tert-butylchlorodimethylsilane

Endpoint summary

Description of key information

The key combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP with the registered substance tert-butyl(chloro)dimethylsilane, concluded a NOAEL for systemic toxicity of ≥90 mg/kg bw/day (the highest dose tested) based on no adverse systemic effects and a LOAEL for local effects in the stomach of 10 mg/kg bw/day (the lowest dose tested). The high dose was limited to 90 mg/kg bw/day based on severe local effects observed in a 14-day range finding study at doses of 100 mg/kg bw/day and above (BSL Bioservice / Eurofins, 2020).

For the inhalation route a 28-day inhalation study with another chlorosilane, dichloro(dimethyl)silane (CAS 75-78-5, WIL, 2014) is used to demonstrate that local effects are dominated by generation of the hydrolysis product, HCl, and that there are no adverse systemic effects.

In a well conducted 90-day gas inhalation study (Toxigenics, 1984) the systemic NOAEC for hydrogen chloride was 20 ppm based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice, which was observed with a LOAEC of 10 ppm.

A good quality 90-day repeated inhalation study for hydrogen chloride has been used to assess the local effects of tert-butyl(chloro)dimethylsilane. In a 90-day repeated inhalation study with HCl, no serious adverse systemic effects were observed in rats and mice exposed up to 50 ppm (approximately 70 mg/m3) for 6 hours per day, 5 days per week. The only significant adverse finding relating to systemic toxicity was decreased body weight at the highest dose level. Local effects on the nasal turbinates of mice were observed at all dose levels tested (10, 20 and 50 ppm). Testing with HCl at higher test concentrations is neither ethically nor technically feasible since severe corrosive effects would lead to discomfort and distress in the test animals. The author of this CSR considers that the apparent systemic effects at 50 ppm in the study were most likely secondary to local corrosive effects at this dose level.

Following uptake of HCl, hydrogen and chloride ions from will enter the body’s natural homeostatic processes and significant systemic effects are unlikely.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18th of April 2019 to 28th of January 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Version / remarks:

Adopted 29th July 2016

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Health Effects guidelines, OPPTS 870/3650

Version / remarks:

Combined repeated dose toxicity study with the reproduction / developmental toxicity screening test. EPA 712-C-00-368, July 2000

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Crl: WI(Han) (Full barrier), derived from a controlled full-barrier maintained breeding system.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Females nulliparous and non-pregnant: yes
- Age at study initiation: approximately 14-15 weeks old
- Weight at study initiation:
males: 318 – 376 g (mean: 348.5 g, ± 20% = 278.8 – 418.2 g)
females: 221 – 258 g (mean: 238.4 g, ± 20% = 190.7 – 286.0 g)
- Fasting period before study: not specified
- Housing: Type IV polysulphone cages or in double decker IVC cages during the premating period for both males and females as well as during the post-mating period for males depending on the mating status. During the mating period, males and females were housed together in ratio 1:1 (male to female). After the confirmation of mating, females were kept individually during gestation/lactation period in type III H, polysulphone cages and males were returned to their original cage. In each cage Altromin saw fibre was used as bedding.
- Diet: Altromin 1324 maintenance diet for rats, ad libitum.
- Water: tap water, sulphur acidified to a pH of approximately 2.8, ad libitum.
- Acclimation period: at least 5 days.

DETAILS OF FOOD AND WATER QUALITY: Certificates of food, water and bedding are filed for two years at BSL Munich and afterwards archived at Eurofins Munich.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 55 ± 10 %
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours dark

IN-LIFE DATES: not specified

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: The test item was dissolved in dried and de-acidified corn oil and thereafter, administered daily.

VEHICLE
- Justification for use and choice of vehicle: The vehicle was selected in consultation with the sponsor based on the test item's characteristics.
- Concentration in vehicle: 0; 2.5; 7.5; 22.5 mg/mL.
- Amount of vehicle: 4 mL/kg bw/day
- Lot/batch no.: MKCG3257 and MKCH1635
- Purity: not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration analysis of formulation samples was performed on the three concentrations, 2.5 mg/mL, 7.5 mg/mL and 22.5 mg/mL in study weeks 1, 4, 7 and in the last week of the study. The mean recoveries observed in the low, medium and high dose groups were 98.0%, 98.6%, and 97.7% of the nominal concentration, respectively.
Nominal concentrations were confirmed for all dose groups, as measured concentrations were within the acceptable criterion of 10%.

However, two samples (one sample from the low dose week 7 and one sample from the middle dose week 7) did not meet this criterion with a recovery of 76.1% and 83.3%, respectively. The low recoveries found in those samples were considered due to technical error in the preparation of formulation samples. Thus, both mentioned samples were excluded from the evaluation of concentration verification.

Duration of treatment / exposure:

In total, maximum of 63 days. The females were exposed during 14 days pre-mating period, up to 14 days mating period and approximately 22 days of gestation and up to post-natal day 12. The males were treated during pre-mating and mating period, up to 29-30 days of treatment. Non-pregnant females were treated for 26 days.

Frequency of treatment:

Daily administration, 7 days per week

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

control

Dose / conc.:

10 mg/kg bw/day (nominal)

Remarks:

Low dose, LD

Dose / conc.:

30 mg/kg bw/day (nominal)

Remarks:

Middle dose, MD

Dose / conc.:

90 mg/kg bw/day (nominal)

Remarks:

High dose, HD

No. of animals per sex per dose:

10 males and 10 females per group.

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The doses were based on a previous dose range finding study and in consultation with the sponsor. In the dose range-finding study inflammatory and degenerative lesions (e.g. erosion, ulceration) of the stomach were noted in male and female animals treated with 100 mg/kg bw/day and higher. Although the highest dose of 90 mg/kg bw/day may not induce toxic effects, higher doses were not considered due to animal welfare reasons. A descending sequence of dose levels were selected to demonstrate any dose-related response and to determine a NOAEL.
- Rationale for animal assignment: random
- Fasting period before blood sampling for clinical biochemistry: not reported
- Rationale for selecting satellite groups: no satellite groups were included
- Post-exposure recovery period in satellite groups: no
- Section schedule rationale: random
- Other: n/a

Positive control:

No

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: General clinical observations were made at least once per day, preferably at the same time each day. The health condition of the animals was recorded. Twice daily, all animals were observed for morbidity and mortality except on weekends and public holidays when observations were made once daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once before the first exposure and thereafter, at least once a week. Clinical observations included spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size. Changes in gait, posture, response to handling as well as the presence of clonic or tonic movements, stereotypes, difficult or prolonged parturition or bizarre behaviour were recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: once before the assignment to the experimental groups, on the first day of dosing and weekly thereafter as well as at the end of the study. During pregnancy, females were weighed on gestation days 0, 7, 14 and 20 and within 24 hours of parturition (day 0 post-partum) as well as on PND 4, PND 9 and PND 13 along with pups. In total, 2 animals from the control group; 4 animals from the low dose group and 2 animals from the middle dose group were weighed on GD 21 instead of GD 20.
All animals were weighed directly before termination. Any animals prematurely sacrificed were weighed prior to the sacrifice.

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
Food consumption was measured on the corresponding days of the body weight measurements after the beginning of the dose administration. Food consumption was not measured during the mating period in males/females or during the post-mating period in males.

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: ophthalmoscopy examination (anterior chamber of the eye and fundus of eye) was included in the functional observations that occurred in the week before the first treatment, during the last week of the treatment and during the last week of the lactation period.
- Dose groups that were examined: 5 randomly selected males and 5 randomly selected females (only lactating) of each group outside their home cage.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the treatment, prior to or as part of the sacrifice of the animals.
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Not specified
- How many animals: 5 randomly selected males and females (only lactating) from each dose group.
- Parameters checked in table were examined: yes, see table 1.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the treatment prior to or as part of the sacrifice of the animals.
- Animals fasted: not specified
- How many animals: 5 randomly selected males and females (only lactating females) of each group
- Parameters checked in table were examined: yes, see table 1

URINALYSIS: Yes
- Time schedule for collection of urine: prior to or as part of the sacrifice of the animals.
- Metabolism cages used for collection of urine: Not specified
- Animals fasted: Not specified
- Parameters checked in table were examined: yes, see table 1.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: in the week before the first treatment and during the last week of the treatment
- Dose groups that were examined: All animals were examined during the week before the first treatment; 5 randomly selected males and females (only lactating females) of each group were examined during the last week of treatment.
- Battery of functions tested: Sensory reactivity to different modalities, grip strength and motor activity assessments and other behavioural observations as well as rearing supported and not supported, urination, defecation, startle/ auditory response, equilibrium reflex, positional passivity, visual placing, fore and hind limb grip strength, tail pinch response, toe pinch reflex, extensor thrust/limb tone, hind limb reflex, righting reflex on the ground, air righting reflex, pupil response, body temperature and ophthalmoscopy (anterior chamber of the eye and fundus of eye).

IMMUNOLOGY: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes, see Table 2

HISTOPATHOLOGY: Yes, see Table 2

Statistics:

A statistical assessment of the results of body weight, food consumption and litter data was performed for each gender by comparing values of dosed with control animals using an one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, parameters of haematology, blood coagulation and clinical biochemistry were statistically analysed by comparing values of dosed with control animals using either a parametric one-way ANOVA and a post-hoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test, based on the results of homogeneity and normality tests. These statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.3.4 software (p<0.05 was considered as statistically significant).

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

A female animal from the control group which was euthanized in moribund condition had previously shown the clinical findings of apathy, reduced spontaneous activity, abnormal breathing dehydration, piloerection, half eyelid closure, lacrimation, exophthalmos and chromodacryorrhea on the day of sacrifice.
Other observed clinical signs in treatment animals included moving the bedding and increased salivation, however, this appeared directly after the administration and thus, considered to be a sign of discomfort or a local reaction of the test item and not adverse systemic effects.
Furthermore, piloerection, crust, hairless area and diarrhoea occurred in single animals without any dose dependency and therefore, not considered as test substance related.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

One female in the control group was euthanized in moribund condition. In the histopathological examination, necrotizing inflammation along with foreign materials containing feed composition in the lesions was observed in the tissues around the intrathoracic organs and tissues. Such inflammatory lesions were noted in the thymus and lungs (recorded as pleuritis), and observed in the subcutis at the neck region, as well. From these findings, the cause of animal’s morbidity was considered to be technical error that happened during the oral gavaging procedure.
All remaining animals survived the scheduled study period.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Treatment with the test item showed no statistically significant or toxicologically relevant effects on body weights or body weight development of male and female animals. Body weight development was comparable between test item-treated groups and their respective control group throughout the treatment period. Slight changes were not considered to be of toxicological relevance.
There were no statistically significant differences in final body weights in both sexes.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

No considerable and statistically significant difference in food consumption of male and female animals between the dose groups and the control group were observed. Slight differences between the test item-treated animals and corresponding controls were only temporary and without a clear dose-dependent trend and thus were not assumed toxicologically relevant.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No toxicologically relevant effect was observed.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The mean percentage of reticulocytes was slightly lower in males compared to control groups, however, due to a lack of dose dependency and without statistical significance, the finding was not considered test substance related. Moreover, the percentage of eosinophils was higher in males in all dose groups with a statistical significance in the low dose group compared to the control group. Furthermore, higher mean percentage of basophils and higher mean percentage of large unstained cells were observed in males in the middle dose group compared to the control group. In both cases, the elevated values were mainly based on the results of one single animal and therefore, not considered to be toxicologically relevant.
The mean percentage of monocytes in females was higher in all dose groups compared to female controls. Middle dose group females had a statistically significantly lower percentage of lymphocytes and a statistically significant higher percentage of neutrophils compared to the females in the control group. In the low dose group females, the mean percentage of basophils was higher in females compared to the control group. In the middle and high dose group females, the mean percentage of large unstained cells was lower compared to the females control group. Due to the lack of dose-dependency or gender consistency, these finding were not considered as toxicologically relevant.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

Lower serum TBA levels were observed in the males in all dose groups whereas slightly higher serum ALAT levels were found in the high group when compared to the control group. Nevertheless, no statistical significance or dose dependency were observed and therefore, these differences were assumed to be not test substance-related.
Statistically higher urea levels in females were observed in the low dose group compared to the control females. In addition, lower serum AP levels were observed in females in all the test substance treated groups. None of these findings were considered to be toxicologically relevant, due to gender inconsistency or dose-dependency.

Urinalysis findings:

effects observed, non-treatment-related

Description (incidence and severity):

Findings of nitrite in the urine and glucose were considered as incidental and not test substance related.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Statistically significant lower body temperature in high dose group males was observed compared to that of the control group males before the treatment. However, lower temperature in the HD group was observed prior to treatment start and thus was not considered test-item related. Statistically significant lower body temperature in middle dose group males was observed compared that of the control group males during the last week of treatment. Lower temperature in the MD group in the last week of treatment was not considered toxicologically relevant as LD and HD group showed no statistically significant differences and no dose-dependent trend was observed.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Statistically significantly higher absolute and relative (to body weight) kidney weights were recorded in high dose group males. The increased renal weight correlated with the histopathological lesions present in the kidneys, particularly with enhanced accumulation of hyaline droplets in the proximal tubules. However, the process for hyaline droplet accumulations is limited to male rats and it is considered that the same process do not occur in female rats, mice of either sex, and higher species of either sex including dogs, primates and humans, because of lack of or little alpha-2u-globulin synthesis.
Other slight to moderate deviations in organ weights of test item treated animals compared to their respective controls followed no consistency or dose-dependency and thus were not considered toxicologically relevant.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

At necropsy, mass of the larynx, abnormal (hard) consistency of the salivary glands, yellow fluid-filled stomach and enlarged pancreas were observed in the female animal, which was euthanized for animal welfare reasons. The histopathological evaluation showed that lesions in the larynx and salivary glands had necrotising inflammations which occurred in the subcutis at the region around the neck and were not the lesions produced in the parenchyma of each organ.
Yellowish fluid-filled thoracic cavity was recorded in one low dose group female. No histological examination was performed to the organs and tissues of this animal. No gross or histomorphological lesions indicating abnormalities in respiratory or circulatory functions were observed in any high dose animals. Therefore, the fluid retention observed in this one low dose group female was considered to be incidental and not test substance-related.
Other findings included red coloured ileum in one middle dose group male as well as yellow fluid-filled thoracic cavity and red-spotted thymus in one control group female. These findings were within the range of normal background changes, observed in rats of this strain and age, and without any corresponding histopathological changes. They were therefore considered to be incidental and not test substance-related.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In the forestomach, inflammation with focal submucosal haemorrhage was observed in one low dose group male as well as in one middle dose group male. Focal/single ulceration in the lesion was also seen for the latter animal. No forestomach lesions were observed in any high dose group animals. In the preliminary study doses higher than 90 mg/kg bw/day were administered to male and female rats and stomach injuries indicating local irritative effects of the test item were observed at all dose levels for both sexes. The forestomach lesions observed in the study were identical to the lesions in the dose range-finding study and therefore they were considered to be treatment-related and adverse changes. Mucous neck cell hyperplasia was observed in the glandular stomach in three high dose males and one high dose female, but it was considered to be an adaptive response to local stimuli and not to be adverse as no necrotic/degenerative or inflammatory changes were noted.
In the kidneys of high dose group males, hyaline droplet accumulation with sporadic single cell death in the proximal tubules as well as increased incidence of tubular basophilia were observed. No such effects were observed in any of the female animals. Hyaline droplets were due to an excessive accumulation of secondary lysosomes within the cytoplasm containing alpha-2u-globulin. This is considered to be a male rat specific effect.
Moreover, the hyaline droplet accumulation in high dose males was accompanied by tubular single cell necrosis and increased incidence of tubular basophilia. These effects were considered to be male rat-specific and non-human-relevant.
No histomorphological changes could be detected in the reproductive organs and tissues. Squamous hyperplasia and hyperkeratosis were observed in one low dose group male as well as one middle dose group male.

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

Treatment with the test item had no effect on serum T4 levels of parental males. No considerable differences were found between dose groups and the corresponding control group of this study.

Key result

Dose descriptor:

NOAEL

Remarks:

systemic effects

Effect level:

>= 90 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No adverse effects observed.

Dose descriptor:

LOAEL

Remarks:

local effects

Effect level:

10 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Critical effects observed:

yes

Lowest effective dose / conc.:

10 mg/kg bw/day (nominal)

System:

gastrointestinal tract

Organ:

stomach

Treatment related:

yes

Dose response relationship:

yes

Conclusions:

In a combined repeated dose oral toxicity study with the reproduction / developmental toxicity screening test with the registered substance tert-butyl(chloro)dimethylsilane, conducted according to OECD Test Guideline 422 and in compliance with GLP, a NOAEL for systemic effects was concluded to be ≥90 mg/kg bw/day based on no adverse effects observed. A local LOAEL of 10 mg/kg bw/day was also concluded based on local effects in the stomach.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

90 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

Klimisch score 1

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1 May 1983 to 18 August 1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes

Limit test:

no

Species:

other: rat and mouse

Strain:

other: Sprague-Dawley rats, Fischer-344 rats, and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data
- Age at study initiation: No data
- Weight at study initiation: No data
- Fasting period before study: No
- Housing: Individually housed in 8 cubic meter stainless steel and glass inhalation chambers.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: One week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Data could not be found in report supplied
- Humidity (%): Data could not be found in report supplied
- Air changes (per hr): Data could not be found in report supplied
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 20 September 1984 To: 20 December 1984

Route of administration:

inhalation: gas

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were housed and exposed in 8 cubic meter stainless steel and glass inhalation chambers.
The test substance was first passed through a regulator and was maintained at a pressure of 50 psig. It was then passed through a flowmeter which measured the flow rate. The gas was then mixed with a supply of filtered, dry air, introduced at the top of the inhalation chamber and exhausted at the bottom. The negative pressure of each test chamber was maintained at 0.1 inches of water. The control chamber was maintained at a positive pressure of 0.02 inches of water.

TEST ATMOSPHERE
- Brief description of analytical method used: Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Duration of treatment / exposure:

90 days

Frequency of treatment:

six hours, five days per week

Dose / conc.:

10 ppm

Remarks:

target concentration

Dose / conc.:

20 ppm

Remarks:

target concentration

Dose / conc.:

50 ppm

Remarks:

target concentration

No. of animals per sex per dose:

31 males and 21 females of each species/strain

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: No data
- Rationale for selecting satellite groups: Interim sacrifice group of 15 males and 10 females sacrificed after the fourth exposure.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily for mortality and clinical signs of toxicity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Weekly

BODY WEIGHT: Yes
- Time schedule for examinations: All animals: just prior to the first exposure (day 1), then weekly, and a final fasted body weight measurement was obtained prior to the 90-day sacrifice.

FOOD CONSUMPTION:
- Just prior to the first exposure (day 1), then weekly for each animal.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At 90 days.
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At 90 days.
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

URINALYSIS: Yes, in 10 males and 10 females.
- Time schedule for collection of urine: At 90 days.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes, for approximately 12 hours.
- Parameters checked in table 1 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

15 males and 10 females per group per strain/species were sacrificed the day following the fourth exposure for pathological examination. After 90 days of exposure 10 males and 10 females per group per strain/species (same animals as those for clinical pathology) were sacrificed for pathological examination.

At the day 5 interim sacrifice the nasal turbinates, trachea, lung and gross lesions were examined microscopically. Organs and tissues examined microscopically at 90 days are summarised in Table 2.

Statistics:

Parametric data such as body weight and food consumption were analysed using an analysis of variance (ANOVA). Statistically significant differences that were noted were further studied by either Tukey's (equal populations) or Scheffe's (unequal populations) Test of Multiple Comparison. Non-parametric data such as organ weight ratios were analysed using a Kruskal-Wallis ANOVA and a Test of Multiple Comparison. Discontinuous data such as appropriate incidences of histopathological findings were compared using CHI-SQUARE or Fischer's Exact Probability Test.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Local effects

Mortality:

mortality observed, treatment-related

Description (incidence):

Local effects

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Relating to local effects

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: One female high dose mouse was found dead on study day 12, and four low dose male mice were found dead on study day 92. In addition, one high dose female mouse was sacrificed in extremis on study day 20. One high dose female Sprague-Dawley rat was found dead on study day 4. However, the study authors noted that the deaths did not appear to be related to exposure to HCl. Clinical signs were consistent with the irritant/corrosive properties of HCl (appendage, tail or lip injury in the form of toe missing/swollen/open/gelatinous, scabbed/deformed/lesion, crusty nose, tissue mass, mouth injury, scabbed nose, crusty muzzle, red stained fur, nasal discharge, crusty eye, poor coat quality

BODY WEIGHT AND WEIGHT GAIN: 50 ppm HCl resulted in decreased body weights in all four strains after four exposures. Following 90 days of exposure B6C3F1 male and female mice and male Sprague-Dawley rats exposed to 50 ppm had biologically significant decreases in body weight.

FOOD CONSUMPTION: After four days of exposure there were statistically significant decreases in food consumption for high dose male Sprague-Dawley rats and male Fischer 344 rats. After 90 days high dose mice had the largest reduction in food consumption. The rats did not show a consistent reduction in food consumption that could be deemed expsoure-related.

HAEMATOLOGY: there were no treatment-related effects.

CLINICAL CHEMISTRY: there were no treatment-related effects.

URINALYSIS: there were no treatment-related effects.

ORGAN WEIGHTS: decrease liver weight in high dose male and female mice and Fischer 344 female rats. The authors noted that this might have been due to the overall reduced body weights.

GROSS PATHOLOGY

HISTOPATHOLOGY: Animals exposed to all concentrations of HCl had minimal to mild rhinitis, which occurred in the anterior portion of the nasal cavity and was dose and time related. Mice also developed varying degrees of cheilitis with accumulations of haemosiderin-laden macrophages involving the perioral tissues at 50 ppm. At all exposure concentrations mice developed oesinophilic globules in epithelial cells lining the nasal turbinates after 90 days of exposure.

Dose descriptor:

NOAEC

Effect level:

20 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Systemic NOAEC based on reduced body weights at 50 ppm.

Dose descriptor:

LOAEC

Effect level:

10 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Local LOAEC based on irritant/corrosive effects seen at all dose levels tested in mice.

Critical effects observed:

no

Conclusions:

In a well conducted 90-day gas inhalation study (reliability score 1) the systemic NOAEC for hydrogen chloride was 20 ppm based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

132 mg/m³

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1 May 1983 to 18 August 1983

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes

Limit test:

no

Species:

other: rat and mouse

Strain:

other: Sprague-Dawley rats, Fischer-344 rats, and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data
- Age at study initiation: No data
- Weight at study initiation: No data
- Fasting period before study: No
- Housing: Individually housed in 8 cubic meter stainless steel and glass inhalation chambers.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: One week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): Data could not be found in report supplied
- Humidity (%): Data could not be found in report supplied
- Air changes (per hr): Data could not be found in report supplied
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 20 September 1984 To: 20 December 1984

Route of administration:

inhalation: gas

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Animals were housed and exposed in 8 cubic meter stainless steel and glass inhalation chambers.
The test substance was first passed through a regulator and was maintained at a pressure of 50 psig. It was then passed through a flowmeter which measured the flow rate. The gas was then mixed with a supply of filtered, dry air, introduced at the top of the inhalation chamber and exhausted at the bottom. The negative pressure of each test chamber was maintained at 0.1 inches of water. The control chamber was maintained at a positive pressure of 0.02 inches of water.

TEST ATMOSPHERE
- Brief description of analytical method used: Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses of chamber scrub samples were performed throughout the study by a method involving the titration of dissolved chlorides with a dilute solution of mercuric nitrate in the presence of a mixed diphenylcarbazone-bromophenol blue indicator. Each test chamber was sampled approximately once per hour. The control chamber was sampled once daily.

Duration of treatment / exposure:

90 days

Frequency of treatment:

six hours, five days per week

Dose / conc.:

10 ppm

Remarks:

target concentration

Dose / conc.:

20 ppm

Remarks:

target concentration

Dose / conc.:

50 ppm

Remarks:

target concentration

No. of animals per sex per dose:

31 males and 21 females of each species/strain

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: No data
- Rationale for selecting satellite groups: Interim sacrifice group of 15 males and 10 females sacrificed after the fourth exposure.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least twice daily for mortality and clinical signs of toxicity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Weekly

BODY WEIGHT: Yes
- Time schedule for examinations: All animals: just prior to the first exposure (day 1), then weekly, and a final fasted body weight measurement was obtained prior to the 90-day sacrifice.

FOOD CONSUMPTION:
- Just prior to the first exposure (day 1), then weekly for each animal.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At 90 days.
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At 90 days.
- Animals fasted: Yes, for approximately 12 hours.
- How many animals: 10 males and 10 females
- Parameters checked in table 1 were examined.

URINALYSIS: Yes, in 10 males and 10 females.
- Time schedule for collection of urine: At 90 days.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes, for approximately 12 hours.
- Parameters checked in table 1 were examined.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

15 males and 10 females per group per strain/species were sacrificed the day following the fourth exposure for pathological examination. After 90 days of exposure 10 males and 10 females per group per strain/species (same animals as those for clinical pathology) were sacrificed for pathological examination.

At the day 5 interim sacrifice the nasal turbinates, trachea, lung and gross lesions were examined microscopically. Organs and tissues examined microscopically at 90 days are summarised in Table 2.

Statistics:

Parametric data such as body weight and food consumption were analysed using an analysis of variance (ANOVA). Statistically significant differences that were noted were further studied by either Tukey's (equal populations) or Scheffe's (unequal populations) Test of Multiple Comparison. Non-parametric data such as organ weight ratios were analysed using a Kruskal-Wallis ANOVA and a Test of Multiple Comparison. Discontinuous data such as appropriate incidences of histopathological findings were compared using CHI-SQUARE or Fischer's Exact Probability Test.

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Local effects

Mortality:

mortality observed, treatment-related

Description (incidence):

Local effects

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Relating to local effects

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: One female high dose mouse was found dead on study day 12, and four low dose male mice were found dead on study day 92. In addition, one high dose female mouse was sacrificed in extremis on study day 20. One high dose female Sprague-Dawley rat was found dead on study day 4. However, the study authors noted that the deaths did not appear to be related to exposure to HCl. Clinical signs were consistent with the irritant/corrosive properties of HCl (appendage, tail or lip injury in the form of toe missing/swollen/open/gelatinous, scabbed/deformed/lesion, crusty nose, tissue mass, mouth injury, scabbed nose, crusty muzzle, red stained fur, nasal discharge, crusty eye, poor coat quality

BODY WEIGHT AND WEIGHT GAIN: 50 ppm HCl resulted in decreased body weights in all four strains after four exposures. Following 90 days of exposure B6C3F1 male and female mice and male Sprague-Dawley rats exposed to 50 ppm had biologically significant decreases in body weight.

FOOD CONSUMPTION: After four days of exposure there were statistically significant decreases in food consumption for high dose male Sprague-Dawley rats and male Fischer 344 rats. After 90 days high dose mice had the largest reduction in food consumption. The rats did not show a consistent reduction in food consumption that could be deemed expsoure-related.

HAEMATOLOGY: there were no treatment-related effects.

CLINICAL CHEMISTRY: there were no treatment-related effects.

URINALYSIS: there were no treatment-related effects.

ORGAN WEIGHTS: decrease liver weight in high dose male and female mice and Fischer 344 female rats. The authors noted that this might have been due to the overall reduced body weights.

GROSS PATHOLOGY

HISTOPATHOLOGY: Animals exposed to all concentrations of HCl had minimal to mild rhinitis, which occurred in the anterior portion of the nasal cavity and was dose and time related. Mice also developed varying degrees of cheilitis with accumulations of haemosiderin-laden macrophages involving the perioral tissues at 50 ppm. At all exposure concentrations mice developed oesinophilic globules in epithelial cells lining the nasal turbinates after 90 days of exposure.

Dose descriptor:

NOAEC

Effect level:

20 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Systemic NOAEC based on reduced body weights at 50 ppm.

Dose descriptor:

LOAEC

Effect level:

10 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Local LOAEC based on irritant/corrosive effects seen at all dose levels tested in mice.

Critical effects observed:

no

Conclusions:

In a well conducted 90-day gas inhalation study (reliability score 1) the systemic NOAEC for hydrogen chloride was 20 ppm based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LOAEC

15 mg/m³

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In a dose range finding study, conducted according to a guideline similar to OECD Test Guideline 407 with deviations and not in compliance with GLP, male and female rats were exposed by oral gavage to 0, 100, 250, 500, 375, 430 mg/kg bw/day tert-butyl(chloro)dimethylsilane in corn oil for 14 days. Local irritative effect in the stomach were reported at all dose levels tested. Moreover, two animals at 500 mg/kg bw/day were sacrificed due to moribund reasons. Inflammatory lesions were considered as the cause of morbidity. The clinical signs observed at 500 mg/kg bw/day included paraparesis, abnormal pinna reflex, abnormal recumbency, reduced spontaneous activity, ataxia, muscular hypotonia, wasp waist, piloerection, and lacrimation. Males dosed with 375 mg/kg bw/day, 430 mg/kg bw/day and 500 mg/kg bw/day showed slight body weight loss compared to control males. Mean food consumption was slightly reduced in all male and female test item-treated groups compared to the respective controls with the exception of the female group treated with 100 mg/kg bw/day. Macroscopic findings of masses at the gastric wall in animals of both sexes dosed with 375 mg/kg bw/day and above were evident during histopathological examination. At the microscopic examination, specific findings were found which started at the dose of 100 mg/ kg bw/day and included inflammatory and degenerative lesions which consisted of erosions, inflammation, hyperplasia, ulceration, hyperkeratosis, mononuclear cell infiltration, epithelial degeneration, and haemorrhage. A NOAEL could not be determined for these local effects (BSL Bioservice, 2019).

In a combined repeated dose oral toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP, doses of 0, 10 (LD), 30 (MD) or 90 (HD) mg/kg bw/day tert-butyl(chloro)dimethylsilane in corn oil were administered daily via oral (gavage) route to male and female rats for a treatment period of up to 63 days. Male and female rats were exposed to the test item during the 14-day pre-mating period and during the mating period (maximum 14 days). Females were also exposed during the gestation period and up to post-natal day (PND) 12 (BSL Bioservice / Eurofins, 2020). During the study the animals were observed for mortality, clinical signs, functional observations, food consumption and body weights on a regular basis; haematological, clinical biochemistry and urinalysis evaluations were performed at terminal sacrifice; reproductive function and effects on reproductive organs were evaluated for males and females; litter observations were performed including the number and sex of pups, stillbirths, live births, runts and the presence of gross abnormalities; anogenital distance of pups was also measured; all animals were examined for macroscopic lesions at gross necropsy; organ weights were recorded and a full histopathological evaluation was performed on the preserved tissues.

No treatment-related mortality was observed for any of the test groups. One control animal died due to error from dosing procedure. No clinical signs indicating systemic toxicity were observed in any of the animals. Moving the bedding and increased salivation were observed in few animals of the test item-treated groups shortly after dose administration or in anticipation thereof and thus were considered to be a sign of discomfort or a local reaction of the test item rather than adverse systemic effects. No test item-related effects were observed on the parameters of the functional observation battery or body temperature of male and female animals and no relevant effects were noted on body weight development or food consumption in any of the dose groups.

No treatment-related effects were observed on the oestrous cycle, pre-coital interval and duration of gestation, reproductive indices or pre- and post-natal parameters. There was a slight dose-dependent trend towards higher pre-implantation loss in test item-treated groups, which was not considered toxicologically relevant as the data were within the historical control data range.

No toxicologically relevant effects in litter observations and pup survival were noted. No toxicologically relevant external gross abnormalities were observed in the pups of test item-treated groups. Statistically significantly shorter anogenital distance was observed in male pups of the MD and HD group and mean nipple retention of male pups was found to be statistically significantly higher in the HD group. Female pups of the HD group showed a statistically significantly shorter anogenital distance. Even though, these changes were within the historical control data range, they could indicate possible endocrine disruption. However, no effects were observed in other parameters such as histopathology of parental reproductive organs and their weights, litter size, sex ratio, pup thyroid /parathyroid weight and thyroxine hormone (T4) to support a possible endocrine disruption modality of the test item.

Treatment with the test item had no effect on serum T4 levels of parental males or 13-day old pups.

The test item had no toxicologically relevant effect on coagulation parameters, haematological parameters or parameters of clinical biochemistry of male and female animals. The test item had no toxicologically relevant effects on urinary parameters analysed in selected animals at the end of the treatment period.

There was a test item-related differences in the kidney weight of HD males, which also correlated with the renal histopathological lesions.

In the forestomach, inflammation with focal submucosal haemorrhage, squamous hyperplasia, hyperkeratosis and ulceration were observed in the LD and MD males. No forestomach lesions were recognized in animals of the HD group. No forestomach lesions were recorded in females. In the preliminary study doses higher than 90 mg/kg bw/day were administered to male and female rats and stomach injuries indicating local irritative effects of the test item were observed at all dose levels for both sexes. The forestomach lesions observed in the study were identical to the lesions in the dose range-finding study and therefore they were considered to be treatment-related and adverse changes. Mucous neck cell hyperplasia was observed in the glandular stomach in the HD group animals, but it was considered to be an adaptive response to local stimuli and to be not adverse as no necrotic/degenerative or inflammatory changes were noted. Enhanced hyaline droplet accumulations with sporadic single cell death and tubular basophilia were observed in the kidneys of HD males but not females and were considered to be a male rat-specific phenomenon with an excessive accumulation of secondary lysosomes within the cytoplasm containing alpha-2u-globulin. Hyaline droplet accumulations were accompanied by tubular single cell necrosis and tubular basophilia. These effects are generally considered to be male rat-specific and non-human relevant.

The study concluded a NOAEL for systemic toxicity of ≥90 mg/kg bw/day (the highest dose tested) based on no adverse systemic effects, and a LOAEL for local effects in the stomach of 10 mg/kg bw/day (the lowest dose tested). The high dose was limited to 90 mg/kg bw/day based on severe local effects observed in a 14-day range finding study at doses of 100 mg/kg bw/day and above.

For the inhalation route a 28-day inhalation study with another chlorosilane, dichloro(dimethyl)silane (CAS 75-78-5, WIL, 2014) is used to demonstrate that local effects are dominated by generation of the hydrolysis product, HCl, and that there are no adverse systemic effects.

In a well conducted 90-day gas inhalation study (Toxigenics, 1984) the systemic NOAEC for hydrogen chloride was 20 ppm based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice, which was observed with a LOAEC of 10 ppm.

A good quality 90-day repeated inhalation study for hydrogen chloride has been used to assess the local effects of tert-butyl(chloryl)dimethylsilane. In a 90-day repeated inhalation study with HCl, no serious adverse systemic effects were observed in rats and mice exposed up to 50 ppm (approximately 70 mg/m3) for 6 hours per day, 5 days per week. The only significant adverse finding relating to systemic toxicity was decreased body weight at the highest dose level. Local effects on the nasal turbinates of mice were observed at all dose levels tested (10, 20 and 50 ppm). Testing with HCl at higher test concentrations is neither ethically nor technically feasible since severe corrosive effects would lead to discomfort and distress in the test animals. The author of this Chemical Safety Report considers that the apparent systemic effects at 50 ppm in the study were most likely secondary to local corrosive effects at this dose level.

Following uptake of hydrochloric acid, hydrogen and chloride ions will enter the body’s natural homeostatic processes and significant systemic effects are unlikely.

Justification for classification or non-classification

Based on the available data, no classification for specific target organ toxicity following repeated exposure is required for tert-butyl(chloro)dimethylsilane according to Regulation (EC) No 1272/2008.