# Aquatic Life Ambient Water Quality Criteria for

Ammonia - Freshwater ( 201 3)

S u m m a r y

EPA has published national recommended ambient water quality criteria for the protection of aquatic life from the toxic effects of ammonia, a constituent of nitrogen pollution

. Th e se recommended criteria will help S tates,

T erritori es, and authorized T ribes update their water quality standards with concentration level s for ammonia in surface waters at or below which aquatic organisms will be protected , if not exceeded more frequently than once every three

years on average

. A cute and chronic criteria were developed to protect organisms from both immediate effects, such as mortality, and longer

term effects on reproduction, growth and

survival , respectively

.

EPA’s final Aquatic Life Ambient Water Quality Criteria for Ammonia

– Freshwater (2013) incorporate scientific views received on EPA's

2009 draft updated ammonia criteria and supersede EPA’s previously recommended 1999

ammonia criteria.

W h a t a r e n a t i o n a l r e c o m m e n d e d a q u a t i c l i f e

a m b i e n t w a t e r q u a l i t y c r i t e r i a ?

A mbient water quality criteria for the protection

of a quatic life are numeric concentrations of pollutants

, with specific associated duration and frequency information

, in surface waters that are protect ive of aquatic life designated uses . Under

C lean W ater A ct s ection 304(a), EPA is required to develop and publish water quality criteria that

reflect the latest scientific knowledge. W ater quality criteria are based solely on data and scientific judgments about the relationship between pollutant concentrations and potential

environ mental and human health effects

. EPA's recommended water quality criteria are not rules, nor do they automatically become part of a

state 's water quality standards. S tates must adopt into their standards water quality criteria that protect the desig nated uses of the water bodies within their area

. These can include scientifically defensible site

- specific criteria that

are different from EPA 's national recommended

criteria

, as long as the site

- specific criteria are protective of the designated use. Water quality

criteria are not effective under the C lean W ater

A ct until they have been adopted into a state’s water quality standards and approved by EPA.

W h a t i s a m m o n i a ?

Ammonia is one of several forms of nitrogen

that ex ist in aquatic environments . U nlike other forms of nitrogen , which can cause nutrient

over

- enrichment of a water body at elevated

concentrations and indirect effects on aquatic

life , ammonia causes direct toxic effects on aquatic life.

Ammonia is produced for commercial fertilizers and other industrial applications. N atural sources of ammonia include the decomposition or breakdown of organic waste matter, gas exchange with the atmosphere, forest fires,

animal and human waste, and nitrogen fixation

processes

.

H o w d o e s a m m o n i a e n t e r s u rf a c e w a t e rs ?

Ammonia can enter the aquatic environment via direct means such as municipal effluent discharges and the excretion of nitrogenous wastes from animals, and indirect means such as nitrogen fixation, air deposition, and runoff from agricultur al lands.

H o w d o e s a m m o n i a a f

f e c t a q u a t i c l i f

e ?

When ammonia is present in water at high enough levels

, it is difficult for aquatic organisms to sufficiently excrete the toxicant, leading to toxic buildup in internal tissues and

blood , and poten ti ally death . Environmental factors, such as pH and temperature

, can affect ammonia toxicity to aquatic animals

. Office of Water 820

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MC 4304T A ugust 201 3W h a t i s t h e h i s t o r y o f E P A ’ s d e v e l o p m e n t o f

a m m o n i a c r i t e r i a ?

EPA first published ammonia criteria for the protection of aquatic life in 1976. The criteria were then updated in 1985 and 1999 to reflect

scientific information available at that time. The 1999 recommended aquatic life criteria for

ammonia were based on the most sensitive endpoints known at the time: the acute criterion

was based on salmonid fish toxicity information,

and the chronic criterion was based on bluegill

sunfish early life stage toxicity

.

In 2003

, EPA became aware of new toxicity

studies indicating the relative sensitivity of

freshwater mussels to ammonia and began to update the 1999 criteria to reflect this new

information

. I n 2009

, f

ollowing external peer review, EPA published draft recommended

ammonia criteria

, for waters with and without

mussels. Since the publication of the draft 2009

ammonia criteria , additional toxicity testing has

validated information on the effects of ammonia on sensitive freshwater gill

- breathing snail species. I n April 2013, EPA finalized the updated ammonia criteria that are applicable nationally , taking into account the latest toxicity

information for freshwater species, including

unionid mussels and gill

- breathing snails

. The

2013 criteria incorporate scientific views

received on the draft (2009) ammonia criteria and supersede EPA’s previously recommended

1999 criteria.

W h a t a r e t h e 2 0 1 3 r e c o m m e n d e d w a t e r

q u a l i t y c r i t e r i a f o r a m m o n i a ?

EPA recommend s an acute criterion magnitude

of 1 7 mg T otal A mmonia N itrogen (TAN) per liter at pH 7 and 20°C for a one

- hour average

duration

, not to be exceeded more than once every three years on average . EPA recommend s

a chronic criterion magnitude of 1.9 mg TAN /L at pH 7 and 20°C for a 30

- day average duration

, not to be exceeded more than once every three

years on average

. In addition, the highest four

day average within a 30

- day period should not

exceed 2.5 times the chronic criterion magnitude (e.g. 1.9 mg TAN /L x 2.5 = 4.8 mg TAN /L at pH 7 and 20°C) more than once in three years on

average

. H o w d o t h e 2 0 1 3 c r i t e r i a c o m p a r e t o t h e

p r e v i o u s l y r e c o m m e n d e d 1 9 9 9 c r i t e r i a a n d

t h e d r a f t 2 0 0 9 c r i t e r i a ?

The 2013 ammonia criteria recommendations take into account the latest freshwater toxicity information for ammonia, including toxicity

studies for sensitive unionid mussels and g ill

breathing snails. These new criteria are based on robust toxicity data available for 69 genera (acute) and 16 genera (chronic)

. T he updated

criteria magnitudes are more stringent than the previously recommended 1999 criteria magnitudes ( see Table 1 )

. The duration

component s of the 1999, 2009 and 2013 criteria

remain the same

- a one

- hour average duration

for the acute criterion and 30

- day average duration for the chronic criterion. The frequency component for the acute and chronic criteri a remains once in three years on average

.

Table 1

. Comparison of past and current EPA

recommended aquatic life water quality criteria magnitudes for ammonia . Criteria magnitudes are expressed as total ammonia nitrogen ( mg TAN /L ) at pH 7 and 20°C

.

Criterion

Duration 1999

Criteria 2009

Draft Update d

Criteria 2013

Final Update d

Criteria

Acute (1

- h ou r average) 24 19 17

Chronic (30

- d ay rolling average) 4.5 * 0.91 * 1.9 *

*Not to exceed 2.5 times the criterion

continuous concentration as a 4

- day average

within a 30

- day period.

Criteria frequency: Not to be exceeded more

than once in three years on average.A d d i t i o n a l E P A R e s o u r c e s

EPA has developed three supporting documents to aid states considering adoption of the 2013

recommended ammonia criteria.

Flexibilities for States Applying EPA’s Ammonia

Criteria Recommendations provides an

overview of a number of implementation approaches available for state consideration, including the recalculation procedure for site

specific criteria derivation, variances, revisions to designated uses, dilution allowances, and compliance schedules. The document describes

how each of these flexibilities fits within a state’s water quality standards adoption and implementation processes.

EPA has also developed a Revised Deletion Process for the Site

- Specific Recalculation

Procedure for Aquatic Life Criteria that describes a recalculation procedure and in cludes a spreadsheet that may be used to derive site

specific water quality criteria for the protection of aquatic life in order to be s t reflect the organisms that reside at a specific site.

A third document, which EPA expect s to publish

in 2013, Techni cal Support Document for Conducting and Reviewing Freshwater Mussel Studies for the Development of Site

- specific Water Quality Criteria for Ammonia

, will help

states determine if sensitive freshwater mussels are present in their waters. Commonly

- used mussel sampling methods will be described and

an overview will be provided of various study approaches, considerations, and limitations, including real

- life examples.

H o w t o V i e w t h e C r i t e r i a D o c u m e n t a n d
S u p p o r t i n g I n f o r m a t i o n

EP A has established an official public docket for

this action under Docket ID No. EPA

- HQ

- OW

2009

- 0921 , accessed at www.regulations.gov

. You may also download the document and supporting information from http://water.epa.gov/scitech/swguidance/standar ds/criteria/aqlife/ammonia/index.cfm

. F o r M o r e I n f o r m a t i o n

Contact Lisa Huff by telephone at (202) 566

- 0787, by email at huff.lisa@epa.gov , o r by mail at U.S. EPA, MC: 4304 T , 1200 Pennsylvania Ave., N.W., Washington, D.C. 20460.