Dibutyltin dichloride

Endpoint summary

Additional information

IN VITRO GENE MUTATION STUDY IN BACTERIA

 

Jagannath D R (1979) was submitted as the key study for this data requirement. Although the study predates GLP, the study was reported to a good standard and performed to a method which is comparable to OECD 471 (prior to the update which introduced additional strains to investigate cross linking.).A reliability score of 2 was assigned to the study. The results of the tests conducted on the test material in the absence of a metabolic activation system were all negative. The results of the tests conducted on the compound in the presence of a rat liver activation system were all negative. The test material did not demonstrate genetic activity in any of the assays conducted in this evaluation and was considered not mutagenic under these test conditions.

 

A further Ames study, Hamasaki et al (1993) was reported to a good standard and in line with good scientific principles. The study was assigned a reliability score of 2. The study only used two strains of Salmonella typhimurium, did not include a strain to assess cross linking, and it was also performed only without metabolic activation and was therefore only provided as supporting information. The results of the study concluded that the mutagenicity assay with S. typhimuruim TA100 and TA98, di-n-butyltin dichloride was found to be mutagenic.

 

Two DNA damage and repair assays were also available for use as supporting information, both sourced from the same publication, but reported separately due to the different methods used, by Hamasaki T et al (1992). Both studies were assigned a reliability score of 2 as they were well documented and performed to a good scientific standard, however both assays did not include metabolic acitivation. The first, an SOS chromotest found that dibutyltin dichloride exhibited genotoxicity at a low dose (0.01 µg/tube). The second, a rec assay also noted that dibutyltin dichloride exhibited genotoxicity at a dose of 10000 µg/disk also without metabolic activation.

 

 

IN VITRO CYTOGENICITY STUDY IN MAMMALIAN CELLS OR IN VITRO MICRONUCLEUS STUDY

 

Reimann R & Gramlich U (1990) was provided as the key study for this data requirement. The study was performed in compliance with GLP and the method was comparable to that of OECD 473. The study was accordingly assigned a reliability score of 2 and considered reliable and adequate for assessment. An evaluation of the clastogenic potential in the human lymphocyte test indicated clastogenic potential of the test material in the human lymphocyte test in vitro at clearly cytotoxic concentrations. From the four assays conducted without and with an extrinsic metabolizing system in two independent studies, one assay without and one with S9 mix gave statistically significant (P < 0.05) increases in the frequency of chromosomal aberrations at the highest concentrations evaluated, whereby in the remaining assays the results were borderline negative. In each assay of this investigation, the test material was tested up to cytotoxic concentrations as indicated by an obvious reduction of the mitotic index.

 

The CHO gene mutation study from the publication by Li AP et al (1982) was provided as a supporting study to this endpoint. The study was conducted to good scientific principles (GLP status was not reported), however the study did not include metabolic activation. The study was accordingly assigned a reliability score of 2. The LC50 value of DBTC for CHO cells, as determined by cloning efficiency, was approximately 0.35 µg/ml (1.12 µM). DBTC induced mutations at the HGPRT gene locus in CHO cells. The mutant frequency increased with dose up to 0.2 µg/ml (0.66 µM) for DBTC. A decrease in mutant frequency was observed at higher concentrations.

 

IN VITRO GENE MUTATION STUDY IN MAMMALIAN CELLS

 

Lang R & Schmitt R (1989) was provided as the key study for this data requirement. The study was well documented, performed in compliance with GLP and to a method comparable to OECD 476. The study was assigned a reliability score of 2 and considered reliable and adequate for use. The study was a HGPRT-test with V79 cells. The test material was found to have cytotoxic effects without metabolic activation by S9 mix at 0.00006 µl/ml and with metabolic activation a clear toxic effect could be observed at 0.0003 µl/ml in the first experiment and at 0.0005 µl/ml in the second assay of the second experiment. The test material did not show a mutagenic potential in the HGPRT/V79 mammalian cell gene mutation test neither in the absence nor in the presence of rat liver S9 mix in two independently performed experiments.

 

IN VIVO MUTAGENICITY

 

Dance C (1991) was provided as the key study for this data requirement. The study was performed in compliance with GLP and according to the guideline OECD 474 (and EU Method B.12). The study was therefore assigned a reliability score of 1 and considered reliable and adequate for assessment. The study investigated the clastogenic action on bone marrow erythrocytes in a micronucleus. The test material showed evidence of induced chromosomal or other damage leading to micronucleus formation in polychromatic erythrocytes of mice treated orally with DBTC at 50 mg/kg and sacrificed 48 or 72 hours later. A biologically and statistically significant increase in the incidence of micronucleated polychromatic cells was observed in the bone marrow of mice treated with DBTC at 50 mg/kg and killed 48 and 72 hours later (0.01<p<0.05): this effect was seen more clearly in females than in males. No such effect was apparent for any group treated with DBTC and killed 24 hours later (p>0.05). Statistically significant increases over controls were also seen in positive control group animals given chlorambucil at 30 mg/kg (p<0.01).

 

A further in vivo mutagenicity study, (Lang R & Wedel JV (1990) was provided as supporting information. The GLP status of the study was not reported and no guidelines were listed. The study was performed to a good scientific standard with a good level of reporting of the methodology and the results. The study investigated the mutagenic potential of the test material in the mouse micronucleus test. The test material failed to show any evidence of mutagenic potential, when administered by gavage up to the toxic dose level of 200 mg/kg in the mouse micronucleus test. Triaziquone, the positive reference, gave the expected mutagenic response. After application of the high dose four males and one female died; after application of the mid dose, one male died. More than half of the animals of the two highest dose groups showed signs of toxicity (e.g. apathy, eyelid closure, ruffled fur).

 

OTHER:

In the second part to the Li AP et al (1982) study, a test was performed to determine the cytotoxicity of the test material to rat lymphocytes. The test is not a standard endpoint and was therefore provided for information purposes only. The study was performed to a good scientific standard with a good level of reporting. The LC50 for lymphocytes as determined by dye-exclusion was approximately 50 µg/ml (0.16 mM). At the same concentration of DBTC, the number of antibody-forming cells (AFC) was reduced to approximately 10 % of the control

Short description of key information:
The following studies were submitted to address the genetic toxicity of the substance:

IN VITRO GENE MUTATION STUDY IN BACTERIA

Jagannath D R (1979) Mutagenicity evaluation of d-n-butylzinndichlorid in the ames salmonella/microsome plate test, Testing Laboratory: Litton Bionetics, Inc., 5516 Nicholson Lane, Kensington, Maryland, 20795, USA. Report No.: 20998. Owner company: Schering AG, D-1 Berlin, 65 Postfach, 650311, Germany. Report date: 1979-05-15

IN VITRO CYTOGENICITY STUDY IN MAMMALIAN CELLS OR IN VITRO MICRONUCLEUS STUDY

Reimann R & Gramlich U (1990). ZK 22.663: Evaluation of the clastogenic potential in the human lymphocyte test. Testing laboratory: Schering AG, Pharmaceutical Research, Bergkamen, Germany. Owner company: Schering AG, Pharmaceutical Research, Bergkamen, Germany. Report No.: IC 1/90. Report Date: 1990-09-17.

IN VITRO GENE MUTATION STUDY IN MAMMALIAN CELLS

Lang R & Schmitt R (1989). ZK 22.663: Evaluation of gene mutations in mammalian cells in culture: HGPRT-test with V79 cells. Testing laboratory: Schering AG, Pharmaceutical Research, Bergkamen, Germany. Owner company: Schering AG, Pharmaceutical Research, Bergkamen, Germany. Report No.: IC 16/89. Report date: 1989-03-30.

IN VIVO MUTAGENICITY

Dance C (1991). Dibutyl tin chloride: assessment of clastogenic action on bone marrow erythrocytes in the micronucleus test. Testing Laboratory: Life Sciences Research Limited, Eye, Suffolk, IP23 7PX, England. Owner company: Atochem North America Incorporated, 900 first Avenue, P.O. Box C, King of Prussia, Pennsylvania, 19406-0018, USA. Report No.: 91/0357. Report date: 1991-11-08

All the above listed in vitro studies were assigned a reliability score of 2 and were designated the key studies for each of the data requirements. The key in vivo study, listed above was assigned a reliability score of 1.

Several further studies were included as supporting information.

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

Although a number of studies produced negative results, there is an overwhelming weight of evidence with indicates that the test material is positive for genetic toxicity. According to directive 67/548/EEC the substance is assigned the classification Mutagenicity category 3 and labelled with R68 – possible risk of irreversible effects. According to Regulation (EC) no 1272/2008 the test substance would be classified as Muta. 2 with the Hazard statement: H341: Suspected of causing genetic defects and should be accompanied with the signal word 'Warning'.