Dodecane-1-thiol

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1983-12-29 to 1984-01-31

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restriction because it was conducted according to GLP, and follows closely to OECD test number 412.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1985

Report date:

1985

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dodecane-1-thiol (CAS # 112-55-0)

IUPAC Name:

Dodecane-1-thiol (CAS # 112-55-0)

Details on test material:

- Name of test material (as cited in study report): dodecane-1-thiol

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. Portage, Michigan
- Age at study initiation: approximately 7 weeks
- Housing: individually caged in stainless steel, suspended wire-mesh cages.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 14 days


ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

other: Ihnalation: vapour (50% of the exposure concentration was in aerosol form at the high concentration)

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: At 7.3 ppm:
Equivalent aerodynamic diameter (µm): 2.1 (week 3) and 2.8 (week 5)
Geometric standard deviation (µm): 1.94 (week 3) and 1.66 (week 5)

Details on inhalation exposure:

Test animals were exposed in a specially constructed Plexiglas inhalation chamber having a capacity of 100 litres. The chamber was designed so that the animals could be introduced into the test atmosphere after the desired vapour concentration was established. Each animal was caged separately during exposure to minimize filtration of inspired air by animal fur.

The temperature of the test atmosphere was 25 deg Celsius and the pressure was 29.79 inches Hg. The average nominal concentration, calculated by dividing the generator weight loss by the total volume of air used during the test, was 5.7 mg/L air at 25 deg Celsius and 29.92 inches Hg. This was the highest attainable concentration with the experimental equipment employed.

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Temperature, humidity, pressure in air chamber: see table in methods section
- Air flow rate: approximately 2000 litres per minute
- Method of particle size determination: Andersen cascade impactor after approximately two and four weeks of exposure in group IV. The aerosol size was expressed in terms of equivalent aerodynamic diameter (EAD) and its geometric standard deviation (GSD). Particle sizes were approximately 2-3 mcm (EAD) an 1.5 to 2 GSD

TEST ATMOSPHERE
- Brief description of analytical method used: Nominal exposure concentrations were calculated on a daily basis by dividing the total weight of test material used during an exposure by the total air volume passed through the chamber during the exposure.

Air was supplied to the exposure chamber by an HVAC system separate from the general Laboratory systems. This air was filtered and the temperature and relative humidity were controlled. Chamber air flowrate (approximately 2000 litres per minute) was recorded once daily for the first 12 exposure days, rather than hourly as specified by the protocol. The airflow rates were recorded hourly for the remaining exposure days. Chamber environmental conditions (temperature and relative humidity) were recorded after 3 and 6 hours of exposure.

Test material atmospheres were generated with a counter-current vaporization system, and a syringe-drive or FMI lab pump delivered test material at a known, constant rate to the top of a glass column filled with a mixture of glass beads. Heated nitrogen was passed up the bead column counter-current to the liquid test material flow so that vaporization occurred within the bead column.

For exposure group IV where a significant amount of the test material was in the aerosol form, both particulate and vapour-phase analyses were performed. The particulate was collected by placing 25 mm glass fibre filters in-line before the sorbent tubes. The test material was eluted from the glass fibre filters with 2 ml hexane and analysed. Measured particle size was approximately 2-3 mcm EAD

The distribution of test material within the chamber was determined for each exposure group. Six points within the animal exposure zone were sampled in each chamber. The sampling apparatus allowed three of the six points and a reference point in the approximate centre of the chamber to be sampled simultaneously with empty cages in place. The results are shown in the other information on methods and material section. There was considerable variation in the distribution of test material in all three chambers. In particular, there appeared to be a concentration gradient between the upper and lower portion of the animal exposure zone, apparently as a result of the dog cages which had considerable solid surface area. Because of this non-homogenous chamber distribution, the position of all cages in each chamber was systematically rotated each exposure day to more nearly equalize the exposure of each animal to the test material.

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

6 hrs/d for 4 weeks

Frequency of treatment:

5 ds/wk

Doses / concentrations

Remarks:

Doses / Concentrations:
0.43 ppm (0.004 mg/L), 1.6 ppm (0.01 mg/L), 7.3 ppm (0.06 mg/L)
Basis:
analytical conc.

No. of animals per sex per dose:

10 per sex per dose

Control animals:

yes, concurrent no treatment

Examinations

Observations and examinations performed and frequency:

All animals were observed for mortality and overt signs of toxicity twice daily. Detailed physical examinations, body weights and food consumption were recorded weekly.

Sacrifice and pathology:

All animals received a complete post mortem examination under the direct supervision of a pathologist. All survivors and all animals sacrificed in extremis from each species were euthanized with sodium pentobarbital.

Other examinations:

Haematological and biochemical tests were conducted on all animals in each exposure group prior to and after exposure, following 16 hrs of fasting. Haematological measurements were determined on whole blood: total leukocye, eryehroeyte count, haemoglobin, haemocrit, differential leukocyte count, haematological indices, mean corpuscular volume (MCV), mean corpuscular haemoglobin (KCH), and mean corpuscular haemoglobin concentration (MCHC)

Biochemical measurements were determined on serum: alkaline phosphatise, aspartaee aminotransferase (AST),alanine aminotransferase (ALT), urea nitrogen, creatinine and glucose

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

CLINICAL SIGNS AND MORTALITY
Pharmacotoxic signs were evident in the rats at the week 1 observation. These signs included ungroomed appearance, squinting of the eyes, swollen ears, and discharge from the nose and mouth. At week 2 gasping, dyspnea, erythema of the ears, alopecia of the head area and high carriage were additional findings. At week 3 and 4 the areas of alopecia became more generalized and dry, cracked peeling of the skin was evident in a number of anatomical locations including the head, feet, legs, and anogenital areas.

BODY WEIGHT AND WEIGHT GAIN
The mean body weight of the Group IV male rats was significantly reduced below that of the controls at all weeks. The mean body weights of the female rats from Group IV tended to be similarly decreased at all four weeks, but the difference was not statistically significant.

FOOD CONSUMPTION
On an absolute basis the food consumption of the high-level exposure group was significantly decreased below the control levels at weeks 1 and 2, in both sexes. At weeks 3 and 4 there was no difference ie food consumption between the high exposure males and controls, while the food consumption of the high exposure females was increased above that of the controls (statistically significant only at week 3). On a relative-to-body weight basis (g/kg/day) the food consumption of both sexes (high exposure) was significantly decreased at week 1, no different at week 2 and significanty increased at weeks 3 anad 4. In mid-exposure males the absolute food consumption was significantly decreased at weeks 2 and 3, for females it was significantly decreased at week 3. On a relative basis, food consumption was significantly decreased at week 3 in both sexes in the mid-exposure group and significantly increased at week 4 in females only.
HAEMATOLOGY
Some significant changes in the levels of MCH in high exposure male rats were observed at 4 weeks, but these were not considered to exposure-related. In male rats statistically significant changes were detected in total leukocyte count, segmented neutrophil count (increased in high exposure group), haematocrit (decreased in high exposure group), and MCV (decreased in mid and high exposure groups). The decreased haematocrits and MCV values for high exposure group males were within the normal historical range (+/- 2 SD of the mean) for male rats of this age, however, the total leukocyte and segmented neutrophil counts were above the normal range. Since the haematocrit levels in high exposure group IV males were also significantly lower than those of the male control animals at 0 week, it seems unlikely that the decreases in hematocrit seen at four weeks were were related to exposure. There were no significant changes in female rats.

SERUM BIOCHEMISTRY

AST and ALT levels were significantly increase in both high exposure group males and females; the magnitude of increases were comparable between the sexes. The AST levels were above the normal range for both sexes, while the ALT levels were outside the normal range for females only. In addition, urea nitrogen levels were significantly increased in the high exposure males (within the normal range.)


ORGAN WEIGHTS
There were no test article related differences in mean organ weight between control and experimental groups. Observed significant changes in some relative organ weights were considered to be related to reduced weight gain.

GROSS PATHOLOGY
occasional regional lymph node enlargement was observed in association with the skin changes.

Effect levels

1

Dose descriptor:

LOAEC

Effect level:

0.06 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: = 60 mg/m3 or 7.3 ppm

2

Dose descriptor:

NOAEC

Effect level:

0.01 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: = 10 mg/m3 or 1.6 ppm

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Pharmacotoxic signs were evident in the rats at the week 1 observation. These signs included ungroomed appearance, squinting of the eyes, swollen ears, and discharge from the nose and mouth. At week 2 gasping, dyspnea, erythema of the ears, alopecia of the head area and high carriage were additional findings. At weeks 3 and 4 the areas of alopecia became more generalized and dry, cracked, peeling of the skin was evident in a number of anatomical locations including the head feet, legs, and anogenital regions.

Test article related microscopic acanthosis, hyperkeratosis and a generalised chronic active inflammation were present in the dermis and epidermis of all high exposure group male and female rats. A seconday regional lymphoid hyperplasia was present in a few rats of both sexes at different dosage levels. No test article related microscopic changes were observed in the respiratory system.

 

ON an absolute basis (g/animal/day) the food consumption of the exposure group IV rats was significantly decreased below control levels at weeks 1 and 2, in both sexes. At weeks 3 and 4 there was no difference in food consumption between the Group IV males and their controls, while the food consumption of group IV females was increased above that of the controls.

Pertinent microscopic changes

Sex	Males				Females
Group Number	I	II	III	IV	I	II	III	IV
Number Examined	10	10	10	10	10	10	10	10
SKIN
- Acanthosis	1			10				10
-Hyperkeratosis				10				10
Inflammation				8				9
LYMPH NODE
Lymphoid hyperplasia		1*		3				1

 

Pertinant macroscopic changes

Sex	Males				Females
Group Number	I	II	III	IV	I	II	III	IV
Number Examined	10	10	10	10	10	10	10	10
Skin -Hair thinned/ crust				10				10
Lymph Node -Enlarged		1		3				2

Group IV male rats had statistically significant changes in total leukocyte count, segmented neutrophil count, and hematocrit, while Groups III and IV saw decreased MCV. There were no significant changes in the female rats.

 

In the rats, AST and ALT levels were significantly increased in both males and females of Group IV. The magnitude of the increases in enzyme levels was comparable in both sexes. In addition, urea nitrogen levels were significantly increased in the Group IV males. The AST levels were above the normal range for both sexes of Group IV, however, the increased ALT levels were outside the normal range only for the females.

Applicant's summary and conclusion

Conclusions:

Toxicological signs were generally limited to skin and related effects in rats exposed to dodecane-1-thiol by whole body inhalation.

Executive summary:

In a short-term repeat dose inhalation toxicity study, dodecane-1-thiol was administered to 10 Sprague-Dawley rats/sex/concentration by whole body exposure at concentrations of 0, 0.5 ppm(0.004 mg/L), 2.0 (0.02 mg/L), or 7.0 (0.06 mg/L) (actual concentrations were: 0.43 ppm (0.004 mg/L), 1.6 ppm (0.01 mg/L), 7.3 ppm (0.06 mg/L)) for 6 hours per day, 5 days/week for a total of 20 days.

 

No deaths occurred in rats during the exposure period. Pharmacotoxic signs were evident in the rats at the week 1 observation. These signs included ungroomed appearance, squinting of the eyes, swollen ears, and discharge from the nose and mouth. At week 2 gasping, dyspnea, erythema of the ears, alopecia of the head area and high carriage were additional findings. At week 3 and 4 the areas of alopecia became more generalized and dry, cracked peeling of the skin was evident in a number of anatomical locations including the head, feet, legs, and anogenital areas. Skin effects were related to microscopic findings: acanthosis, hyperkeratosis and a generalized chronic active inflammation were present in the dermis and epidermis of all high exposure group male and female rats. A secondary regional lymphoid hyperplasia was present in a few rats of both sexes at different dosage levels. No test article related microscopic changes were observed in the respiratory system. The mean body weight of the Group IV male rats was significantly reduced below that of the controls at all weeks. The mean body weights of the female rats from Group IV tended to be similarly decreased at all four weeks, but the difference was not statistically significant. On an absolute basis the food consumption of the high-level exposure group was significantly decreased below the control levels at weeks 1 and 2, in both sexes. The LOAEC was 7.3 ppm (0.06 mg/l), based on the above findings. The NOAEC was 1.6 ppm (0.01 mg/L).

 

This study received a Klimisch score of 1 and is classified as reliable without restriction because it was conducted according to GLP, and follows closely to OECD test number 412.