiation gets inside the human body, it decays there, and so the dose is never 'low,'" he said.

Read alsoEC allocates EUR 550 mln for Chornobyl projects since disasterThe Nuclear Energy Institute, a Washington-based pro-nuclear energy lobby group, said studies have "found no evidence of increases in solid cancers, decreased fertility or congenital malformations" because of Chernobyl.

Keith Baverstock, a former radiation adviser for the World Health Organization and now with the University of Eastern Finland, believes Chernobyl will kill between 30,000 and 60,000 people.

"There are doctors and scientists in Ukraine who don't think we have the whole story and it needs to be investigated, but it hasn't," said Baverstock, whose research focuses on how radiation impacts human health. "It could be that we need to change the way we think about biology to understand this effect."

Ukraine's health ministry said contaminated parts of the country outside the Chernobyl Exclusion Zone — a restricted 20-mile radius from the power plant — show lower levels of harmful radioactive elements, such as cesium-137 and strontium-90.

Data provided to USA TODAY by the health ministry also said more than 2 million people continue to receive ongoing medical observation, treatment or support because of the accident 30 years ago. Of these, 453,391 are children.

Read alsoDonors raise about EUR 90 mln for Chornobyl ISF completionThe initial accident on April 26, 1986, killed at least 28 people when an explosion during a routine test destroyed reactor No. 4 at the plant in Pripyat, Ukraine, then part of the former Soviet Union. The reactor was later entombed in a sarcophagus of steel and concrete to contain the radiation, but it started leaking. A new cover for the reactor is due to be completed in 2017.