Sandy RaimondoMace G. Barron

Office of Research and Development/NHEERLGulf Ecology Division

2 November 2005

Development and Improvement Development and Improvement of ICE/ACE of ICE/ACE

for Predictive Toxicologyfor Predictive Toxicology

OverviewOverview

• Background: ICE/ACE development

• Current Research: ICE/ACE Validation and Improvement

ICE and ACE Software DevelopmentICE and ACE Software Development

Developed by Sonny Mayer (GED) and Colleagues

ICE (Interspecies Correlation Estimation)

Estimates acute toxicity for a species, genus or family from a surrogate species

ACE (Acute to Chronic Estimation)

Estimates chronic toxicity from raw acute toxicity data

Significance:

• Addresses second largest source of variation in toxicity data – variation of species within a chemical

• Fills data gaps by estimating toxicity of untested species

ICE: Interspecies Correlation Estimations

How ICE worksHow ICE works

LC50: concentration that

kills 50% of organisms

LD50: dose that kills 50%

Uses existing correlations of toxicity values (LC50, LD50) between a surrogate species and a predicted taxa (species, genus, or family)

Acute toxicity estimates using Acute toxicity estimates using interspecies correlationsinterspecies correlations

1.0 2.0 3.0 4.0

1.0

2.0

3.0

Rainbow Trout (log 96-h LC50)

Cap

e F

ear

shin

er (

log

96-

h L

C50

)

X = -0.025 + 1.098Xr = 0.991

2 1

1.0 2.0 3.0 4.0

1.0

2.0

3.0

Rainbow Trout (log 96-h LC50)

Cap

e F

ear

shin

er (

log

96-

h L

C50

)

X = -0.025 + 1.098Xr = 0.991

2 1

ICE estimates LC50 from surrogate species LC50 and available species correlation

Current ICE Uses: EPA Program Offices

• Office of Water (OW): draft Ambient Water Quality Criteria (AWQC) guidelines, endangered species

• Office of Pesticide Programs (OPP): qualitative use in risk assessment currently being implemented.

Ecological Risk Assessment (ERA)• Generate species sensitivity distribution• Define risk management level

Endangered Species Risk Assessment• Surrogate test species are toxicologically

representative of endangered species (Mayer et al.)• ICE can be used to estimate toxicity to T&E species

using existing correlations (147 LC50s; 20 species)

ICE: Applications

Provides estimated chronic toxicity for species with only acute data

ACE: Acute to Chronic Estimations

Significance:

Acute: ie.96-hour LC50/ LD50

Chronic: long-term, sublethal

• Reduced reliance on acute to chronic ratios based on multiple species and chemicals

• Being considered by OPP for qualitative use in risk assessment

ACE: Acute to Chronic Estimations

Application:

How ACE Works

ACE Chronic Mortality PredictionACE Chronic Mortality Prediction

a=NOEC

0.010 0.021 0.0421/tim e (h)

10

8.0

6.0

4.0

2.0

Lo

gN

OE

C(µ

g/L

)at

each

tim

ep

erio

d

a=NOEC

0.010 0.021 0.0421/tim e (h)

10

8.0

6.0

4.0

2.0

Lo

gN

OE

C(µ

g/L

)at

each

tim

ep

erio

d

a=NOEC

0.010 0.021 0.0421/tim e (h)

10

8.0

6.0

4.0

2.0

Lo

gN

OE

C(µ

g/L

)at

each

tim

ep

erio

d

10

8

6

4

2

00.140

12.01.0

0.080.06DOSE

(ug/L)TIM E (DAY)

EXTRA RESPONSE

(% )

0.040.02

0.0 020

4060

80100

Linear Regression Analysis (LRA)

Accelerated Life Testing (ALT)

Uses raw survival data to estimate chronic mortality

Limitations of ICE and ACE

• validation and uncertainty (ICE, ACE)

• data poor (e.g., ICE wildlife)

• flexibility-power (ICE)

Expand Datasets(QA/QC)

New Software

ICE

Validation, Refinement, Expansion

ACE

Validation

Improved Tool Functionality

Future Direction of ICE/ACE

1. Model Validation: Regression analysis

2. Model Refinement: Stepwise regression

3. Model Expansion: Power and number of models

4. QA/QC: Bootstrap validation

5. Defining Assumptions / Developing user guidelines: multivariate analyses

6. New Software

ICE Improvement Procedure

ICE Improvement Procedure

1. Model Validation: Assessment of existing significant correlations

Aquatic ICE models (P<0.01)• Species: 565• Genus: 195• Family: 291

Validation dataset for aquaticsAmbient Water Quality Criteria (AWQC) data

• 88 chemicals (12 pesticides)• 279 species• 1458 new data points

ICE Validation ExampleRainbow Trout Surrogate - Pesticides only

R2 = 0.95

-2

-1

0

1

2

3

4

5

6

-1 0 1 2 3 4 5

Log10 ICE predicted LC50

Lo

g1

0 A

ctu

al L

C5

0

< 3x difference

> 3x difference

2. Model Refinement

Stepwise Regression• Finds the best fit model• Quality of data• Power of model• Mode of action

Model improvement through reduction (filter by MOA, species, data quality)

Rainbow Trout Surrogate - Pesticides only

R2 = 0.95

-2

-1

0

1

2

3

4

5

6

-1 0 1 2 3 4 5

Log10 ICE predicted LC50

Lo

g1

0 A

ctu

al L

C5

0

ICE Improvement Procedure

3. Model ExpansionIncrease power of the models

• Many existing models have N=3• More data increases likelihood of significant correlations

Increase the number of significant correlations

ICE Wildlife Correlations (P ≤ 0.01)

Original Current

62 152

ICE Improvement Procedure

Model improvement through addition (species, chemical)

ICE Improvement Procedure

4. QA/QC of all refined and improved modelsBootstrap validation of all improved models

Rainbow Trout Surrogate - Pesticides only

R2 = 0.95

-2

-1

0

1

2

3

4

5

6

-1 0 1 2 3 4 5

Log10 ICE predicted LC50

Lo

g1

0 A

ctu

al L

C5

0

• data points are randomly removed

• model is recreated• removed data are used

to validate model• up to 1000 replicates

Multivariate Analysis• mode of action• chemical class• species• life history

• model fit (yes or no)• degrees of freedom• model R2, p-value

Rainbow Trout Surrogate - Pesticides only

R2 = 0.95

-2

-1

0

1

2

3

4

5

6

-1 0 1 2 3 4 5

Log10 ICE predicted LC50

Lo

g1

0 A

ctu

al L

C5

0

User Guidance

ICE Improvement Procedure

6. Updated Software (2007)

Selectable datasets

Interactive program

user can enter in new dataset for species not in ICE (ie. endangered species) and ICE will build predictive model based on internal data

Broader applicability

Wider user base

ICE Improvement Procedure

ACE Validation and User Guidance

Validate using expanded dataset• Original validation used 30 fish acute: chronic data pairs• Expanded validation dataset

>150 datasets

Define where models are robust• MOA• Chemical Classes• Species

Develop new user guidance• Multivariate Analyses• Improve value to user

R2 = 0.95

-2

-1

0

1

2

3

4

5

-4 -2 0 2 4 6

Log10 ACE ALT

Log1

0 S

urvi

val M

AT

C

< 5x difference

> 5x difference

• Manuscript: Wildlife Toxicity Estimation• Manuscript: Validation of ICE• Manuscript: Validation of ACE• Technology transfer

2007: Updated ICE Software

2006 Anticipated Products & Outcomes: