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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: A reliable QSAR model (ECOSAR) was used to estimate long-term toxicity to invertebrates.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The QSAR model, Ecological Structure Activity Relationships (ECOSAR) v 1.1 Anionic Surfactant Class Program was used to estimate long-term toxicity to invertebrates.
Test organisms (species):
other: daphnid
Key result
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
0.024 mg/L
Validity criteria fulfilled:
yes
Conclusions:
A reliable QSAR model (Ecological Structure-Activity Relationship (ECOSAR) Anionic Surfactant Model (version 1.1) was used to predict the chronic aquatic toxicity of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. to daphnids. The 21 day No Effect Concentration was 0.024 mg/L. The Ecological Structure-Activity Relationship (ECOSAR) Anionic Surfactant Model (version 1.1) predicted chronic aquatic toxicity values are considered valid and fit for purpose. A calculated value from a QSAR model is considered valid and fit for purpose if the following conditions are met: 1) Results are derived from a (Q)SAR model whose scientific validity has been established; 2) The substance falls within the applicability domain of the (Q)SAR model; 3) Results are adequate for the purpose of classification and labelling and/or risk assessment and 4) Adequate and reliable documentation of the applied method is provided.

1) Results are derived from a (Q)SAR model whose scientific validity has been established

ECOSAR had been utilized by the scientific community for prediction of aquatic toxicity since the 1990’s. While developed by the US EPA, the program underwent an independent peer review as a part of the development of the Organization for Economic Cooperation and Development (OECD) principles established for quantitative structure-activity relationship ((Q)SAR) validation. As of 2011, ECOSAR has been the subject of 20 peer reviewed publications regarding its validation and performance.

Also ECOSAR has been incorporated into the OECD Toolbox and was considered a top performer for use in profiling chemicals. Inclusion in the OECD toolbox requires specific documentation, validation and acceptability criteria and subjects ECOSAR to international use, review, providing a means for receiving additional and on-going input for improvements.

ECOSAR is listed as one of the QSARs tools for use in predicting aquatic toxicity values in the Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for the environment and Chapter R.6: QSARs and grouping of chemicals.

In summary, ECOSAR has had its scientific validity established repeatedly.

2) The substance falls within the applicability domain of the (Q)SAR model

Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. is considered an anionic surfactant of the alkyl benzene sulfonate class. This particular class has a specially designated QSAR model within ECOSAR. The toxicity of this class of substances is determined by the number of carbons in the hydrophobic portion of the molecule (i.e., the linear alkyl chain). The results are parabolic with the maximum toxicity observed with a carbon chain length of 16.

According to Clements, RG et al (1996), the anionic surfactant model is valid for carbon chain lengths between 10 and 18. Since Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. contains molecules with 15 and 16 carbon chain lengths, it is within the model constraints.

3) Results are adequate for the purpose of classification and labelling and/or risk assessment

ECOSAR’s Alkyl Benzene Sulfonate model uses the following equations for calculation of aquatic toxicity:

Class Organism Endpoint Equations
Anionic Surfactant Daphnid 48 LC50 10^((((AVG_NUM_CARBONS - 16)^2) - 42.466)/12.368)
Anionic Surfactant Daphnid 21 NEC (10^((((AVG_NUM_CARBONS - 16)^2) - 10.643)/12.935))/6.5

The equations have the following statistics (Clements, RG et al 1996):
Number of substances = 14
Correlation coef (r2) = 0.624

These correlation coefficients indicate the ECOSAR Anionic Surfactant model calculates results that are equivalent to those generated experimentally and are, hence, adequate for the purpose of classification and labelling and/or risk assessment.

In addition to the correlation coefficient generated from the training set, the validity of the model can also be supported by a comparison of the measured acute toxicity data for Daphnia magna and that predicted by the model. The measured EC50 was 0.26 mg/L with 95% confidence limits of 0.24-0.28 mg/L, while the ECOSAR predicted daphnid EC50 is 0.16 mg/L. The values are not significantly different and provide confidence in the validity of the model.

4) Adequate and reliable documentation of the applied method is provided

Documentation of the ECOSAR model and anionic surfactant QSAR is provided in Mayo-Bean, K. et al (2011a and b).

References

Clements, RG, Nabholz, JV and Zeeman, R. 1996. Estimating Toxicity of Industrial Chemicals to Aquatic Organisms Using Structure-activity Relationships.

ECHA (2008) “Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals”.

ECHA (2008) “Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for the environment”.

Mayo-Bean, K, Nabholz, JV, Clements, R, Zeeman, M, Henry, T, Rodier, D, Moran, K, Meylan, WM and Ranslow, P. 2011a. Methodology Document for the Ecological Structure-Activity Relationship Model (ECOSAR) Class Program.

Mayo-Bean, K, Nabholz, JV, Meylan, WM, Howard, PH and Moran-Bruce, K. 2011b. Operation Manual for the Ecological Structure-Activity Relationship Model (ECOSAR) Class Program.
Executive summary:

A reliable QSAR model (Ecological Structure-Activity Relationship (ECOSAR) Anionic Surfactant Model (version 1.1) was used to predict the chronic aquatic toxicity of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. to daphnids. The 21 day No Effect Concentration was 0.024 mg/L.

Description of key information

There are not adequate reliable measured data for the long-term toxicity to invertebrates for Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. However, there is a reliable predicted value of 0.024 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.024 mg/L

Additional information

A reliable QSAR model (Ecological Structure-Activity Relationship (ECOSAR) Anionic Surfactant Model (version 1.1) was used to predict the chronic aquatic toxicity of Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. to daphnids. The 21 day No Effect Concentration was 0.024 mg/L.

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