The federal Clean Water Act (CWA) focuses on 126 chemicals that were
designated as "priority pollutants" in 1977. Although many other toxic
chemicals are also being released to water, the Clean Water Act does
not cover them, despite its name.
The 126 priority pollutants can be subject to several different kinds of
regulatory activity, some based on considerations of water quality and
some based on the technologies available for pollution control in
different industrial sectors. The Environmental Protection Agency
establishes criteria for the quality of ambient water (lakes and
streams, for example) that identify the concentration levels of
specific chemicals that will not pose unacceptable risks to human or
aquatic life. These criteria are not enforceable legal standards.
However, they can serve as the scientific foundation of water quality
standards set by states, which are enforceable. Separately, U.S. EPA
also sets limits on the discharge of priority pollutants ("effluent
limits") by various types of industries. These limits are generally
based on the "best available technology economically achievable" for
controlling discharges. Such technology may or may not succeed in
keeping discharges below levels that adversely affect water quality.
See a list of the
chemicals covered by the Clean Water Act (CWA)
More information about the Clean Water Act: