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Administrative data

Description of key information

Tert-dodecanethiol is skin irritating but not irritating for the eyes and for respiratory tract.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin irritation: in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The study was performed before the publication of OECD Test guideline for in vitro studies.
Qualifier:
according to guideline
Guideline:
OECD Guideline 404 (Acute Dermal Irritation / Corrosion)
Deviations:
yes
Remarks:
temperature and humidity sometimes outside of the target ranges; animals were more than 2 to 4 months old; body weight of animal No. 194 was higher than 3.5 kg (3.6 kg); animals were sacrificed several days after the end of the observation period
Qualifier:
according to guideline
Guideline:
EU Method B.4 (Acute Toxicity: Dermal Irritation / Corrosion)
Deviations:
yes
Remarks:
idem above
GLP compliance:
yes (incl. QA statement)
Species:
rabbit
Strain:
New Zealand White
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Breeder: Charles River Laboratories (Châtillon-sur-Chalaronne, France)
- Age at study initiation: 2 to 5 months old
- Weight at study initiation: 3.387 +/- 0.218 kg
- Housing: individual Pajon cages
- Diet (e.g. ad libitum): free access to 110 pelleted diet
- Water (e.g. ad libitum): drinking water filtered by a FG Millipore membrane, provided ad libitum
- Acclimation period: at least 5 days before the beginning of the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 +/- 3°C
- Humidity (%): 30 to 70%
- Air changes (per hr): 12 cycles/hour of filtered, non-recycled air
- Photoperiod (hrs dark / hrs light): 12 h/ 12 h (7:00 - 19:00)

IN-LIFE DATES: From: 23 December 2009 To: 02 February 2010
Type of coverage:
semiocclusive
Preparation of test site:
other: clipped
Vehicle:
unchanged (no vehicle)
Controls:
not required
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied: 0.5 mL
Duration of treatment / exposure:
3 minutes, 1 hour, 4 hours.
Observation period:
1 hour, 24, 48 and 72 hours after removal of the dressing, and then daily until the end of the observation period.
Number of animals:
Three males
Details on study design:
TEST SITE
- Area of exposure: anterior left flank: application for 3 minutes; anterior right flank: application for 1 hour; or the posterior right flank:
application for 4 hours of the animals.
- coverage: 6 cm2
- Type of wrap if used: gauze pad was held in contact with the skin by means of an adhesive hypoallergenic aerated semi-occlusive dressing and a restraining bandage.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): dry cotton pad
- Time after start of exposure: at removal of each dressing.

SCORING SYSTEM:
Dermal irritation was evaluated for each animal according to the following scoring scale:

Erythema and eschar formation:
no erythema 0
very slight erythema (barely perceptible) 1
well-defined erythema 2
moderate to severe erythema 3
severe erythema (beet redness) to slight eschar formation (injuries in depth) 4

Edema formation
no edema 0
very slight edema (barely perceptible) 1
slight edema (edges of area well-defined by definite raising) 2
moderate edema (raised approximately 1 millimeter) 3
severe edema (raised more than 1 millimeter and extending beyond area
of exposure) 4

Any other lesions were noted.
Irritation parameter:
erythema score
Basis:
animal #1
Time point:
24/48/72 h
Score:
3
Max. score:
3
Reversibility:
not reversible
Irritation parameter:
erythema score
Basis:
animal #2
Time point:
24/48/72 h
Score:
3
Max. score:
3
Reversibility:
not reversible
Irritation parameter:
erythema score
Basis:
animal #3
Time point:
24/48/72 h
Score:
3
Max. score:
3
Reversibility:
not reversible
Irritation parameter:
edema score
Basis:
animal #1
Time point:
24/48/72 h
Score:
0
Max. score:
0
Irritation parameter:
edema score
Basis:
animal #2
Time point:
24/48/72 h
Score:
0
Max. score:
0
Irritation parameter:
edema score
Basis:
animal #3
Time point:
24/48/72 h
Score:
0
Max. score:
0
Irritant / corrosive response data:
After a 3-minute exposure (animal No. 194)
A very slight to moderate erythema (grades 1 to 3) was observed from day 1 until day 11.
Dryness of the skin was noted from day 6 until day 15.

After a 1-hour exposure (animal No. 194)
A very slight or well-defined erythema (grade 1 or 2) was observed from day 1 until day 11.
Dryness of the skin was noted from day 7 until day 14.

After a 4-hour exposure (three animals)
A well-defined or moderate erythema (grade 2 or 3) was noted all over the observation period in 2/3 animals (Nos. 194 and 199), associated with a very slight edema (grade 1) on days 6 and 7 in one of them (No. 194).
In the third animal (No. 198), very slight to moderate erythema (grades 1 to 3) was noted all over the observation period, except on days 8 and 9 for which an important dryness of the skin masked the evaluation of erythema.
Dryness of the skin was recorded from day 5 or 7 until day 13 or 15 in all animals.
Mean scores over 24, 48 and 72 hours for each animal were 3.0, 3.0 and 3.0 for erythema and 0.0, 0.0 and 0.0 for edema.
Interpretation of results:
Category 2 (irritant) based on GHS criteria
Conclusions:
Tert-Dodecylmercaptan was irritating when applied topically to rabbits.
Executive summary:

In a study performed according to OECD guideline #404 and GLP, t-Dodecyl mercaptan was first applied for periods of 3 minutes, 1 hour and 4 hours to a single male New Zealand White rabbit. Since the test item was neither severely irritant nor corrosive on this first animal, it was then applied sequentially for 4 hours to two other animals. A single dose of 0.5 mL of the undiluted test item was applied to the closely-clipped skin of one flank. The test item was held in contact with the skin by means of a semi-occlusive dressing. Cutaneous reactions were observed approximately 1 hour, 24, 48 and 72 hours after removal of the dressing, and then daily until the end of the observation period. The mean values of the scores for erythema and edema were calculated for each animal.

After a 3-minute exposure (one animal), a very slight to moderate erythema was observed from day 1 until day 11. Dryness of the skin was noted from day 6 until day 15. After a 1-hour exposure (one animal), a very slight or well-defined erythema was observed from day 1 until day 11. Dryness of the skin was noted from day 7 until day 14. After a 4-hour exposure (three animals), a well-defined or moderate erythema was noted all over the observation period in 2/3 animals, associated with a very slight edema on days 6 and 7 in one of them. In the third animal, very slight to moderate erythema was noted all over the observation period, excepted on days 8 and 9 for which an important dryness of the skin masked the evaluation of erythema. Dryness of the skin was recorded from day 5 or 7 until day 13 or 15 in all animals. Mean scores over 24, 48 and 72 hours for each animal were 3.0, 3.0 and 3.0 for erythema and 0.0, 0.0 and 0.0 for edema. Under these experimental conditions, tert-dodecylmercaptan was irritating when applied topically to rabbits.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Eye irritation

Link to relevant study records
Reference
Endpoint:
eye irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants)
Version / remarks:
7 September 2009
Deviations:
no
Guideline:
OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)
Version / remarks:
26 July 2013
Results were interpreted according to this updated guideline to determine GHS/CLP classification.
GLP compliance:
yes
Species:
other: bovine cornea
Details on test animals or tissues and environmental conditions:
The bovine eyes, supplied by Joseph Morris Abattoir, were excised by an abattoir employee and collected as soon after slaughter as possible (excised at 13.00 hours, 15 June 2010). Instructions were given to avoid damaging the corneas during excision. Excised eyes were maintained and transported to the laboratory, at ambient temperature, in sufficient HBSS, containing 1% (v/v) penicillin/streptomycin solution, to cover all the eyes in the receptacle. The eyes were used within 4 hours of slaughter (incubation of mounted corneas commenced at 15.22 hours, 15 June 2010.)
Vehicle:
unchanged (no vehicle)
Controls:
other: positive and negative substances
Amount / concentration applied:
750µl
Duration of treatment / exposure:
10 min
Observation period (in vivo):
2 h
Details on study design:
METHOD

Preparation of corneas:
All eyes were carefully examined, macroscopically, for defects (opacity, scratches, pigmentation, cuts, etc.) and those exhibiting defects were discarded. The tissue surrounding the eyeball was carefully pulled away and the cornea dissected leaving approximately 2 to 3 mm of sclera present around the cornea. The isolated corneas were stored in a petri dish containing HBSS plus 1% penicillin/streptomycin solution until all the corneas had been
dissected. Once all the corneas had been dissected, they were rinsed in fresh HBSS plus 1% penicillin/streptomycin solution prior to mounting. The corneas were mounted in the cornea holders with the endothelial side against the O-ring of the posterior half of the holder. Each cornea was gently flattened over the O-ring and holder surface with a wetted, gloved finger to expel any air. The anterior half of the holder was then positioned on top of the cornea and secured with screws. Both compartments of the holder were filled with cMEM, using a syringe. The posterior compartment was always filled first to return the cornea to its natural shape. Care was taken to ensure no air bubbles were present within the holders. The holders were then plugged and incubated, in an upright position, for 60 minutes ± 5 minutes at 32°C ± 1°C in a waterbath. The waterbath temperature remained within the limits of 32°C ± 1°C throughout the experiment. At the end of the 60 minute incubation period, the medium was removed from both the anterior and posterior compartments using a pipette tip attached to a vacuum pump. The compartments were refilled with fresh cMEM. Again care was taken to ensure no air bubbles were present within the holders. The posterior compartment was then plugged and the basal opacity measurements performed.

Opacity measurement:
The opacitometer measured the light transmission through the centre of each mounted cornea, displaying a numerical opacity value (arbitrary unit). The opacity of each cornea was measured by reading each holder in the right-hand chamber of the calibrated opacitometer. Once the basal opacity of all the corneas had been measured, the mean basal opacity value was calculated. Corneas with an opacity value greater than 7 units were discarded. The mean basal opacity value of the corneas was then calculated and three corneas with opacity values close to the mean value were chosen for use as negative control corneas.

Test substance pH:
An estimate of the pH of the test substance was determined using pH test sticks and recorded.

Treatment groups:
Corneas were treated in triplicate with either the test substance, positive control (ethanol) or negative control (0.9% sodium chloride solution).
The controls and their results were shared with several studies performed in the same assay.

Treatment of corneas:
The test substance, Tertiododecylmercaptan, a colourless liquid, and the positive control (ethanol) were tested undiluted. Immediately prior to treatment, the medium was removed from the anterior compartment of the holder using a pipette tip attached to a vacuum pump, taking extra care to ensure all excess liquid had been removed. Seven hundred and fifty µl (750 µl) of test substance, positive control or negative control was introduced into the anterior part of each holder. Following application, the anterior compartment was plugged and the holder turned to a horizontal position and slightly rotated to ensure uniform distribution of the test substance over the surface of the cornea. The test material or controls were in contact with the cornea for a total of 10 minutes (± 30 seconds). Each holder was incubated in a horizontal position at 32°C ± 1°C in a waterbath.
Following incubation, the test substance, positive and negative controls were removed and the epithelial surface of the cornea washed, at least three times or until the wash medium (MEM with phenol red) was clear and there was no discolouration. The wash medium was added via the holes on the top of the holder. After each wash, the wash medium was removed using a pipette tip attached to a vacuum pump. The test material, Tertiododecylmercaptan, required three washes.
The anterior compartment was then filled with cMEM taking care to ensure no air bubbles were present in the compartment. Once all the air bubbles had been removed, the anterior compartment was re-plugged and the holders returned to the waterbath and incubated, in an upright position, for two hours ± 10 minutes at 32°C ± 1°C.
Following completion of the two hour incubation period, the medium was removed from both compartments and replaced with fresh cMEM. The posterior compartment was re-plugged and the opacity of each cornea measured and recorded. The opacity values obtained at this stage were used in calculating the final In Vitro Irritancy Score.
Throughout the assay the corneas were examined for opaque spots or other irregularities.

Permeability determination:
The sodium fluorescein stock solution (4 mg/ml) was thawed prior to commencing the permeability incubation. Following the final opacity measurement, the medium was removed from the anterior compartment of the holder. One ml (1ml) of the sodium fluorescein solution was added to the anterior compartment using a micropipette. Following addition of the sodium fluorescein solution to the anterior side of the holder, the compartment was plugged and the corneas incubated in a horizontal position at 32°C ± 1°C for 90 ± 5 minutes in a waterbath.
Following incubation, the medium in the posterior compartment was mixed by drawing approximately 2.5 ml gently up and down a 5 ml syringe, with a needle attached, three times. An aliquot of the mixed medium from the posterior compartment was removed and transferred to a 1 cm path length cuvette. A spectrophotometer was adjusted to read at 490nm (OD490) and a sample of cMEM read (OD = 0.061). The spectrophotometer was blanked using this solution prior to reading the permeability samples. Any solution giving an OD490 value above 1.8 was diluted 1 in 5 with cMEM.

Criteria for determination of a valid test:
The positive control should elicit an In Vitro Irritancy Score that falls within two standard deviations of the historical mean for the laboratory. The negative control mean opacity change value should be 2.0 and the permeability mean value 0.1.

ASSESSMENT OF RESULTS

Opacity:
The change in the opacity of each cornea was calculated by subtracting the initial basal opacity from the post-treatment opacity measurement. The mean change in opacity for the negative control corneas was calculated and was subtracted from the change in opacity of each treated cornea to obtain the corrected opacity value. The mean corrected opacity change value of each treatment group (of three corneas) was calculated from the individual corrected opacity values of the treated corneas.

Permeability (OD490):
The corrected permeability value (OD490) of each treated cornea was calculated by subtracting the mean negative control cornea value from the permeability value of each cornea. The mean corrected permeability value of each treatment group was calculated from the individual corrected permeability values of the treated corneas.

In Vitro Irritancy score calculation:
The In Vitro Irritancy Score (IVIS) was calculated using the following formula:
In Vitro Irritancy Score = Corrected Opacity Value + (15 x Corrected OD490 Value)
The IVIS was calculated for each individual treatment and positive control cornea. The mean IVIS value for each treatment group was calculated from the IVIS of each individual cornea in the treatment group.

Irritation parameter:
in vitro irritation score
Value:
-0.5
Vehicle controls validity:
not examined
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Irritation parameter:
cornea opacity score
Value:
-0.333
Vehicle controls validity:
not examined
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Irritation parameter:
fluorescein leakage
Value:
-0.013
Vehicle controls validity:
not examined
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation

pH determination:

The pH of the test substance, measured using pH sticks, was approximately 7.0.

BCOP results:

Throughout the assay the corneas were examined for opaque spots or other irregularities. Following treatment with the test substance, Tertiododecylmercaptan, the corneas were noted as clear. The corneas treated with the positive control, ethanol, were opaque and the corneas treated with the negative control, 0.9% saline, were clear. The results of the BCOP assay are summarised in the enclosed table.

Interpretation of results:
GHS criteria not met
Remarks:
Not eye irritating
Conclusions:
Tertiododecylmercaptan, elicited an In Vitro Irritancy Score of -0.5 ± 0.6 and was predicted to be a non eye irritant.
Executive summary:

The potential ocular irritancy of t-dodecyl mercaptan was assessed in vitro in the Bovine Corneal Opacity and Permeability Assay (BCOP) performed following OECD guideline #437 and GLP. Ethanol was tested in parallel as a positive control. The assay uses isolated bovine corneas as a means of assessing the ocular corrosivity or severe irritancy potential of test substances in vitro. The isolated corneas were obtained as a by-product of the meat production industry. Two endpoints, corneal opacity and permeability, were measured and combined to give an In Vitro Irritancy Score which can be used to classify and rank test substances as potential eye irritants.Tertiododecylmercaptan, elicited an In Vitro Irritancy Score of -0.5 ± 0.6 and was predicted to be a non eye irritant.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Additional information

Skin irritation


In a study performed according to OECD guideline #404 and GLP, tert-dodecanethiol was first applied for periods of 3 minutes, 1 hour and 4 hours to a single male New Zealand White rabbit (CIT 2010). Since the test item was neither severely irritant nor corrosive on this first animal, it was then applied sequentially for 4 hours to two other animals. A single dose of 0.5 mL of the undiluted test item was applied to the closely-clipped skin of one flank. The test item was held in contact with the skin by means of a semi-occlusive dressing. Cutaneous reactions were observed approximately 1 hour, 24, 48 and 72 hours after removal of the dressing, and then daily until the end of the observation period. The mean values of the scores for erythema and edema were calculated for each animal. After a 3-minute exposure (one animal), a very slight to moderate erythema was observed from day 1 until day 11. Dryness of the skin was noted from day 6 until day 15. After a 1-hour exposure (one animal), a very slight or well-defined erythema was observed from day 1 until day 11. Dryness of the skin was noted from day 7 until day 14. After a 4-hour exposure (three animals), a well-defined or moderate erythema was noted all over the observation period in 2/3 animals, associated with a very slight edema on days 6 and 7 in one of them. In the third animal, very slight to moderate erythema was noted all over the observation period, excepted on days 8 and 9 for which an important dryness of the skin masked the evaluation of erythema. Dryness of the skin was recorded from day 5 or 7 until day 13 or 15 in all animals. Mean scores over 24, 48 and 72 hours for each animal were 3.0, 3.0 and 3.0 for erythema and 0.0, 0.0 and 0.0 for edema. Under these experimental conditions, tert-dodecanethiol was irritating when applied topically to rabbits.


 


Eye irritation



  • in vitro study


The potential ocular irritancy of tert-dodecanethiol was assessed in vitro in the Bovine Corneal Opacity and Permeability Assay (BCOP) performed following OECD guideline #437 and GLP (HLS 2010). Ethanol was tested in parallel as a positive control. The assay uses isolated bovine corneas as a means of assessing the ocular corrosivity or severe irritancy potential of test substances in vitro. The isolated corneas were obtained as a by-product of the meat production industry. Two endpoints, corneal opacity and permeability, were measured and combined to give an In Vitro Irritancy Score which can be used to classify and rank test substances as potential eye irritants. Tert-dodecanethiol, elicited an In Vitro Irritancy Score of -0.5 ± 0.6 and was predicted to be a non eye irritant. 


 



  • in vivo study


An old rabbit study is available on tert-dodecanethiol but this study cannot allow to conclude on eye irritation based on CLP criteria and the laboratory where the study was performed is found to use fraudulent practices in some of their studies and reports (it is not possible to verify the scientific credibility of the study). 


Undiluted tertiary dodecyl mercaptan was instilled into the right eye of five albino rabbits, New Zealand strain, at a volume 0.1 ml and observations for ocular irritancy were conducted according to the method of Draize. 


Slight eye irritation of tert-dodecanethiol was observed in rabbits. No effect on cornea and iris scores were observed in the 5 treated rabbits. However, some effects on conjunctivae were observed (scores ≠ 0) but the "conjunctivae" score corresponding to “global” conjunctivae score including redness score, chemosis score and discharge score which are multiplied by 2. The separate values of each redness, chemosis or discharge are not available in the report. 


For each animal, the following global conjunctivae were obtained (mean 24-48-72h): 2.66, 2.66, 4, 2.66, 2.66. When these values were divided by 2, the following values were obtained : 1.33, 1.33, 2, 1.33, 1.33. Considering the CLP criteria, tert-dodecanethiol is not considered as eye irritating.


Indeed, according to the CLP criteria, a substance is considered as eye irritating (category 2) if at least 3 out of 5 rabbits show a mean score per animal of: ≥ 1 for corneal opacity and/or ≥ 1 for iritis and/or ≥ 2 conjunctival erythema (redness) and/or ≥ 2 conjunctival oedema (swelling, chemosis).


 


Respiratory tract irritation


The available data (TNO 2017) did not show any significant signs of respiratory tract irritation during a 90-day inhalation exposure.

Justification for classification or non-classification

According to the available data and CLP criteria, tert-dodecanethiol acid should be classified as skin irritant (category 2, H315).