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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Key study:- Bouwman (2010) OECD 305, EU Method C.13, Based on the result found at the highest concentration tested, the BCF of dioctyltin oxide is expected to be at least less than 100 based on the results with dioctytin bis(2-ethylhexyl thioglycolate) and therefore the substance is not expected to bioconcentrate

This conclusion is identical with the result of an UK-CA assessment of the study. which confirmed the low potential for bioaccumulation of the assess dioctyltin compounds (including DOTTG as impurity of DOTE), although the study showed limitations due to the properties of the assessed subsnces like

low solubility

rapid reaction with water

analytical limitations

Exposure considerations:

Exposure of  DOTTG to the environment is negligible based on the following:processes and facts:

•       Waste water treatment

•       Complete transformation of DOTTG during manufacturing of PVC articles

•       Results of screening studies

Key value for chemical safety assessment

BCF (aquatic species):
100 dimensionless
BMF in fish (dimensionless):
100

Additional information

The key study, Bouwman (2010), was performed in line with GLP and in accordance with standardised guidelines OECD 305 and EU Method C.13. The study was performed on a surrogate substance dioctyltin bis(2-ethylhexyl thioglycate) which like all octyltin compounds is anticipated to hydrolyse to dioctyltin oxide very rapidly in water. The fish in the study are therefore expected to have been exposed to the same organotin species that would occur if the test had been performed using dioctyltin oxide. The study was therefore assigned a reliability score of 2 in accordance with the principles for assessing data quality as outlined in Klimisch (1997).

The bioconcentration of dioctytin bis(2-ethylhexyl thioglycolate) in rainbow trout exposed to 0.25 and 2.5 µg/L of dioctytin bis(2-ethylhexyl thioglycolate) for 30 days in a flow-through system was determined to be 1294 and 99 respectively based on measured dioctyltin.

The high BCF value found at the 0.25 µg/L concentration was due to the limitations in the sensitivity of the analytical methods employed in the study and could not be further improved.

Based on the result found at the highest concentration tested, the BCF is at least less than 100 and therefore the substance is not expected to bioconcentrate.