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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Link to relevant study record(s)

Description of key information

The following studies have been submitted to address the toxicity to algae and cyanobacteria endpoint:
Steger-Hartmann T (1999). Growth inhibition test of di-n-butyltin oxide (ZK 26385) on the green algae Scenedesmus subspicatus. Testing laboratory: Schering AG, Experimentelle Toxikologie, D-13342 Berlin, Germany. Report no.: IC28. Owner company: Schering AG, Experimentelle Toxikologie, Berlin, Germany. Study number: TXST19980234. Report date: 1999-02-17.
The Steger-Hartmann and Wendt study, as a stand alone study it is a relaibility 1, however as it is used for read-across purposes, the study has been assigned a reliability 2 (reliable with restrictions). The data presented is on the substance dibutyltin oxide.
Odersma. H, Hanstveir. A.O, & de Haan. H.P.M (2004) Dibutyltin bis (2-ethy1hexylmercaptoacetate) (CAS# 10584-98-2 DBT(EHMA)): Determination of the effect on the growth of the fresh water green alga Scenedesmus subspicatus. Testing Laboratory: TNO Physiological Sciences, Location Zeist, Utrechtsweg 48, P.O. Box 360, 3700 AJ Zeist, The Netherlands. Owner Company: Organotin Environmental Programme (ORTEP) Association Stabilizer. Report No.: 010.45228/01.30. Report date: 2004-06-02.
The study was assigned a reliability score of 2 and considered suitable for assessment. The study was performed in compliance with GLP and according to the guideline OECD 201.
A further study was provided as supporting information:
Grade R (1993) Growth Inhibition Test of Irgastab T 22 M to Green Algae (Scenedesmus subspicatus). Testing Laboratory: Ciba-Geigy Ltd. Product Safety Ecotoxicology, R-1066.P, CH-4002 Basel, Switzerland. Owner company: Ciba-Geigy Ltd, AD - Division, CH-4002 Basel, Switzerland. Report No.: 928292. Report date: 1993-04-26
The study was provided as supporting information only as the test material on which the study was performed contained 65% of the substance of interest. The study was assigned a reliability score of 2.

Key value for chemical safety assessment

Additional information

Read-across from dibutyltin oxide to diisotridecyl 3,3'-[(dibutylstannylene)bis(thio)]dipropionate concerning aquatic toxicity endpoints was considered appropriate as dibutyltin and octyltins are known to hydrolyse rapidly in water (as presented by Yoder 2003, under the data requirement hydrolysis), and form, in the case of dibutyltins, dibutyltin oxide.

Read across from DBT-2EHMA (CAS: 10584-98-2) has also been used for this endpoint as this is considered the most structurally similar organotin substance with regards to diisotridecyl 3,3'-[(dibutylstannylene)bis(thio)]dipropionate.

Due to the similarity between these test substances and registration substance, it is considered justified to read across to this study.

- The Steger-Hartmann T (1999) was performed in accordance with the OECD guideline 201. The study was therefore assigned a reliability score of 1 and considered adequate for the assessment of the toxicity of the test material to algae, however the reliability will be reduced to 2 as the study is being used for read-across purposes.

Di-n-butyltin oxide was incubated in an aqueous solution including nutrients with an algae population of Scendesmus subspicatus for a test duration of 72 hours. The increase in biomass and growth rate of each concentration were compared to those of the controls, and the inhibition was calculated. The observed reduction in growth was not prominent and showed no concentration-dependence. It was therefore interpreted as not being substance-related. the biomass and growth rates could not be calculated. A saturated solution of di-n-butyltin oxide is not toxic to the green algae Scenedesmus subspicatus.

The EC50 (72 h) for biomass and growth rate was determined to be ≥ 1.6 mg/l. DBTO had an inhibitory effect on the growth of algae at all concentrations, observable after 24 hours. However, there was no concentration dependence and it did not exceed 40% and 20% for biomass and growth rate respectively, even after 72 hours. Therefore the observed effects were regarded as not substance-related.

This study is being used as read across from Dibutyltin oxide; CAS No. 818-08-6.

- The Odersma. H, Hanstveit. A.O, & de Haan. H.P.M (2004) was performed in accordance with the OECD guideline 201, in compliance with GLP. The study was assigned a reliability score of 2 and considered reliable and adequate for assessment.The toxicity of dibutyltin bis (2-ethylhexylmercaptoacetate) to the fresh water green alga Scenedesmus subspicatus was determined in a 72-h growth inhibition. The NOEC was ≥120 µg Sn/L, equivalent to ≥646 µg DBT(EHMA)/L. The ErC50 value was >120 µg Sn/L, equivalent to >646 µg DBT(EHMA)/L. The EbC50 value was >120 µg Sn/L, equivalent to >646 µg DBT(EHMA)/L.

This study is being used as read across from dibutyltin bis(2-EHMA); CAS: 10584-98-2.

 

- Grade R (1993) was provided as a supporting study. The study was performed in compliance with GLP to a good scientific standard; accordingly the study was assigned a reliability score of 2. The acute toxicity to Green Algae (Scenedesmus subspicatus) was assessed in a 72 hour Algal inhibition test. The final measured concentrations tested were 0, 0.19, 0.29, 0.63, 1.1 and 2.5 mg/L. The EC50 (48 h) found to be 0.56 mg/L with 95 % confidence limits of 0.44 and 0.70 mg/L.

This study is being used as read across from dibutyltin bis(2-EHMA); CAS: 10584-98-2.

Key value for chemical safety assessment:

The EC50 (72 h) ≥ 1.6 mg/l

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