	United States

Environmental Protection Agency	Office of Water (4304T)	                
               SEQ CHAPTER \h \r 1 EPA-822-F-09-006

December 2009

	Draft 2009 Update of Aquatic Life Ambient Water Quality Criteria for
Ammonia - Freshwater

EPA is publishing draft national recommended ambient water quality
criteria for the protection of aquatic life for ammonia. These criteria
are based on EPA’s Guidelines for Deriving Numerical National Water
Quality Criteria for the Protection of Aquatic Organisms and Their Uses
(1985), EPA 822/R-85-100. EPA is publishing these draft criteria in
order to receive scientific input from the public.   

What are aquatic life water quality criteria?

Aquatic life water quality criteria are numeric values that protect
aquatic life from the harmful effects of pollutants in surface water.
Under section 304(a) of the Clean Water Act (CWA), water quality
criteria are based solely on data and scientific judgments about the
relationship between pollutant concentrations and environmental and
human health effects; economic or social impacts do not influence
criteria recommendations.

EPA’s national recommended water quality criteria provide guidance to
states, territories and authorized tribes in adopting water quality
criteria that meet the requirements of the CWA. They are not regulations
themselves and do not impose legally binding requirements on EPA,
states, territories, authorized tribes or the public.  

How were these water quality criteria for ammonia derived?

EPA derived these aquatic life water quality criteria for ammonia based
on the Agency’s 1985 Aquatic Life Criteria Guidelines. These
guidelines provide consistent, scientifically-based procedures for
deriving ambient water quality criteria for the protection of aquatic
organisms and their uses. Toxicity data and other information on the
effects of ammonia were obtained from reliable sources and subjected to
both internal and external peer review.  The draft criteria update
incorporates all toxicity data available since the last criteria update
including new data on larval and juvenile freshwater mussels to reflect
the latest science.     

What are the draft aquatic life water quality criteria for ammonia?

Freshwater:  Freshwater aquatic organisms and their uses should not be
affected unacceptably if – 

1. The one-hour average concentration of total ammonia nitrogen (in mg
N/L) does not exceed, more than once every three years on the average,
the CMC (acute criterion), which is dependent on the aquatic organisms
present. 

2A. The thirty-day average concentration of total ammonia nitrogen (in
mg N/L) does not exceed, more than once every three years on the
average, the CCC (chronic criterion), which is dependent on the aquatic
organisms present.

2B. In addition, the highest four-day average within the 30-day period
should not exceed 2.5 times the CCC.

The acute and chronic criteria concentrations are expressed as functions
of temperature and pH, such that values differ across sites, and differ
over time within a site.  See draft criteria document (pp. 34-38) for
actual equations describing this function.  As temperature decreases,
invertebrates, but not fish, become less sensitive to ammonia, and below
a particular temperature threshold, fish become the most sensitive
genera.  

Acute Criteria:  At pH=8, where freshwater mussels are present, the
criterion concentration ranges from 1.90 mg N/L at 30° C to 9.81 mg N/L
at 0° C.  At pH=8, where freshwater mussels are absent the criterion
concentration ranges from  3.29 mg N/L at 30° C to 9.99 mg N/L at 0°
C.

Chronic Criteria:  At pH=8, where freshwater mussels are present,
irrespective of whether fish early life stages (ELS) are present or
absent, the criterion ranges from 0.186 mg N/L at 30° C to 0.817 mg N/L
at 0° C.  When freshwater mussels are absent, the values range from
1.33 mg N/L at 30° C to 2.32 mg N/L at 0° C at times when fish ELS are
present, and from 1.33 mg N/L at 30° C to 5.87 mg N/L at 0° C at times
when fish ELS are absent.

	Draft 2009 Ammonia Criteria 

(at pH 8 and 25°C)	Current 1999 Criteria

(at pH 8 and 25°C)

Acute	2.9 mg N/L mussels present

5.0 mg N/L mussels absent	5.6 mg N/L salmon present

Chronic	0.26 mg N/L mussels present

1.8 mg N/L mussels absent	1.2 mg N/L fish early life stages present

Note: These criteria values are appropriate at the standard normalized
pH and temperature; the criteria values are a function of the
variability of pH and temperature.

The water quality criteria for ammonia saltwater are not being updated
at this time.

Where can I find more information on the draft aquatic life water
quality criteria for ammonia?

Contact Lisa Huff, U.S. EPA, Health and Ecological Criteria Division
(4304T), 1200 Pennsylvania Ave., N.W., Washington, D.C. 20460; (202)
566-0787; huff.lisa@epa.gov.

You can find the Federal Register notice on national recommended water
quality criteria online at
http://www.epa.gov/waterscience/criteria/ammonia. EPA has also
established an official public docket for this action under Docket ID
No. EPA-HQ-OW-2009-0921

Scientific views on these draft criteria will be accepted for 90 days
(upon Federal Register publication) via the docket webpage.  The docket
can be accessed at www.regulations.gov.

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