FUKUSHIMA—A citizens’ group here has released an English radiation-level map for eastern Japan created with input from 4,000 volunteers in response to requests from abroad ahead of the Tokyo Olympics.

“We want people outside Japan to understand the reality of radioactive contamination following the nuclear accident,” said Nahoko Nakamura, a representative of Minna-No Data Site (Everyone's Data Site), which published the map.

The Fukushima No. 1 nuclear power plant experienced a triple meltdown in March 2011 after a tsunami knocked out its cooling systems during the Great East Japan Earthquake.

Titled “Citizens’ Radiation Data Map of Japan,” the 16-page booklet summarizes the content of the original Japanese map, released in November last year. It also shows projected declines in radiation levels by 2041.

The Japanese version was based on results of land contamination surveys conducted over three years at the request of Everyone's Data Site.

About 4,000 volunteers took soil samples at 3,400 locations in 17 prefectures in eastern Japan, including Fukushima and Tokyo, and measured radiation levels. The map was compiled with advice from experts.

The group raised 6.23 million yen ($57,500) from 1,288 individuals through a crowdfunding campaign. So far, 15,000 copies have been sold.

Nakamura said the group decided to produce an English version after it received inquiries about the Japanese map from researchers and others overseas in the run-up to the Tokyo Olympics.

Everyone's Data Site spent about four months creating the English map, working through e-mail and online chats with five volunteer translators overseas, including an American and a Canadian.

The English edition sells for 500 yen, excluding tax. For more information, contact Everyone's Data Site at (minnanods@gmail.com).