TUESDAY, Dec. 7 (HealthDay News) -- U.S. researchers who recently found high levels of polybrominated diphenyl ether (PBDE) flame retardants in butter say it is the worst documented case of food contamination with PBDE in the country.

It's also the first time that this type of food contamination is believed to be the result of PBDEs in a food's packaging.

The researchers found that one in 10 samples of butter bought at five Dallas grocery stores had PBDE levels more than 135 times higher than the average of the other nine samples. Levels of deca-BDE -- a PBDE compound widely used in electronics, textiles, cable insulation, and car and aircraft components -- were more than 900 times higher in the contaminated samples than in the other nine samples.

Studies in rodents have linked deca-BDE with thyroid hormone changes and neurobehavioral changes.

As the researchers continued their investigation, they found that PBDE levels in the butter's paper wrapper were more than 16 times higher than levels found in the butter. It's not clear whether the paper was contaminated before or after it reached the butter packaging plant, and the actual source of contamination is not known.

The study is published online Dec. 7 and in an upcoming print issue of the journal Environmental Health Perspectives.

The findings highlight the need for a U.S. regulatory program that tests food for persistent organic pollutants such as PBDEs, said lead author Arnold Schecter of the University of Texas School of Public Health and colleagues in a news release from the journal.

More information

The U.S. Agency for Toxic Substances and Disease Registry has more about PBDEs.