Academic researchers worldwide, including veterans of research on the Chernobyl accident, are poring over releases of data on population exposure rates to radioactive fallout from the Fukushima nuclear disaster. But they are finding that making any sense of the data is proving very difficult.

One problem is that data are strewn across many individual web pages on several websites, for example, those of Japan’s science ministry, here and here, the health ministry, the Nuclear and Industrial Safety Agency,and the International Atomic Energy Agency. Moreover, the data are often in different units, with few descriptive details of, for example, sampling techniques used.

The Japanese government does appear to be making efforts to be open about data, though. Summary maps (provided by the US Department of Energy) of aerial radiation monitoring have also been extremely useful, researchers say, though no geographical information system data of the maps is available from the website.

“The problem is that it is very difficult to get a real picture of the exposure of the population,” says Elisabeth Cardis, a radiation epidemiologist at the Centre for Research in Environmental Epidemiology in Barcelona, Spain, “I’ve been poring through many reports from many different bodies, and the information is very confusing.” Measures for the same zone sometimes differ greatly between reports, and it’s not made clear how measurements were made, she says. There’s a need for a critical review of all the available data, she says.

With Japan preoccupied with efforts to deal with the huge aftermaths of the 11 March earthquake and tsunami, and now having a nuclear disaster on its hands, researchers are loathe to criticize the accessibility of the data to outside academic researchers. “I don’t think we can be too critical about demanding data” under the circumstances, says Richard Wakeford, an epidemiologist at the Dalton Nuclear Institute at the University of Manchester, UK. Far more data are available to academics outside the country than in the days immediately following the earthquake on 11 March, he adds. Most importantly, the people who need it most — the Japanese and other radiation protection officials on the front line — will likely be getting much fuller data (much in Japanese) than is contained in the English summaries being posted on websites, he says. But he agrees that “it’s not easy to find your way around the data”.

Scientists say that what is also frustrating is that much of the data are being published in 1990’s-style static pdfs — whereas we are now in an Internet-era of web services and machine-readable data — making the computation of data from the hundreds of pdf files — next to impossible without huge manual efforts to extract the numbers. Providing even simple spreadsheets, or csv files, would make analysis of the multiple releases of data much easier to compute and provide a fuller picture of all the data, they say. Metadata, such as the latitude and longitude of the sites sampled, is also lacking or absent. ""There is all this data being produced, but you can do nothing with it, you can’t get any meaning out of it," says Keith Baverstock, a radiobiologist at the University of Eastern Finland’s Kuopio Campus. What’s needed, he says, is for an independent group to “harmonize and process the data, and put out as quickly as possible an evidence-based risk assessment to the public and government.”

Researchers say that they largely trust the Japanese government data, but are more sceptical of that produced by TEPCO, the operator of the Fukushima plant. TEPCO has also been criticized for reporting erroneous data during the current crisis – see here. TEPCO should do more to provide accurate data more openly and in a more timely fashion, says Shunichi Yamashita, head of the Atomic Bomb Disease Institute at the Graduate School of Biomedical Sciences, Nagasaki University. He adds that he would like to see the government send its own teams to the Fukushima plant to get independent data on the reactor status, and environmental and health impacts at the site.

For full coverage of the Fukushima disaster, go to Nature’s news special.