Persistent, bioaccumulative and toxic pollutants (PBTs) are long-lasting substances that can build up in the food chain to levels that are harmful to human and ecosystem health. These contaminants can be transported long distances and move readily from land to air and water. Because of their persistence and bioaccumulative properties, they do not break down easily and are particularly difficult to clean up. Many of these substances are human-made and have only been in existence for a relatively short period of history. Other of these substances are natural elements, such as mercury. It is the refinement and concentrated human use of these substances that creates the problem. EPA is concerned not only with historical PBT problem chemicals, such as DDT and PCBs, but also with PBT chemicals currently in production (such as mercury) and new chemicals with similar properties entering commerce today or in the future.
Why are Persistent, bioaccumulative and toxic pollutants (PBTs) a problem?
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