Skin and Ocular Testing
Short Time Exposure (STE)
Test Method for Serious Eye Damage
Background Information
• The Short Time Exposure (STE) test method
is an in vitro method used for regulatory
hazard classification and labelling of
chemicals that induce serious eye damage
or irritation.
‘While the STE test method
is not considered to be a
complete replacement for the in
vivo rabbit eye test, it is suitable
for use as part of a tiered
testing strategy for regulatory
classification and labeling.’
Draft Guideline for the Testing
of Chemicals: The Short Time
Exposure In Vitro Test Method
for Identifying i) Chemicals
Inducing Serious Eye Damage
and ii) Chemicals Not Requiring
Classification for Eye Irritation
or Serious Eye Damage.
Organisation for Economic
Cooperation and Development
(OECD), 18th June 2014
1
• The STE method can be used as an
initial step in a top-down approach to
identify substances inducing serious
eye damage (i.e., UN GHS Category 1
without further testing), or as part of a
tiered testing strategy to identify chemicals
(substances and mixtures) that do not
require classification for eye irritation or
serious eye damage (i.e., UN GHS No
Category). In the latter situation, additional
testing is required to establish a definitive
classification.
• The STE method was developed as in vitro
(non-animal) alternative to the animal-based
rabbit eye test. Although not considered a
complete replacement, it is suitable as part
of a tiered screening strategy for regulatory
classification and labelling.
• The STE test model has undergone
validation by JSAAE (Japanese Society
for Alternatives to Animal Experiments)
and JaCVAM (Japanese Center for the
Validation of Alternative Methods) with a
peer review of the studies conducted by
NICEATM/ICCVAM. These studies indicate
the STE method has an accuracy of 85%
when compared with the in vivo rabbit eye
test.
•The in vitro STE method evaluates the
cytotoxicity of chemicals on corneal
epithelial cells using the MTT assay.
To find out more contact enquiries@cyprotex.com
Protocol
Method
Short Time Exposure Test Method
Model Used
Staten Seruminsitut Rabbit Cornea (SIRC) cell
line
Concentrations
5% and 0.05%
Number of Replicates
3
Exposure Times
5 min at room temperature
Controls
Positive control = 0.01% Sodium Lauryl Sulfate
(SLS) in saline
Negative control = SIRC cell culture media
Vehicle controls = Saline, saline containing 5%
DMSO and mineral oil
Endpoint
MTT
The in vitro STE method evaluates cytotoxicity of chemicals on corneal epithelial cells.
Viability
at 5%
at 0.05%
UN GHS
Classification
>70%
>70%
No Category
≤70%
>70%
Unable to Classify
≤70%
≤70%
Category 1
Table 1
Classification of Chemicals in the Short Time Exposure Assay.
Table 2
Viability of the STE Proficiency Chemicals
(Mean ± Standard Deviation; n=3 individual
assays) with the Resulting UN GHS
Categorisation.
Chemical
Cyprotex assessed the proficiency chemicals recommended in the draft OECD
test guideline, and correctly categorised ten out of ten of the proficiency chemicals
according to the expected classification listed in the draft guidance.
Mean Viability ± Standard Deviation
UN GHS
Categorisation
5%
0.05%
Benzalkonium
chloride
23.1 ± 2.6
21.5 ± 2.4
Category 1
Sodium Lauryl
Sulfate
17.8 ± 3.1
24.0 ± 2.9
Category 1
1-Octanol
18.8 ± 1.4
103.9 ± 2.3
Unable to Classify
Butyrolactone
52.2 ± 9.7
118.2 ± 1.9
Unable to Classify
Cyclopentanol
24.3 ± 5.1
118.2 ± 1.0
Unable to Classify
2-Ethoxyethyl
acetate
103.1 ± 12.6
122.2 ± 6.5
No Category
Dodecane
104.3 ± 6.2
109.1 ± 7.3
No Category
Glycerol
97.7 ± 7.5
123.5 ± 7.3
No Category
111.9 ± 13.5
116.2 ± 7.8
No Category
96.3 ± 5.9
118.7 ± 9.1
No Category
Methyl isobutyl
ketone
n,n-Dimethylguanidine
sulfate
References
1
Draft Guideline for the Testing of Chemicals: The Short Time Exposure In Vitro Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye
Irritation or Serious Eye Damage. Organisation for Economic Cooperation and Development (OECD) 18th June 2014