Dibutyltin dilaurate

Endpoint summary

Description of key information

The following studies are available to address the repeat dose (oral) toxicity endpoint:
Waalkens-Berendsen DH (2003) Dibutyldichlorostannane (CAS # 683-18-1): Reproduction/developmental toxicity screening test in rats, TNO, Project Organisation, Ecotoxicology, Utrechtseweg 48, P.O. Box 370, 3700 AJ Zeist, The Netherlands, Report No.: V 4906, Organotin Environmental Programme (ORTEP) Association, Stabilizer Task Force. Report Date.: 2003-12-04.
Barnes, J. M. and Stoner, H. B. (1958). Toxic properties of some dialkyl and trialkyl tin salts. Brit. J. Industr. Med., 1958, 15, 15.
Gaunt, I. F., Colley, J., Grasso, P., Creasy, M. and Gangolli, S. D. (1968). Acute and Short-term Toxicity Studies on Di-n-butyltin Dichloride in Rats. Fd Cosmet. Toxicol. Vol. 6, pp. 599-608. Pergamon Press 1968. Printed in Great Britain.
Penninks A. H. & Seinen W. (1982). COMPARATIVE TOXICITY OF ALKYLTIN AND ESTERTIN STABILIZERS. Fd Chem. Toxic. Vol. 20. pp. 909 to 916.
Dr. Salsbury's Laboratories (1961). Toxicity of Chemical Compounds, Rat Trial No. R-23a-61, Project No. 043. Testing laboratory: Dr. Salsbury's Laboratories. Report no.: R-23a-61. Owner company: ATOFINA Chemicals Inc.
The Gaunt et al (1968) study has been allocated a Klimisch core of 2 on the basis that the study predates GLP; however, method was comparable to OECD Guideline 408. The effect of DBT exposure on the thymus of was not assessed in this study. 
The Penninks and Seinen (1982) study has also been allocated a Klimisch score of 2 on the basis that the study is a short-term feeding study with no information on the stability of the test substance in the diet or homogeneity of the test diets provided.
The Barnes and Stoner (1958) study has been allocated a Klimisch score of 4.
The Dr Salsubry's Laboratories study has been allocated a Klimisch score of 2 on the basis that the study predates GLP and because there is insufficient information on the test material.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

0.62 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

NOAEL in study determined for test substance DBTC (M=303.84 ) NOAEL is adjusted for higher molecular mass of DBTL ( 631.5582)
factor 631.55/304.84= 2.07 => NOAEL = 0.3 * 2.07 = 0.621 mg DBTL / kg bw/ day

Additional information

Repeated-dose oral toxicity data for the substance are limited to an old pre-GLP (Dr Salisbury's Laboratories, 1961) dietary study in which groups of rats received the substance in the diet for either 28 or 90 days at dosages up to 2000 ppm. The overal NOEL was set at 400 ppm (equivalent to 26.6 mg/kg bw/day) while 1000 ppm was considered to be the maximal tolerated dose for longer duration exposure. The study did not include thymus among the organs weighed and/or examined. All other studies submitted for this endpoint were performed on dibutyltin dichloride.

A robust review of data for organotin compounds (including dibutyltin) by the EU’s Scientific Panel on Contaminants in the Food Chain (SPCFC, 2004) appears to include the other studies reported above, with the exception of an OECD 421 study. The available data for repeat-dose (subchronic) studies are restricted to rats, exposed to dibutyltin chloride. Determination of NOAELs is variable, but thymus weight is considered a critical endpoint. In a first study (Gaunt et al., 1968), the NOAEL was set at 40 ppm (equivalent to 2 mg/kg bw/day) but thymus was not included among the organs weighed at termination. Another study (Pennincks et al., 1982) concludes reduction of relative thymus weight of approximately 45% at a dose level as low as 50 ppm in diet (equivalent to 2.5 mg/kg bw/day) administered for 14 days. The modern fully compliant OECD 421 study (Waalkens-Berendsen, 2003) identifies an effect level at approximately 2 mg/kg bw/day and NOAEL at 0.3 m/kg bw/day. Since an in vitro study demonstrated that DBTC can be used as an anchor compound following oral exposure, and 2-2.5 mg/kg bw/day appears a borderline effect level, a NOAEL of 0.3 mg/kg bw/day is considered amply protective and appropriate for setting DNELs.

A read-across approach was considered appropriate from dibutyltin chloride to other dibutyltins. Under gastric conditions dibutyltins are hydrolysed to form dibutyltin chloride. This is demonstrated in various dibutyltin compounds presented in the TNO report V5047, (presented as individual reports as under Toxicokinetics).

Justification for classification or non-classification

The substance is classified with R48/R25 according to Directive 67/548/EEC. According to Regulation (EC) no 1272/2008 the test substance would be classified as aSTOT Rep. Exp. 1 with Hazard statement: H372: Causes damage to thymus through prolonged or repeated exposureand should be accompanied with the signal word 'Danger'.

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