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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Migrated phrase: estimated by calculation
Adequacy of study:
key study
1 (reliable without restriction)

Data source

Reference Type:
study report

Materials and methods

Principles of method if other than guideline:
Not applicable; model calculation according to the Atkinson calculation method.
GLP compliance:
Not relevant

Test material

Constituent 1
Chemical structure
Reference substance name:
Pyridine-2-thiol 1-oxide, sodium salt
EC Number:
EC Name:
Pyridine-2-thiol 1-oxide, sodium salt
Cas Number:
Molecular formula:
sodium (1-oxo-1λ⁵-pyridin-2-yl)sulfanide

Study design

Estimation method (if used):
-Atkinson calculation method
-AOPWIN (Atmospheric Oxidation Program v1.91

Results and discussion

Any other information on results incl. tables

The total OH radical reaction rate constant (kOH) is given by:

kOH=    k (H-atom abstraction from C-H and O-H bonds)

               + k (OH radical addition to aromatic rings)

               + k (OH radical addition to fused rings)

               + k (OH radical interaction with N-, S- and OH-containing groups)


For Sodium pyrithione kOHis:


kOH= k (H-atom abstraction from C-H and O-H bonds) + k (OH radical interaction with N-, S- and OH-containing groups) + k (OH radical addition to aromatic rings) + k (OH radical addition to fused rings)


The hydrogen abstraction (H-atom abstraction from C-H bonds) has a value of

               k = 0.0000 cm3molecule-1sec-1(no hydrogen abstraction).


The OH radical interaction with N- and OH-containing groups has a value of

               k = 0.0000 × 10-12cm3molecule-1sec-1(aromatic nitrogen).


The OH radical addition to aromatic rings has a value of

k = 2.3854 × 10-12cm3molecule-1sec-1


The OH radical addition to fused rings has a value of

k = 0.000 × 10-12cm3molecule-1sec-1


The overall OH rate constant is estimated to be:


               kOH= 2.3854 × 10-12cm3molecule-1sec-1.

The tropospherical half life is calculated from the overall OH radical reaction rate constant using the equation:


t1/2 = ln2/KOH x [OH]

[OH] = the model default OH radical concentration in the troposphere of 1.5 x 106molecule-cm3(12 hours irradiation per day).


For zinc pyrithione the calculated tropospherical half life is:

0.693/(2.3854E-12 x 1.5E6) = 193678 seconds = 53.8 hours


Applicant's summary and conclusion

Sodium pyrithione degrades quickly in the atmosphere by reaction with OH radicals, having a half life of 53.8 hours. Considering that sodium pyrithione is non-volatile (vapour pressure <4.6 x 10exp-5 Pa), significant pollution of the air by the use of sodium pyrithione can be excluded. 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 Regulation EC 1907/2006.