LOS ANGELES (Tribune News Service) — Think of the most radioactive landscapes on the planet and the names Chernobyl and Fukushima may come to mind.

Yet research published Monday suggests that parts of the Marshall Islands in the central Pacific, where the United States conducted 67 nuclear tests during the Cold War, should be added to the list.

In a peer-reviewed study, Columbia University researchers report that soil on four isles of the Marshall Islands contains concentrations of nuclear isotopes that greatly exceed those found near the Chernobyl and Fukushima nuclear power plants. On one isle, those levels are reported to be 1,000 times higher.

All four of the islands are currently uninhabited, and three of the four — Bikini, Enjebi and Runit — are in atolls where nuclear testing took place. But one of the islands, Naen, which measures less than an acre, is in Rongelap Atoll, nearly 100 miles away.