This entity identifies substance-of-interest to the EPA. This isn't everything in the world, but
it is a finite, stable list and the list will grow.
Substances are neither good nor bad because that sort of assessment needs the context within which
the substance exists. However there are substances are characteristically bad...
The purpose is to focus aspects of environmental management on something with identifiable /
definable characteristic. From the perspective of the EPA a great many diverse substances have
sommething in common: EPA is trying to manage (or help others try to manage) them.
An ENVIRONMENTALLY SIGNIFICANT SUBSTANCE is not just any substance. The only substances that make
it on this list are or will become special to the EPA.