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Model Report

Ecological Structure Activity Relationships

Last Revision Date: 07/02/2010 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

Ecological Structure Activity Relationships
Model Overview/Abstract:
Ecological Structure Activity Relationships, v1.00a, February 2009
ECOSAR (Ecological Structure Activity Relationships) is a personal computer software program that is used to estimate the toxicity of chemicals used in industry and discharged into water. The program predicts the toxicity of industrial chemicals to aquatic organisms such as fish, invertebrates, and algae by using Structure Activity Relationships (SARs). The program estimates a chemical's acute (short-term) toxicity and, when available, chronic (long-term or delayed) toxicity. ECOSAR uses SARs to predict the effective concentrations (EC) from chemical structure; structure via SMILES or chemical class functional groups; SARs sorted by chemical class. SARs express the correlations between a compound's physicochemical properties and its aquatic toxicity. SARs measured for one compound can be used to predict the toxicity of similar compounds belonging to the same chemical class. ECOSAR v1.00a contains over 120 chemical classes and over 440 SARs based on publicly available and confidential experimental data. Additional acute and chronic toxicity values for data poor classes are estimated through the use of acute-to-chronic ratios (ACRs).
Keywords: SAR, Structure Activity Relationships, aquatic toxicity, acute, chronic, fish, Daphnia, algae, ecotoxicity, SMILES notation, Octanol/water partitioning coefficient (KOW)
Model Technical Contact Information:
Agency Contact:
Kelly E. Mayo-Bean, U.S. EPA
Risk Assessment Division (7403M)
1200 Pennsylvania Ave., N.W.
Washington, DC 20460-0001
Phone: 202-564-7662
Fax: 202-564-9063
email: mayo.kelly@epa.gov

Developer Contact:
Bill Meylan
Syracuse Research Corporation
Environmental Science Center
301 Plainfield Road, Suite 350
Syracuse, NY 13212
Phone: 315 452-8421
Email: meylan@srcinc.com

Philip H. Howard
Syracuse Research Corporation
Environmental Science Center
301 Plainfield Road, Suite 350
Syracuse, NY 13212
Phone: 315 452-8417
Email: howardp@srcinc.com

Model Homepage: http://www.epa.gov/opptintr/newchems/tools/21ecosar.htm
Substantive Changes from Prior Version: 80 chemical classes (and associated data sets) added to the program in v1.00a
Plans for further model development: Additional SAR calculations will be added as data become available, and as resources allow.

User Information Back to Top
Technical Requirements
Computer Hardware
Minimum requirements are an IBM-compatible computer with an 80386 or 80286 processor and 640 KB RAM. At least 512 to 550 KB RAM must be free for acceptable performance, and expanded memory will improve performance.
Compatible Operating Systems
Software Required: Microsoft Windows 95 or later (including 98, ME, NT, XP and Vista).
Other Software Required to Run the Model
Download Information
Download and install ECOSAR at no cost from the U.S. EPA website at: http://www.epa.gov/oppt/newchems/tools/21ecosar.htm
Using the Model
Basic Model Inputs
Octanol/water partitioning coefficient (KOW) and molecular weight. Charge density and other information may also be required for some chemical classes. Descriptions of chemical structures, using Simplified Molecular Input Line Entry System (SMILES) notation. SMILES is a widely used language for describing chemical structures.
Basic Model Outputs
SAR class, ECs (Acute and Chronic effects levels in mg/L or ppm), warnings when EC is greater than S, and Kow and MW limitations for SAR
User Support
User's Guide Available?
ECOSAR User’s Guide (2009). Risk Assessment Division (7403), Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave., N.W., Washington, DC 20460. Available at: http://www.epa.gov/oppt/newchems/tools/ecosarusersguide.pdf
Other User Documents
ECOSAR Technical Reference Manual (2009). Risk Assessment Division (7403), Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave., N.W., Washington, DC 20460. Available at: http://www.epa.gov/oppt/newchems/tools/ecosartechfinal.pdf
Availability of User Support
SAR equations are available to User through the “Help” function within ECOSAR, and questions may be sent to technical contacts (contact information is provided on the web site).
User Qualifications
The program requires a basic understanding of organic chemistry, ecotoxicology, SARs, and SMILES notation. Users must also know how to estimate OW for situations where measured or estimated data are not available. Most SARs in ECOSAR were developed using KOW values predicted using KOWWIN which is a computer program available within the EPISuite program available from the U.S. EPA at no cost from: http://www.epa.gov/oppt/exposure/pubs/episuite.htm

Model Science Back to Top
Problem Identification
Structure Activity Relationships, or SAR, is a technique routinely used by EPA to estimate aquatic toxicity of chemicals being reviewed by the U.S. Environmental Protection Agency (EPA) in response to Pre-Manufacture Notices mandated by Section 5 of the Toxic Substances Control Act (TSCA). ECOSAR makes EPA's SAR methods for aquatic toxicity conveniently available through an easy-to-use computer program.
Summary of Model Structure and Methods
Regression-based (Q)SARs; Expert system (overall prediction depends on application of multiple models/rules and use of data in a knowledge base)
Model Evaluation
Individual SARs are validated with measured data as valid measured test data become available; SARs validated by comparing predicted ECs with measured ECs via ratios (perfect predition = 1), ratios within +/- 10X considered accurate. Test chemicals were a random assortment of industrial chemicals. Not all SARs have been individually validated. See U.S. EPA/EC Joint Project on the Evaluation of (Quantitative) Structure Activity Relationships: Final report (17MB PDF ) and OECD's Monograph: Joint Project on the Evaluation of (Quantitative) Structure Activity Relationships (159KB PDF) Minimum Pre-Market Data/Structure Activity Relationships Study
Hulzebos EM, Posthumus R. 2003;
Kaiser KLE, et al. 1999;
Moore DRJ, Breton RL, and MacDonald DB. 2003;
Nabholz JV, et al. 1993;
Posthumus R, Sloof W. 2001
Key Limitations to Model Scope
Any discrete chemical structure with a correct SMILES notation may be evaluated in ECOSAR and aquatic toxicity effects levels will be produced, however, results are not reliable unless SARs for that chemical have been programmed into ECOSAR.
Case Studies
Boethling, R. S. and Nabholz, J. V. 1997.
Cash and Clements, 1996.
Kaiser et al, 1997.
Lynch, D. G., Macek, G. J., Nabholz, J. V., Sherlock, S. M., and Wright, R. 1994.
PPG's Comparison of Measured Aquatic Toxicity Data with EPA SAR Predictions (PDF) (6 pp., 83K)

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