Water Quality Criteria:Implications for Testing
Russell EricksonU.S. Environmental Protection Agency
Mid-Continent Ecology Division, Duluth, MN, USA
The McKim Conference on the Use of QSARs and Aquatic Toxicology in Risk Assessment
June 27-29, 2006
U.S.EPA Water Quality Criteria for the Protection of Aquatic Life
• Aquatic Life Criteria (ALC) issued by the U.S.EPA Office of Water define limits on chemical exposures which are considered sufficient to preclude unacceptable effects on aquatic communities.
• Procedures are described in “Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses” (Stephan et al., 1985, U.S.EPA).
• Used in regulatory programs to limit discharge of toxic chemicals, in evaluations of aquatic resource condition from monitoring data, and in setting clean-up goals for Superfund sites and other assessments.
• 1-hr average exposure concentrations are allowed to exceed the CMC only once in three years on average.
• The “Criterion Maximum Concentration” (CMC) is set equal to one-half of the FAV.
U.S.EPA Aquatic Life CriteriaAcute Toxicity Data Use
• Mean LC50s for tested species & genera are designated “Species/Genus Mean Acute Values” (SMAVs, GMAVs).
• The “Final Acute Value” (FAV) is set equal to the fifth percentile of GMAVs, or a SMAV of an important species.
• 48- or 96-hr LC50s are required for at least eight aquatic animal species encompassing a specified range of taxa.
Time
0 20 40 60 80 100
Co
nce
ntr
atio
n
0.0
0.5
1.0
1.5
2.0
Time
0 20 40 60 80 100
Co
nce
ntr
atio
n
0.0
0.5
1.0
1.5
2.0
Time
0 20 40 60 80 100
Co
nce
ntr
atio
n
0.0
0.5
1.0
1.5
2.0
Time
0 20 40 60 80 100
Co
nce
ntr
atio
n
0.0
0.5
1.0
1.5
2.0
Time
0 20 40 60 80 100
Co
nce
ntr
atio
n
0.0
0.5
1.0
1.5
2.0
Genus Rank
0 10 20 30 40 50 60
GM
AV
(u
g C
u/L
)
1
10
100
1000
10000
FAV=12
Arthropods
Molluscs
FishOther Phyla
U.S.EPA Aquatic Life CriteriaChronic Toxicity Data Use
• “Chronic values” (CV) are set to the EC20 or the mean of the NOEC&LOEC for the most sensitive of survival, growth, or reproductive endpoints from tests with minimum duration of several days to a few months, depending on species.
• The “Final Chronic Value” (FCV) is set equal to the fifth percentile of GMCVs for at least eight animal genera, the FAV divided by the average SMAV:SMCV ratio for at least three species, or an SMCV of an important species.
• The “Criterion Continuous Concentration” (CCC) is set equal to the FCV or a value based on plant toxicity data.
• 4-day average exposure concentrations are allowed to exceed the CCC only once in three years on average.
• Protection of endangered/threatened species must be based on extrapolations from tested species.
• Testing requirements do not reflect different modes-of-action among chemicals.
U.S.EPA Aquatic Life CriteriaTest Data Issues
• For chemicals barely meeting minimum acute toxicity data requirements, important taxa might not be addressed.
• For chronic toxicity, important response endpoints as well as important taxa might not be addressed.
• Although minimum acute toxicity data requirements are limited, most chemicals do not meet these requirements.
Genus Rank
0 10 20 30 40 50 60
GM
AV
(u
g C
u/L
)
1
10
100
1000
10000
FAV=12
Arthropods
Molluscs
FishOther Phyla
Species A Toxicity Value
0 1 2 3 4
Spe
cies
B T
oxic
ity V
alue
0
1
2
3
4
Species A Toxicity Value
0 1 2 3 4
Spe
cies
B T
oxic
ity V
alue
0
1
2
3
4
U.S.EPA Aquatic Life CriteriaBenefits from Predictive Toxicity Tools
• Extrapolation tools for relative effect concentration differences among chemicals, species, and endpoints.
• Methods to predict toxicity mechanisms for different taxonomic groups to guide acute and chronic testing strategies.
• QSARs for point estimates or lower bounds of effect concentrations for species and endpoints of interest.
Genus Rank
1 2 3 4 5 6 7 8 9 10
GM
AV
or
GM
CV
0
2
4
6
8
10
Genus Rank
1 2 3 4 5 6 7 8 9 10
GM
AV
or
GM
CV
0
2
4
6
8
10
Genus Rank
2 4 6 8 10
GM
AV
or
GM
CV
0
2
4
6
8
10