Document ID No.: EPA 705-G-2020-3708
Fish Bioconcentration Data Requirement:
Guidance for Selection of Number of Treatment
[Supplement to OCSPP Test Guideline 850.1730]
July 15, 2020
Disclaimer: The contents of this document do not have the force and
effect of law and are not meant to bind the public in any way. This
document is intended only to provide clarity to the public regarding
existing requirements under the law or agency policies.
Office of Pesticide Programs
Office of Chemical Safety and Pollution Prevention
U.S. Environmental Protection Agency

I. Purpose
The purpose of this document is to clarify EPA recommendations for the number
of treatment concentrations needed to result in acceptable fish bioconcentration factor
(BCF) studies for pesticide registration. EPA routinely requires BCF studies to determine
whether pesticide active ingredients have the potential to accumulate in fish, enter the food
chain, and cause adverse effects in fish-eating predators such as aquatic mammals and
birds of prey.
In April 2017, EPA was approached by an outside party, the National Centre for
the Replacement, Refinement and Reduction of Animals in Research (NC3R), with a
suggestion to modify the test guideline for the BCF study to reduce the number of animals
used in BCF testing, by reducing the number of concentration levels used from three (two
positive doses and one control) to two (one positive level and one control).
NC3R stated that this would be "[i]n the interest of international harmonization and
reducing unnecessary animal testing" because "[a]t the moment the Japanese and US EPA
guideline require that two concentrations are always tested, which is in contrast to the
OECD Test Guideline[']; therefore, many companies are understandably continuing to test
two concentrations to ensure acceptance within these regions."
This modification has the potential to reduce the number of fish used by one-third.
EPA has considered NC3R's suggestion and has considered/evaluated data in its own
holdings as part of that consideration. This paper documents this analysis and results of
EPA's analysis of this proposal.
II. Issue
According to pesticide data requirements set forth in Part 158 of Title 40 in the Code of
Federal Regulations (40 CFR part 158)2, Fish Bioconcentration Factor (BCF) data (OCSPP
Guideline 850.1730; USEPA 20163) are required to support applications for pesticide
registrations under the following conditions: the octanol-water partition coefficient (Kow) of the
chemical is >1000 (log Kow > 3.0); the use pattern results in potential exposure to fish and other
nontarget aquatic organisms; or, the hydrolytic half-life of the chemical is >5 days at pH 5, 7
and 9. As part of the exposure phase of the study, the guideline specifies the use of at least two
test concentrations which are a factor of 10 apart, plus the appropriate control(s), in order to
document that the potential to bioconcentrate is independent of the concentration of the test
substance. The 850.1730 guidance states:
"(hi) Treatment concentrations. To document that the potential to
bioconcentrate is independent of the concentration of the test substance,
1	Test Guideline issued by the Organisation for Economic Co-operation and Development (OECD) are available
online at
2	Information about the EPA data requirements for pesticide registration and related test guidelines is available
online at

bioconcentration values for the test substance should be determined using
at least two concentrations during the exposure phase which are a factor
of 10 apart, plus the appropriate control(s). Preliminary toxicity tests or a
range-finding test can be used to establish the appropriate test solution
concentrations for the definitive test. The two concentrations selected
should not stress or adversely affect the fish."
Analysis presented to EPA's Office of Pesticide Programs (OPP) by the National Centre
for the Replacement, Refinement and Reduction of Animals in Research (Creton et al. 2013;
Burden et al. 2014) documents that for a wide range of pesticides and industrial chemicals, the
BCF factors obtained from high and low doses do not differ by a factor that would lead to a
difference in conclusions regarding the potential for the tested chemical to exceed regulatory
criteria for bioconcentrating substances. Using this information, the OECD (2017) has proposed
to increase acceptance of studies across international authorities by specifying the conditions
under which one test concentration is acceptable. Section III of this document describes the
results of the OECD's analysis.
However, there are well-documented cases of concentration-dependent BCF factors, such
as for essential metals (McGreer et al. 2003). Also, Beek et al. 2000 provides examples of
compounds with demonstrated bioconcentration behavior despite high water solubility or low
lipophilicity {i.e., log Kow< 3), such as quaternary ammonium compounds, and anionic
surfactants. These data indicate that BCF studies should be designed carefully for chemicals
whose bioconcentration behavior is not expected to correlate with their log Kow. This is addressed
in TG305, section 2.4 (Ionising chemicals).
III. Analysis and Proposed Resolution
OECD analyzed a data set for precision and accuracy of BCF estimations based on one
or two test concentrations. OECD conducted an analysis (TG305, section 2.5.1) of a data set of
40 anonymized compounds provided by the German environmental agency (UBA) that were
tested at two concentrations. This analysis showed that the mean percent difference in BCF
between high and low test levels was about 2.2%, with a standard deviation of 32% (TG305,
Table 2-1). This analysis further showed that an allowable Maximum Percent Difference
(MPD) of 50% in the BCF between low and high test concentrations reduces "discordance," or
disagreement as to whether the test signifies that the tested chemical qualifies as "B," or
bioconcentrating, to a minimum (TG305, section 2.5.1, paragraph 72). OPP reviewed, and
agrees with, OECD's analysis.
Using the approach described above, OPP conducted an analysis to determine when a
single concentration would be adequate for OPP regulatory purposes. To make an adequacy
determination, OPP needs a BCF point of departure. While OPP has not established a BCF value
of regulatory concern per se, it has used a BCF of 1,000 as a point of departure for devoting
additional resources to evaluate bioaccumulation risks for a pesticide. The initial basis for the
consideration of a BCF value of approximately 1,000 as a point of departure for bioaccumulation
evaluation is linked to information developed at a meeting sponsored by the American Society
for Testing and Materials held in 1976 which was published in the open literature two years later

(Cairns et al. 1978)) and which was reaffirmed in Cairns and Dickson (1995). Furthermore, a
BCF value of 1,000 has been suggested by a variety of sources to denote chemicals warranting
consideration for bioaccumulation potential (Cairns et al. 1978, Akerman and Coppage 1979,
AIBS 1978, ASTM 1978, Kimerle et al. 1978, Maki and Duthie 1978, and Stern and Walker
1978). More recent evaluations have similarly supported a BCF of 1,000 as a point of departure
(USEPA, 1998, 1999a, 1999b). Considering the consistency in the historical application of a
BCF value of 1,000 as a point of departure triggering evaluation of bioaccumulation, OPP
decided to use 1,000 as the point of departure for this evaluation of the adequacy of single
concentration BCF studies in the context of pesticide risk assessment evaluation.
Using OECD's approach described above, applying a MPD of 50% to a BCF value of
1,000 as a consistent and reasonable point of departure for bioaccumulation evaluation efforts,
EPA determined that a BCF test using one concentration level with results equal to or less than
667 would not require a second concentration level. However, those exceeding a value of 667
would require testing at a second concentration level to determine whether the active ingredient
meets the "B" criterion of BCF = 1,000.
IV.	Conclusion
Based on the information described above, OPP will accept a single treatment level
concentration if the BCF value is less than or equal to 667. Based on historical data submission,
OPP expects that most submitted Fish Bioconcentration Factor (BCF) studies will only need
one treatment concentration. As always, companies must ensure that the study results meet the
other guideline specifications and the raw data are determined to be scientifically sound. OPP
recommends that the selected concentration avoid toxic or metabolic effects in the fish that
might affect the outcome of the study yet also be high enough to provide quantifiable
concentrations of residues of concern in both fish tissue and water. OPP expects companies to
describe in their study reports their rationale for any selected test concentration and how the
results for the BCF study using that concentration align with the acceptance criteria outlined in
Section III of this document.
EPA expects that this policy change will result in savings of approximately 240 test
animals per year as well as EPA, industry, and laboratory resources in conducting and
reviewing BCF studies.
V.	References
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In Analyzing the Hazard Evaluation Process, Dickson, K.L., Maki, A.W., and Cairns, J., Jr.,
(eds.). 1979. Water Quality Section, American Fisheries Society, Washington,
DC.,pp. 68-73.
American Institute for Biological Sciences (AIBS). 1978. " Criteria and Rationale for Decision
Making in Aquatic Hazard Evaluation (Third Draft)," Aquatic Hazards of Pesticides Task Group
of the American Institute of Biological Sciences. In Estimating the Hazard of Chemical
Substances to Aquatic Life, STP 657, American Society for Testing and Materials, Phila., PA.,

pp. 241-273.
American Society for Testing and Materials (ASTM). "Proposed Working Document for the
Development of an ASTM Draft Standard on Standard Practice for a Laboratory Testing Scheme
to Evaluate Hazard to Non-Target Aquatic Organisms," ASTM Subcommittee E35.21 on Safety
to Man and Environment. In Estimating the Hazard of Chemical Substances to Aquatic Life,
STP 657, American Society for Testing and Materials, Phila., PA., pp. 202-237.
Beek, B., S. Bohling, U. Bruckmann, C. Franke, U. Johncke, G. Studinger, 2000. The
assessment of bioaccumulation. In: Beek, B. (ed) Bioaccumulation: New Aspects and
Developments. The Handbook of Environmental Chemistry, vol. 2J. Springer.
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Cairns, J, Jr. and Dickson, K.L., 1995. Ecological hazard/risk assessment: lessons learned and
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CFR. 2018. Code of Federal Regulations Title 40 (Protection of the Environment), Chapter I
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Kimerle, R.A., Gledhill, W.E., and Levinskas, G.J., 1978. Environmental safety assessment of
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USEPA, 1998. Proposed Category for persistent, Bioaccumulative, and Toxic Chemical
Substances. 63 FR 53417, Oct. 5, 1998.
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Thresholds for Certain PBT Chemicals; Addition of Certain PBT Chemicals; Community
Right-to-Know Toxic Chemical Reporting. 64 FR 58666, Oct. 29, 1999.
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