Appendix B to Part 132 -- Great Lakes Water Quality
Initiative
METHODOLOGY FOR DERIVING BIOACCUMULATION FACTORS
Great Lakes States and Tribes shall adopt provisions consistent with (as
protective as) this appendix.
I. Introduction
A. The purpose of this methodology is to describe procedures for deriving
bioaccumulation factors (BAFs) to be used in the calculation of Great Lakes
Water Quality Guidance (Guidance) human health Tier I criteria and Tier II
values and wildlife Tier I criteria. A subset of the human health BAFs are also
used to identify the chemicals that are considered bioaccumulative chemicals of
concern (BCCs).
B. Bioaccumulation reflects uptake of a substance by aquatic organisms
exposed to the substance through all routes (i.e., ambient water and food), as
would occur in nature. Bioconcentration reflects uptake of a substance by
aquatic organisms exposed to the substance only through the ambient water. Both
BAFs and bioconcentration factors (BCFs) are proportionality constants that
describe the relationship between the concentration of a substance in aquatic
organisms and its concentration in the ambient water. For the Guidance in this
part, BAFs, rather than BCFs, are used to calculate Tier I criteria for human
health and wildlife and Tier II values for human health because they better
account for the total exposure of aquatic organisms to chemicals.
C. For organic chemicals, baseline BAFs can be derived using four methods.
Measured baseline BAFs are derived from field-measured BAFs; predicted baseline
BAFs are derived using biota-sediment accumulation factors (BSAFs) or are
derived by multiplying a laboratory-measured or predicted BCF by a food-chain
multiplier (FCM). The lipid content of the aquatic organisms is used to account
for partitioning of organic chemicals within organisms so that data from
different tissues and species can be integrated. In addition, the baseline BAF
is based on the concentration of freely dissolved organic chemicals in the
ambient water to facilitate extrapolation from one water to another.
D. For inorganic chemicals, baseline BAFs can be derived using two of the
four methods. Baseline BAFs are derived using either field-measured BAFs or by
multiplying laboratory-measured BCFs by a FCM. For inorganic chemicals, BAFs are
assumed to equal BCFs (i.e., the FCM is 1.0), unless chemical-specific
biomagnification data support using a FCM other than 1.0.
E. Because both humans and wildlife consume fish from both trophic levels 3
and 4, two baseline BAFs are needed to calculate either a human health criterion
or value or a wildlife criterion for a chemical. When appropriate, ingestion
through consumption of invertebrates, plants, mammals, and birds in the diet of
wildlife species to be protected may be taken into account.
II. Definitions
Baseline BAF. For organic chemicals, a BAF that is based on the
concentration of freely dissolved chemical in the ambient water and takes into
account the partitioning of the chemical within the organism; for inorganic
chemicals, a BAF that is based on the wet weight of the tissue.
Baseline BCF. For organic chemicals, a BCF that is based on the
concentration of freely dissolved chemical in the ambient water and takes into
account the partitioning of the chemical within the organism; for inorganic
chemicals, a BCF that is based on the wet weight of the tissue.
Bioaccumulation. The net accumulation of a substance by an organism as
a result of uptake from all environmental sources.
Bioaccumulation factor (BAF). The ratio (in L/kg) of a substance's
concentration in tissue of an aquatic organism to its concentration in the
ambient water, in situations where both the organism and its food are exposed to
and the ratio does not change substantially over time.
Bioconcentration. The net accumulation of a substance by an aquatic
organism as a result of uptake directly from the ambient water through gill
membranes or other external body surfaces.
Bioconcentration factor (BCF). The ratio (in L/kg) of a substance's
concentration in tissue of an aquatic organism to its concentration in the
ambient water, in situations where the organism is exposed through the water
only and the ratio does not change substantially over time.
Biota-sediment accumulation factor (BSAF). The ratio (in kg of organic
carbon/kg of lipid) of a substance's lipid-normalized concentration in tissue of
an aquatic organism to its organic carbon-normalized concentration in surface
sediment, in situations where the ratio does not change substantially over time,
both the organism and its food are exposed, and the surface sediment is
representative of average surface sediment in the vicinity of the organism.
Depuration. The loss of a substance from an organism as a result of
any active or passive process.
Food-chain multiplier (FCM). The ratio of a BAF to an appropriate BCF.
Octanol-water partition coefficient (KOW). The ration of the
concentration of a substance in the n-octanol phase to its concentration in the
aqueous phase in an equilibrated two-phase octanol-water system. For log KOW, the log of the octanol-water partition coefficient is a base 10
logarithm.
Uptake. Acquisition of a substance from the environment by an organism
as a result of any active or passive process.
III. Review and Selection of Data
A. Data Sources. Measured BAFs, BSAFs and BCFs are assembled from
available sources including the following:
1. EPA Ambient Water Quality Criteria documents issued after January 1, 1980.
2. Published scientific literature.
3. Reports issued by EPA or other reliable sources.
4. Unpublished data.
One useful source of references is the Aquatic Toxicity Information Retrieval
(AQUIRE) database.
B. Field-Measured BAFs. The following procedural and quality assurance
requirements shall be met for field-measured BAFs:
1. The field studies used shall be limited to those conducted in the Great
Lakes System with fish at or near the top of the aquatic food chain (i.e., in
trophic levels 3 and/or 4).
2. The trophic level of the fish species shall be determined.
3. The site of the field study should not be so unique that the BAF cannot be
extrapolated to other locations where the criteria and values will apply.
4. For organic chemicals, the percent lipid shall be either measured or
reliably estimated for the tissue used in the determination of the BAF.
5. The concentration of the chemical in the water shall be measured in a way
that can be related to particulate organic carbon (POC) and/or dissolved organic
carbon (DOC) and should be relatively constant during the steady-state time
period.
6. For organic chemicals with log Kow greater than four, the
concentrations of POC and DOC in the ambient water shall be either measured or
reliably estimated.
7. For inorganic and organic chemicals, BAFs shall be used only if they are
expressed on a wet weight basis; BAFs reported on a dry weight basis cannot be
converted to wet weight unless a conversion factor is measured or reliably
estimated for the tissue used in the determination of the BAF.
C. Field-Measured BSAFs. The following procedural and quality
assurance requirements shall be met for field-measured BSAFs:
1. The field studies used shall be limited to those conducted in the Great
Lakes System with fish at or near the top of the aquatic food chain (i.e., in
trophic levels 3 and/or 4).
2. Samples of surface sediments (0-1 cm is ideal) shall be from locations in
which there is net deposition of fine sediment and is representative of average
surface sediment in the vicinity of the organism.
3. The Kow s used shall be acceptable quality as described in
section III.F below.
4. The site of the field study should not be so unique that the resulting BAF
cannot be extrapolated to other locations where the criteria and values will
apply.
5. The tropic level of the fish species shall be determined.
6. The percent lipid shall be either measured or reliably estimated for the
tissue used in the determination of the BAF.
D. Laboratory-Measured BCFs. The following procedural and quality
assurance requirements shall be met for laboratory-measured BCFs:
1. The test organism shall not be diseased, unhealthy, or adversely affected
by the concentration of the chemical.
2. The total concentration of the chemical in the water shall be measured and
should be relatively constant during the steady-state time period.
3. The organisms shall be exposed to the chemical using a flow-through or
renewal procedure.
4. For organic chemicals, the percent lipid shall be either measured or
reliably estimated for the tissue used in the determination of the BCF.
5. For organic chemicals with log Kow greater than four, the
concentrations of POC and DOC in the test solution shall be either measured or
reliably estimated.
6. Laboratory-measured BCFs should be determined using fish species, but BCFs
determined with molluscs and other invertebrates may be used with caution. For
example, because invertebrates metabolize some chemicals less efficiently than
vertebrates, a baseline BCF determined for such a chemical using invertebrates
is expected to be higher than a comparable baseline BCF determined using fish.
7. If laboratory-measured BCFs increase or decrease as the concentration of
the chemical increases in the test solutions in a bioconcentration test, the BCF
measured at the lowest test concentration that is above concentrations existing
in the control water shall be used (i.e., a BCF should be calculated from a
control treatment). The concentrations of an inorganic chemical in a
bioconcentration test should be greater than normal background levels and
greater than levels required for normal nutrition of the test species if the
chemical is a micronutrient, but below levels that adversely affect the species.
Bioaccummulation of an inorganic chemical might be overestimated if
concentrations are at or below normal background levels due to, for example,
nutritional requirements of the test organisms.
8. For inorganic and organic chemicals, BCFs shall be used only if they are
expressed on a wet weight basis. BCFs reported on a dry weight basis cannot be
converted to wet weight unless a conversion factor is measured or reliably
estimated for the tissue used in the determination of the BAF.
9. BCFs for organic chemicals may be based on measurement or radioactivity
only when the BCF is intended to include metabolites or when there is confidence
that there is no interference due to metabolites.
10. The calculation of the BCF must appropriately address growth dilution.
11. Other aspects of the methodology used should be similar to those
described by ASTM (1990).
E. Predicted BCFs. The following procedural and quality assurance
requirements shall be met for predicted BCFs:
1. The Kow used shall be of acceptable quality as described in
section III.F below.
2. The predicted baseline BCF shall be calculated using the equation:
predicted baseline BCF = Kow
where:
Kow = octanol-water partition coefficient.
F. Octanol-Water Partition Coefficient (Kow). 1. THE
VALUE OF Kow used for an organic chemical shall be determined by
giving priority to the experimental and computational techniques used as
follows:
Log Kow < 4:
------------------------------------------------------------------------
Priority Technique
------------------------------------------------------------------------
1......................................... Slow-stir.
1......................................... Generator-column.
1......................................... Shake-flask.
2......................................... Reverse-phase liquid
chromatography on C18
chromatography packing with
extrapolation to zero
percent solvent.
3......................................... Reverse-phase liquid
chromatography on C18
chromatography packing
without extrapolation to
zero percent solvent.
4......................................... Calculated by the CLOGP
program.
------------------------------------------------------------------------
Log Kow > 4:
------------------------------------------------------------------------
Priority Technique
------------------------------------------------------------------------
1................................. Slow Stir.
1................................. Generator-column.
2................................. Reverse-phase liquid chromatography
on C18 chromatography packing with
extrapolation to zero percent
solvent.
3................................. Reverse-phase liquid chromatography
on C18 chromatography packing
without extrapolation to zero
percent solvent.
4................................. Shake-flask.
5................................. Calculated by the CLOGP program.
------------------------------------------------------------------------
2. The CLOGP program is a computer program available from Pomona College. A
value of Kow that seems to be different from the others should be
considered an outlier and not used. The value of Kow used for an
organic chemical shall be the geometric mean of the available Kow s
with highest priority or can be calculated from the arithmetic mean of the
available log Kow with the highest priority. Because it is an
intermediate value in the derivation of a BAF, the value used for the Kow of a chemical should not be rounded to fewer than three significant
digits and a value for log Kow should not be rounded to fewer than
three significant digits after the decimal point.
G. This methodology provides overall guidance for the derivation of BAFs, but
it cannot cover all the decisions that must be made in the review and selection
of acceptable data. Professional judgment is required throughout the process. A
degree of uncertainty is associated with the determination of any BAF, BSAF, BCF
or Kow. The amount of uncertainty in a baseline BAF depends on both
the quality of data available and the method used to derive the BAF.
H. Hereinafter in this methodology, the terms BAF, BSAF, BCF and Kow refer to ones that are consistent with the procedural and quality
assurance requirements given above.
IV. Four Methods for Deriving Baseline BAFs
Baseline BAFs shall be derived using the following four methods, which are
listed from most preferred to least preferred:
A. A measured baseline BAF for an organic or inorganic chemical derived from
a field study of acceptable quality.
B. A predicted baseline BAF for an organic chemical derived using
field-measured BSAFs of acceptable quality.
C. A predicted baseline BAF for an organic or inorganic chemical derived from
a BCF measured in a laboratory study of acceptable quality and a FCM.
D. A predicted baseline BAF for an organic chemical derived from a Kow of acceptable quality and a FCM.
For comparative purposes, baseline BAFs should be derived for each chemical
by as many of the four methods as available data allow.
V. Calculation of Baseline BAFs for Organic Chemicals
A. Lipid Normalization. 1. It is assumed that BAFs and BCFs for
organic chemicals can be extrapolated on the basis of percent lipid from one
tissue to another and from one aquatic species to another in most cases.
2. Because BAFs and BCFs for organic chemicals are related to the percent
lipid, it does not make any difference whether the tissue sample is whole body
or edible portion, but both the BAF (or BCF) and the percent lipid must be
determined for the same tissue. The percent lipid of the tissue should be
measured during the BAF or BCF study, but in some cases it can be reliably
estimated from measurements on tissue from other organisms. If percent lipid is
not reported for the test organisms in the original study, it may be obtained
from the author; or, in the case of a laboratory study, lipid data for the same
or a comparable laboratory population of test organisms that were used in the
original study may be used.
3. The lipid-normalized concentration, Cl, of a chemical in tissue
is defined using the following equation:
