United States
Environmental Protection
  Office of Water
 November 2015
Draft Aquatic Life Ambient  Water Quality
Criteria  Update  for Cadmium  - 2015
EPA is updating its national recommended ambient
water quality criteria for cadmium in order to reflect
the latest scientific information. The updated criteria
reflect the inclusion of 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 draft updated
criteria document has undergone an external peer
review that was completed in 2015.
EPA will accept written comments from the public
for 60 days once announced in the Federal Register.
EPA will then consider the comments that were
submitted, and revise and publish the final criteria
document. Once finalized, EPA's water quality
criteria for cadmium will provide recommendations
to states and tribes authorized to establish water
quality standards under the Clean Water Act.
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 rainbow trout, the most sensitive species. 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 draft
2015 updated national recommended aquatic life
criteria for cadmium using the best available science.
                             What is Cadmium?
                             Cadmium is a relatively rare, naturally occurring
                             metal found in mineral deposits and distributed
                             ubiquitously at low concentrations in the
                             environment. Cadmium's primary industrial uses are
                             manufacturers of batteries, pigments, plastic
                             stabilizers, metal coatings, alloys and electronics.
                             Recently cadmium has been used in manufacturing
                             nanoparticles for 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. 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
                             Ambient water quality criteria for the protection of
                             aquatic life are numeric concentrations of pollutants,
                             with specific recommendations on the  duration and
                             frequency of those concentrations, in surface waters
                             that are protective of aquatic life designated uses.
                             Under Clean Water Act section  304(a),  EPA is
                             directed to develop and publish water quality
                             criteria that reflect the latest scientific  knowledge.
                             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 2015 Draft Recommended Water
Quality Criteria for Cadmium?
In the 2015 draft, EPA recommends:
•  the one-hour freshwater acute criterion maximum
   concentration not exceed 2.1 u.g/L.
•  the four-day average freshwater chronic criterion
   magnitude not exceed 0.73u.g/L
•  the one-hour estuarine/marine acute criterion
   maximum concentration not exceed 35 u.g/L.
•  the four-day average estuarine/marine chronic
   criterion magnitude not exceed 8.3 u.g/L.
The recommended frequency of exceedance for the
above  is no more than once every three years.
How Do the Draft  2015 Criteria  Compare to the
Previously Recommended 2001  Criteria?
The draft 2015 updated criteria reflect data for 70
new species and 49  new genera. The draft 2015
freshwater acute criterion (2.1 micrograms per liter)
for dissolved cadmium is approximately the same as
the 2001 acute criterion (2.0 micrograms per liter).
The draft 2015 freshwater chronic  criterion (0.73
micrograms per liter) for dissolved cadmium is
slightly higher (less stringent) compared to the 2001
criterion (0.25 micrograms per liter). These modest
increases are primarily due to the inclusion of new
toxicity studies. As in the 2001 criteria, the draft
2015 freshwater acute criterion was derived to be
protective of endangered species and lowered
further to  protect the commercially and
recreationally important rainbow trout. In addition,
the duration of the 2015 acute criterion was
changed to one-hour. Both changes are consistent
with EPA's current aquatic life criteria guidelines.
The draft 2015 estuarine/marine acute criterion for
dissolved cadmium (35 micrograms per liter) is
slightly 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 draft 2015 estuarine/marine
chronic criterion (8.3 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 draft 2015 criteria for
dissolved cadmium can be found in Table 1.
Table 1. Summary of 2015 Draft Aquatic Life AWQC
for Cadmium.

(Total Hardness =
100 mg/L as CaCO3)a
2015 AWQC Update
dissolved Cd)c
2.1 ug/Lb
35 ug/L
dissolved Cd)
0.73 ug/L
8.3 ug/L
a Freshwater acute and chronic criteria are hardness-dependent
and were normalized to a hardness of 100 mg/L as CaCOs to allow
the presentation of representative criteria values.
b Lowered to protect the commercially and recreationally
important species (rainbow trout), as per the 1985 Guidelines,
Stephen et al. (1985).
°The duration of the 2015 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:
Where can  I find more information?
Please contact Mike Elias by email at