In June, construction workers unearthed more than 20 rusty barrels from beneath a soccer pitch in Okinawa City. The land had once been part of Kadena Air Base — the Pentagon's largest installation in the Pacific region — but was returned to civilian usage in 1987. Tests revealed that the barrels contained two ingredients of military defoliants used in the Vietnam War: the herbicide 2,4,5-T and 2,3,7,8,-TCDD dioxin. Levels of the highly toxic TCDD in nearby water measured 280 times the safe limit.

The Pentagon has repeatedly denied storing of defoliants — including Agent Orange — on Okinawa. Following the discovery, it distanced itself from the barrels; a spokesperson said the Defense Department was investigating whether they had been buried after the land's return in 1987, and a U.S. government-sponsored scientist suggested they may merely have contained kitchen or medical waste. However, the conclusions of the Japanese and international scientific community were unequivocal: Not only did the barrels disprove Pentagon denials of the presence of military defoliants in Japan, but the polluted land also posed a threat to the health of local residents and required immediate remediation.

The Pentagon is the largest polluter on the planet, producing more toxic waste than the top three U.S. chemical manufacturers combined. In 2008, 25,000 of its properties within the U.S. were found to be contaminated, and more than 100 of these were classified by the Environmental Protection Agency as Superfund sites, meaning they warranted urgent cleanup.