Ammonia
Fact Sheet: 1999 Update
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United States
Environmental Protection
Agency |
Office of Water
4305 |
EPA-823-F-99-013
December 1999 |
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The U.S. Environmental Protection Agency (EPA) is publishing
a 1999 Update of Ambient Water Quality Criteria for Ammonia (1999
Ammonia Update). The 1999 Ammonia Update contains EPA's most recent
freshwater aquatic life criteria for ammonia, superseding all previous
EPA recommended freshwater criteria for ammonia. The 1999 Ammonia
Update pertains only to fresh waters. It does not change or supersede
the EPA's aquatic life criterion for ammonia in salt water, published
in Ambient Water Quality Criteria for Ammonia (Saltwater) in 1989.
Background
Under the Clean Water Act, EPA is required to publish and periodically
update ambient water quality criteria. These criteria reflect the
latest scientific knowledge on the effects of water pollutants on
public health and welfare, aquatic life, and recreation. These criteria
guide states, territories, and authorized tribes in developing water
quality standards and ultimately provide a basis for controlling
discharges or releases of pollutants into our nation's waterways.
Ambient water quality criteria are based solely on data and scientific
judgments on the relationship between pollutant concentrations and
the effects on aquatic life, human health, and the environment.
These criteria do not reflect consideration of economic impacts
or the technological feasibility of reducing chemical concentrations
in ambient water.
1999 Ammonia Update
The 1999 Update of Water Quality Criteria for Ammonia incorporates
comments received from the 1998 Update. The 1999 Update contains
EPA's most recent freshwater aquatic life criteria for ammonia and
supersedes all previous freshwater aquatic life ammonia criteria.
The new criteria reflect recent research and data since 1984, and
are a revision of several elements in the 1984 Criteria, including
the pH and temperature relationship of the acute and chronic criteria
and the averaging period of the chronic criterion. As a result of
these revisions, the acute criterion for ammonia is now dependent
on pH and fish species, and the chronic criterion is dependent on
pH and temperature. At lower temperatures, the dependency of the
chronic criterion is also dependent on the presence or absence of
early life stages of fish. The temperature dependency in the 1999
Update results in a gradual increase in the criterion as temperature
decreases, and a criterion that is more stringent, at temperatures
below 15 C, when early life stages of fish are expected to be present.
EPA's recommendations in the 1999 Update represent a change from
both the 1984 chronic criterion, which was dependent mainly on pH,
and from the 1998 Update, in which the chronic criterion was dependent
on pH and the presence of early life stages of fish.
Additional Information
EPA is issuing a Federal Register notice of availability
for the 1999 Update, which summarizes changes in the 1999 Update
and describes EPA's recommendations for implementing the criteria.
The full text of the Federal Register notice is available
at http://www.epa.gov/waterscience/standards/ammonia/
on the Internet. For additional information, contact Office of Science
and Technology, U.S. EPA, 1200 Pennsylvania Avenue NW, Washington
DC, 20460.
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