There is currently no way to know how widespread this kind of chemical contamination is in food. Emily Sohn writes in Discovery News:
As part of an ongoing investigation into chemicals in our food supply, scientists found extremely high concentrations of a flame-retardant compound in a supermarket sample of brand-name butter.
It is the first documented case of serious contamination in food in the United States with a class of chemicals known as PBDEs, or polybrominated diphenyl ethers.
Commonly used in furniture and electronics, among other products, PBDEs are known to disrupt hormone function and have been associated with a range of health concerns, including cancer as well as reproductive, developmental, and neurological problems.
Since no federal agencies currently track levels of chemicals like these in food, there is no way to know how widespread this kind of chemical contamination is in butter or other products. But it clearly happens at least sometimes.
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