About 7,587 people contract cancer each year in Japan due to diagnostic X-ray exposure, according to an estimate by researchers at the University of Oxford.

The researchers have estimated that 3.2 percent of people aged 75 and under diagnosed with cancer each year contracted it during diagnostic X-rays, which are used in conventional radiography and imaging techniques such as computerized tomography.

The figure is the highest among the 15 developed countries cited in the study, published last week in the British medical journal Lancet.

After Japan, the next highest figure is 1.8 percent in Croatia and 1.5 percent in Germany.

The lowest percentage was 0.6 percent for Britain and Poland.

The Oxford researchers said they estimated the likely extent of cancer risk based on the annual number of diagnostic X-rays undertaken in the 15 developed countries and other data.

"Our calculations depended on a number of assumptions, and so are inevitably subject to considerable uncertainty," the team said.

German researchers in an accompanying commentary criticized the calculations, saying they fail to consider the benefits of X-ray examinations.

These include the earlier detection of cancer and the possibility of early treatment.