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EC number: 223-296-5
CAS number: 3811-73-2
guideline study NaPT was found to be hydrolytically stable (Table 5.1.1).
In a GLP
study conducted according to US guideline Federal Register Vol. 50, No.
188 (Friday 27 1985) Rules and Regulations, p. 39252.(similar to OECD
111) (5.1.2.001) at a concentration of 140 mg/L, no DT50for
hydrolysis could be determined even after 28 days in pH 3, 7, and 11
study of the photolysis rate of sodium pyrithione has been carried out.
In a GLP
study conducted according to US guideline US FDA Technical Assistance
Document, Guideline 3.10 Photodegradation. 1987.) (5.1.3.001, EZPTF
7011-121) at a concentration of 10 mg/L, DT50for
photolysis were determined to be <10 minutes at pH 5 and 7 and <15
minutes at pH 9. Degradants were not identified in this study.
further study of the aqueous photolysis rate of pyrithione has also been
conducted (refer to Table 5.1.2).
(5.1.3.003, EZPTF 7011-123) was conducted to determine the influence of
concentration on photolysis rates. Photolysis
was done in deionized water with zinc pyrithione concentrations of 0.1-1
μg/L, which are much closer to predicted environmental concentrations
than those of the other two studies. Exposure
to natural sunlight (42° N latitude) was done in quartz tubes at noon
during the months of July through October. ZnPT
was shown to have considerable absorptivity in the range of 290-400 nm,
where photoactive solar radiation is available and photolysis in natural
sunlight was very rapid. Measured
photolysis half-lives ranged from 1.1 to 1.4 minutes in deionized water. Simultaneous
exposure of the actinometer (o‑nitrobenzaldehyde) solutions allowed the
calculation of photolysis disappearance quantum yields. Reproducibility
at the very low concentrations used in this study required that several
exposure experiments be run for each test compound and the results
quantum yield for ZnPT at 3.15 x 10-9M and 3.15 x 10-10M
was 0.17 ± 0.06 (n = 4). This
study also demonstrated that three metallic complexes of pyrithione
(Zinc, Copper and Sodium) all exhibited the same photolysis rate at
environmentally relevant concentrations.
This point is
regarded not to be relevant because:
vapour pressure of NaPT is very low, resulting in negligible exposure to
calculation according to the Atkinson calculation method (5.1.1.001,
ESPTF 7031-001) indicates a short half-life (53.8 hours) of sodium
pyrithione in the atmosphere.
pyrithione is hydrolytically stable.
pyrithione passes the ready biodegradability test according to OECD 301B
and biodegradation is rapid in soil, water-sediment, and STP. The
degradation profile is well identified passing through several transient
degradants to a final somewhat persistent degradant 2‑pyridine sulphonic
is extremely rapid—again leading to the final somewhat persistent
degradant 2‑pyridine sulphonic acid (PSA).
final degradant, PSA, passes the ready biodegradability test according
to OECD 301B.
Table 5.1.1 Hydrolysis
Guideline /Test method
Initial TS concentration, C0[mg/L]
Reaction rate constant, Kh
Coefficient of correlation, r2
Federal Register Vol. 50, No. 188 (Friday 27 1985) Rules and Regulations, p. 39252. (similar to OECD 111)
pH 3; 7; and 11
25 ± 1°C(pH 5, 7 and 9 fw)
25 ± 1°C(pH 8.2 sw)
No detectable degradation
Stanley et al (1996)
Table 5.1.2 Photolysis
Initial molar TS concentration
Total recovery of test substance[% of appl. a.s.]
Photolysis rate constant (kcp)
Direct photolysis sunlight rate constant (kpE)
Reaction quantum yield (fcE)
US FDA Technical Assistance Document, Guideline 3.10 Photodegradation. 1987.
pH 5 buffer:0.12 to 0.18 min-1
pH 7 buffer:0.15 to 0.19 min-1
pH 9 buffer:
Not reported, not applicable to the testing guideline.
Half lives under the conditions of this study were <10 minutes in pH 5 and 7 buffer and
<15 minutes in pH 9 buffer.
Croudace, Gilbert, Woods (1996)
Methods used are similar to the requirements of OPPTS 835.2210 and OPPTS 830.7050
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)
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
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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