Dibutyltin di(acetate)

Toxicity to aquatic algae and cyanobacteria

Description of key information

There are two key studies for this endpoint, one adresses freshwater algae and the other adresses marine species.
Freshwater algae:
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. Owner company: Schering AG, Experimentelle Toxikologie, Berlin, Germany. Report No.: IC28. Company study No.: TXST19980234. Report date: 1999-02-17.
The study was performed to the guideline OECD 201, with a good level of reporting in the methodology and results. The study was assigned a reliability score of 2 as the study was performed on dibutyltin oxide, and read-across to the substance in question. Di-n-butyltin oxide had an inhibitory effect on the growth of the algae at all chosen concentrations. The inhibition was already observed after 24 hours.  This was not concentration dependent and did not exceed 40% and 20 % for biomass integral and growth rate, even after 72 hours. The observed effects were not regarded as substance-related. The EC50 was given as >1.6 mg/L.
Marine algae:
Walsh G. E., McLaughlan L. L., Lores E. M., Louie M. D. & Deans C. H. (1985). Effects of organotins on growth and survival of two marine diatoms, Skeletonema costatum and Thalassiosira pseudonana. Chemosphere 14: 383-392. Testing laboratory: U. S. Environmental Protection Agency Environmental Research Laboratory, Gulf Breeze, Florida, 32561, USA. This study was allocated a reliability score of 2 as the study was not conducted in line with good scientific principles, the quality of the results were considered acceptable. EC50s for algal growth after 72 hr exposure to dibutyltin diacetate were 35 and 127 µg/L, for S. costatum and T. pseudonana, respectively.  The LC50 and EC50 for lethality for 72 hr exposure by S. costatum were >500 and 304 µg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.6 mg/L

EC50 for marine water algae:

35 µg/L

Additional information

Freshwater algae:

Steger-Hartmann T (1999) studied the growth inhibition of di-n-butyltin oxide on the green algae Scenedesmus subspicatus. This study was allocated a reliability score of 2 and is the key study for this endpoint. Dibutyltin oxide was used to read across to dibutyltin di(acetate). The study was performed to the OECD guideline 201. The EC50 of Scenedesmus subspicatus exposed to dibutyltin oxide was reported as >1.6 mg/L

Read-across between dibutyltin compounds to to dibutyl diacetate 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.

Marine algae:

Walsh G. E. et al. (1985) was allocated as the key study for assessment of the toxicity of dibutyltin di(acetate) to marine algae.

This study has been allocated a Klimisch score of 2 as the study was not conducted in line with standard test guidelines but in line with sound scientific principles, so the quality of the results from the study can be considered acceptable. The lowest EC50 value determined from the two species studied in the test was used as the key value. EC50s for algal growth after 72 hr exposure to dibutyltin diacetate were 35 and 127 µg/L, for S. costatum and T. pseudonana, respectively. The LC50 and EC50 for lethality for 72 hr exposure by S. costatum were >500 and 304 µg/L, respectively.