PBT Chemicals: Persistent, Bioaccumulative, Toxic

How can pesticides no one has used for decades be found in birds and fish in some of the most remote locations of the globe? These chemicals—along with many carpet treatments, flame retardants, and other additives still commonly found in building products—are persistent, bioaccumulative toxic chemicals (PBTs). While many toxic substances become less potent over time, PBTs can become more harmful the longer they persist due to their activity in ecosystems. Some, like arsenic, are naturally occurring, but many are human-made. Other naturally occurring ones, like mercury and lead, are released into the environment in greater concentrations due to human activities like burning coal.

Persistence means a chemical does not readily break down in the environment. PBTs can be transported long distances through air and ocean currents and the atmosphere. They can remain in soil and silt for decades, being absorbed by plants and microorganisms. The persistence threshold for testing and potential regulation by the U.S. Environmental Protection Agency (EPA) is a half-life longer than two months.