&EPA
United States
Environmental Protection
Agency
Office of Water
EPA 822-F-16-003
March 2016
Aquatic Life Ambient Water Quality Criteria
Update for Cadmium - 2016
Summary
EPA has updated its national recommended aquatic
life ambient water quality criteria for cadmium in
order to reflect the latest scientific information. The
updated criteria account for many new laboratory
aquatic toxicity tests with cadmium published since
EPA's 2001 criteria document. In addition, the effect
of total hardness on cadmium toxicity was also
revised using the newly acquired data. The updated
criteria document has undergone an external peer
review that was completed in 2015 and a 60 day
public comment period.
EPA's water quality criteria for cadmium provides
recommendations to states and tribes authorized to
establish water quality standards under the Clean
Water Act.
Background
EPA published the original national recommended
cadmium aquatic life criteria in 1980 with
subsequent revisions in 1985, 1990, 1996 and 2001.
In 1985, acute toxicity values were lowered to better
protect the commercially and recreationally
important rainbow trout. In 2001, criteria were
developed for dissolved cadmium instead of total
recoverable cadmium to more accurately account
for bioavailability and reflect the latest EPA policy for
metals risk assessment. Each update has included
updated science and additional aquatic toxicity
studies. EPA developed the 2016 national
recommended aquatic life criteria for cadmium using
the best available science.
What is Cadmium?
Cadmium is a naturally occurring metal found in
mineral deposits and is distributed widely at low
concentrations in the environment. Cadmium's
primary industrial uses are for the manufacturer of
batteries, pigments, plastic stabilizers, metal
coatings, alloys and electronics. Recently, cadmium
has been used in manufacturing nanoparticlesfor
use in solar cells and color displays.
How Does Cadmium Enter Surface Waters?
Cadmium enters the environment by natural and
human processes, however, human sources, such as
mining and urban processes, are responsible for
contributing approximately 90 percent of the
cadmium found in surface waters.
How Does Cadmium Affect Aquatic Life?
Cadmium is a non-essential metal with no biological
function in aquatic life. Acute exposure causes
increased mortality in aquatic organisms. Chronic
exposure leads to adverse effects on growth,
reproduction, immune and endocrine systems,
development and behavior in aquatic organisms.
What are National Recommended Aquatic Life
Criteria?
Ambient water quality criteria for the protection of
aquatic life are numeric concentrations of pollutants
in surface waters that are protective of aquatic life
designated uses, with specific recommendations on
the duration and frequency of those concentrations.
Under Clean Water Act section 304(a), EPA is
directed to develop and publish water quality
criteria that reflect the latest scientific knowledge.
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Water quality criteria are based solely on data and
scientific judgments about the relationship between
pollutant concentrations and potential
environmental 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. States must adopt into their
standards water quality criteria that protect the
designated 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 Clean
Water Act until they have been adopted into state
water quality standards and approved by EPA.
What Are the 2016 Recommended Water
Quality Criteria for Cadmium?
EPA recommends the:
One-hour freshwater acute criterion maximum
concentration not exceed 1.8 u.g/L at a total hardness
of 100 mg/L as CaCO3.
Four-day average freshwater chronic criterion
concentration not exceed 0.72 u.g/L at a total
hardness of 100 mg/L as CaCO3.
One-hour estuarine/marine acute criterion maximum
concentration not exceed 33 u.g/L.
Four-day average estuarine/marine chronic criterion
concentration not exceed 7.9 u.g/L.
The recommended frequency of exceedance for the
above is no more than once every three years.
How Do the 2016 Criteria Compare to the
Previously Recommended 2001 Criteria?
The 2016 criteria reflect data for 75 new species and
49 new genera. The 2016 freshwater acute criterion
(1.8 micrograms per liter) for dissolved cadmium is
slightly lower than the 2001 acute criterion (2.0
micrograms per liter). The 2016 freshwater chronic
criterion (0.72 micrograms per liter) for dissolved
cadmium is slightly higher (less stringent) compared
to the 2001 criterion (0.25 micrograms per liter).
These modest changes are primarily due to the
inclusion of new toxicity studies. As in the 2001
criteria, the 2016 freshwater acute criterion was
derived to be protective of aquatic species and was
lowered further to protect the commercially and
recreationally important rainbow trout. In addition,
the duration of the 2016 acute criterion was
changed to one-hour. Both changes are consistent
with EPA's current aquatic life criteria guidelines.
The 2016 estuarine/marine acute criterion for
dissolved cadmium (33 micrograms per liter) is lower
(more stringent) than the 2001 acute criterion (40
micrograms per liter), which is primarily due to the
addition of new toxicity studies for sensitive genera.
The 2016 estuarine/marine chronic criterion (7.9
micrograms per liter) is also slightly more stringent
than the 2001 chronic criterion (8.8 micrograms per
liter), due the consideration of more species in the
chronic criterion development. The 2016 criteria for
dissolved cadmium can be found in Table 1.
Table 1. Summary of 2016 Draft Aquatic Life AWQC
for Cadmium.
Freshwater
(Total Hardness =
100 mg/L as CaCO3)a
Estuarine/marine
2016 AWQC Update
Acute
(1-hour,
dissolved Cd)c
1.8 ug/Lb
33 ug/L
Chronic
(4-day,
dissolved Cd)
0.72 ug/L
7.9 ug/L
Freshwater acute and chronic criteria are hardness-dependent
and were normalized to a hardness of 100 mg/L as CaCO3 to allow
the presentation of representative criteria values.
b Lowered to protect a commercially and recreationally important
species (rainbow trout), as per the 1985 Guidelines, Stephen et al.
(1985).
°The duration of the 2016 acute criteria was changed to 1-hour to
reflect the 1985 Guidelines-based recommended acute duration.
How to View the Criteria Document and
Supporting Information:
EPA has established an official public docket for this
action under Docket ID No. EPA-HQ-OW-2015-0753,
accessed at www.regulations.gov. You may also
download the document and supporting information
from EPA's aquatic life criteria website at:
http://www.epa.gov/wqc/aquatic-life-criteria-
cadmium
Where can I find more information?
Please contact Mike Elias by email at
elias.mike@epa.gov.
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