Japanese researchers have detected high levels of polychlorinated biphenyls (PCBs) in mongooses found near two U.S. military bases in Okinawa. PCBs are one of the most toxic chemical waste categories on the planet, with strong persistence in the environment and high resistance to biodegradation. PCBs have been shown to cause cancer in animals and to lead to cancer in humans as well. Research must be undertaken to determine why high levels of PCBs were found near U.S. military bases.

The team of researchers from Ehime University and Meio University found a high average level of PCBs throughout the animals' bodies and much higher levels of PCBs in their livers. Those levels are said to be much higher than in other parts of Okinawa or in other animals such as cats, boars or raccoons found elsewhere in Japan.

Mongooses were chosen for the study because they have a relatively narrow range of movement and often live close to residential areas. The PCBs they soaked up are highly soluble in fats and can easily accumulate in all types of organisms, with those at the highest levels of the food chain most affected.