Pyrithione zinc

Endpoint summary

Additional information

The information contained within this robust summary document comes from studies which are in the ownership of Arch Chemicals Inc. and which are protected in several regions globally. This information may not be used for any purpose other than in support of the Chemical safety Report submitted by Arch Chemicals Inc. under RegulationEC 1907/2006.

Zinc pyrithione has tested negative for genotoxicity in a number ofin vitroandin vivomutagenicity assays including primate and human peripheral lymphocytes.

All studies proved negative with the exception of onein vitroassay carried out in Chinese hamster V79 (fibroblast) cells. In this study, zinc pyrithione was observed to induce chromosomal aberrations in the presence and the absence of metabolic activation. Based on this finding the required trigger study is anin vivomouse micronucleus assay which was carried out.Under the conditions of this test zinc pyrithione failed to induce any signs of genotoxicity.

In addition, the secondary trigger study is an unscheduled DNA synthesis (UDS) study in the rat and the sodium salt of pyrithione was evaluated in the UDS.  The results from the UDS indicated that pyrithione (tested as sodium pyrithione) failed to induce a mean net nuclear grain count of plus five or greater over the control and vehicle control indicating a clear negative result for inducing DNA synthesis. The two highest concentrations of sodium pyrithione tested induced cytotoxicity demonstrating that sufficient test article was delivered to the test system

Based on the wealth of negative mutagenicity and genotoxicity studies inin vitroandin vivotest systems, zinc pyrithione is not genotoxic.

Table25:Summary of genotoxicityin vitro

Method	Results	Remarks	Reference
EEC Council Directive 2000/32, Annex 4D; OECD 471 (1997); ICH S24 Genotoxicity: Specific aspects of regulatory tests, Step 5. GLP Salmonella typhimurium: TA 1535, TA 1537, TA 98, TA 100, TA 102	Experiment 1; strains TA1535, TA 1537, TA 98, TA 100: 0; 6.25;12.5; 25.0; 50.0; 100 µg/plate Experiment 1; strain TA 102: 0; 3.13; 6.25; 12.5; 25.0; 50 µg/plate Experiment 2; strains TA 1535, TA 1537, TA 98, TA 100: 0; 1.56; 3.13; 6.25; 12.5; 25.0; 50.0 µg//plate Experiment 2, strain TA 102: 0; 1.56; 3.13; 6.25; 12.5; 25.0; 35.0 µg a.s./plate The test substance did not induce two-fold increases in the number of revertant colonies in the plate incorporation or pre-incubation assay, at any dose level, in any tester strain, in the absence or presence of S9 metabolism.	Reliability – 1 Purpose flag Study result type Test material: ZPT powder 97.9%	Scarcella O, Brightwell J (2002) (unpublished)
Bacterial reverse mutation test (Ames). US EPA 84-2, which complies with OECD 471 guidelines. GLP (self certification by the laboratory) S.typhimurium TA98, TA100, TA1535 and TA1538	-         -S9: 0.03 – 10 µg/plate +S9: 10 – 333 µg/plate In the initial assay, no positive responses were observed with any of the strains. Because of the lack of toxicity, strains were tested at higher concentrations and no positive responses were observed. In the confirmatory assay, no positive responses were observed.	Reliabilty – 1 Purpose flag Study result type Test material: Zinc Omadine, 48% Dispersion	San R and Shelton J (1990) (unpublished)
In vitro chromosomal aberration assay in mammalian cells. GLP study complies with OECD 473 guideline. Chinese hamster lung fibroblasts (V79 cell line)	Expt. 1; +/- S9 – 0, 0.0488, 0.0977, 0.395, 0.781, 1.56, 3.13 and 6.25 µg/ml Expt. 2: -29 @ 20 and 31 hrs – 0, 0.12, 0.023, 0.047, 0.094, 0.188, 0.375, 0.75, 1.5 and 3.0 µg/ml Expt. 2: +S9 0, 0.047, 0.094, 0.188, 0.375, 0.75, 1.5, 3.0, 6.0 and 12.0 µg/ml Test substance induced an increase in the number of cells with aberrations (including and excluding gaps) in the presence and absence of S9 metabolised at the highest dose tested when scored at 20 hrs and at 0.75 µg/ml when scored at 31 hrs.	Reliability – 1 Purpose flag Study result type Test material: ZPT powder, 97.9%	Ciliutti P, Brightwell J (2002) (unpublished)
Cytogenicity test in mammalian cells. Japanese guideline, which complies with OECD 472 guideline. GLP  Human Peripheral lymphocytes.	0.4 and 1.2 µg/ml Direct method: no differences were noted in frequencies of structural aberrations or polyploidy between the test article and control. Metabolic activation method: no differences were noted in frequencies of structural aberrations or polyploidy between the results of the metabolic activation method test with S9 Mix and the results of the metabolic activation method test without S9 Mix, as well as, between the test article treated groups and the control group.	Reliability – 1 Purpose flag Study result type Test material: Zinc Omadine powder, 96.3%	Ohta K (1992) (unpublished)
Gene mutation in mammalian cells. EEC Council Directive 2000/32, Annex 4E; OECD 476 (1997) GLP Chinese hamster V79 cells	Level 1 S9 – 0.391; 0.293; 0.195; 0.0977; 0.0488; 0.0244 (µg/mL) Level 1 S9+ 6.25; 4.69; 3.13; 1.56; 0.781; 0.391 (µg/mL) Level 2 S9 – 0.587; 0.391; 0.261; 0.174; 0.116; 0.0773 (µg/mL) Level 2 S9 + 6.25; 4.17; 2.78; 1.85; 1.23 (µg/mL) No reproducible five-fold increases in mutant numbers or mutant frequency were observed following treatment with the test substance at any dose level, in the absence or presence of S9 metabolism. The test substance does not induce gene mutation in Chinese hamster V79 cells after in vitro treatment under the reported experimental conditions.	Reliability – 1 Purpose flag Study result type Test material ZPT powder 97.9%	Cinelli S, Brightwell J (2002) (unpublished)
Gene mutation in mammalian cells. US EPA 84-2, which complies with OECD 476 guideline. GLP (self certification by the laboratory) Chinese hamster CHO/HGPRT assay	Initial assay: - S9: 0.25 – 2.0 µg/ml and + S9: 5 – 30 µg/ml Confirmatory assay: - S9: 0.25 – 2.2 µg/ml and + S9: 2.5 – 30 µg/ml The test substance produced a single positive point in one dose in the initial assay without metabolic activation. This observation was not reproduced in the confirmatory assay. Similarly, two positive points were noted in the confirmatory assay in the presence of metabolic activation. These points were only slightly increased above the normal spontaneous mutation frequency. They were also not dose related and were not seen in the initial assay.	Reliability – 1 Purpose flag Study result type Test material: Zinc Omadine, 48% Dispersion	Jacobson-Kram D and Sigler C (1990) (unpublished)

Table26: Summary of genotoxicityin vivo

Method	Results	Remarks	Reference
“In vivo Mammalian erythrocyte micronucleus test” (1997) OECD 474 GLP  Oral (gavage) Mouse, Crl:NMRI BR 5m + 5f per dose One application	24 and 48 hrs post dose 800, 1000 & 1300 mg/kg No statistically significant increase in the amounts of micronucleated polychromatic erythrocytes was observed at any dose tested compared to the negative controls, at neither 24 nor 48 hours after treatment. The test substance does not produce relevant increases of the numbers of micronuclei in polychromatic erythrocytes after in vivo treatment of mice of either sex of the test strain at doses of 800, 1000 and 1300 mg/kg bw.	Reliability – 1 Purpose flag Study result type Test Article: ZPT powder, 97.9%	Bornatowicz N (2001) (unpublished)
Micronucleus test US EPA 84-2, which complies with OECD 474 guideline. GLP (self certification by the laboratory)  Once by Intraperitoneal injection,Mouse, ICR 15 per sex per Group	24, 48 and 72 hours post dosing. 0, 11, 22 and 44 mg/kg bw Negative No changes in the ratios of polychromatic erythrocytes to total erythrocytes or increases in micronucleated polychromatic erythrocytes were observed in the treated groups.	Reliability – 1 Purpose flag Study result type Test material: Zinc Omadine 48% dispersion	Putman D and Morris M (1990) (unpublished)
Mammalian cytogenicity test. Japanese MITI guideline. GLP MonkeyCynomolgus 4 per sex per Group Once daily for 28 days	On the day after 28 days dosing period. 0, 5.5, 11 and 22 mg/kg bw/day Negative No significant differences were noted in the average frequencies of structural aberrations or polyploidy between the test article treated groups and the control group.	Reliability – 1 Purpose flag Study result type Test material: Zinc Omadine powder, 96.3%	Ohta K (1992) (unpublished)
Mammalian rat hepatocytes primary culture/DNA Repair Test GLP  Rat hepatocytes from one rat, 1x10 -5 viable hepatocytes Two hr incubation at 37 degrees C, cells serum free medium containing test article and 3H-thymidine was added to eachculture.	0.067, 0.050, 0.167, 0.50, 1.67, 5.0, 16.7, 50.0, 166.7 and 500 ng/ml Negative After 7-days of exposures, autoradiographs were developed and UDS “repair” synthesis evidenced by a net increase in black silver grains over the nucleus is quantified by determining nuclear and cytoplasmic grain counts.	Reliability – 1 Purpose flag Study result type Test material:  NaPT 40% aqueous solution	Berfknecht TR (1987) (unpublished)

Endpoint Conclusion: No adverse effect observed (negative)