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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
Data is from computational model developed by USEPA
Qualifier:
according to guideline
Guideline:
other: Modeling database
Principles of method if other than guideline:
Estimation of 96 hr EC50 value of test chemical by modelling Database - ECOSAR v.1.11. The ECOSAR Class Program is a computerized version of the ECOSAR analysis procedures as currently practiced by the Office of Pollution Prevention and Toxics (OPPT).  It has been developed within the regulatory constraints of the Toxic Substances Control Act (TSCA).  It is a pragmatic approach to SAR. The structure-activity relationships (SARs) presented in this program are used to predict the aquatic toxicity of chemicals based on their similarity of structure to chemicals for which the aquatic toxicity has been previously measured.  Most SAR calculations in the ECOSAR Class Program are based upon the octanol/water partition coefficient (Kow).  Various surfactant SAR calculations are based upon the average length of carbon chains or the number of ethoxylate units.
GLP compliance:
no
Analytical monitoring:
not required
Vehicle:
no
Test organisms (species):
other: green algae
Test type:
static
Water media type:
freshwater
Total exposure duration:
96 h
Remarks on exposure duration:
Estimated data
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
186.317 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Neutral Organics SAR (Baseline Toxicity)
Validity criteria fulfilled:
not specified
Conclusions:
Based on the prediction done using the EPI Suite ECOSAR version 1.10, the short term toxicity on green algae was predicted for test chemical. The estimated EC50 values for aquatic green algae after 96 hours was 186.317 mg/l on the basis of growth rate.
Executive summary:

Using the EPI Suite ECOSAR version 1.10, the short term toxicity on green algae was predicted for test chemical. On the basis of effects observed in a static freshwater system, the effect concentration EC50 value for the substance is estimated to be 186.317 mg/l for green algae for 96 h duration. Based on this value, it is concluded that the test chemical can be considered as non-toxic to green algae at environmentally relevant concentrations and considered not-classified as per the CLP classification criteria.

Description of key information

Using the EPI Suite ECOSAR version 1.10, the short term toxicity on green algae was predicted for test chemical. On the basis of effects observed in a static freshwater system, the effect concentration EC50 value for the substance is estimated to be 186.317 mg/l for green algae for 96 h duration. Based on this value, it is concluded that the test chemical can be considered as non-toxic to green algae at environmentally relevant concentrations and considered not-classified as per the CLP classification criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:
186.317 mg/L

Additional information

Three studies including predicted data from validated tools and experimental data from authoritative database of test chemical and its structurally similar read across has been reviewed for toxicity aquatic algae endpoint and their results are summarized below

 

In first study using the EPI Suite ECOSAR version 1.10, the short term toxicity on green algae was predicted for test chemical. On the basis of effects observed in a static freshwater system, the effect concentration EC50 value for the substance is estimated to be 186.317 mg/l for green algae for 96 h duration. Based on this value, it is concluded that the test chemical can be considered as non-toxic to green algae at environmentally relevant concentrations and considered not-classified as per the CLP classification criteria.

 

In another study the toxicity of test chemical to aquatic algae was determined by performing the experiment for 8 d, the test microorganism used in the study was Microcystis aeruginosa. The EC3 value of test chemical was determined to be 78 mg/L after the exposure of test chemical to aquatic algae Microcystis aeruginosa for 8 days.

 

In last study the experiment was conducted to determine the effect of test chemical on aquatic algae by using OECD guideline 201 (Alga, Growth Inhibition Test), the test organisms used in this study was green alga Chlorella vulgaris. The test chemical solution was prepared by adding 70mg of test chemical in 350 ml of BBM to get the final concentration of 200 mg/L. The remaining test solutions were prepared by dilution from the above stock solution. To have a better growth and visibility of cells, the initial cell density of the culture was kept 1 X 10E4cells/ml. Care was taken to have a homogeneous solution for the experiment. The experiment was carried out in 100mL conical flasks which were carefully autoclaved and sterilized. The test solution in each of these test vessels was kept constant which is 60 ml so that a sufficient amount of head space was left.

  For the assessment of algal growth, the test was conducted in replicates. The control flask was maintained in triplicates as recommended in the OECD guideline and the test concentration were selected in geometric series which were maintained in duplicates. To obtain a quantitative concentration-response relationship by regression analysis, a linearizing transformation of the response data into probit was performed. Using the same, effective concentration (EC) were determined.

Algal growth was calculated daily by counting the cells microscopically with the help of haemocytometer. For microscopic observations the cultures were observed daily with the help of a microscope to verify a normal and healthy appearance of the algal culture and also to observe any abnormal appearance of the algae (as may be caused by the exposure of the test item). Apart from this, the cell count of each test vessel was also noted with the help of a microscope and haemocytometer. By spectrophotometer the absorbance values of each test vessel and control vessel was noted at 680nm.The BBM was taken as blank for both control and test vessels. The absorbance value of each vessel was in line with the average specific growth rate.

 After 72 hours of exposure to test chemical to various nominal test concentrations, EC50 was determined to be >200 mg/l graphically and through probit analysis. Based on the EC50, it can be concluded that the chemical was not toxic and can be consider to be not classified as per the CLP classification criteria.

 

By considering the results of all the studies mentioned above it is concluded that EC50 value of test chemical is in range of 186.317 mg/L to >200mg/L. On the basis of this range EC50 value the test chemical it is considered nonhazardous to aquatic algae cannot classified as per the CLP classification criteria.