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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vivo
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Minor deviations with no effect on the results: - Purity and stability were not stated. - According to guideline, the observations should be made at 30-60 minutes and at 24, 48, and 72 hours after patch removal and not 24 hours, 48 hours and 72 days after start of exposure. - A modified Draize scoring system was used in this study. - According to the guideline the test substance should be moistened with water. In this study the test patch was moistend with water for application instead of the test substance. - The water supply was not unrestricted. - in the study report it was stated that observations were made at 30-60 minutes after patch removal. In the result table data were listed for an observation at 4-hours.
Justification for type of information:
Read-across
The basis for the read-across concept for this project is the equilibrium between sulfites, hydrogensulfites, and metabisulfites in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:[1],[2]
SO2 + H2O <->`H2SO3´ H2SO3<->H+ + HSO3- <-> 2H+ +SO32- 2HSO3- <->H2O +S2O52 –
As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfites, hydrogensulfites and metabisulfites. Additionally, it is known that sodium dithionite disproportionates in water to form sodium hydrogen sulfite and sodium thiosulfate (equation II) so that this substance can also be added to the read-across concept.[2],[1]
It is expected for this case that the substance is not stable enough under physiological conditions to fulfil the requirements of study guidelines and so the products of decomposition have to be considered.
2 S2O42-+ H2O→2HSO3-+ S2O32 -

All sulfite, hydrogensulfite and metabisulfite substances are highly soluble in water, establishing upon dissolution an equilibrium that depends on solution pH as follows: ,

1. SO2 + H2O <-> H2SO3
2. H2SO3 <-> H+ + HSO3- <-> 2H+ + SO32-
3. 2 HSO3- <-> H2O + S2O52-

Under oxidising conditions, e.g., in surface waters, sulfite is oxidized to sulfate catalytically by (air) oxygen or by microbial action. A half-life of 77 hour was measured in deionized water, already suggesting substantial abiotic degradation. However, the presence of metal cations in the environment, such as copper, iron and manganese, accelerates the oxidation rate. In soils, HSO3- and SO32- ions are unstable and quickly oxidise. Further, because of the instability of SO32-, metal sulfites are generally too soluble to persist in soils. Thus, the most stable and predominant sulfur form in freshwater and in all but highly reduced environments is sulfate (SO42-). In highly reduced soils and sediments, sulfites may be reduced to sulfides (Lindsay, 1979; OECD SIDS, 2012).

Only the properties of the sulfite anion are considered relevant determinants of environmental toxicity since respective cations, i.e. ammonium, calcium, magnesium, sodium and potassium, are not assumed to contribute substantially to differences therein. Sulfite, although naturally present in the environment and also a metabolite and intermediate of sulfur-containing amino acids in organisms, may have an impact on the environment at elevated levels. Sulfites do not bioaccumulate.

In sum, unrestricted read-across between the sulfites, hydrogensulfites and metabisulfites is justified.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1989
Report Date:
1989

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 404 (Acute Dermal Irritation / Corrosion)
Version / remarks:
1981-05-12
Deviations:
yes
Remarks:
, see "rationale for reliability"
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
- Name of test material (as cited in study report): Potassium sulphite

Test animals

Species:
rabbit
Strain:
Vienna White
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Savo; Med. Versuchstierzuchten GmbH; 7964 Kisslegg/Allgäu FRG
- Weight at study initiation: mean weight 2.56 kg (Individual weights of the three test animals:2.78 kg, 2.22 kg, and 2.68 kg)
- Housing: The animals were individually housed. The animals were housed in fully air-conditioned rooms. Cage made of stainless steel with wire mesh walk floors. Floor area: 40 cm X 51 cm. No bedding in the cages.Sawdust in the waste trays.
- Diet: Kliba 341, 4 MM; Firma Klingentalmuehle AG, CH- 4303 Kaiseraugst, Switzerland (about 130 g per animal per day)
- Water: About 250 ml tap water per animal per day
- Acclimation period: At least 8 days before the beginning of the study; same housing conditions as during the study.

ENVIRONMENTAL CONDITIONS
- Temperature: 20 - 24 °C
- Relative humidity: 30 - 70 %
- Photoperiod (hrs dark / hrs light): 12/12

Test system

Type of coverage:
semiocclusive
Preparation of test site:
shaved
Vehicle:
water
Controls:
no
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): A dose of 0.5 g of the unchanged test substance.
Duration of treatment / exposure:
4 hours
Observation period:
72 hours; Readings of skin irritation at 30 - 60 minutes after removal of the test patches and 24 h, 48 h and 72 h after the beginning of application.
Number of animals:
3 male rabbits
Details on study design:
TEST SITE
The fur of the rabbits was clipped at least 15 hours before the beginning of the study.The application area was 2.5 cm X 2.5 cm on the upper third of the back or flanks. The test patch (2.5 cm X 2.5 cm) was covered with a dose of 0.5 g of the unchanged test substance and has been moistened with aqua dest.. Test patches were secured in position with a porous dressing (four layers of absorbant gauze and porous bandage). The untreated skin sites of the same animals was used as negative control.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The test substance was removed with lutrol and lutrol/water (1:1).
- Time after start of exposure: At the end of the exposure period

SCORING SYSTEM: Modified Draize scoring system
Evaluation of erythema (R) and oedema (ED):
0 = none
1 = very slight
2 = well-defined
3 = moderate to severe
4 = severe to very severe

Results and discussion

In vivo

Resultsopen allclose all
Irritation parameter:
erythema score
Basis:
mean
Remarks:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
4
Remarks on result:
other: The readings were made 24 h, 48 h and 72 h after the beginning of application
Irritation parameter:
edema score
Basis:
mean
Remarks:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
4
Remarks on result:
other: The readings were made 24 h, 48 h and 72 h after the beginning of application
Irritation parameter:
erythema score
Basis:
mean
Remarks:
animal #2
Time point:
24/48/72 h
Score:
0
Max. score:
4
Remarks on result:
other: The readings were made 24 h, 48 h and 72 h after the beginning of application
Irritation parameter:
edema score
Basis:
mean
Remarks:
animal #2
Time point:
24/48/72 h
Score:
0
Max. score:
4
Remarks on result:
other: The readings were made 24 h, 48 h and 72 h after the beginning of application
Irritation parameter:
erythema score
Basis:
mean
Remarks:
animal #3
Time point:
24/48/72 h
Score:
0
Max. score:
4
Remarks on result:
other: The readings were made 24 h, 48 h and 72 h after the beginning of application
Irritation parameter:
edema score
Basis:
mean
Remarks:
animal #3
Time point:
24/48/72 h
Score:
0
Max. score:
4
Irritant / corrosive response data:
Very slight erythema was observed in two animals at the 4-hour reading, which had disappeared at the 24 hour reading.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The substance is not irritating to the skin based on an in vivo study (OECD 404).
According to the EC Regulation No. 1272/2008 and subsequent regulations, the test item is not classified as skin irritant.