Not enough is yet known to fully evaluate the long-term health effect of the Chernobyl disaster, experts argue.
The damaged reactor at Chernobyl
Twenty years after the nuclear incident, it is still not clear what the full effect on people exposed to radioactive materials will be.
Estimates of the number of people who will die as a result have ranged from 9,000 to 93,000 deaths.
But writing in Nature, experts said it was simply too soon to say what the final toll would be.
Sixty-two deaths have so far been attributed directly to Chernobyl.
There have been 4,000 cases of thyroid cancer, mainly in children and young adults, resulting in 15 deaths.
A draft version of the UN's Chernobyl Forum last year suggested up to 4,000 deaths could be linked to the incident.
But this figure was based on the 600,000 people exposed to high levels of radiation.
The full report suggested another 5,000 of the 6.8 million people exposed to lower levels would also die - but this figure did not appear in the 50-page executive summary.
All of this data was from a 1996 study.
Explaining why the 4,000 figure was given prominence in the report, Melissa Fleming, a press officer for the International Atomic Energy Agency told Nature that it was to counter the much higher estimates which had previously been seen.
"It was a bold action to put out a new figure that was much less than conventional wisdom."
It is much lower than the 93,000 figure given by Greenpeace in its evaluation of the Chernobyl impact published this week.
Writing in the journal, Dr Dillwyn Williams a thyroid cancer expert from Strangeways Research Laboratories, Cambridge, UK, and Dr Keith Baverstock, an environmental specialist from the University of Kuopio in Finland, said lessons could be learnt from history.
They said the aftermath of the atomic bombs dropped on Nagasaki and Hiroshima by the US was that 20 years is too soon to be able to predict all the consequences of fallout.
The radiation exposure was different in Japan - where the bombs led to whole body radiation.
After Chernobyl, exposure was largely from radioactive particles inhaled or ingested by people living nearby - except for those working near the reactor.
But the scientists say the Japanese Radiation Effects Research Foundation, which was set up to study the bombs' legacy, is a good model for monitoring the effect of Chernobyl.
The thyroid cancers seen have been linked to high levels of radioactive isotopes of iodine.
But radioactive iodine can also concentrate in the salivary glands, the stomach and the breast tissue.
There are already indications that the breast cancer rate in Gomel, Belarus, and other heavily contaminated areas, is double that which would be expected.
Drs Williams and Baverstock add: "If a full, independent study of the consequences of the world's worst nuclear accident is not established, and its results not widely published for all to assess, wildly differing claims will continue, and public mistrust of the nuclear industry will grow further."
Other experts say wrangling over numbers is hampering survivors' recovery.
Louisa Vinton, who manages Chernobyl projects for the UN Development Programme, said myths about radiation had created a "paralysing fatalism".
The mental health of people in the area had suffered, with seven million being labelled as victims of the accident, and aid to the area had created a culture of dependency, which might have encouraged exaggerated fears of ill health among residents, she said.
The worst-hit areas will be radioactive for centuries; but much of the abandoned area will be habitable within decades.
The Chernobyl Forum says the 30-km exclusion zone around the plant is likely to remain in place.
But it suggested that, in other areas, roads should be rebuilt and people encouraged to start up farms and hospitals.