Frequent Questions

What should I know about persistent bioaccumulative toxic (PBT) chemicals?

Starting in 2000, EPA established more stringent reporting thresholds for persistent bioaccumulative toxic (PBT) chemicals originally on, or added to, the TRI chemical list.  PBT chemicals are of particular concern not only because they are toxic, but also because they remain in the environment for long periods of time, are not readily destroyed, and build up or accumulate in body tissue.  The TRI PBT chemicals include dioxin and dioxin-like compounds, lead and lead compounds, mercury and mercury compounds, polycyclic aromatic compounds (PACs), polychlorinated biphenyls (PCBs), and certain pesticides, among other chemicals.

For more detailed information about the Agency's multimedia strategy for priority PBT chemicals, visit EPA's Office of Prevention, Pesticides, and Toxic Substances Web site at

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