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.

Hydrolysis

In two guideline studies ZnPT was found to be relatively hydrolytically stable (Table 5.1.1).

Photodegradation in water

Three studies of the aqueous photolysis rate of zinc pyrithione have been conducted (refer to Table 5.1.2).

 

Photodegradation in air

This point is regarded not to be relevant because:

-         the vapour pressure of ZnPT is very low, resulting in negligible exposure to the atmosphere.

-         the calculation according to the Atkinson calculation method (5.1.1.001) indicates a short half-life (8.69 hours) of pyrithione zinc in the atmosphere.

Table  5.1.1 Hydrolysis

Guideline / Test method	pH	Temperature [°C]	Initial TS concentration, C0 [mg/L]	Reaction rate constant, Kh	Half-life, DT50	Coefficient of correlation, r^2	Reference
EPA 161-1 (similar to OECD 111)	pH 5, 7 and 9 (fw) pH 8.2 (sw)	25 ± 1°C(pH 5, 7 and 9 fw) 25 ± 1°C(pH 8.2 sw)	2.0 mg/L	0.00703 d^-1at 25°C (pH 5 fw) 0.00576 d^-1at 25°C (pH 7 fw) 0.00562 d^-1at 25°C (pH 9 fw) 0.00721 d^-1at 25°C (pH 8.2 sw)	DT50values at: pH 5: 98 days (25°C) pH 7: 120 days (25°C) pH 9: 123 days (25°C) pH 8.2 (sw): 96 days (25°C)	0.9994 0.9804 0.9291 0.9248	Reynolds (1995)
Federal Register Vol. 50, No. 188 (Friday 27 1985) Rules and Regulations, p. 39252.	pH 3, 7 and 11	25 ± 1°C	5 mg/L	4.6 x 10^-4h^-1at pH 3, 0 at pH 7 7.1 x 10^-4h^-1at pH 11,	DT50values at: pH 3: 63 days pH 7: >1 year pH 11: 41 days	0.76 n.a. 0.97	Stanley, Croudace, Magor (1996)
EPA 161-1 (similar to OECD 111)	pH 5, 7 and 9 (fw) pH 8.2 (sw)	25 ± 1°C(pH 5, 7 and 9 fw) 25 ± 1°C(pH 8.2 sw)	0.05 mg/L (copper pyrithione)	0.00301 d^-1at 25°C (pH 5 fw) 0.00639 d^-1at 25°C (pH 7 fw) 0.0939 d^-1at 25°C (pH 9 fw) 0.0536 d^-1at 25°C (pH 8.2 sw)	DT50values at: pH 5: 230 days (25°C) pH 7: 108 days (25°C) pH 9: 7.4 days (25°C) pH 8.2 (sw): 12.9 days (25°C)	0.9257 0.9895 0.9982 0.9991	Key Study Fenn (1999)

Table 5.1.2        Photolysis

Guideline / Test method	Initial molar TS concen­tration	Total recovery of test substance [% of appl. a.s.]	Photolysis rate constant (k^cp)	Direct photolysis sunlight rate constant (kpE)	Reaction quantum yield (f^cE)	Half-life (t1/2E)	Reference
US FIFRA 161-2	2 μg/mL (6.3 x 10^-6M)	95.9 (in pH 9 buffer) 101.0 (in asw)	pH 9 buffer: 0.05208min^-1 pH 8.2 (artificial sea water): 0.0395min^-1	Not reported, not applicable to the testingguideline.	Not reported, not applicable to the testing guideline.	Half lives under the conditions of this study were 13.3 minutes in pH 9 buffer and 17.5 minutes in artificial seawater.	Croudace, Gilbert, Woods (1996)
US FDA Technical Assistance Document, Guideline 3.10 Photodegradation. 1987	5 μg/mL (16 x 10^-6M)	Not applicable Non-radiolabelled test substance.	pH 5: 0.16 to 0.27min^-1 pH 7: 0.38 to 0.49min^-1 pH 9: 0.44 to 0.47min^-1	Not reported, not applicable to the testing guideline.	Not reported, not applicable to the testing guideline.	<7 minutes for pH 5, 7 and 9 (corrected to UK Midsummer sunlight).	Reynolds (1996)
Methods used are similar to the requirements of OPPTS 835.2210 and OPPTS 830.7050	1x10^-3μg/mL, 1x10^-4μg/mL (3.15x10^-9M, 3.15x10^-10M)	Not applicable Non-radiolabelled test substance.	0.483 min^-1to 0.631 min.^-1(depending on the weather conditions)	0.2201 to 0.2869min^-1	0.17 ± 0.06	3.0 /10.6 min (latitude 40 summer/ winter) 3.1 /22.2 min (latitude 50 summer /winter)	Key Study Fenn (2005)